DESIGN AND METHOD OF SUPPLYING A THERMOPLASTIC FILAMENT

专利摘要:
An extrusion-based production system (300), comprising: a filament roll with a thermoplastic filament (2); at least one assembly with: an entrance (3) for receiving the filament; an outlet (4) for dispensing the filament, a channel (5) between the inlet and outlet; a first and second rotatable component (10, 20), respectively, rotatable about a first / second axis (12, 22), and having first / second external ridges (11, 21), wherein when a filament is inserted into the channel and the at least one assembly is rotated relative to the filament (2), the rotatable components rotate about their respective axis, and the axes move about the filament such that the components essentially roll over the filament, and the outer ridges (11) ) penetrate at least partially into the filament (2). A method of feeding a thermoplastic filament.
公开号:BE1026877B1
申请号:E20195742
申请日:2019-10-28
公开日:2020-07-22
发明作者:Jonathan Palmaers
申请人:Ind Constructies Symons Besloten Vennootschap Met Beperkte Aansprakelijkheid；
IPC主号:

专利说明:

4- BE2019 / 5742 APPARATUS AND METHOD OF SUPPLYING A THERMOPLASTIC FILAMENT
DOMAIN OF THE INVENTION The present invention relates to devices and methods for feeding a filament in an extrusion-based system. More specifically, the present invention relates to an extrusion-based production system with a filament feed mechanism, and a method of feeding a filament that is or comprises a thermoplastic material, e.g. an additive manufacturing device, e.g. a 3D printer .
BACKGROUND OF THE INVENTION Extrusion-based systems where a filament of a thermoplastic material is fed, melted, and deposited on an object to be formed are known in the art, e.g., in the field of 3D printers.
FIG.1 shows a schematic block diagram of a known extrusion-based system. It includes a filament spool 101 on which a filament 102 is wound. The filament is fed to an extruder 103 through a curved path. The extruder 103 of FIG. 1 has a feed mechanism based on two nip rollers 107, 108. By rotating these rollers 107, 108 at an adjustable speed, the feed speed of the material can be controlled. A heating unit 104 melts the filament, and the molten material is deposited through a nozzle 105. By moving the nozzle X, Y, Z in three directions by a displacement mechanism (not shown), and by delivering the filament at an appropriate speed, a 3D object can be formed layer by layer on a substrate 106. The system is controlled by an external computer (not shown), which computer contains, for example, a 3D model of the object to be formed.
FIG. 2 (a) and FIG. 2 (b) show a problem that may arise under certain circumstances with this system, e.g., when the nip rolls want to advance the filament 102, but due to insufficient force, instead scrape material from the filament. It will be clear that this will disrupt the production process drastically.
US7896209B2 describes another known system, as shown in FIG. 3 to FIG. 5 of the present document. FIG. 3 shows a front view of an extrusion-based digital production system 300 including a building chamber 312, and a substrate 314, a gantry 316, an extrusion head 318, and a filament feed source 320, with extrusion head 318 including a drive mechanism 322. The driving mechanism 322 is a filament driving mechanism using a rotatable component 330 with an internal threaded surface 332 (see FIG. 5), for feeding successive portions of filament 324 from filament supply source 320 during a build operation with the system.
300.
FIG. 4 shows how an electric motor 334 drives the rotatable component 330.
2. BE2019 / 5742 FIG. 5 illustrates how the internal threads of the rotatable component 330 mesh with the filament 324 to advance the filament.
There is always room for improvements or alternatives.
SUMMARY OF THE INVENTION It is an object of the present invention to provide an extrusion-based production system.
It is also an object of the present invention to provide a method of supplying a thermoplastic filament in an extrusion-based production system.
It is a specific object of embodiments of the present invention to provide an assembly, and a filament feeding system, and a method for feeding a thermoplastic filament into an extrusion-based production system, with an accurate throughput (e.g., with a very linear curve of supplied quantity of material versus requested / set quantity of material, or e.g. with a very flat ratio of supplied quantity of material versus requested / set quantity of material).
It is an object of certain embodiments of the present invention to provide a filament feed mechanism and a corresponding method with a reduced risk of heating and / or melting and / or scraping the filament within the feed mechanism.
To this end, the present invention provides an assembly, a filament feeding system, an extrusion-based production system, and a method according to embodiments of the present invention.
In a first aspect, the present invention provides an extrusion-based production system comprising: a filament roll with a thermoplastic filament to be extruded; and at least one assembly for feeding the thermoplastic filament, the at least one assembly comprising: an inlet for receiving the thermoplastic filament; an outlet for dispensing the filament, the inlet and the outlet defining a channel within which the filament will move; at least two rotatable components comprising a first rotatable component and a second rotatable component; the channel being at least partially located between the first component and the second component; wherein the first rotatable component is rotatable about a first axis and has first external ridges, said first axis being spaced a first distance from the channel such that the first external ridges penetrate at least partially into the channel; the second rotatable component being rotatable about a second axis different from the first axis and having second external ridges, said second axis being a second distance from the channel such that the second external ridges penetrate at least partially into the channel; with the first and second rotatable
3. BE2019 / 5742 component are mounted such that, when the thermoplastic filament is introduced into the channel and when the assembly is rotated relative to the filament, the first rotatable component rotates about the first axis, and the second rotatable component rotates about the second axis, and the first and second axes move around the filament in such a manner that the first and second rotatable components roll substantially over a surface of the thermoplastic filament, and that the first and second external ridges are approximately 0.05 mm to about 0.25 mm penetrate into the thermoplastic filament.
As a result, at least one groove is formed in the filament, so that the filament can be moved axially accurately without breaking the filament.
In one embodiment, the ridges are provided to penetrate to a depth approximately equal to 0.06 mm, or approximately 0.08 mm, or approximately 0.10 mm, or approximately 0.11 mm, or approximately 0.12 mm, or about 0.13 mm, or about 0.14 mm, or about 0.15 mm, or about 0.18 mm, or about 0.20 mm, or about 0.22 mm, or about 0.23 mm; or about 0.24 mm.
The filament preferably has a circular cross section.
The channel is preferably a cylindrical channel.
Preferably, the first distance is equal to the second distance.
It is an advantage that the assembly is extremely suitable for driving the thermoplastic filament in the axial direction, due to engagement of the ridges in the filament.
It is a very great advantage that the rotatable components mainly roll over the filament, but are also partly pressed into the filament, because such movement exhibits mainly "rolling friction", and only a small or reduced "drag friction". slip). As a result, the filament advances more smoothly and accurately, and the torque applied to the filament is greatly reduced.
The filament has a known (predetermined) diameter. This diameter can be standardized.
Preferably, the external ridges have a pointed end (in radial direction, away from the axis of rotation), or a pointed end, or an end with a circular cross section, or an end with a triangular cross section, or an end with a trapezoidal cross section, or a section with a convex end. By "end" is meant the part that penetrates into the filament ".
Thus, in other words, the outer ridges roll mainly or largely over the filament, one end of which penetrates into the filament and grooves or runs in the grooves already made, thus axially displacing the filament.
Preferably, the outer diameter of the rotatable components is at least twice the diameter of the filament, preferably at least a factor of 3, or at least a factor of 4, or at least a factor of 5, but at most a factor of 15, or at most a factor 12, or at most a factor of 10.
In one embodiment, the assembly further comprises the thermoplastic filament,
included in the channel.
In one embodiment, the axes of the rotatable components are substantially parallel, i.e. parallel, or intersecting at an angle of at most 15 °.
In one embodiment, each of the at least two rotatable components is in contact with the thermoplastic filament by means of at least three different back segments that are axially offset from each other (longitudinally of the filament).
In other words, if the ridges form a screw thread, in this embodiment at least 3 "threads" or "tips" of the screw thread are in contact with the filament. Or if the external ridges form discs or rings or dishes, then at least 3 discs or rings or dishes are in contact with the filament. Thus, if the assembly contains two rotatable components, there are at least 6 different engagement locations of the rotatable components and the filament. Thus, if the assembly includes three rotatable components, each with at least three spine segments engaged with the filament, there are at least 9 different locations of engagement of the rotatable components and the filament.
In one embodiment, the assembly further includes at least four bearings; and the first and second rotatable components are each mounted by means of two of the at least four bearings.
In one embodiment, the at least one assembly further includes a ring gear; and each of the at least two rotatable components further includes a gear wheel that engages the ring gear to synchronously rotate at least the first component and the second component about their respective axis.
Such a drive is similar to a planetary gear or a planetary gear with a ring gear, in which the gears of the rotatable components function as planet gears or planet gears.
In one embodiment, the at least one assembly further includes a central gear with a central opening for passing the filament; and each of the at least two rotatable components includes a gear meshing with the central gear to rotate the first component and the second component synchronously about their respective axis.
Thanks to the synchronous rotations, it is ensured that the tracks in the filament do not overlap, and that the tracks do not erode.
Such a drive is similar to a planetary gear or a planetary gear with a central sun gear ("sun gear"), the gears of the rotatable components acting as planet gears or "planet gear".
In embodiments where the drive mechanism has at least three components, the third component also includes a gear that engages the center
5. BE2019 / 5742 sprocket to rotate the three sprockets synchronously around their respective axis.
In one embodiment, the assembly further comprises a third and a fourth component positioned so that the channel is at least partially located in the space between the first and the second and the third and the fourth component, and wherein the third component and the fourth component each has a surface that touches or nearly touches the channel.
Preferably, the first and second components are opposed to the channel, and also the third and fourth components are opposed to the channel.
In this embodiment, the filament is substantially clamped between the first and the second rotatable component. The third and fourth components only serve to keep the filament within the channel. Preferably, at least a portion of the surface of the third and fourth components that can come into contact with the filament is smooth, e.g., polished and / or coated.
In one embodiment, the first axis of the at least one assembly is substantially parallel to the channel; and the second axis is substantially parallel to the channel; and the first ridges form a first external screw thread; and the second ridges form a second external screw thread; and the movements of the at least two rotatable components are synchronized by gears.
Preferably, the pitch of the second external thread is equal to the pitch of the first external thread.
The first and second external threads are preferably helical, with a constant pitch. The threads can be single threads, or can be multiple threads.
In these embodiments, the rotatable components with shafts parallel to the channel and with threads ensure that the filament will move axially with respect to the assembly.
In this embodiment, annular grooves or recesses are formed in the filament. Thanks to the synchronization by means of gears, the annular grooves can be clearly separated and remain separated, and the grooves can be prevented from fading and / or merging, which would reduce the accuracy.
It is an advantage of this assembly that it has an almost perfect transfer characteristic, with a very linear behavior (filament output speed versus filament requested speed), or a very flat transfer ratio, up to a certain maximum back pressure.
In one embodiment, the at least one assembly further comprises a third rotatable component with a third external thread, the third rotatable component being rotatable about a third axis different from the first and second axes, the third axis being substantially parallel to the channel and located at such a distance from the channel that the third external thread at least partially penetrates the channel, and wherein
.6- BE2019 / 5742 the channel is at least partially located between the first component and the second component and the third component; and wherein the third rotatable component is mounted such that when a filament (e.g., of standardized dimensions) is introduced into the channel and when the assembly is rotated relative to the filament, the third rotatable component rolls substantially over a surface of the filament.
It is an advantage of this embodiment that rotation of the third component about the third axis contributes to the filament advancing through the channel due to engagement of the third external threads and the filament.
It is an advantage of this embodiment that rotation of the third component about the third axis helps to reduce the friction between the filament and the third component, making filament advancement smoother and / or more precise.
In an embodiment, the first axis of the at least one assembly is provided to cross the filament at an angle of 1.0 ° to 9.0 °; and the second axis is provided to cross the filament at an angle of 1.0 ° to 9.0 °; and the first ridges form a plurality of first rings; and the second ridges form a plurality of second rings.
In these embodiments, the rotatable inclined axis components relative to the channel cause the filament to move axially relative to the assembly.
A great advantage of this embodiment is that the rotational movements of the rotatable components about their respective axes do not have to be explicitly synchronized by means of gears. In other words, a major advantage of this embodiment is that these gears can be omitted, which is easier to produce, and which is lighter in weight, so easier to drive.
In one embodiment, the assembly further includes a third rotatable component rotatable about a third axis different from the first and second axes; and the third axis crosses the channel at an angle of 1.0 ° to 9.0 °; and the first, second and third ridges comprise a plurality of rings.
Preferably, the second axis takes the position of the first axis after it has been displaced by 120 ° around the filament, and preferably the third axis takes the position of the first axis after it has been displaced by 240 ° around the filament. So at any point in time, none of the axes are parallel or parallel to the channel, but are intersecting.
In one embodiment, the first, second and third rotatable components are formed and positioned such that the at least one groove formed by the first, second and third ridges forms a single helix, or two individual helixes, or three individual helixes.
In one embodiment, each of the rotatable components includes at least three or at least four or at least five or at least seven rings.
In one embodiment, the plurality of rings on each rotatable component are equidistant rings. In other words, in this embodiment, the rings of each rotatable component are considered to be a constant distance apart.
BE2019 / 5742 In one embodiment, the plurality of rings all have the same external diameter.
In one embodiment, at least one of the plurality of rings has a first external diameter; and at least one other of the plurality of rings has a second external diameter, different from the first diameter.
In this way, for example, a gradually increasing, or a constant penetration depth of the rings in the filament can be obtained.
In one embodiment, the extrusion-based production system further comprises: at least one rotation-limiting unit disposed at the entrance or exit of the at least one assembly to limit filament torsion.
In one embodiment, the filament supply system further comprises: at least one pinch roller assembly disposed at the entrance or exit of the assembly to limit filament torsion.
In one embodiment, the rotation-limiting unit comprises at least two nip rollers or at least two pressure rollers.
In one embodiment, the filament roll is arranged such that a filament from the filament roll is introduced into the entrance of the assembly along a curved curve.
In one embodiment, the extrusion-based production system further comprises: at least one driving mechanism provided to rotate the at least one assembly relative to the filament.
In one embodiment, the drive mechanism is operatively connected to a toothed pulley of the at least one assembly.
Preferably, the drive mechanism is a synchronous drive mechanism.
In one embodiment, the extrusion-based production system comprises: a first assembly provided for moving the filament in a first direction; and a second assembly similar to the first assembly, arranged to also move the filament in the first direction; and a driving mechanism provided to rotate the rotatable components of the first assembly in a first direction relative to the filament, and rotate the rotatable components of the second assembly in a second direction relative to the filament, opposite to the filament. first direction, in order to reduce or substantially eliminate torsional forces exerted by the first assembly.
It is an advantage of this embodiment that the first torque exerted by the first assembly on the filament, even if small, and the second torsion generated by the second assembly (even if small) counteract each other, so that the resulting torque is further reduced.
It is an advantage of cascading two assemblies that the axial force applied to the filament is increased, e.g. substantially doubled. This further increases the risk of the filament shifting relative to the ridges or serrations
8. BE2019 / 5742 reduced.
In one embodiment, the drive mechanism includes an electric motor and a synchronous drive, e.g., a toothed drive belt, or a chain or sprockets.
In one embodiment, the at least one drive mechanism further includes an electric motor for rotating the at least one assembly relative to the filament.
In one embodiment, the at least one drive mechanism further includes a drive belt for coupling the at least one assembly to the electric motor.
In one embodiment, the electric motor is a hollow shaft motor, and the hollow shaft is configured to receive the filament, and the motor is configured to rotate the at least one assembly relative to the filament.
In one embodiment, the extrusion-based production system further comprises a control unit, which is communicatively connectable to an external computer and is provided to receive information for controlling the at least one drive mechanism.
For example, the control unit may be configured to receive position information, and an amount of material to be deposited at the received position.
In one embodiment, the extrusion-based production system further comprises a heating element provided to melt the thermoplastic filament passed through.
In one embodiment, the extrusion-based production system is a 3D printer.
In a second aspect, the present invention also provides a method of feeding a thermoplastic filament into an extrusion-based production system comprising a filament roll having a thermoplastic filament (2) to be extruded; and at least one assembly comprising: an inlet for receiving the thermoplastic filament to be extruded; an outlet for dispensing the filament, the inlet and the outlet defining a channel within which the filament will move; at least two rotatable components comprising a first rotatable component and a second rotatable component; the channel being at least partially located between the first component and the second component; wherein the first rotatable component is rotatable about a first axis and has first external ridges, said first axis being spaced a first distance from the channel such that the first external ridges penetrate at least partially into the channel; the second rotatable component being rotatable about a second axis different from the first axis and having second external ridges, said second axis being a second distance from the channel such that the second external ridges penetrate at least partially into the channel; and wherein the method comprises the steps of: a) introducing the thermoplastic filament into the channel; b) rotating the first rotatable component about the first axis, and rotating the second rotatable component about the second axis, and moving the first and the second axis around the filament in such a way that the first and the second rotatable component mainly rolls over a surface of the filament and the first and second external ridges are approximately 0.05 mm
-9. BE2019 / 5742 to penetrate about 0.25 mm into the thermoplastic filament.
In a third aspect, the present invention also provides an assembly for feeding the thermoplastic filament, comprising: an inlet for receiving the thermoplastic filament to be extruded; an outlet for dispensing the filament, the inlet and the outlet defining a channel within which the filament will move; at least two rotatable components comprising a first rotatable component and a second rotatable component; the channel being at least partially located between the first component and the second component; wherein the first rotatable component is rotatable about a first axis and has first external ridges, said first axis being spaced a first distance from the channel such that the first external ridges penetrate at least partially into the channel; the second rotatable component being rotatable about a second axis different from the first axis and having second external ridges, said second axis being a second distance from the channel such that the second external ridges penetrate at least partially into the channel; the first and second rotatable components being mounted such that, when the thermoplastic filament is introduced into the channel and when the assembly is rotated relative to the filament, the first rotatable component rotates about the first axis, and the second rotatable component rotates about the second axis, and the first and second axes travel around the filament in such a manner that the first and second rotatable components roll substantially over a surface of the thermoplastic filament; and wherein the first axis is substantially parallel to the channel; and wherein the second axis is substantially parallel to the channel; and wherein the first ridges form a first external screw thread; and wherein the second ridges form a second external screw thread; and wherein the movements of the at least two rotatable components are synchronized by gears.
In one embodiment, the first and second rotatable components are mounted such that the first and second external ridges penetrate about 0.05 mm to about 0.25 mm into the thermoplastic filament.
In one embodiment, the assembly further includes a third rotatable component with a third external thread.
BRIEF DESCRIPTION OF THE FIGURES With specific reference to the figures, it is emphasized that the details shown are by way of example only and only for illustrative discussion of the various embodiments of the present invention. They are presented for the purpose of providing what is believed to be the most useful and forthcoming description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show more structural details of the invention than is necessary for a fundamental understanding of the invention. The description in combination with the figures makes clear to those skilled in the art how the various forms of the invention are
-10- BE2019 / 5742 can be implemented in practice.
FIG. 1 shows a schematic block diagram of a known extrusion-based system. It includes a feed mechanism based on two pinch rollers or pinch rollers.
FIG. 2 shows a problem that can arise under certain circumstances with the system of FIG. 1.
FIG. 3 to FIG. 5 illustrate another known extrusion-based system.
FIG. 3 shows a front view of an extrusion-based digital production system, known in the art, with a drive mechanism using a rotatable component with an internal threaded surface.
FIG. 4 is an enlarged view of the drive mechanism of FIG. 3, wherein a motor drives a component with an internal screw thread.
FIG. 5 is an enlarged representation of how the internal threads engage the filament, groove the filament, and thus advance the filament.
FIG. 6 to FIG. 12 and FIG. 14 to FIG. 19 illustrate a first exemplary embodiment of an assembly as may be used in embodiments of the present invention FIG. 6 shows an arrangement (English: "arrangement") of three rotatable components with ridges (or projections) in the form of external threads engaged with a filament. The axes of the rotatable components are parallel to the channel.
FIG. 7 is a sectional view showing how the threads of the components of FIG. 6 intervenes with the filament.
FIG. 8 is an enlarged view of a portion of FIG. 7.
FIG. 9 shows an exploded view of the three rotatable components of FIG. 6 and an assembly comprising these three rotatable components, with bearings and gears.
FIG. 10 shows (left) an assembly based on the components of FIG. 9, in assembled form. Together with the motor and the belt and the clamping rollers, the whole forms a filament feeding system.
FIG. 11 shows a cross section of the feed mechanism of FIG. 10 in the planes alpha and beta.
FIG. 12 shows an example of a filament feeding system as can be used in embodiments of the present invention.
FIG. 13 shows an example of a planetary gear drive known in the art of variable transmission systems.
FIG. 14 (a) shows a top view (direction A-A in FIG. 9) on the rotatable components and the filament.
FIG. 14 (b) extensively illustrates how the threads engage the filament.
FIG. 15 shows how, in the first embodiment, the movements of the rotatable components (rotation about their axis + displacement of the axis around the filament) are synchronized
-11- BE2019 / 5742 can be by means of gears and a ring gear.
FIG.16 to FIG.19 are screenshots (English: "screenshots") of a computer simulation showing the movement of one of the components. As shown, the component is rotated about its own axis, and the axis itself is moved around the filament.
FIG. 20 to FIG. 24 show a second exemplary embodiment of a feed mechanism according to the present invention, as a variant of the first embodiment, without a ring gear but with a central gear. The central gear has an opening. This embodiment also has three externally threaded rotatable components.
FIG. 20 is a top view of the three components and the central gear.
FIG. 21 is a perspective view showing the relative position of the components and the filament and the central gear.
FIG. 22 shows an exploded view of the three rotatable components and the central gear of FIG. 22, and an assembly comprising these three rotatable components, as well as bearings, and gears.
FIG. 23 shows a top view of FIG. 22 in which two planes alpha and beta are defined, and a portion is cut away for illustrative purposes.
FIG. 24 shows a cross section of the assembly of FIG. 22 in the planes alpha and beta shown in FIG. 23.
FIG. 25 shows a filament feeding system showing a light variant of the assembly of FIG. 24, namely with a toothed pulley.
FIG. 26 to FIG. 29 show some examples of single threads, and multiple threads, with different pitches, that can be used in embodiments of the present invention.
FIG. 30 and FIG. 31 show examples of how single or multi-threaded rotatable components engage the filament and form rings on the filament.
FIG. 32 and FIG. 33 illustrate a third exemplary embodiment of (a part of) an assembly according to the present invention, as a variant of the first embodiment. It contains only two rotatable threaded components, but two additional holders or mechanical guides.
FIG. 34 to FIG. 42 illustrate a fourth exemplary embodiment of an assembly and a filament feeding system, as proposed by the present invention.
FIG. 34 shows an arrangement of three rotatable components comprising a plurality of ridges (or projections) in the form of rings. The axes of the rotatable components are not parallel to the channel, but have a small angle.
FIG. 35 illustrates on the basis of an unfold how the rings of the rotatable components can be arranged (with an axial shift) so that they run in the same grooves of the filament. This can also be considered as a timeline, which clearly shows that the points of application with the filament shift in the axial direction of the
12- BE2019 / 5742 filament with time.
FIG. 36 and FIG. 37 show examples of how rotatable components with rings are arranged as in FIG. 34 and FIG. 35 intervene in the filament, forming one or more spirals or helixes on the filament, thereby advancing the filament.
FIG. 38 (a) and FIG. 38 (b) show an exemplary filament driving system based on the arrangement of FIG. 34, in front view and in sectional view.
FIG. 39 shows the filament driving system of FIG. 38 (a) with synchronous drive.
FIG. 40 is a perspective view of a two-assembly filament drive system according to the fourth embodiment, driven in the opposite direction. (the upper assembly drive wheel is driven clockwise relative to the rest of the assembly, while the lower assembly drive wheel is driven counterclockwise against the rest of the assembly, or vice versa).
FIG. 41 shows a cross section of the filament driving system of FIG. 40.
FIG. 42 is a front view of the filament drive system of FIG. 40. It clearly shows that the axes of the rotatable components are inclined in a different direction. The two assemblies are synchronized by drive from the same motor.
FIG. 43 shows a test setup with a filament drive system according to FIG. 10, in perspective view.
FIG. 44 to FIG. 46 shows a top view of some exemplary pressure rollers or pinch rollers as may be used in embodiments of the present invention.
FIG. 47 shows a graph showing the ratio of the amount of material delivered as a function of the amount of material requested, based on data measured with the test set-up of FIG. 43.
DETAILED DESCRIPTION OF THE INVENTION The invention will be further explained by way of exemplary embodiments. However, the invention is not limited to this, but only by the claims.
In the present invention, the terms "rolls" and "rotatable components" are used synonymously.
Throughout this document, the term "filament engaging mechanism" or simply "engaging mechanism" is used to refer to an arrangement of at least two or at least three rotatable components arranged around a cylindrical channel, as shown, for example, in FIG. 6 (first embodiment) or FIG. 22 (second embodiment) or FIG. 32 (third embodiment) or FIG. 34 (fourth embodiment).
In this document, the terms pinch rollers, pinch rollers and pressure rollers are used as a synonym.
FIG.1 shows a schematic block diagram of a known extrusion-based
13- BE2019 / 5742 system. It includes a feed mechanism based on two pressure rollers or pinch rollers (English: "pinch roller system" or "pinch feeder system") 107, 108. The principle of operation of the system 100 of FIG. 1 has already been discussed in the background section.
FIG. 2 shows a problem that may arise under certain circumstances with the system of FIG. 1, e.g., when the nip rolls want to advance the filament 102, but instead scrape material from the filament.
The dotted curve of FIG. 47 shows a typical curve of such a transit system. The X axis shows the requested amount of material (e.g. the set amount of material to be deposited, as requested by an external computer (not shown)). The Y-axis shows the ratio of the quantity of material supplied (starting flow rate) and the quantity of material requested (requested flow rate). As can be seen, this ratio (subject to the necessary corrections and compensation) is close to 100% for relatively low flow rates (in the example, less than about 3 mm ° / s), but at higher flow rates the ratio decreases, e.g. due to slip occurs, e.g. because the heating element 104 with nozzle 105 cannot follow sufficiently, and exerts an upward pressure force on the filament 102. As shown, the deviation is speed dependent. The pinch rollers 107, 108 can follow up to a certain value (in the example up to the force occurring at 3 mm / S), but from a certain value "slip" occurs, and the teeth of the pinch rollers go in less or less. scrape more material away from the filament 102. As a result, the amount of material supplied will be less than the requested amount of material, which is of course detrimental to the quality and finish of the workpiece to be produced. In practice, this means that the maximum extrusion speed of the feed system shown in FIG. 1 with the curve of FIG. 47 is limited to a maximum of about 3 mm ° / sec for optimal quality, and to about 5 mm ° / sec for a deviation of 5%. Above this, the quality of the product produced decreases very quickly.
FIG. 3 to FIG. 5 illustrate another known extrusion-based system 300. FIG. 3, FIG. 4 and FIG. 5 of the present invention is a copy of FIG. 1 and FIG. 11 and FIG. 4 of US7896209B2, respectively.
The system of FIG. 3 has already been discussed in the background section. FIG. 4 shows that the system 300 includes a drive mechanism with a motor 334 which drives a rotatable internally threaded component 330 via a belt. FIG. 5 illustrates how the internal threads 332 of the rotatable component 330 mesh with the filament 324 to advance the filament.
Further research has shown that this system has several drawbacks. For example, there is great friction between the rotatable component 330 and the filament 324, because the threads cut into the filament like a knife and are pulled through, allowing the filament 324 to heat up and melt locally before it enters the filament.
“14- BE2019 / 5742 heating unit has arrived. This requires a fairly strong motor, the molten material can clog parts of the feed system, the amount of material supplied is less well defined, and when the system is shut down, the molten material will harden, causing the rotatable component to get stuck.
The inventors propose a completely different solution, namely a solution based on rotatable components with external ridges (e.g. external screw thread or with rings or discs), wherein the rotatable components and ridges are dimensioned and mounted so that the external ridges penetrate slightly the filament, but with the exception of these ridges, that the rotatable components roll substantially over the surface of the filament.
More specifically, the inventors propose an assembly for use in an extrusion-based production system, the assembly comprising: an inlet for receiving a filament to be extruded; - an outlet for delivering the filament, the inlet and the outlet defining a channel within which the filament will move; - at least two rotatable components, comprising a first rotatable component and a second rotatable component; - wherein the channel is at least partly located between the first component and the second component; wherein the first rotatable component is rotatable about a first axis and has first external ridges, said first axis being spaced a first distance from the channel such that the first external ridges penetrate at least partially into the channel; wherein the second rotatable component is rotatable about a second axis different from the first axis and has second external ridges, said second axis being located a second distance from the channel such that the second external ridges penetrate at least partially into the channel; - wherein the first and second rotatable components are mounted such that, when a thermoplastic filament is introduced into the channel and when the assembly is rotated relative to the filament, the first rotatable component rotates about its axis (the first axis), and the the second rotatable component rotates about its axis (the second axis), and the first and the second axis move around the thermoplastic filament in such a manner that the first and the second rotatable component roll substantially over a surface of the thermoplastic filament and that the first and second external ridges penetrate at least 0.05 mm into the thermoplastic filament to form at least one groove in the filament, and to move the filament axially.
Such an assembly can be used to form a filament feeding system, or a complete extrusion-based production system, eg in a so-called 3D printer.
Different embodiments based on these principles are possible. After this
BE2019 / 5742 four embodiments will be discussed in more detail, but of course the invention is not limited thereto, but only by the claims.
FIRST EMBODIMENT: FIG. 6 to FIG. 12 and FIG. 14 to FIG. 19 show the main aspects of a first exemplary filament feeding system 900.
FIG. 6 shows an arrangement of three rotatable components 10, 20, 30 with respective shafts 12, 22 and 32, and with respective external threads 11, 21, 31 in engagement with the filament 2. In one variant, the assembly can e.g. or five or six rotatable components.
The external thread partially penetrates the filament, which usually comprises a thermoplastic material. This gives a good grip on the filament, and the risk of accidental axial shift (English: "slip") is minimal.
In contrast to the system of FIG. 5, where the threads enter the filament at only one position (right side in FIG. 5), the filament is penetrated in at least two or at least three different positions in the system of the present invention.
However, the main advantage is due to the displacement of the shafts relative to the filament. Where the axis of the rotatable component in the system of FIG. 5 assumes a fixed position, the axes of the system of the present invention move over an imaginary cylinder surface. The main effect of this is that the friction between the rotatable components, on the one hand, and the filament, on the other, is essentially a "rolling friction", similar to a wheel rolling over a road surface. This offers several advantages. For example, a less powerful motor is required (which translates to a lower cost), and the filament is heated (much) less, reducing the risk of filament melting, feed mechanism clogging, and motor seizure be avoided.
During operation, the filament 2 will move axially in the space between the rotatable components in the direction of the arrow. (see also FIG. 15b).
FIG. 7 is a cross-sectional view of the first threaded rotatable component 10, showing how the ends of the thread 11 engage the filament 2. The same naturally occurs for the other rotatable components 20, 30.
FIG. 8 is an enlarged view of a portion of FIG. 7.
It is noted that in FIG. 7 and FIG. 8 only one type of external screw thread 11 is shown, namely with an isosceles triangular cross section, but of course the invention is not limited thereto, and other suitable cross sections can also be used, eg screw thread with an isosceles triangle, or screw thread with a pointed end but curved flanks, or threaded end with a circular cross section, or thread with a trapezoidal cross section, etc.
BE2019 / 5742 It is important that the radial end of the thread can partially penetrate and thus intervene with the filament. This can be achieved by placing the rotatable components at a suitable distance from the filament. In practice, the pressure of the ridges against the filament will cause a plastic deformation, as a result of which the filament will have permanent recesses or grooves 6 or notches. Surprisingly, it has been found that these notches form individual rings, e.g. circular rings, and therefore not a helix shape.
Although not shown in FIG. 7 and FIG. 8, the screw thread can also be made slightly conical, eg in a manner in which the screw thread hardly penetrates, if at all, in the filament 2 near the entrance of the feed mechanism (eg near position X in FIG. 7), so that the filament can easily be placed between the components can be positioned, and gradually penetrates deeper near the exit of the feed mechanism (eg near position Y in FIG. 7), so that there is a very good grip between the rotatable components and the filament 2, which reduces the chance of unintentional shifting ( English: "slip") is greatly reduced, or is minimal.
FIG. 9 shows an exploded view of the three rotatable components of FIG. 6 and an assembly comprising these three rotatable components 10, 20, 30. The components 10, 20, 30 are mounted at the top and bottom by means of bearings 43, 45, e.g. ball bearings. These bearings, in turn, are mounted in corresponding recesses 51 in a lower portion 46 and upper portion 41 of a container structure ("carrier"). The top part 41 can be fastened to the bottom part 46, for example, by means of bolts.
Components 10, 20, 30 further include, at the top (or bottom), a sprocket 44 which engages an internally toothed sprocket, hereinafter further referred to as ring gear or cogwheel 42. The gears 44 move in a similar manner to the ring gear 42 as is the case with known planetary gears (as shown, for example, shown in FIG. 13), where the gear wheel 1301 can rotate freely about its axis, and the sun gear 1302 is omitted.
The assembly 900 can be rotated with respect to the filament in several ways: e.g. (i) by rotating the top portion 41 of the holder structure relative to clamp rollers 55, or e.g. (ii) through the bottom part 46 of the holder structure. rotate relative to clamp rollers 55, or e.g. (ii) by rotating the ring gear 42 relative to the clamp rollers. As shown (in dotted line), the filament 2 is clamped sideways between pinch rollers or pinch rollers or pressure rollers 55 to prevent or limit torsion of the filament.
The clamping rollers 55 ensure that the filament cannot be twisted indefinitely due to the engagement of the threads of the rotatable components.
The clamping rollers 55 resist torsion of the filament about its longitudinal axis, but allow linear displacement of the filament in the longitudinal direction. Although not the primary focus of the present invention, the pinch rollers 55 may optionally have additional features to counteract such torsion, e.g. as shown in FIG. 44 to FIG. 46.
Unlike the system 100 of FIG. 1, the pinch rollers are in
17-BE2019 / 5742 embodiments of the present invention are not powered, and they do not determine the throughput. When the filament comes from a filament spool (as is usually the case), and when the filament is fed to the entrance under an arc, the arc shape helps to limit torsion of the filament.
FIG. 10 shows (left) an assembly based on the components of FIG. 9, in assembled form. Together with the motor 53, e.g. a stepper motor, and the toothed belt 52 and the clamping rollers 55, the whole forms a filament feeding system. In alternative embodiments, the toothed belt 52 can also be replaced by a chain drive or gear drive or the like.
FIG. 11 shows a cross section of the assembly of FIG. 10. It is clearly visible how the shaft of the rotatable component 30 is mounted in bearing 43 and bearing 45. In this example, the shaft of the rotatable component protrudes beyond the threaded cylindrical body. Alternatively, if the diameter of the rotatable component is sufficiently large, it is also possible to build the bearing into the cylindrical body, as shown in FIG. 24. In the example of FIG. 10 and FIG. 11, the ring gear 42 is rotatably disposed relative to the holder structure 46, 41 by means of one or more bearings (e.g. sleeve bearing or ball bearing). One skilled in the art of planetary drives will understand that, in the presence of the filament 2, rotation of the top portion 41 relative to the container structure will cause rotation of the three components 10, 20, 30 about their respective axes 12, 22, 32, as well as a displacement of these axes over a virtual cylinder circumference around the central channel 5 or around the filament 2, but also that the ring wheel 42 rotates about its own axis at a speed different from the rotation speed of the holder structure 41, 46. Not for professionals familiar with planetary gears this is much more difficult to understand.
Anyway, in this way, the above-mentioned substantially "rolling motion" of the rotatable components 10; 20, 30 over the circumference of the filament 2. By appropriate sizing, eg choice of dimensions (eg a suitable outer diameter of the rotatable element) and suitable positions (eg with an equal angular distance of 120 °, and a distance "d1" from the channel 5 which ensures that the threads penetrate into the filament to a desired depth, e.g., from about 0.05 mm to about 0.25 mm, e.g. about equal to 0.06 mm, or about 0.08 mm, or about 0.10 mm, or about 0.11 mm, or about 0.12 mm, or about 0.13 mm or about 0.14 mm, or about 0.15 mm, or about 0.18 mm or about 0.20 mm, or about 0, 22 mm), the filament 2 is clamped radially between the rotatable components 10, 20, 30 with an appropriate tension. This tension must be sufficiently large that the screw thread at least partially penetrates the filament, e.g. as shown in FIG. 8.
The part that is driven, in the example of FIG. 10, toothed pulley 58,
BE2019 / 5742 may be provided with an external serration or grooves for engagement of a toothed belt 52 (see FIG. 10). In this way, the risk of slippage between motor shaft 54 of motor 53 (eg a stepper motor) and the driven component is greatly reduced, or even completely eliminated.
In alternative embodiments, another synchronous drive can also be used, such as, for example, a chain drive, or a gear with a gear reduction or a gearbox or the like.
FIG. 12 shows an example of a filament feed system 1200 comprising a motor 53 and an assembly 900 as described above built into a housing 57.
In the example, the filament 2 is fed over a curved curve and stretched between two pinch rollers 55 to the entrance 3. This substantially avoids or largely limits torsion of the filament. In the example, toothed pulley 58 is driven by a toothed belt 52. Due to the drive mechanism 53, 52 and the internal gear mechanism 42, 44, the three rotatable components 10, 20, 30 roll substantially over the surface of the filament, but because the threads 11 , 21, 31 of the rotatable components penetrate slightly into the filament, some torque is still applied to the filament, causing the filament to slightly twist (estimated to be less than 45 °), but this has no noticeable effect on axial displacement of the filament 2 and thus at the feed speed of the filament.
As will become more apparent with reference to FIG. 16 to FIG. 19, it is a great advantage of this driving mechanism that the rotatable components 10, 20, 30 have to travel a relatively large displacement for only a small axial displacement 55 (see FIG. 18) of the filament 2.
Indeed, in order to move the filament 2 over the distance 55, the shaft 12 must rotate N around the filament a number of times. This number N is approximately equal to d_rol / d_filament, where d_rol is the outer diameter of the rotatable component, and d_filament is the outer diameter of the filament. In the prototype of FIG. 33 this value is approximately equal to 6.4. After this, the rotatable component was rotated about 1.0 times around its own axis.
This large angular displacement (in the example: 6.4 rpm) contributes to the high accuracy and the large gear ratio of the filament feed system, which is favorable for the motor selection. In fact, the feed mechanism acts as an inherent gearbox, avoiding an external gear transmission, resulting in reduced cost and weight.
Referring back to FIG. 12. Another great advantage is that the motor 53 can run at a relatively high speed, and only has to deliver a small torque (eg: torque ") (eg less than 0.13 Nm, eg less than 0.10 Nm, eg less than 0.08 Nm, eg less than 0.05 Nm, eg less than 0.2 Nm) This is extremely beneficial for relatively small motors, both stepper motors, DC brushless motors and AC brushless engines.
-19- BE2019 / 5742 As known, the power delivered (P) is equal to the product of the torque (T) and the speed (w). For example, compared to the system described in US7896209B2, the required torque will be much lower due to rolling friction (in the present invention) versus dragging or abrasive friction and heating (in US'209B2). The net result is that a motor of a smaller power can be chosen, which is again favorable in terms of price and weight. The reduced weight of the feed mechanism in turn contributes to a higher accuracy and / or a higher speed of the overall system, due to the lower inertia (e.g. less vibrations).
FIG. 13 shows an example of a planetary gear drive known in the art of variable transmission systems. The first and second embodiments of the present invention show similarities to this system.
In the example of FIG. 13, three gears 1304 are rotated about their axis due to engagement of the gears 1304 with a ring with internal teeth, herein referred to as "ring gear", and the shafts of the gears 1304 will move along a virtual circle The relative angular rotations of the three gears 1304 are mutually synchronized, which is advantageous for the threads to run in the same track on the filament The relative positions of the gears 1304 (in this example) are determined by rotating the triangular component 1303, which is called carrier (English: "carrier").
The planetary drive of FIG. 13 has both a central gear 1302 and a ring gear 1301. However, this is not necessary for the present invention. In a simplified form, the central gear 1302 can be omitted, and the ring gear 1301 causes the gears 1304 (read: rotatable components) to move synchronously.
Alternatively, the ring gear 1301 can be omitted, and the central gear 1302 ensures the synchronous movement of the gears 1304 (read: rotatable components).
FIG. 14 (a) and FIG. 14 (b) illustrate how the three rotatable components 10, 20, 30 of FIG. 6 can be rotated and moved relative to the filament 2.
The gears 44a, 44b, 44c of the rotatable components 10, 20, 30 of the filament feed mechanism of FIG. 15 perform a similar movement relative to the ring gear 42 as the gears 1304 relative to the ring gear 1301 of the classic planetary gear drive 1300 of FIG. 13, in the sense that the shafts 12, 22, 32 of the gears 444, 44b, 44c move synchronously over a virtual circumference, and that these gears 44a, 44b, 44c rotate synchronously about their respective shafts 12, 22, 32.
FIG. 15 is a perspective view of FIG. 14 (a), from a viewpoint other than FIG. 6.
The ring gear 42 preferably has a number of teeth which is an integer multiple of it
-20- BE2019 / 5742 number of rotatable components (in the example of FIG. 15: three). This has the effect that the rotatable components can be easily "mounted" with an angular rotation of their threads of 360 ° / 3 = 120 °, according to their physical position.
In the case of four rotatable components (not shown), these rotatable components are preferably located at 90 ° around the filament, and their respective threads are preferably also rotated at 90 °. This is simple when the number of teeth of the gears 44 is a multiple of four.
In the specific example of FIG. 6 and FIG. 15, the number of teeth of the gears 44 is twenty one (21), which is an integer multiple of 3, and the number of teeth of the ring gear is fifty-one (51), also a multiple of 3. FIG. 16 to FIG. 19 have already been discussed above. SECOND EMBODIMENT: FIG. 20 to FIG. 25 illustrate a second exemplary embodiment of an assembly, and a filament feeding system comprising such an assembly.
The second embodiment can be seen as a variant of the first embodiment, with the main similarities: - that it also comprises three rotatable components with screw thread, - that the movements of the three rotatable components are synchronized by gears; and with the main differences: - that ring gear 42 is omitted, and - that a central gear 48 with a central opening is added.
Everything described above for the first embodiment also applies for the second embodiment, mutatis mutandis.
The movements of the rotatable components 10, 20, 30 about their respective axes and around the filament 2 are identical as described for the first embodiment, with the major advantage of "rolling friction" and virtually no "drag friction".
The four gears 44a-44c and 48 ensure that the movements of the rotatable components remain synchronized. This is important so that the threads 11, 21, 31 of the rotatable components 10, 20, 30 engage the same grooves of the filament, or if one or more rolls are to form their own track, the threads remain in their own track, and the different tracks maintain their spacing on the filament.
Without synchronization of the rollers, the threads of the rollers can eventually run outside the grooves already formed, which can damage the grooves and greatly reduce the accuracy of the system.
FIG. 20 is a plan view of the three rotatable components 10, 20, 30 and the
BE2019 / 5742 central gear 48 with the central opening 49. This opening 49 has a diameter which is slightly larger than the outer diameter of the filament 2. This opening can for instance have an inner diameter in the range of 2 to 8 mm, or from 3 to 5 mm, so that the filament can slide through without significant friction.
FIG. 21 is a perspective view showing the relative position of the rotatable components 10, 20, 30 and of the filament 2 and of the central gear 48. In this example, the central gear 48 has exactly the same dimensions as the gears 44a-44c of the rotatable components, and all have 24 teeth, but this is not strictly necessary, and the system will also work as the central gear 48 other sizes and would have a different number of teeth. If the rotatable components mutually occupy a position of 120 ° around the filament (see FIG. 20), the number of teeth of both the central gear 48 and the gears 44 of the rotatable components is preferably an integer multiple of three. This makes it possible to mount the rotatable components with a mutual angular rotation of 0 °, 120 ° and 240 ° respectively (see also FIG. 31). FIG. 22 shows an exploded view of the three rotatable components and the central gear of FIG. 22, and an assembly comprising these three rotatable components. Here, too, the rotatable components 10, 20, 30 are preferably mounted in bearings 43 (top), 45 (bottom), which bearings are permanently mounted in a container structure (also called "carrier"). In the example of FIG. 22, the container structure includes a lower portion 41 and an upper portion 46 that can be bolted together. As can be understood in the meantime, also in the second embodiment the rotatable components are not driven directly, but indirectly. Since the ring gear 42 has been omitted, the components can be driven in two other ways: (i) by rotating the central gear 58 around the filament (or in practice, relative to the pressure rollers, not shown in FIG. 22); or (ii) by rotating the bottom portion 46 or the top portion 41 of the assembly around the filament (or in practice, relative to the pressure rollers). In either case, as a result, the rotatable components will rotate about their respective axes, and these axes will move around the filament. FIG. 23 shows a top view of FIG. 22 in which two planes alpha and beta are defined, and a portion is cut away for illustrative purposes. FIG. 24 shows a cross section of the assembly of FIG. 22 in the planes alpha and beta shown in FIG. 23. FIG. 25 shows a filament feeding system 2500 which is an assembly according to the second
BE2019 / 5742 embodiment, very similar to that of FIG. 20 to FIG. 24. As shown, the filament feed system 2500 includes a motor 53 (e.g., a stepper motor) driving a toothed belt 52, which in turn drives a toothed pulley 58, which in this example is connected to the upper portion 41 of the support structure. .
As shown, here too, filament 2 is passed through a rotation limiting unit, e.g., between two nip rollers 55, to limit or prevent rotation of the filament. These pinch rollers 55 are free-running, and thus do not determine the speed at which the filament is advanced. Preferably, the filament 2 is also supplied from a filament spool (not shown) via a curved curve. This curved curve also contributes to prevent torsion of the filament 2.
The embodiments have hitherto only been shown with a single screw thread (one helix), but the invention is not limited thereto, and the invention will also work with a multi screw thread (multiple helixes).
FIG. 26 to FIG. 28 show some examples of a rotatable single thread component with a pitch of 0.5mm or 1.0mm or 1.5mm respectively.
FIG. 29 shows a variant of the component of FIG. 28 with a 1.5 mm pitch but with a multiple thread, in the example shown a triple thread.
FIG. 30 (a) is a schematic representation of an arrangement (English: "arrangement") with three rotatable components, each with a single thread pitch 1.5 mm, with the three components oriented at the same angle in the container structure (as shown) by a black dot). Since the components themselves are shifted 120 ° relative to the filament, the threads of the different components engage the filament at different heights, as shown in FIG. 30 (b). In other words, in this embodiment, three sets of tracks are formed in the filament. Thanks to the synchronization, these tracks remain at a predetermined distance from each other.
In a variant of FIG. 30 (a), (not shown) with the second component rotated 120 ° relative to the first, and the third component rotated 240 ° relative to the first, the threads of the three components will all be in the same series of circular tracks from the filament 2.
In another variant of FIG. 30 (a), (not shown) with the second component rotated 0 ° relative to the first, and the third component rotated 240 ° relative to the first, the threads of the first and third components will be in the same series circular traces of the filament 2, but the second component will form its own series of traces in the filament.
-23. BE2019 / 5742 FIG. 31 (a) is a schematic representation of an arrangement (English: "arrangement") with three rotatable components, each with a triple thread pitch 1.5 mm. In the example, the three components are rotated 120 ° to one another, but since there are three helixes, it makes no difference whether the components are rotated 0 ° or 120 ° or 240 ° relative to each other.
FIG. 31 (b) shows that there are many more points of engagement between each component and the filament, and that the threads of the threads of all components run in all tracks.
Depending on the deformation properties of the thermoplastic filament (eg: plastic or elastic), a deeper penetration over a smaller number of points of application may or may not be better than a less deep penetration over a larger number of points of application, but essentially the operation is the same.
From this it can be understood that as long as the threads continue to run in the tracks despite an upward thrust from the melting unit, there will be no significant shift ("slip") between the rollers and the filament resulting in a perfectly linear behavior of the curve of FIG. 47, regardless of the set filament speed. Slip will only occur when the counteracting force becomes so great that the teeth of the screw threads are pressed out of the tracks. In the experimental set-up of FIG. 43 with an ABS filament of 1.75 mm diameter, a nozzle of 0.4 mm and a temperature of 230 ° C, the behavior was essentially perfectly linear up to a flow rate of about 13 mm / S.
THIRD EMBODIMENT: FIG. 32 and FIG. 33 show a third exemplary embodiment of a feed mechanism 3200 according to the present invention. Not all parts are shown in FIG. 32 and FIG. 33, so as not to overload the figure.
This third embodiment can be considered as a variant of the first embodiment, the main differences being: () that this embodiment comprises only two rotatable threaded components arranged so that the filament is positioned exactly in the middle between the first and second axis, and (ii) that the system further has two mechanical guides 30, 50 to hold the filament within the channel. These guides are not rotatable about their axis, but they rotate with respect to the cogwheel 42. The filament 2 is substantially clamped between the two threaded rotatable components 10, 20, and is advanced by the threads of these two components on a similar way as described above.
The two guides 30 and 50 are preferably a short distance from the filament 2, and preferably exhibit a very low friction with the filament 2. The latter can be realized in known ways, e.g. by choice of material (e.g. by using a plastic that
BE2019 / 5742 shows low friction with the material of the filament 2), and / or by using smooth or polished or coated guides, or in other known ways.
Everything described above for the first embodiment also applies for this third embodiment, mutatis mutandis. The main advantage, namely that there is mainly rolling friction between the rotatable components 10, 20 and the filament 2, also applies here.
Although some dragging friction occurs between the filament and the two guides 30, 50, the filament is preferably not clamped between these guides 30, 50. These guides serve only to hold the filament in place in the channel. The lateral force with which the filament is pressed against the mechanical guides is only a fraction of the radial force with which the first and second components push their threads into the filament.
Although not shown explicitly, for this arrangement with only two rotatable components, an assembly similar to that of FIG. 9, and a filament driving system similar to that of FIG. 10 to be built.
Although not explicitly shown, a variant of the arrangement of FIG. 32 and FIG. 33 without ring gear 42 but with an internal gear with an opening (as in the second embodiment) is also possible. This embodiment is especially suitable for filament diameters of at least 2.50 mm.
FOURTH EMBODIMENT: FIG. 34 to FIG. 42 show a fourth exemplary embodiment of an arrangement and assembly and filament feeding system of the present invention. Not all parts are shown in every figure, so as not to overload the figures.
When for the first, second and third embodiments it was said that the axes of the rotatable components are "substantially parallel" to the channel, then it is meant: perfectly parallel within a tolerance of at most +/- 0.5 °, or at most +/- 0.4 °, or at most +/- 0.3 °, or at most +/- 0.25 °, or at most +/- 0.20 °.
The fourth embodiment can be seen as a variant of the first embodiment, the main similarities being that: ij) there are multiple points of engagement (different in the height direction) between each rotatable component and the filament (e.g. at least three or at least four or at least five ); ii) that the filament is clamped between three rotatable components which are mutually positioned with an angular displacement of about 120 ° relative to each other, whereby automatic centering takes place; id) that there is substantially "rolling friction" between the rotatable components (or "rolls") and the filament, requiring only a small amount of force to cause the rotatable components to roll substantially over the filament;
25. BE2019 / 5742 iv) that the "dragging friction" is minimal or minor, as a result of which the filament is locally or hardly heated up by contact with the rotatable components, so that the spores remain virtually intact and are not hollowed out.
The main differences from the first embodiment are: i) that the rotatable components do not have a helical or helical back or elevation, but a plurality of equidistant annular ridges or elevations, e.g. at least two, or at least three, or at least four or at least five ridges ; ii) that the axes of the rotatable components are not parallel to the channel, but that their carriers deliberately form intersecting lines with an angle in the range of 1.0 ° to 9 °, or in the range of 1.25 ° to 8 °, or in the range from 1.5 ° to 8.0 °, or in the range from 2.0 ° to 5.0 °, e.g. approximately equal to 1.75 °, or approximately equal to 2.0 ° , or about equal to 2.25 °, or about equal to 2.5 °, or about equal to 2.75 °, or about equal to 3.0 °, or about equal to 3.25 °, or about equal to 3.5 °, or about equal to 3.75 °, or about equal to 4.0 °, or about equal to 5 °, or about equal to 6 °, or about equal to 7 °; il) that the angular rotations of the rotatable components around their axis do not have to be synchronized in order to prevent them from forming (slowly) extending grooves on the filament. It suffices that their positions have a fixed "offset" (see FIG. 35). This is also one of the biggest advantages of this fourth embodiment, because it allows the installation to be greatly simplified. More specifically, both the ring gear 42 and the central gear 48 can be omitted, as well as the gears 44a-44c; iv) the grooves on the filament will not form circular rings, but one or more spiral shapes.
With reference to FIG. 35 will recognize one skilled in the art that the filament in an assembly according to the fourth embodiment will not experience a substantial difference in the "backs" contact points of the three rotatable components of FIG. 34 or with the "threads" of the three rotatable components of FIG. 6. In both cases, the filament experiences penetration of a disc-shaped or saucer-shaped object at a certain angle of inclination (eg, in the range of 1.0 ° to 8.0 °).
Depending on the implementation, there may be a slight difference in depth of penetration, as "straight" threads in principle engage equally deep at the top and bottom, which is not the case for "equally sized circular ridges", but the depth of penetration can be adjusted in both cases. In the case of threads, the threads can, for example, be conical. In the case of the circular ridges, rings with different diameters can be used (eg smaller diameter in the middle, larger diameter at the bottom and the rotatable component at the top).
Regarding accuracy, it is important with single threaded rotatable components that the components have angular offset (as explained in
-26- BE2019 / 5742 FIG. 31a), to run in the same circular grooves on the filament. In the rotatable components with rings, the angular position of the component about its axis is not important, but the axial displacement is important (see FIG. 35). If the three rotatable components are identical, if no offset is applied in the height direction (Z) between the rotatable components, then each rotatable component will form its own spiral groove (by rolling indentation) on the filament, resulting in several such spiral grooves will be formed in the filament. If the grooves are too close together, they can erode and be damaged. This is detrimental to accuracy.
By choosing a suitable offset in the height direction (Z) between the rotatable components, it is possible to run the rotatable components in one and the same spiral groove. This allows the ridges to penetrate deeper into the filament, and thus to exert a higher radial pressure on the filament.
If the ridges are pointed (eg with a triangular cross-section or a truncated triangle or trapezoidal), the filament will also show a greater tendency to center the (spiral) grooves with respect to the ridges. In this way, all engagement points work together to achieve the same axial displacement of the filament.
Further optimization is possible by not giving the ridges of a rotatable component the same outer diameter, but by taking ridges with different outer diameters. Indeed, if all ridges have the same outer diameter, one spine penetrates deeper into the filament than the other ridges, due to the angle of inclination between the axes and the filament. If desired, the penetration depth can be made approximately equal for the different ridges by appropriately changing the diameters.
It is of course also possible to choose the diameters such that the penetration depth gradually increases from the entrance to the exit of the channel. Those skilled in the art who have the advantage of the present disclosure can easily choose suitable diameters. Other considerations are of course also possible.
As for maximum throughput and linearity between requested (set) and actual obtained speed (or flow), the graph of FIG. 47 also applies to the fourth embodiment, as long as the ridges continue to run in the tracks. Linearity is only lost when the counterforce (eg from the melting unit) becomes so great that the ridges start to run outside the tracks already formed.
Referring to the figures of the fourth embodiment.
FIG. 34 shows the mutual position and orientation of three identical rotatable components 10, 20, 30 with a plurality of circular ridges, without vertical offset.
FIG. 35 shows the mutual position and orientation of three rotatable components 10,
-27- BE2019 / 5742 20, 30, with vertical offset (exaggerated for illustrative purposes), or of three different components with built-in offset. The offset can be selected such that the ridges of the different components 10, 20, 30 engage in the same spiral groove on the filament. It is noted that the ridges of the components of FIG. 35 are quite close to each other, but of course it doesn't have to be that way.
FIG. 36 and FIG. 37 show examples of how rotatable components with rings are arranged as in FIG. 34 and FIG. 35 intervene in the filament, forming one or more spirals or helixes on the filament, thereby advancing the filament.
FIG. 38 (a) and FIG. 38 (b) show an exemplary filament driving system based on the arrangement of FIG. 34, in perspective and sectional view. This assembly or filament driving system can be made more compact than that according to the first embodiment, because the gears can be omitted.
FIG. 39 shows the filament driving system of FIG. 38 (a) with synchronous drive.
FIG. 40 to FIG. 42 show a variant of the filament driving system of FIG. 39, with two assemblies according to the fourth embodiment, driven in the opposite direction.
The upper assembly drive wheel is driven clockwise relative to the rest of the assembly, while the lower assembly drive wheel is driven counterclockwise against the rest of the assembly, or vice versa. An advantage of this drive system is that the torque applied to the segment by the top assembly is largely offset by the torque applied by the bottom assembly.
FIG. 40 shows the filament drive system in perspective view.
FIG. 41 shows a cross section of the filament driving system of FIG. 40.
FIG. 42 is a front view of the filament drive system of FIG. 40. It clearly shows that the axes of the rotatable components are inclined in a different direction. The two assemblies are synchronized by drive from the same motor. Depending on a shift between the first and second assemblies, it can be chosen whether the lower assembly follows the same tracks as the upper assembly or not.
In the figures shown, the filament is fed from a filament roll according to a curved curve. Optionally, two pinch rollers (not shown) can also be added to the system to further limit torque.
FIG. 43 shows a test view of a filament feed system according to an embodiment of the present invention, in perspective view. The filament feeding system of FIG. 43 includes a base plate 64 to which is attached an assembly 67, which is driven by a stepper motor 62 by means of a synchronous drive belt
-28- BE2019 / 5742
63.
A filament of a thermoplastic plastic material (eg ABS) is fed from a filament roll (not shown), preferably via a curved curve (not shown) to a pinch roller assembly or pinch roller assembly 66. The system further includes a heating element 68 (English: "liquefier") to melt the filament, with a temperature sensor and a nozzle. While not strictly necessary for operation, the filament feed system also has an optional encoder 61 (e.g., an optical encoder) to measure the filament feed speed. This was used to measure the graph shown in FIG. 47. Furthermore, the system of FIG. 43 two optional connections 65 for water cooling. The filament feed system can be movably arranged in known ways (see, e.g., FIG. 3) in a three-dimensional space, e.g. to form a 3D printer. In this way, a 3D object can be printed layer by layer, under the control of an external computer.
FIG. 44 to FIG. 46 shows a top view of some exemplary pressure rollers or pinch rollers as may be used in embodiments of the present invention.
The pinch rollers of FIG. 44 and FIG. 45 are configured to make at least one upright groove in the filament, and because of the engagement in this groove, the pinch rollers can prevent the torque from extending beyond (e.g. above) the pinch rollers.
The pinch rollers of FIG. 46 have a V shape configured to clamp the filament between four surface segments.
FIG. 47 shows a graph showing the ratio of the amount of filament material delivered in function of the requested (or set) amount of material, based on data measured with the experimental set-up of FIG. 43, using a filament feed mechanism according to the first embodiment.
Perhaps one of the main advantages of the present invention is that the feed system remains linear (or the ratio of the delivered amount of material to the requested amount of material remains constant) regardless of the throughput speed, up to a certain value (in the example approximately equal to 13 mm / S This maximum throughput may differ when using a different type of material, and / or a different filament thickness, and / or when choosing a different nozzle of the heating element, but the fact is that the measured throughput shows almost 100% linearity to a certain value.
The same test set-up with the same heating element and the same nozzle and the same filament but with a feed system with pressure rollers (English: pinch feeder system) showed the behavior according to the dotted curve.
It will be clear that a higher speed, but above all a higher quality can be achieved by using a filament feeding system according to the
BE2019 / 5742 present invention. As far as known to the inventors, the majority of 3D printers use a pressure roller system, perhaps even more than 90%. The importance of the present invention should therefore not be underestimated.
FINALLY, In all of the above-mentioned embodiments, the rotatable components may be, for example, made of brass, steel, hardened steel, Aluminum alloys, Titanium, or Titanium alloys. Optionally, a coating can be applied to increase the service life, eg a hard coating that offers good resistance to wear.
REFERENCES 100, 300 Extrusion-based Production System 3200, 3400 Setup 900, 2200, 3800 Assembly 1000, 1200, 2500, 3900, 4000 Filament Feed System 3400 Test Setup 101 Filament Spool 102 Filament 103 Extruder 104 Heating Unit (English: "Liquefier") 105 Nozzle ( English: "nozzle") 106 substrate 312 build chamber 314 substrate 316 portal 318 extrusion head 320 filament feed source 322 drive mechanism 324 filament 330 rotatable component 332 internal thread surface 334 electric motor 334 2 filament 3 inlet 4 outlet 5 channel 6 groove (in filament) 7 bent segment ( of the filament) 10 first component
-30- BE2019 / 5742 11 first external thread 12 first shaft 13 first gear d1 distance from first shaft to channel 20 second component 21 second external thread 22 second shaft 23 second gear d2 distance from second shaft to channel 30 third component 31 third external thread 32 third shaft 33 third gear d3 distance from third shaft to channel 41 (first part of) carrier (English: "carrier") 42 ring gear (also called "gear ring"), (English: "ring gear") 43 bearings or bushings or sleeves 44 planet gear or planet gears 45 planet bearings or bushings or sleeves 46 (second part of) carrier 47 planet carrier a, B plane 48 central gear 49 central opening or central passage 50 fourth component 51 recesses in the holder 52 toothed belt 53 motor (eg stepper motor) 54 motor shaft 55 pinch rollers 56 bearing (s) 57 housing 58 timing belt pulley 61 encoder (to measure speed) 62 stepper motor 63 synchronous drive belt 64 base plate, housing 65 water cooling connection g 66 pinch roller assembly (or: pinch roller assembly)
-31- BE2019 / 5742 67 filament feed mechanism 68 heating element (with temperature sensor and nozzle) 1300 planetary gear drive

权利要求:
Claims (23)
[1]
An extrusion-based production system comprising: - a filament roll with a thermoplastic filament (2) to be extruded; and - at least one assembly (900; 2200; 3200; 3800) for feeding the thermoplastic filament (2), the at least one assembly comprising: - an inlet (3) for receiving the thermoplastic filament (2) ; - an outlet (4) for delivering the filament (2), the inlet and the outlet defining a channel (5) within which the filament (2) will move; - at least two rotatable components (10, 20) comprising a first rotatable component (10) and a second rotatable component (20); - wherein the channel (5) is at least partly located between the first component (10) and the second component (20); - wherein the first rotatable component (10) is rotatable about a first axis (12) and has first external ridges (11), said first axis (12) being located at a first distance (d1) from the channel such that the first external ridges (11) penetrate at least partially into the channel (5); - wherein the second rotatable component (20) is rotatable about a second axis (22) different from the first axis (12) and has second external ridges (21), said second axis (22) at a second distance (d2) from the channel is located such that the second external ridges (21) at least partially penetrate into the channel (5); - wherein the first and second rotatable component (10, 20) are mounted such that when the thermoplastic filament is inserted into the channel and when the assembly is rotated relative to the filament (2), the first rotatable component (10) rotates about the first axis (12), and the second rotatable component (20) rotates about the second axis (22), and the first and the second axis move around the filament in such a way that the first and the second rotatable component ( 10, 20) substantially roll over a surface of the thermoplastic filament, and that the first and second external ridges penetrate about 0.05 mm to about 0.25 mm into the thermoplastic filament.
[2]
An extrusion-based production system according to claim 1, wherein each of the at least two rotatable components is in contact with the thermoplastic filament by means of at least three different back segments that are axially offset from each other.
[3]
An extrusion-based production system according to any one of the preceding claims, wherein the at least one assembly (900) further comprises a ring gear (42); and wherein each of the at least two rotatable components (10, 20, 30) further includes one
33. BE2019 / 5742 sprocket (13, 23, 33) which engages the ring gear (42) to synchronize at least the first component (10) and the second component (20) about their respective axis (12, 22). run.
[4]
An extrusion-based production system according to any one of the preceding claims, wherein the at least one assembly (2200) further comprises a central gear (48) with a central opening (49) for passing the filament (2); and wherein each of the at least two rotatable components (10, 20) includes a gear (13, 23) that engages the central gear (48) to synchronize the first component (10) and the second component (20) about their turn the respective shaft (12, 22).
[5]
An extrusion-based production system according to any one of the preceding claims, wherein the at least one assembly (3200) further comprises a third and a fourth component (30, 50) positioned such that the channel (5) is at least partially located in the space between the first (10) and the second (20) and the third (30) and the fourth component (40), and wherein the third component (30) and the fourth component (50) each have a surface that the channel ( 5) touches or nearly touches.
[6]
An extrusion-based production system according to any one of the preceding claims, wherein the first axis (12) of the at least one assembly (900; 2200; 3200) is substantially parallel to the channel (5); and - wherein the second axis (22) is substantially parallel to the channel (5); and - wherein the first ridges (11) form a first external screw thread; and - wherein the second ridges (21) form a second external screw thread; - and in which the movements of the at least two rotatable components (10, 20) are synchronized by means of gears (42, 13, 23).
[7]
An extrusion-based production system according to claim 6, wherein the at least one assembly (900; 2200) further comprises a third rotatable component (30) with a third external thread (31), the third rotatable component (30) being rotatable about a third axis (32) different from the first and the second axis (12, 22), said third axis (32) being substantially parallel to the channel (5) and located at such a distance (d3) from the channel that the third external screw thread (31) at least partially penetrates into the channel (5), and wherein the channel (5) is at least partly located between the first component (10) and the second component (20) and the third component (30) ; - and wherein the third rotatable component (30) is mounted such that when a filament is introduced into the channel and when the assembly is rotated at
BE2019 / 5742 relative to the filament (2), the third rotatable component (30) substantially rolls over a surface of the filament.
[8]
An extrusion-based production system according to any one of claims 1 to 5, wherein the first axis (12) of the at least one assembly (3800) is provided to cross the filament (5) at an angle of 1.0 ° to 9.0 °; - wherein the second shaft (22) is arranged to cross the filament (5) at an angle of 1.0 ° to 9.0 °; and - wherein the first ridges (11) form a plurality of first rings; and wherein the second ridges (21) form a plurality of second rings.
[9]
An extrusion-based production system according to claim 8, wherein the at least one assembly (3800) further comprises a third rotatable component (30) rotatable about a third axis (32) different from the first and the second axis (12, 22); - and wherein the third axis (32) is provided to cross the filament (5) at an angle of 1.0 ° to 9.0 °.
[10]
An extrusion-based production system according to claim 9, wherein the first, second and third rotatable components (10, 20, 30) are formed and positioned such that the at least one groove formed by the first, second and third ridges is a single helix shapes, or two individual helixes, or three individual helixes.
[11]
An extrusion-based production system according to any one of claims 8 to 10, wherein the plurality of rings on each rotatable component are equidistant.
[12]
An extrusion-based production system according to any one of claims 8 to 11, wherein the plurality of rings all have the same external diameter; or wherein at least one of the plurality of rings has a first external diameter and wherein at least one other of the plurality of rings has a second external diameter, different from the first external diameter.
[13]
An extrusion-based production system, according to any one of the preceding claims, further comprising: at least one rotation-limiting unit arranged at the entrance (3) or at the exit (4) of the at least one assembly, in order to limit torsion of the filament .
[14]
An extrusion-based production system, according to any one of the preceding claims, further comprising: at least one pinch roller assembly arranged at the entrance (3) or at the
35. BE2019 / 5742 outlet (4) of the at least one assembly, in order to limit filament torsion.
[15]
An extrusion-based production system according to any one of the preceding claims, wherein the filament roll is arranged such that the filament from the filament roll is introduced into the entrance (3) of the at least one assembly according to a curved curve.
[16]
An extrusion-based production system according to any one of the preceding claims, further comprising: at least one driving mechanism provided to rotate the at least one assembly relative to the filament.
[17]
An extrusion-based production system according to any one of the preceding claims, comprising: - a first assembly provided for moving the filament in a first direction; and a second assembly similar to the first assembly, arranged to also move the filament in the first direction; - and a driving mechanism provided for rotating the rotatable components of the first assembly in a first direction relative to the filament, and rotating the rotatable components of the second assembly in a second direction relative to the filament, opposite to the first direction, in order to reduce or substantially eliminate torsional forces exerted by the first assembly.
[18]
An extrusion-based production system according to any one of claims 15 to 17, wherein the drive mechanism further comprises an electric motor for rotating the at least one assembly relative to the filament (2).
[19]
An extrusion-based production system according to claim 17, wherein the drive mechanism further comprises a drive belt for coupling the at least one assembly to the electric motor.
[20]
An extrusion-based production system according to claim 18 or 19, wherein the electric motor is a hollow shaft motor, the hollow shaft is configured to receive the filament, and the motor is configured to rotate the at least one assembly relative to the filament (2).
[21]
An extrusion-based production system according to any one of claims 16 to 20, further comprising a control unit communicatively connectable to an external computer and provided to receive information for controlling the at least one drive mechanism.
-36- BE2019 / 5742
[22]
An extrusion-based production system according to any one of the preceding claims, further comprising a heating element provided to melt the passed thermoplastic filament.
[23]
A method of passing a thermoplastic filament (2) into an extrusion-based production system (100, 300, 4000) comprising a filament roll with a thermoplastic filament (2) to be extruded; and at least one assembly comprising the following: - an inlet (3) for receiving the thermoplastic filament (2) to be extruded; - an outlet (4) for delivering the filament (2), the inlet and the outlet defining a channel (5) within which the filament (2) will move; - at least two rotatable components (10, 20) comprising a first rotatable component (10) and a second rotatable component (20); - wherein the channel (5) is at least partly located between the first component (10) and the second component (20); - wherein the first rotatable component (10) is rotatable about a first axis (12) and has first external ridges (11), said first axis (12) being located at a first distance (d1) from the channel such that the first external ridges (11) penetrate at least partially into the channel (5); - wherein the second rotatable component (20) is rotatable about a second axis (22) different from the first axis (12) and has second external ridges (21), said second axis (22) at a second distance (d2) from the channel is located such that the second external ridges (21) at least partially penetrate into the channel (5); and the method comprising the steps of: a) introducing the thermoplastic filament (2) into the channel (5); b) rotating the first rotatable component (10) about the first axis (12), and rotating the second rotatable component (20) about the second axis (22), and moving the first and the second axis about the filament in such a manner that the first and second rotatable components roll substantially over a surface of the filament (2) and that the first and second external ridges penetrate about 0.05 mm to about 0.25 mm into the thermoplastic filament .

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同族专利:

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公开号 | 公开日

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CN113165826A|2021-07-23|

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JP2022515715A|2022-02-22|

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EP3921262A1|2021-12-15|

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US20220024131A1|2022-01-27|

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WO2020109886A1|2020-06-04|

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BE1026877A1|2020-07-13|

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法律状态:
2020-08-26| FG| Patent granted|Effective date: 20200722 |

优先权:

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申请号 | 申请日 | 专利标题

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BE201805836|2018-11-29|

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