• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    Plasticizing unit (1) for an injection molding machine, comprising a plasticizing screw (4) displaceably and rotatably mounted in a cylinder bore of an axially extending plasticizing cylinder, wherein a screw head space (3) is arranged between an injection nozzle of the plasticizing cylinder and a screw tip of the plasticizing screw (4) a plurality of ultrasonic transducers (5) is arranged at different axial positions of a wall (2) of the plasticizing cylinder and an evaluation unit (8) is provided, which is adapted from signals of the ultrasonic transducers (5) to an axial temperature profile in the screw antechamber (3) create.
    公开号:AT516452A1
    申请号:T639/2014
    申请日:2014-08-14
    公开日:2016-05-15
    发明作者:Bernhard Dipl Ing Dr Praher
    申请人:Engel Austria Gmbh；
    IPC主号:
    专利说明:

    The present invention relates to a plasticizing unit for an injection molding machine having the features of the preamble of claim 1 and a method having the features of the preamble of claim 7.
    Applicant's AT 512 647 B1 discloses a method for determining a radial temperature profile in a plasticizing cylinder of a plasticizing unit of the generic type. The method uses the principle of transit time measurement of ultrasound signals.
    Also known are: The use of contact thermometers, which are used in a wall-locking manner with a wall of the plasticizing cylinder. For mounting the contact thermometers, sensor bores are required on the wall of the plasticizing cylinder. The high pressures cause high mechanical stresses for the temperature sensors.
    Accordingly, such sensors are designed to be very stable. This robust sheathing leads to very long response times, which in turn makes dynamic control during the metering difficult or impossible. Another disadvantage of wall-mounted contact thermometers is the fact that only the temperature at the edge of the plastic melt can be measured. - The use of infrared thermometers, which are wall-mounted in a wall of the plasticizing cylinder. For mounting the contact thermometers, sensor bores are required on the plasticizing cylinder. The response times are significantly better than with contact thermometers, but here too, only the melt temperature at the edge (depending on the type of plastic and penetration depth of the infrared radiation, typically 1-8 mm) is measured. Furthermore, errors can occur due to scattering and reflection of the infrared radiation. The emission coefficient of the plastic melt must be determined in a calibration measurement. - Laser-induced fluorescence. For the installation of the optical accesses, sensor bores are required on the plasticizing cylinder. Via a laser beam, fluorescent dyes are added to the plastic. The resulting fluorescence is directed via a confocal array via a light guide into a spectrometer. By means of the laser-induced fluorescence (if the plastic melt is transparent to the laser radiation and the fluorescence radiation), an averaging of the radial temperature measurement can be carried out by adjusting the focus position of the fluorescence spectrometer Laser is varied in the plastic melt. The entire instrumentation (laser, spectrometer, optical access) is very complex and the permanent use in industrial environment to classify as critical.
    When plasticizing, the quality of the plasticized melt may adversely affect the temperature fluctuations in the plasticizing cylinder.
    The object of the invention is to provide a plasticizing unit of an injection molding machine, in which the quality of the plasticized melt influencing temperature fluctuations can be detected, and to provide a corresponding method.
    This object is achieved by a plasticizing unit having the features of claim 1 and a method having the features of claim 7.
    Advantageous embodiments are defined in the dependent claims.
    The undesirable fluctuations in the product quality of injection-molded plastic parts are mainly attributable to unfavorable axial temperature profiles (temperature gradients) of the plasticized melt, since these are generally much higher than the radial temperature profiles. The axial temperature profiles are caused by the shortening of the effective screw length during the metering of the plastic melt into the screw antechamber. To enable active control or regulation of the melt temperature during
    Metering (eg by means of back pressure and / or speed of the screw) requires the measurement of the axial melt temperature. The invention enables this in a simple manner.
    Advantages of the Invention: - No holes are required through the wall of the plasticizing cylinder for the ultrasonic transducers. - The temperature of the plastic melt is averaged over the entire diameter of the cylinder bore (not just at the edge). The invention enables very fast response times. - No calibration is necessary per se: The measurement of the speed of sound at various positions is sufficient to detect axial temperature differences. This is due to the almost constant pressure in the antechamber during the metering back.
    The invention will be discussed in detail for various embodiments with reference to Figures 1 to 3.
    A plasticizing unit 1 for an injection molding machine in the form of a rotatable plasticizing screw 4 displaceably mounted in a cylinder bore of a plasticizing cylinder (with wall 2) is shown by the metering of plasticized plastic in the area between the injection nozzle (not shown) and the top of the plasticizing screw 4 (FIG. Auger 3) the plasticizing screw 4 is moved away from the injection nozzle. In the process, a so-called mass cushion forms in the antechamber 3.
    If an ultrasound pulse is transmitted through a plastic melt along a sound path S (between an ultrasound transmitter and an ultrasound receiver), the transit time t running time of the pulse through the melt results from the formula
    where cl, s (P, O) denotes the longitudinal speed of sound, independent of the pressure p and the temperature, at a position s along the sound path S.
    Is the longitudinal speed of sound Cl as a function of the pressure p and the temperature Tbekannt (by calibration measurements or preferably by looking in the skilled worker known tables which indicate the duration of sound for various plastics - this is possible because in the screw antechamber when dosing at least approximately a constant Pressure prevails) can be concluded from the transit time measurement on the average temperature along the sound path S.
    To measure the axial temperature distribution in the screw antechamber 3 ultrasonic transit time measurements are carried out at several axial positions. The measurements can be carried out by means of so-called reflection or transmission measurements.
    The reflection measurement is shown in FIG. An axial measurement of the melt temperature in the screw antechamber 3 takes place.
    An ultrasonic transducer array with a plurality of ultrasonic transducers 5 is attached to the wall 2 of the plasticizing cylinder along the screw antechamber 3. Alternatively, it is also possible with an ultrasonic transducer 5 to be measured alternately at different axial positions over a plurality of injection molding cycles.
    An ultrasonic pulse sent into the plasticizing cylinder is reflected at the upper edge of the cylinder bore. Part of the sound energy continues to pass through the plasticized plastic melt, is reflected at the lower edge of the cylinder bore and runs back to the ultrasonic transducer. From the difference of the transit times of the reflections at the upper or lower edge (Wn or Wen) of the cylinder bore and the known diameter of the cylinder bore dzyiinder can on the speed of sound (at the back pressure pstau during the dosing) and thus on the average melt temperature Tm along of the sound flow path are closed:
    The measurement at different axial positions results in an axial temperature profile in the screw antechamber 3. The calculation takes place in an evaluation unit 8 shown in FIG.
    In the transmission measurement, shown in Figure 2, two opposite ultrasonic transducer arrays 6, 7 are mounted with ultrasonic transducers 5 at different axial positions along the Schneckenvorraums 3 on the wall 2 of the plasticizing, one ultrasonic transducer array as the transmitter array 6 and the opposite ultrasonic transducer array as a receiver array 7 is used. Alternatively, even with two ultrasonic transducers 5 (transmitter and receiver) can be measured alternately at different axial positions over several injection molding cycles.
    A transmitted from an ultrasonic transducer 5 of the transmitter array 6 in the plasticizing cylinder passes through the first half of the wall 2 of the plasticizing, further through the plastic melt and then through the second half of the wall 2 of the plasticizing to the opposite ultrasonic transducer 5 of the receiver array 7. From the so measured total life tgesamt of the ultrasonic pulse nor the maturities ts, te have to be deducted by the wall 2 of the plasticizing. These can be determined by reflection measurements by means of the ultrasonic transducers 5 in the transmitter or receiver array 6, 7. The speed of sound cL results
    The measurement at different axial positions results in an axial temperature profile in the screw antechamber 3. The calculation takes place in an evaluation unit 8 shown in FIG.
    The measurement of te is relatively expensive. Assuming that a nearly rotationally symmetric temperature profile prevails in the wall 2, te is approximately equal to ts. This can be dispensed with the measurement of te.
    The invention can be used to the
    Add up to produce a favorable for the injection molding temperature distribution.
    FIG. 3 shows an arrangement for controlling or regulating the melt temperature in the screw antechamber 3 during the metering (for example, for reflection measurements, and also transmission measurements could be used).
    When dosing, the measurement is started. As soon as the plasticizing screw 4 retracts and the sound running path is thus free at one position, a sound velocity measurement can take place at the respective position. An advantage of the arrangement is the fact that the pressure (back pressure) in the screw antechamber 3 is known and approximately constant and it is not necessary to calculate the pressure and temperature-dependent melt temperature directly from the measured sound velocities.
    Only the change of the speed of sound at different axial positions is sufficient to determine axial temperature differences (axial temperature gradient). The conversion of the ultrasonic transit times into sound velocities or temperatures takes place in an evaluation unit 8. The calculated sound velocities or temperature values are used by a control or regulating unit 9 for machine parameters (eg back pressure, preferably the screw speed) via a motor M driving the plasticizing screw be influenced so that a drop in temperature in the antechamber 3 due to a shortened screw length of the plasticizing screw 4 can be compensated.
    This influencing preferably takes place from cycle to cycle, that is to say not necessarily during a cycle of the plasticizing unit 1 or of the injection molding machine, of which the plasticizing unit 1 is a part.
    The evaluation unit 8 and the control unit 9 can be physically designed together in one component.
    In all embodiments, the ultrasonic transducers 5 are applied to the wall 2 of the plasticizing, so are not in holes in the wall 2, which break through the wall 2. It would be conceivable to arrange the ultrasonic transducer 5 sunk in blind holes in the wall 2, z. B. in space problems with mounted on the plasticizing heating bands.
    Advantageously, the ultrasonic transducers 5 are pressed against the wall 2 of the plasticizing cylinder, for example via magnetic holding means. The attachment of an ultrasonic gel between the ultrasonic transducers 5 and the wall 2 is advisable. If passive cooling of the ultrasonic transducers 5 by the ambient air is insufficient, active cooling can also be provided.
    权利要求:
    Claims (9)
    [1]
    1. plasticizing unit (1) for an injection molding machine, having a plasticizing screw (4) displaceably and rotatably mounted in a cylinder bore of an axially extending plasticizing cylinder, wherein a screw head space (3) is arranged between an injection nozzle of the plasticizing cylinder and a screw tip of the plasticizing screw (4) is arranged, characterized in that a plurality of ultrasonic transducers (5) is arranged at different axial positions of a wall (2) of the plasticizing and an evaluation unit (8) is provided which is adapted from signals of the ultrasonic transducer (5) has an axial Temperature profile in the antechamber (3) to create.
    [2]
    2. plasticizing unit according to claim 1, wherein a single ultrasonic transducer array along the Schneckenvorraums (3) arranged ultrasonic transducers (5) on one side of the wall (2) is provided, wherein the ultrasonic transducer array is formed as a transmitting and receiving array.
    [3]
    3. Plasticizing unit according to claim 1, wherein two ultrasonic transducer arrays lying opposite one another, with ultrasound transducers (5) arranged along the screw prechamber (3), are mounted on the wall 2 of the plasticizing cylinder, an ultrasound transducer array being the transmitter array (6) and the opposing ultrasound transducer array being the receiver array (5). 7) is formed.
    [4]
    4. plasticizing unit according to at least one of claims 1 to 3, wherein the ultrasonic transducer (5) - preferably by magnetic holding means - are pressed against the wall (2) of the plasticizing.
    [5]
    5. plasticizing unit according to at least one of claims 1 to 4, wherein between the ultrasonic transducers (5) and the wall (2) an ultrasound gel is arranged.
    [6]
    6. plasticizing unit according to at least one of claims 1 to 5, wherein a control or regulating unit (9) is provided which communicates with the evaluation unit (8) and which is adapted to machine parameters of the plasticizing screw - preferably the screw speed - via a to influence the plasticizing screw driving motor (M) so that a temperature drop in the screw antechamber (3) due to a shortened screw length of the plasticizing screw (4) can be compensated.
    [7]
    7. A method for creating a temperature profile in the screw antechamber (3) of a plasticizing unit (1) of an injection molding machine using at least one ultrasonic transducer (5), wherein the plasticizing unit (1) has a plasticizing cylinder with a wall (2), characterized in that off different axial positions of the wall (2) of the plasticizing cylinder by means of at least one ultrasonic transducer (5) obtained signals an axial temperature profile is created.
    [8]
    8. The method of claim 7, wherein the signals are obtained at the different axial positions by repositioning the at least one ultrasonic transducer (5).
    [9]
    9. The method of claim 7, wherein the signals at the different axial positions by a plurality of ultrasonic transducers (5) are obtained.
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    同族专利:
    公开号 | 公开日
    CN105365182A|2016-03-02|
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    DE102015010589A1|2016-02-18|
    AT516452B1|2016-08-15|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    US4740146A|1986-07-25|1988-04-26|Peter Angelbeck|Apparatus for measuring and controlling the wall thickness of plastic pipes|
    JPH08276490A|1995-04-07|1996-10-22|Mitsui Toatsu Chem Inc|Measurement of melting position of resin in cylinder of extrusion molding machine and operation of the extrusion molding machine|
    US5951163A|1996-10-16|1999-09-14|National Research Council Of Canada|Ultrasonic sensors for on-line monitoring of castings and molding processes at elevated temperatures|
    DE102013013902A1|2012-09-12|2014-03-13|Engel Austria Gmbh|Method for determining temperature of melt in melt chamber of injection molding machine, involves calculating temperature curve in melt chamber as function of average temperature in propagation paths and minimum distances of paths|
    DE19944709A1|1998-09-24|2000-04-27|Barmag Barmer Maschf|Polymer melt guiding arrangement for production of fibers, films or small strips uses ultrasonic sensors for controlling process parameters|
    SG91321A1|2000-03-27|2002-09-17|Sumitomo Heavy Industries|Method for controlling an injection molding machine capable of reducing variations in weight of molded products|
    DE102009004946B4|2008-10-22|2015-04-09|Sikora Aktiengesellschaft|Method and device for measuring the temperature of a plasticized plastic at the exit of an extruder|AT520465B1|2017-09-25|2019-10-15|Engel Austria Gmbh|Shaping machine with a plasticizing unit|
    FR3073775B1|2017-11-23|2020-12-25|Arianegroup Sas|EXTRUSION PLANT EQUIPPED WITH A CONTROL SYSTEM SUITABLE TO DETECT ANY ANOMALY|
    法律状态:
    优先权:
    申请号 | 申请日 | 专利标题
    ATA639/2014A|AT516452B1|2014-08-14|2014-08-14|Plasticizing unit for an injection molding machine|ATA639/2014A| AT516452B1|2014-08-14|2014-08-14|Plasticizing unit for an injection molding machine|
    DE102015010589.2A| DE102015010589A1|2014-08-14|2015-08-10|Plasticizing unit for an injection molding machine|
    US14/825,599| US20160046055A1|2014-08-14|2015-08-13|Plasticizing unit for an injection molding machine|
    CN201510498392.3A| CN105365182A|2014-08-14|2015-08-14|Plasticizing unit for an injection molding machine|
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