JP3597355B2 - Method for stabilizing actual weighing completion position of injection molding machine and weighing control device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to metering control of an injection molding machine, in particular, after the injection of the injection molding machine, the raw material resin is transferred from the hopper to the front of the heating cylinder by the rotation of the screw, kneaded, and a certain amount is measured in the next cycle. TECHNICAL FIELD The present invention relates to a method for stabilizing an actual weighing completion position for optimizing a weighing process in preparation for injection of a weighing device and a weighing control device.
[0002]
[Prior art]
An important requirement for determining the quality of a molded article in injection molding is stabilization of the weight of the molded article. Such stabilization of the weight requires that the raw material resin injected by the injection molding machine is always a constant amount, and accurate weighing is required as a prerequisite thereof.
In a conventional injection molding machine, the raw resin in the hopper is fed into a heating cylinder, where it is retained at the tip of the screw while being melted. At this time, the front end face of the annular check ring attached to the outer periphery of the tip of the screw is pushed by the molten resin flow and is in contact with the tip end side of the screw. Flow into the retaining chamber at the tip of the screw.
[0003]
Then, in the injection step, when the tip of the screw advances, the check ring does not advance, and the check ring abuts against the check sheet constituting the leading edge of the screw, thereby preventing the backflow of the molten resin. Have been.
[0004]
However, in this type of injection molding machine, there is a phenomenon that the screw gradually retreats even if the rotation of the screw is stopped after the measurement process is completed. This phenomenon is caused by the fact that when the molten resin plasticized and kneaded by the rotation of the screw is sent to the retaining chamber on the front side of the screw, even if the rotation of the screw is stopped, the molten resin The pressure P1 of the resin is slightly higher (P1> P2) than the pressure P2 of the resin sent into the retaining chamber. Therefore, even if the measuring process is completed and the rotation of the screw is stopped, the molten resin is fed into the retaining chamber, and when the screw is slightly retracted and P1 = P2, the screw is completely stopped from retreating.
[0005]
Further, in such a screw retreat phenomenon, since the state of P1> P2 is satisfied as described above, the molten resin pressure P2 in the retaining chamber further rises, and the outflow to the outside of the machine through the nozzle passage is stopped. Not be able toThis causes drooling, a phenomenon of resin leakage from the tip of the nozzle., Which may cause defective molded products.That is, the drooling is caused by the molten resin pressure P2 on the side of the retaining chamber in the heating barrel and the resin pressure of the molten resin retained in the screw portion such as the valley when the rotation of the screw is stopped due to the completion of the measuring step. It occurs due to the difference in resin pressure from P1.
[0006]
In order to solve such a problem in the conventional injection molding machine, a screw is rotatably and advancing and retracting in a heating cylinder, and a position detecting means for detecting a retreating position due to stagnation of molten resin in the screw is provided. In the weighing stroke from the stagnation start time to the stagnation completion time of the molten resin, when entering the weighing control stroke section immediately before the stagnation completion, at least the condition of the nozzle portion and the stagnation chamber predetermined by the molding material are set. A pattern selecting means for selecting a back pressure lowering pattern; and a means for lowering the back pressure of the staying chamber based on a signal from the pattern selecting means when the position detecting means detects that the metering control stroke section has been entered. A metering control device for an injection molding machine has been proposed (Japanese Patent Publication No. 4-78090).
[0007]
The metering control device of the injection molding machine according to this proposal reduces at least the back pressure of the staying chamber in a fixed pattern when the metering control stroke immediately before the completion of the stay is entered in the entire metering stroke. The rotation speed is also reduced.
[0008]
In this case, how to reduce the back pressure in the final metering control stroke section is determined by cooling the resin in the nozzle hole. That is, depending on the type of the resin, the nozzle setting temperature, the size and the shape of the nozzle hole (straight or inverted taper), the fluidity of the resin in the nozzle hole portion is reduced, and the effect of preventing the resin leakage (drooling) occurs. Since this is different, this is configured so that the operator can select one pattern from various patterns set in advance and manually determine it.
[0009]
Further, the rotation speed of the screw is determined by the amount of oil supplied from a hydraulic source that rotates the hydraulic motor at the time of metering, but is set so as to be a constant low rotation speed at the time of entering the final metering control stroke section. You.
[0010]
On the other hand, in contrast to the method of lowering the back pressure, as a measurement control method of an injection molding machine capable of performing the measurement of the molten resin with high accuracy, the back pressure or the position of the screw near the end of the step of plasticizing the resin is used. A change is detected in advance, a reference screw back pressure or a reference screw position near the end of the plasticizing process is determined and set in the control device, and the screw is retracted according to the reference screw back pressure or the reference screw position. Detects the screw back pressure near the end of the plasticization process of the resin by open loop control, and based on the detected screw back pressure, the reference screw back pressure without irregular fluctuations that approximates the screw back pressure during open loop control And the screw back pressure is controlled to be equal to this reference screw back pressure. To improve degrees, measurement control method of an injection molding machine to be able to perform precision molding has been proposed (Japanese Patent Laid-Open No. 5-92461).
[0011]
[Problems to be solved by the invention]
However, in the above-described metering control in the conventional injection molding machine, in the former in which the back pressure is reduced in the final metering control stroke section, one pattern is selected from various patterns preset by the operator. However, since it is determined manually, the control operation becomes complicated, and the screw stop position is affected by variations in the resin pressure and back pressure in the heating cylinder, screw rotation speed, and screw retreat speed at the completion of weighing. However, there is a difficulty that it is difficult to stabilize.
[0012]
In the latter metering control method (suck-back method) in which the screw is retracted near the end of the plasticizing step, when the screw is retracted, the supply of pressurized oil to the injection cylinder is switched. Screw stop position is difficult to stabilize.
[0013]
Therefore, as a result of intensive studies, the inventor of the present invention has determined that the screw in the heating cylinder is retracted, and the measurement of the screw is started at the time of the measurement control of the injection molding machine for plasticizing and measuring the raw material resin to be filled in the mold. The position and the weighing completion position are respectively set, the screw rotation speed and the screw back pressure are respectively set in accordance with the set screw positions, and the connection and arrangement are made to the injection cylinder for controlling the movement of the screw. Holding the directional switching valve provided in the hydraulic circuit at the neutral position, plasticizing and weighing the raw resin by rotating the screw and retreating while rotating, stopping the rotation of the screw at the weighing completion setting position Complete weighing,Here, once the screw back pressure is set to zero or lower than the set back pressure at the time of measurement, the screw is further retracted by the resin pressure.Retreat this screwdidBy blocking the screw back pressure in the hydraulic circuit at the position or controlling the screw back pressure to increase, the variation of the actual weighing completion position can be significantly reduced. It has been found that the variation in weight can be significantly reduced.
[0014]
Accordingly, an object of the present invention is to improve the accuracy of the actual weighing completion position, achieve the stabilization of the weight of the molded product, and prevent air from entering the molten resin and resin leakage at the tip of the nozzle portion. It is an object of the present invention to provide a method for stabilizing an actual measurement completion position of an injection molding machine and a measurement control device, which can eliminate the problem and always optimize the measurement process.
[0015]
[Means for Solving the Problems]
In order to achieve the above object, a method for stabilizing an actual metering completion position of an injection molding machine according to the present invention comprises the steps ofAnd screw injection means for controlling the axial movement of the screw, and rotating the screw while rotating the screw.Raw resin to be filled into the moldIn the screw part in the heating barrelPlasticizationMeltingIGuiding a predetermined amount of molten resin from the screw portion to a retaining chamber formed at the tip of the heating barrel with rotation of the screw.In the metering control method for an injection molding machine for metering byAxialWeighing start positionFor stopping the rotation of the drive motor.Weighing complete positionAnd a position further retracted by a predetermined amount than the weighing completion position for stopping the retreat of the screwSet eachA position setting detecting means for detecting that the screw has reached the set position, and a hydraulic circuit for controlling the supply of pressure oil to the injection cylinder via a direction switching valve are connected and arranged. A back pressure block switching valve for shutting off a line from the injection cylinder to the tank when a part of the return line through which the pressurized oil is discharged from the injection cylinder to the tank during the metering process is activated. A back pressure control proportional valve for controlling a back pressure generated in the return line when the back pressure block switching valve is not operated is provided downstream of the back pressure block switching valve. The oil passage is branched and connected, and the screw is provided in the hydraulic circuit until the screw reaches a position further retracted by a predetermined amount from the set measurement start position than the measurement completion position.Holds directional valve in neutral positionBy limiting the return line from which the pressure oil is discharged from the injection cylinder to the tank to the branch-connected oil passage, it is possible to control the screw back pressure, and from the set measurement start position. The screw is rotated, and when the screw retreats and reaches the weighing completion position, the rotation driving means is rotated.Stop drivingStopping the screw rotation and operating the back pressure control proportional valve to reduce the screw back pressure generated in the return line to zero or lower than the back pressure at the time of measurement, and further to the molten resin retained in the retention chamber The screw is set to be lower than the pressure, and in a state where the back pressure is generated, the screw is retained by the pressure of the molten resin retained in the retaining chamber until the screw reaches a position further retracted by a predetermined amount than the measurement completion position. When the screw reaches a position further retracted by a predetermined amount than the metering completion position, the back pressure block switching valve is actuated.Block back pressure orBy operating the back pressure control proportional valve without operating the back pressure block switching valve,To increase the screw back pressureProvide a commanding controller to stop the screw from retreatingThatCompositionalFeatures.
[0016]
Further, in the present invention, the metering control device for performing the method of stabilizing the actual metering completion position of the injection molding machine controls the rotation of the screw in the heating barrel.Screw rotation drive means to giveTogether withAxial direction of the screwCombine the injection cylinder that controls the movement, andWhile rotatingRaw resin to be filled into the moldPlasticizing and melting at the screw portion in the heating barrel, and guiding a predetermined amount of molten resin from the screw portion to a retaining chamber formed at the tip of the heating barrel with rotation of the screw.In a measuring control device of an injection molding machine for measuring, the screwAxialWeighing start positionFor stopping the rotation of the drive motor.Weighing complete positionAnd a position further retracted by a predetermined amount than the weighing completion position for stopping the retreat of the screw.Set eachPosition setting detecting means for detecting that the screw has reached the set position,A hydraulic circuit for controlling supply of pressurized oil is connected to the injection cylinder via a directional switching valve, and the hydraulic circuit is connected to the injection cylinder during the screw weighing process.At the return line where the pressurized oil is discharged from the injection cylinder to the tank.In part,A back that shuts off the line from the injection cylinder to the tank when activated.Switching valve for pressure blockA back pressure for controlling a back pressure generated in the return line when the back pressure block switching valve is not operated.Proportional valve for pressure controlOn the downstream side of the back pressure block switching valve.The oil path provided is branched and connected, and the screwFrom the set weighing start position to the position further retracted by a predetermined amount than the weighing completion position,Provided in the hydraulic circuitSaidHolds directional valve in neutral positionBy limiting the return line from which the pressurized oil is discharged from the injection cylinder to the tank to the branch-connected oil passage, it is possible to control the screw back pressure,SaidThe screw is rotated from the set weighing start position, the screw moves backward, and when the screw reaches the weighing complete position, the rotation driving means is turned off.Stop drivingStopping the screw rotation and operating the back pressure control proportional valve to reduce the screw back pressure generated in the return line to zero or lower than the back pressure at the time of measurement, and further to the molten resin retained in the retention chamber The screw is set to be lower than the pressure, and in a state where the back pressure is generated, the screw is retained by the pressure of the molten resin retained in the retaining chamber until the screw reaches a position further retracted by a predetermined amount than the measurement completion position. When the screw reaches a position further retracted by a predetermined amount than the metering completion position, the back pressure is blocked by operating the back pressure block switching valve, or the back pressure block switching valve is operated. Without actuationOperate the pressure control proportional valveScrewTo increase the back pressureOrderControllerTo stop the retraction of the screwThatCompositionalFeatures.
In this case, the second control valve includes a back pressure block switching valve and a back pressure control proportional valve, and operates the back pressure block switching valve at a position where the screw is retracted by the predetermined amount. The communication between the oil chamber of the injection cylinder and the back pressure control proportional valve may be interrupted.
[0017]
【Example】
Next, an embodiment of a method for stabilizing the actual weighing completion position of an injection molding machine according to the present invention will be described in detail below with reference to the accompanying drawings in relation to a weighing control device that performs this method.
[0018]
FIG. 1 shows a schematic configuration of a control device of an injection molding machine for implementing a method of stabilizing an actual measurement completion position according to the present invention. In FIG. 1, reference numeral 10 denotes a heating barrel. An injection screw 12 for measuring and injecting the molten resin is inserted through the heating barrel 10.
[0019]
The nozzle portion 10 a of the heating barrel 10 on the tip end side of the screw 12 is arranged to face the nozzle touch portion 14 a communicating with the cavity 16 of the mold 14. The other end of the screw 12 is provided with a piston portion 12a and inserted into the injection cylinder 18, and a screw rotation hydraulic motor 20 is further coupled to an extension shaft portion 12b of the screw 12. .
[0020]
Further, a screw position detector 22 for detecting the movement position of the screw 12 is provided.
[0021]
On the other hand, the injection cylinder 18 is provided with a hydraulic circuit 30 which supplies pressure oil for performing an injection operation via a direction switching valve 24 and is connected to a hydraulic source 26 and a tank 28, respectively. I have. A part of the hydraulic circuit 30 (the B port side of the injection cylinder 18 to which the pressure oil is supplied at the time of the injection operation) is connected via a back pressure block switching valve 32 and a back pressure control proportional valve 34, respectively. , A branch oil passage 35 connected to the tank 28 is provided.
[0022]
Then, the position detection signal detected by the screw position detector 22 is compared with the position set value set in the position setter 36 by the comparator 38 to determine whether back pressure block or back pressure control is performed. . When the back pressure block is performed, the controller 42 is energized by the signal switch 40 to operate the back pressure block switching valve 32. When the back pressure control is performed, the controller 44 is energized by the signal switch 40 to operate the back pressure control proportional valve 34.
[0023]
Next, the metering control according to the present invention by the control device of the injection molding machine having the above-described configuration will be described with reference to the operating characteristics shown in FIGS.
[0024]
First, as shown in FIG. 2A, a screw from a weighing start position to a weighing completion position in a weighing process is supplied to a controller (not shown) of a screw rotation hydraulic motor 18 that drives the screw 12 to rotate. The rotation speed is set. As shown in FIG. 2C, the screw back pressure from the weighing start position in the weighing process to the weighing completion position and the retreat position after weighing completion is set for the back pressure control proportional valve 34 as well. You. The set value of the screw rotational speed and the set value of the screw back pressure differ depending on the mold, the molded product, and the resin used. Further, the screw back pressure at the screw back pressure set value up to the retreat position after the completion of the metering can be set to zero.
[0025]
Therefore, assuming that the injection is completed and the screw 12 is at the forward limit, the metering control is immediately started. That is, with the start of the measuring process, the direction control valve 24 is held at the illustrated neutral position, and the screw 12 retreats as the plasticizing process of the resin raw material supplied from the hopper proceeds as appropriate. In this case, the retracted position of the screw 12 is detected by the screw position detector 22, and based on the detected screw position signal, the screw rotation speed and the screw back pressure are respectively controlled to the set values. Then, when the screw 12 reaches the metering completion set position, the rotation of the screw is stopped.
[0026]
The actual screw rotation speed and the actual screw back pressure BP actually measured in such a measuring step (plasticizing step) have characteristic curves as shown in FIGS. 2B and 2D, respectively. That is, the actual screw rotation speed and the actual screw back pressure decrease from the metering completion setting position of the screw 12 (the rotation stop of the screw 12). In this case, the measured actual resin pressure Pr of the molten resin retained in the retaining chamber of the heating barrel 10 is a characteristic curve as shown in FIG. 2 (e).
[0027]
Therefore, in the present invention, based on the characteristic curve of the actual resin pressure Pr, the resin pressure Pr is set between the metering completion setting position of the screw 12 (the rotation stop of the screw 12) and the retreat setting position after the metering completion. At the position, it was confirmed that the molten resin retained in the retaining chamber of the heating barrel 10 was lower than the resin pressure point Pr0 at which no resin leaked from the tip of the nozzle portion 10a.
[0028]
However, between the weighing completion set position where the screw 12 moves and the retreat setting position after weighing completion, the controller 42 is urged by the signal switch 40 to operate the back pressure block switching valve 32. Then, by stopping the screw back pressure or increasing the screw back pressure, the screw is stopped from retreating, and a proper amount of the molten resin is always measured to measure the amount of the molten resin for injection in the next cycle. Can be achieved.
[0029]
Therefore, in the present invention, the retreat position after the completion of the weighing based on the above-mentioned weighing completion setting position of the screw 12 (the rotation stop of the screw 12) is set, and the screw 12 reaches the retreat setting position after the completion of the weighing. At this time, the controller 42 is energized by the signal switch 40 to operate the back pressure block switching valve 32 to block the screw back pressure.
[0030]
Alternatively, when the screw 12 reaches the retreat set position after the completion of the metering, the controller 44 is urged by the signal switch 40 to operate the proportional valve 34 for controlling the back pressure. , So as to increase the screw back pressure.
[0031]
In this way, according to the present invention, with a relatively simple configuration, the screw 12 is stopped at a proper retreat position after the metering completion position of the screw 12, and the fixed amount of the proper molten resin is measured. In addition to this, it is possible to reliably prevent resin leakage (drooling) from the tip of the nozzle portion of the molten resin.
[0032]
Therefore, when the measured values of the actual weighing completion position after successive shots by the injection molding machine according to the above-described stabilization method of the present invention and the actual weighing completion position by the conventional device were compared, as shown in FIG. The result was obtained. That is, according to the conventional apparatus, the variation width of the actual weighing completion position is 0.40 mm with respect to the weighing completion position, whereas the variation width of the actual weighing completion position with respect to the retreat position after completion of weighing according to the present invention. The variation width can be significantly reduced to 0.03 mm, and it has been confirmed that the variation in the weight of the molten resin between the injection molding shots can be significantly improved.
In the above description, the screw position detector 22 and the position setting device 36 constitute a position setting detecting means in the present invention, and the comparator 38, the signal switch 40, and the controllers 42 and 44 are the controllers in the present invention. Make up. Further, the direction switching valve 24 constitutes a first control valve in the present invention, and the back pressure block switching valve 32 and the back pressure control proportional valve 34 constitute a second control valve in the present invention. Further, the retreat position or the retreat set position after the completion of the weighing constitutes a position further retreated by a predetermined amount than the weighing complete position in the present invention.
[0033]
The preferred embodiment of the present invention has been described above. However, the present invention is not limited to the above-described embodiment, and many design changes can be made without departing from the spirit of the present invention.
[0034]
【The invention's effect】
As described above, the method for stabilizing the actual metering completion position of the injection molding machine according to the present invention uses the screw in the heating barrel.And screw injection means for controlling the axial movement of the screw, and rotating the screw while rotating the screw.Raw resin to be filled into the moldIn the screw part in the heating barrelPlasticizationMeltingIGuiding a predetermined amount of molten resin from the screw portion to a retaining chamber formed at the tip of the heating barrel with rotation of the screw.In the metering control method for an injection molding machine for metering byAxialWeighing start positionFor stopping the rotation of the drive motor.Weighing complete positionAnd a position further retracted by a predetermined amount than the weighing completion position for stopping the retreat of the screwSet eachA position setting detecting means for detecting that the screw has reached the set position, and a hydraulic circuit for controlling the supply of pressure oil to the injection cylinder via a direction switching valve are connected and arranged. A back pressure block switching valve for shutting off a line from the injection cylinder to the tank when a part of the return line through which the pressurized oil is discharged from the injection cylinder to the tank during the metering process is activated. A back pressure control proportional valve for controlling a back pressure generated in the return line when the back pressure block switching valve is not operated is provided downstream of the back pressure block switching valve. The oil passage is branched and connected, and the screw is provided in the hydraulic circuit until the screw reaches a position further retracted by a predetermined amount from the set measurement start position than the measurement completion position.Holds directional valve in neutral positionBy limiting the return line from which the pressure oil is discharged from the injection cylinder to the tank to the branch-connected oil passage, it is possible to control the screw back pressure, and from the set measurement start position. The screw is rotated, and when the screw retreats and reaches the weighing completion position, the rotation driving means is rotated.Stop drivingStopping the screw rotation and operating the back pressure control proportional valve to reduce the screw back pressure generated in the return line to zero or lower than the back pressure at the time of measurement, and further to the molten resin retained in the retention chamber The screw is set to be lower than the pressure, and in a state where the back pressure is generated, the screw is retained by the pressure of the molten resin retained in the retaining chamber until the screw reaches a position further retracted by a predetermined amount than the measurement completion position. When the screw reaches a position further retracted by a predetermined amount than the metering completion position, the back pressure block switching valve is actuated.Block back pressure orBy operating the back pressure control proportional valve without operating the back pressure block switching valve,To increase the screw back pressureProvide a commanding controller to stop the screw from retreatingAs a result, the variation in the actual weighing completion position can be significantly reduced, and thereby the variation in the weight between shots during injection molding can be greatly reduced. Stabilization of the weight of the article can be achieved.
[0035]
In addition, the metering control device of the injection molding machine according to the present invention controls the rotation of the screw in the heating barrel.Screw rotation drive means to giveTogether withAxial direction of the screwCombine the injection cylinder that controls the movement, andWhile rotatingRaw resin to be filled into the moldPlasticizing and melting at the screw portion in the heating barrel, and guiding a predetermined amount of molten resin from the screw portion to a retaining chamber formed at the tip of the heating barrel with rotation of the screw.In a measuring control device of an injection molding machine for measuring, the screwAxialWeighing start positionFor stopping the rotation of the drive motor.Weighing complete positionAnd a position further retracted by a predetermined amount than the weighing completion position for stopping the retreat of the screw.Set eachPosition setting detecting means for detecting that the screw has reached the set position,A hydraulic circuit for controlling supply of pressurized oil is connected to the injection cylinder via a directional switching valve, and the hydraulic circuit is connected to the injection cylinder during the screw weighing process.At the return line where the pressurized oil is discharged from the injection cylinder to the tank.In part,A back that shuts off the line from the injection cylinder to the tank when activated.Switching valve for pressure blockA back pressure for controlling a back pressure generated in the return line when the back pressure block switching valve is not operated.Proportional valve for pressure controlOn the downstream side of the back pressure block switching valve.The oil path provided is branched and connected, and the screwFrom the set weighing start position to the position further retracted by a predetermined amount than the weighing completion position,Provided in the hydraulic circuitSaidHolds directional valve in neutral positionBy limiting the return line from which the pressurized oil is discharged from the injection cylinder to the tank to the branch-connected oil passage, it is possible to control the screw back pressure,SaidThe screw is rotated from the set weighing start position, the screw moves backward, and when the screw reaches the weighing complete position, the rotation driving means is turned off.Stop drivingStopping the screw rotation and operating the back pressure control proportional valve to reduce the screw back pressure generated in the return line to zero or lower than the back pressure at the time of measurement, and further to the molten resin retained in the retention chamber The screw is set to be lower than the pressure, and in a state where the back pressure is generated, the screw is retained by the pressure of the molten resin retained in the retaining chamber until the screw reaches a position further retracted by a predetermined amount than the measurement completion position. When the screw reaches a position further retracted by a predetermined amount than the metering completion position, the back pressure is blocked by operating the back pressure block switching valve, or the back pressure block switching valve is operated. Without actuationOperate the pressure control proportional valveScrewTo increase the back pressureOrderControllerTo stop the retraction of the screwBy adopting the configuration, in a relatively simple configuration, there is an advantage that mixing of air into the molten resin at the tip of the nozzle portion, leakage of the resin, and the like can be eliminated, and the stop accuracy of the measurement completion position can be significantly improved. can get.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a control device of an injection molding machine showing an embodiment of a method of stabilizing an actual measurement completion position according to the present invention.
FIGS. 2A and 2B show screw characteristics at the time of weighing of an injection molding machine obtained by the method for stabilizing the actual weighing completion position according to the present invention, wherein FIG. 2A is a waveform diagram of a screw rotation speed set value, and FIG. ) Is a waveform diagram of the actual screw rotation speed, (c) is a waveform diagram of the screw back pressure set value, (d) is a waveform diagram of the actual screw back pressure, and (e) is a waveform diagram of the actual resin pressure in the heating cylinder. is there.
FIG. 3 is a waveform diagram showing a comparison between the method of stabilizing the actual measurement completion position according to the present invention and the stabilization characteristic of the actual measurement completion position in the conventional measurement control device.
[Explanation of symbols]
10 heating barrel
10a Nozzle part
12 Injection screw
12a Piston part
12b Extension shaft
14 Mold
14a Nozzle touch section
16 cavities
18 Injection cylinder
20 Hydraulic motor for screw rotation
22 Screw position detector
24 Directional valve
26 Hydraulic power source
28 tanks
30 hydraulic circuit
32 Switching valve for back pressure block
34 Proportional valve for back pressure control
35 branch oilway
36 Position setting device
38 Comparator
40 signal switch
42,44 Controller

Claims (3)

With coupling the screw rotation drive means for imparting rotation to the screw within the heating barrel combines the injection cylinder for controlling the axial movement of the screw, the raw resin to be filled in the mold while rotating the screw the Measuring control of an injection molding machine that plasticizes and melts at a screw portion in a heating barrel and guides a predetermined amount of molten resin from the screw portion to a stagnation chamber formed at the tip of the heating barrel with rotation of the screw and weighs it. In the method,
A measurement start position in the axial direction of the screw, a measurement completion position for stopping the rotation of the drive motor, and a position further retracted by a predetermined amount than the measurement completion position for stopping the retreat of the screw are set, respectively . Position setting detecting means for detecting that the screw has reached the set position,
A hydraulic circuit for controlling the supply of pressure oil to the injection cylinder via a direction switching valve is connected and arranged,
At the part of the return line where the pressure oil is discharged from the injection cylinder to the tank during the screw measuring step,
A switching valve for a back pressure block that shuts off a line from the injection cylinder to the tank when it is activated;
An oil in which a back pressure control proportional valve for controlling a back pressure generated in the return line when the back pressure block switching valve is not operated is provided downstream of the back pressure block switching valve. Fork the road,
By maintaining the directional control valve provided in the hydraulic circuit at a neutral position until the screw reaches a position further retracted by a predetermined amount than the weighing complete position from the set weighing start position , pressure oil is released. By limiting the return line discharged from the injection cylinder to the tank to the branch-connected oil path, it is possible to control the screw back pressure,
The screw is rotated from the set measurement start position, the screw moves backward, and when the screw reaches the measurement completion position, the drive of the rotation driving means is stopped to stop screw rotation and the back pressure control. Operate the proportional valve to reduce the screw back pressure generated in the return line to zero or
It is set to be lower than the back pressure at the time of measurement, and also lower than the pressure of the molten resin retained in the retention chamber,
In a state where the back pressure is generated, the screw is retracted by the pressure of the molten resin retained in the retaining chamber until the screw reaches a position further retracted by a predetermined amount than the measurement completion position,
When the screw reaches a position further retracted by a predetermined amount than the measurement completion position, the back pressure is blocked by operating the switching valve for the back pressure block, or
Alternatively, a controller for instructing to increase the screw back pressure by operating the back pressure control proportional valve without operating the back pressure block switching valve is provided to stop the retreat of the screw. the method for stabilizing the actual metering completion position shall be the. With coupling the screw rotation drive means for imparting rotation to the screw within the heating barrel combines the injection cylinder for controlling the axial movement of the screw, the raw resin to be filled in the mold while rotating the screw the Measuring control of an injection molding machine that plasticizes and melts at a screw portion in a heating barrel and guides a predetermined amount of molten resin from the screw portion to a stagnation chamber formed at the tip of the heating barrel with rotation of the screw and weighs it. In the device,
A measurement start position in the axial direction of the screw, a measurement completion position for stopping the rotation of the drive motor, and a position further retracted by a predetermined amount than the measurement completion position for stopping the retreat of the screw are set , respectively . Position setting detecting means for detecting that the screw has reached the set position,
A hydraulic circuit for controlling the supply of pressure oil to the injection cylinder via a direction switching valve is connected and arranged,
At the part of the return line where the pressure oil is discharged from the injection cylinder to the tank during the screw measuring step,
When it is actuated, and the back pressure block switch valve which closes the passage to the tank from the injection cylinder,
An oil in which a back pressure control proportional valve for controlling a back pressure generated in the return line when the back pressure block switching valve is not operated is provided downstream of the back pressure block switching valve. Fork the road,
It said screw until it reaches a position further predetermined amount back from the metering completed position from the set measurement start position, by holding the directional control valve which is provided in front Symbol hydraulic circuit to the neutral position, pressure oil By limiting the return line discharged from the injection cylinder to the tank to the branch-connected oil passage, it is possible to control the screw back pressure,
The screw is rotated from the set measurement start position, the screw moves backward, and when the screw reaches the measurement completion position, the drive of the rotation driving means is stopped to stop screw rotation and the back pressure control. Operate the proportional valve to reduce the screw back pressure generated in the return line to zero or
It is set to be lower than the back pressure at the time of measurement, and also lower than the pressure of the molten resin retained in the retention chamber,
In a state where the back pressure is generated, the screw is retracted by the pressure of the molten resin retained in the retaining chamber until the screw reaches a position further retracted by a predetermined amount than the measurement completion position,
When the screw reaches a position further retracted by a predetermined amount than the measurement completion position, the back pressure is blocked by operating the switching valve for the back pressure block, or
Alternatively, a controller for instructing to increase the screw back pressure by operating the back pressure control proportional valve without operating the back pressure block switching valve is provided to stop the retreat of the screw. Metering control device of an injection molding machine.   In claim 2, the second control valve includes a back pressure block switching valve and a back pressure control proportional valve, and operates the back pressure block switching valve at a position where the screw is retracted by the predetermined amount. And disconnecting the communication between the oil chamber of the injection cylinder and the proportional valve for controlling the back pressure.

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