JP5565699B2 - Purging method for electric injection device - Google Patents

Description

  The present invention relates to a purge method for discharging a resin material in a cylinder barrel at the time of resin material change or color change at the end of molding of an injection molding device, and in particular, a resin material remaining in a cylinder barrel of an electric injection device. The present invention relates to a purge method.

  For example, an electric injection device is attached to the front plate to prevent the tip of the screw from colliding with the tip of the cylinder barrel due to a malfunction of a servo motor that drives a screw mechanism that moves the screw forward in the axial direction. The cylinder barrel, the screw arranged to be movable forward and backward in the axial direction in the cylinder barrel, and the pressure plate to which the screw is connected by a coupling are moved forward and backward with respect to the front plate. The end face on the front plate side of the coupling for connecting the screw to the pressure plate and the end face on the pressure plate side of the cylinder barrel where the screw is arranged abut so as to prevent the screw from moving forward over a certain stroke. Is known.

In the above conventional electric injection device, as shown in FIG. 1, the front plate side end face of the coupling that connects the screw to the pressure plate even if the screw moves forward at the maximum speed in the injection process at the control screw advance position. And a predetermined gap S1 set so as to stop without contacting the pressure plate side end face of the cylinder barrel where the screw is arranged.
Further, as shown in FIG. 2, when the end surface on the front plate side of the coupling that connects the screw to the pressure plate and the end surface on the pressure plate side of the cylinder barrel where the screw is disposed contact the tip end of the screw. The screw tip and the cylinder barrel tip are provided with a predetermined gap S0 so as not to collide with the tip of the cylinder barrel.
Thus, in the conventional electric injection device, at the screw advance position for control, the tip of the screw and the tip of the cylinder barrel have a predetermined gap S4 that is the sum of the gaps S1 and S0. (See Patent Document 1)

  In a conventional injection molding apparatus, a purging method is known in which the molten resin in a cylinder barrel is changed in a resin material or color at the end of molding in a process as shown in FIG. In this purging method, an operation of rotating a screw to measure a predetermined amount and then moving the screw forward, or an operation of continuously rotating the screw is performed alone or in combination. That is, at the end of molding, the supply of the resin material is stopped, the screw is advanced, and then a metering operation is performed to rotate and retract the screw. The screw advancing and retreating operations are repeated a predetermined number of times, or the molten resin staying in the cylinder barrel is purged by continuously rotating the screw at the screw advancing position. Further, after the resin material or color is changed, the above operation is performed for purging. (See Patent Document 2)

  By the way, when the conventional purge operation is performed by the conventional electric injection device, the purge is performed at the screw advance position having the gap S4 obtained by adding S1 and S0 between the screw tip and the cylinder barrel tip. In the purge, in the gap S4, the shearing speed of the resin material flowing through the gap and the peeling force acting on the resin material adhering to the surface of the screw tip and the cylinder barrel tip in accordance with the shearing speed are controlled. In particular, it is difficult to replace the resin material on the tip surface of the screw and the barrel head tip surface with a new resin material. For this reason, a large amount of resin material and time are required for purging.

JP 2002-307516 A JP-A-4-334428

  The present invention has been made in view of the problems of the above-described conventional electric injection device. When purging, the injection material purging method can quickly and easily change the resin material and the color. The purpose is to provide.

  According to a first aspect of the present invention, there is provided a purge method for an electric injection device comprising a screw collision prevention means for preventing the screw from moving forward by a predetermined stroke or more, and driving the screw forward by a servo motor. A method for purging an electric injection device, wherein the screw is set to be immovable in the forward direction, the screw is continuously rotated at a predetermined rotational speed for a predetermined time, and the backward movement of the screw is changed to a molten resin. A first purging step for continuously discharging the molten resin in the cylinder barrel by applying a predetermined back pressure and setting the screw to be movable in the front-rear direction, and rotating the screw at a predetermined rotation A metering operation in which the screw is rotated by a number, a predetermined back pressure is applied to the molten resin to move the screw backward by a predetermined stroke, and the measured molten resin A second purging step for intermittently discharging the molten resin in the cylinder barrel, and a continuous rotation of the screw in the first purging step. The advance position is set in front of the advance position of the screw injection operation in the second purge step, and the first purge step and the second purge step are continuously repeated a predetermined number of times. And

According to a second aspect of the present invention, there is provided a purge method for an electric injection device according to the first aspect, wherein the screw in the first purge step is moved from an advance position of the screw injection operation in the second purge step. The screw movement to the continuous rotation advance position is performed at a predetermined screw advance speed set at a low speed.
According to a third aspect of the present invention, there is provided a purge method for an electric injection device according to the first aspect, wherein the back pressure and screw rotation speed set values in the first purge step are the second purge. It is characterized by being set to a value larger than the set value in the process.

  According to a fourth aspect of the present invention, there is provided a purge method for an electric injection device comprising a screw collision prevention means for preventing the screw from moving forward beyond a predetermined stroke, and the screw advance is driven by a servo motor. A method for purging an electric injection device, wherein the screw is set to be immovable in the forward direction, the screw is continuously rotated at a predetermined rotational speed for a predetermined time, and the backward movement of the screw is changed to a molten resin. A first purging step for continuously discharging the molten resin in the cylinder barrel by applying a predetermined back pressure and setting the screw to be movable in the front-rear direction, and rotating the screw at a predetermined rotation A metering operation in which the screw is rotated by a number, a predetermined back pressure is applied to the molten resin to move the screw backward by a predetermined stroke, and the measured molten resin And a second purge step for intermittently discharging the molten resin in the cylinder barrel, wherein the first purge step or the second purge is performed. The process is selectively used and repeated a predetermined number of times.

According to a fifth aspect of the present invention, there is provided a purge method for an electric injection device according to the fourth aspect, wherein the screw advance position in the second purge step is changed to the screw advance position in the first purge step. The screw movement is performed at a predetermined screw advance speed set to a low speed.
According to a sixth aspect of the present invention, there is provided a purge method for an electric injection device according to the fourth aspect, wherein the back pressure and screw rotation speed set values in the first purge step are the second purge. It is characterized by being set to a value larger than the set value in the process.

When rotating the screw, the advance position of the screw is set in front of the advance position of the injection process so that the gap between the screw tip and the cylinder barrel tip is reduced. As the speed increases, the peeling force of the resin material adhering to the surface of the screw tip and the cylinder barrel tip accompanying the shear rate increases, and the resin material and color can be changed quickly. This reduces the resin material required for purging and the purging time.
Since the screw movement from the screw advance position in the injection process to the screw advance position in the purge process is performed at a predetermined low speed, the screw overruns and the collision prevention means of the screw does not come into contact.

The resin material purge operation by the continuous rotation of the screw and the resin material purge operation by the screw rotation backward (metering operation) and screw non-rotation forward (injection operation) are selectively performed. Resin material change and color change can be performed quickly and easily.
Set the back pressure setting value in the resin material purge operation by the continuous rotation of the screw larger than the back pressure setting value in the resin material purge operation by the screw rotation backward (metering operation) and screw non-rotation forward (injection operation). Therefore, when the screw is continuously rotated, the screw does not move backward, and the resin material can be continuously and efficiently discharged from the cylinder barrel. This reduces the amount of resin used and shortens the purge time.

It is sectional drawing of the principal part of an electrically driven injection apparatus. It is sectional drawing which shows the state which inhibited the advance of the screw. It is explanatory drawing which shows the process of resin material change and color change by this invention. It is sectional drawing which shows the relationship between the front-end | tip of a screw and a cylinder barrel front-end | tip part in the 1st purge process of this invention. It is explanatory drawing which shows the process of the conventional resin material change and color change.

Hereinafter, the configuration of the electric injection device 10 used in an embodiment of the present invention will be described with reference to FIGS.
In FIG. 1, reference numeral 11 denotes a front plate, which is provided to face an end plate (not shown), and the front plate 11 and the end plate are similarly connected by a tie bar (not shown). A cylinder barrel 12 is attached to the central portion of the front plate 11, and a screw 13 is inserted into the cylinder barrel 12 so as to be capable of moving forward and backward in the axial direction. The support hole formed in the front plate 11 includes a ball nut 14.
Reference numeral 15 denotes a pressure plate that is slidable in the axial direction of the screw 13. A bearing member 16 having a load cell and a drive shaft 17 are attached to the center of the pressure plate 15.

  A ball screw shaft 18 is rotatably attached to the pressure plate 15, and a pulley 19 is provided at one end of the ball screw shaft 18 on the pressure plate 15 side. The ball screw shaft 18 is screwed with a ball nut 14 attached to the front plate 11, and the rotation of an electric servomotor for screw back and forth (not shown) is transmitted to the pulley 19 via a winding drive means (not shown). , The pressure plate 15 is configured to move back and forth with respect to the front plate 11. Due to the forward movement of the pressure plate 15, the screw 13 moves forward relative to the cylinder barrel 12.

  A key groove is machined in the shaft end portion on the pressure plate side of the screw 13 and is fitted into a shaft hole provided in the driven shaft 20 so that the screw 13 does not move in the axial direction of the driven shaft 20 by the coupling 21. It is attached. A driven shaft 20 and a screw rotation pulley 22 are attached to the drive shaft 17 and transmitted to the screw rotation pulley 22 via a screw rotation electric servo motor (not shown) and a winding drive means (not shown). The screw 13 is configured to transmit the rotation of the drive shaft 17 via the driven shaft 20 and the key 23.

FIG. 1 shows a state in which the screw 13 is in the screw operation advance position. When the screw 13 moves forward at a predetermined speed and stops in the injection process, the front plate of the coupling 21 even if it overruns due to control characteristics. A predetermined gap S <b> 1 is provided in which the side end surface 24 and the pressure plate side end surface 25 of the cylinder barrel 12 do not contact each other.
2 shows that the screw 13 moves forward from the state of FIG. 1 by the predetermined gap S1 and moves to the most advanced position, and the end surface 24 on the front plate side of the coupling 21 connected to the pressure plate 15 and the screw 13 are This shows a state in which screw advance beyond a certain stroke is prevented by abutting against the pressure plate side end face 25 of the cylinder barrel 12 arranged.

L1 in FIG. 2 indicates the length from the end surface 24 on the front plate side of the coupling 21 connecting the screw 13 to the tip of the outer diameter portion of the screw head 13a provided at the tip of the screw 13, and L2 indicates the cylinder The length from the end face 25 on the pressure plate side of the barrel 12 to the outer diameter of the screw head 13a extending in the axial direction of the screw 13 to the tip of the cylinder barrel 12 is shown.
Then, the dimensions of each component are set so that L2 is longer than L1, and the end surface 24 on the front plate side of the coupling 21 and the end surface 25 on the pressure plate side of the cylinder barrel 12 on which the screw 13 is disposed abut. Even when the gap is zero and the screw 13 is in the most advanced position in FIG. 2, the tip of the cylinder barrel 12 does not collide with the tip of the outer diameter portion of the screw head 13a. Is provided.
Since it comprised in this way, as shown in FIG. 1, in the control screw advance position, the front-end | tip part of the cylinder barrel 12 and the front-end | tip part of the screw 13 have the total clearance S4 of predetermined clearance S0 and S1.

The operation of the electric injection apparatus 10 having the above configuration will be described. A screw rotating electric servo motor (not shown) is driven to rotate the screw 13. The cylinder barrel 12 is provided with a hopper (not shown). A resin material is supplied from the hopper, and the supplied resin material is plasticized and melted in the cylinder barrel 12 and sent to the tip of the screw 13.
Due to the reaction force of the molten resin fed forward of the screw, the screw 13 moves backward in the direction of the end plate disposed on the side opposite to the screw of the pressure plate 15, and moves backward by a predetermined stroke and stops. When the screw 13 is retracted, the ball screw 18 and the electric servomotor for moving the screw back and forth are rotated, and resistance is generated in the backward operation of the screw 13 by controlling the electric servomotor for moving the screw forward and backward with a predetermined torque. This resistance is the pressure applied to the resin sent to the front of the screw, that is, the back pressure of the molten resin.

When the set value of the back pressure, which is the resistance of the backward movement of the screw 13, is smaller than the extrusion pressure of the resin with respect to the pressure that the screw 13 rotates and pushes the resin material forward, the screw 13 moves backward to perform the weighing operation. When the pressure is set higher than the extrusion pressure of the resin, the screw 13 is continuously rotated without moving at that position. In the electric injection apparatus having the above-described configuration, the screw 13 can be selected from the continuous rotation operation and the metering operation by setting the screw 13 in a rotating state and changing the setting of the back pressure.
The forward movement of the screw 13 rotates the ball screw 18 and the electric servomotor for moving the screw forward and backward, and the pressure plate 15 moves forward by controlling the electric servomotor for moving the screw forward and backward at a predetermined rotational speed. As the pressure plate 15 moves forward, the screw 13 advances in the cylinder barrel 12, and the molten resin stored in the screw tip is discharged through a nozzle 12b provided at the cylinder barrel tip.

  The end surface 24 on the front plate side of the coupling 21 connected to the pressure plate 15 and the end surface 25 on the pressure plate side of the cylinder barrel 12 on which the screw 13 is disposed abut on each other, so that the screw advances mechanically over a certain stroke. However, the present invention is not limited to this configuration. For example, it is output based on the deviation between the set injection pressure and the current injection pressure. Compare the magnitude relationship between the speed command output from the position loop and the speed command output from the position loop, and perform the speed loop control based on the speed command with the smaller value to drive the screw forward / backward electric servo motor to exceed a certain stroke A configuration using a form that electrically prevents the screw from moving forward may be used.

Next, a resin material purging method using the electric injection apparatus 10 having the above-described configuration will be described with reference to FIGS.
In the purge method of the present invention, in FIG. 3, (1) the electric injection device 10 is moved backward after the molding is completed, and then the screw 13 is advanced to the injection operation advance position. (2) The screw 13 is rotated at the forward position of the injection operation to discharge all the resin material in the hopper and the cylinder barrel 12, supply new material to the hopper, and switch to the purge mode. (3) The screw 13 is advanced to the screw continuous rotation advance position at the advance speed (low speed) Vp programmed in advance. (4) The screw 13 is rotated at a pre-programmed back pressure Pp capable of maintaining the screw continuous rotation advance position and the set rotation speed R1, and the supplied resin material is discharged from the tip of the nozzle 12b. (5) After the set time t1, the preset back pressure programmed in advance is set to 0 (zero) Mpa and the set rotational speed R2, and the measuring operation is performed up to the purge weighing position. (6) When the purge metering position is reached, the metering operation is stopped, and the screw 13 is advanced to the injection operation advance position at the set speed V1. (7) The operations of (3) to (6) are repeated N times the set number of times, and the purge operation is terminated. The forward speed (low speed) Vp of the present invention is a speed at which stop control is possible without overrun at the set screw continuous rotation forward position.

The first purge step in FIG. 3 shows the steps (3) and (4), and the second purge step shows the steps (5) and (6).
In the above description, a purge method that omits the second purge step and repeats the first purge step a set number of times, or a purge method that omits the first purge step and repeats the second purge step a set number of times is selected. Is possible.

As described above, in the present invention, the screw 13 is held at a position so as not to retreat due to the extrusion pressure of the resin, and the screw 13 is continuously rotated to discharge the resin material from the tip of the nozzle 12b. It was set as the structure put ahead. With this configuration, the gap between the tip of the screw 13 and the tip of the barrel head 13a can be set small, and the shear rate of the resin material flowing through this gap is increased. For this reason, the shearing force due to the flow of the resin acting on the surface of the screw tip and the barrel head tip is increased, and the material change and color change performance is improved.
Further, when the screw 13 is driven at the same number of rotations, the shear rate of the barrel head tip portion opposed to the screw tip portion due to the rotation becomes faster when the gap between the screw tip portion and the barrel head tip portion is smaller. For this reason, the shearing force due to the flow of the resin acting on the surface of the screw tip and the barrel head tip is increased, and the material change and color change performance is improved.

FIG. 4 shows a state in which the screw 13 is in the screw continuous rotation advance position. When the screw 13 moves forward and stops at a predetermined advance speed Vp in the purge process, the coupling 21 even if it overruns due to control characteristics. A predetermined gap S3 is provided in which the front plate side end surface 24 of the cylinder and the pressure plate side end surface 25 of the cylinder barrel 12 do not contact each other.
The gap S3 is set to be smaller by S32 than the gap S1 at the injection operation advance position shown in FIG. Since it comprised in this way, in the screw continuous rotation advance position of a purge process, the front-end | tip part of the cylinder barrel 12 and the front-end | tip part of the screw 13 have the total clearance S5 of predetermined clearance S0 and S3. The total gap S5 is set to be smaller by S2 than the total gap S5 at the injection operation advance position, whereby the shear rate of the resin at the screw tip can be increased.

In the present invention, the most advanced position of the screw is the position of the screw where the end face 24 on the front plate side of the coupling 21 and the end face 25 on the pressure plate side of the cylinder barrel 12 on which the screw 13 is abutted and the gap is zero. Indicates. The gap between the end face 24 on the front plate side of the coupling 21 and the end face 25 on the pressure plate side of the cylinder barrel 12 on which the screw 13 is disposed is S1, and the screw continuous rotation advance position is the front position of the coupling 21. The position of the screw in which the gap between the end surface 24 on the plate side and the end surface 25 on the pressure plate side of the cylinder barrel 12 where the screw 13 is disposed is set to S3.
The gap S3 is smaller than S1, and the screw continuous rotation advance position is closer to the screw head side than the injection advance position.

As described above, in the conventional electric injection device provided with means for preventing the collision between the screw tip portion and the barrel head tip portion, the operation is performed at the screw advance position of the injection operation when performing material change or color change. I was trying. In the present invention, when the screw is continuously rotated, the advancement position of the screw is set in front of the advancement position of the screw in the injection operation, and the material shearing speed is improved by increasing the shear rate of the resin at the screw tip. It was.
Thus, when purging using an electric injection device equipped with means for preventing the collision between the screw tip and the barrel head tip, the resin material on the screw tip surface and the barrel head tip surface is a new resin material. This makes it easy to replace the resin material and the color.

Electric injection device 10
Cylinder barrel 12
Screw 13
Screw advance speed Vp in the first purge step
Screw rotation speed R1 in the first purge process
Back pressure Pp in the first purge process
Set time t1
Screw advance speed V1 in the second purge step
Screw rotation speed R2 in the first purge process
Number of repetitions of purge process N
Screw clearance S1 at the forward position of the screw injection operation
The clearance at the continuous rotation forward position of the screw S3

Claims (3)

A method for purging an electric injection device comprising a screw collision preventing means for preventing the screw from moving forward by a predetermined stroke, and driving the screw forward by a servo motor,
The screw is set so as not to move in the forward direction, and the screw is continuously rotated at a predetermined rotational speed for a predetermined time, and the backward movement of the screw is prevented by applying a predetermined back pressure to the molten resin. A first purge step for continuously discharging the molten resin in the cylinder barrel;
A weighing operation in which the screw is set to be movable in the front-rear direction, the screw is rotated at a predetermined rotational speed, a predetermined back pressure is applied to the molten resin, and the screw is moved backward by a predetermined stroke. A second purging step for intermittently discharging the molten resin in the cylinder barrel, comprising an injection operation for discharging the molten resin by a forward movement of the screw,
The continuous rotation advance position of the screw in the first purge step is set in front of the screw injection advance position in the second purge step, and the first purge step and the second purge step are performed. A purge method for an electric injection device, which is continuously repeated a predetermined number of times. The screw movement from the screw injection operation advance position in the second purge step to the continuous rotation advance position of the screw in the first purge step is performed at a predetermined screw advance speed set at a low speed. The purge method for an electric injection device according to claim 1, wherein 2. The electric type according to claim 1, wherein set values of the back pressure and screw rotation speed in the first purge step are set to values larger than the set values in the second purge step. Method of purging the injection device.

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