JP2933169B2 - Method and apparatus for controlling injection pressure-holding process of injection molding machine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for controlling an injection holding pressure process of an injection molding machine.

2. Description of the Related Art As a method of controlling a pressure holding process of an injection molding machine, a process is shifted from an injection filling process to a pressure holding process, and after maintaining a predetermined pressure for a predetermined time, the process of the injection pressure holding process is terminated. Is common.

In the conventional method of controlling the pressure-holding step by pressure and time, a cylinder and a nozzle of an injection molding machine and each part of a resin filling path such as a sprue, a runner, a land, and a gate in a mold are used. In the case where the temperature changes or the substantial viscosity of the molten resin changes due to the mixing of the recycled material, the amount of the resin filled in the mold cavity cannot be kept constant at a predetermined holding pressure. There was a disadvantage.

For example, if the temperature of each part at the time of the current molding operation rises compared to the temperature of each part of the filling path at the time of completing the reference condition setting, the substantial viscosity of the molten resin becomes fluid and overfilling easily occurs. As the weight of the product increases, the holding pressure is directly transmitted into the mold cavity, so that the molten resin having a high fluidity protrudes from the parting line, and the shape defect such as burrs is easily caused. On the other hand, when the temperature of each of the parts during the molding operation is lower than the reference temperature, there is a problem that the viscosity of the molten resin increases and insufficient filling occurs, so that shape defects such as sink marks are likely to occur. .

In a normal injection molding operation, after the mold cavity is filled with the resin, first, the filling path having the smallest cross-sectional area, that is, the molten resin is hardened at the gate portion and the resin is injected into the mold cavity. The so-called gate seal phenomenon, which prevents filling and backflow of resin from inside the mold cavity, occurs.However, with the conventional method of controlling the pressure-holding process by pressure and time, the pressure-holding pressure is maintained for a certain time regardless of the presence or absence of the gate seal. , The pressure is not transmitted into the mold cavity by the gate seal, meaningless pressure-holding operation sometimes hinders the speeding up of the molding cycle.
Conventionally, there is no technology to directly detect the presence or absence of a gate seal.
Usually, the time for maintaining the holding pressure is estimated to be the time from when the molten resin is filled into the mold cavity to when the gate is sealed, and is set to a longer time.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned disadvantages of the prior art, to keep the filling amount of the resin in the mold cavity constant irrespective of a change in the viscosity of the molten resin, and more desirably, to make the pressure holding operation meaningless. It is an object of the present invention to provide a method and an apparatus for controlling an injection pressure-holding step of an injection molding machine, which enable a high-speed molding cycle without performing the above steps.

Means for Solving the Problems The present invention provides a timer for measuring a dwell time, a screw position detection means for detecting a screw position, and a screw position detected by the screw position detection means reaching a set dwell completion position. And a pressure holding time completion determining means for determining whether or not the timer has timed the set pressure holding time, wherein the screw position is set before the set pressure holding time is reached. The injection pressure-holding step is terminated when either the pressure-holding time is reached before the screw position reaches the pressure-holding time before the screw position reaches the set pressure-holding completion position.

In particular, the pressure holding time is measured by measuring the elapsed time after shifting to the pressure holding step, and the screw position is detected, and the screw pressure position is set before the measured time reaches the set time. The injection pressure-holding step is terminated when either of the following conditions is satisfied, or when the measured time reaches the set time before the screw position reaches the pressure-holding completion position where the screw position is set.

Operation In the injection pressure holding process, when the screw reaches the pressure holding completion position before the set pressure holding time is reached, or when the screw does not reach the pressure holding completion position but reaches the set pressure holding time. The injection holding pressure process is completed. Especially,
At least, the pressure holding time is measured by measuring the elapsed time after shifting to the pressure holding process, and the screw position is detected, and the pressure holding is completed before the measured time reaches the set time. When you reach the position,
If one of the measurement times reaches the set time before the screw position reaches the pressure holding completion position, the injection pressure holding step is terminated.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 is a block diagram showing an electric injection molding machine according to one embodiment of the present invention and a main part of a control system of the injection molding machine.
Reference numeral 2 denotes a screw, and reference numeral 2 denotes an injection servomotor that drives the screw 1 in the axial direction. The injection servomotor 2 is equipped with a pulse coder 3 constituting a part of a screw position detecting means, and the screw 1 is provided with a pressure sensor 4 for detecting a reaction force of the molten resin acting in the screw axis direction. .

Reference numeral 100 denotes a numerical controller (hereinafter referred to as an NC device) as a control device for controlling the injection molding machine.
100 is a microprocessor for NC (hereinafter referred to as CPU) 10
8 and a CPU 110 for a programmable machine controller (hereinafter referred to as PMC). The PMC CPU 110 has a ROM 113 storing a sequence program for controlling a sequence operation of the injection molding machine such as an injection holding pressure process, and a temporary data storage device. A RAM 106 used for storage and the like is connected. CPU108 for NC
The ROM 111 that stores a management program for controlling the entire injection molding machine and a servo circuit that drives and controls servomotors for each axis for injection, clamping, screw rotation, ejector, etc. It is connected. In FIG. 3, only the servomotor 2 for injection and the servo circuit 101 of the servomotor 2 are shown. Reference numeral 103 denotes a non-volatile shared RAM composed of a bubble memory and a CMOS memory, a memory unit for storing an NC program for controlling each operation of the injection molding machine, and a setting for storing various set values, parameters, and macro variables. The setting memory section has torque limit values PI and PH for defining the upper limit of the injection pressure (holding pressure) of the injection molding machine by the operation of the NC device 100, and performs injection during the injection molding operation. Injection / holding pressure switching position ST set based on the screw position to switch from (filling) to holding pressure, and
The injection holding pressure switching pressure PT which is set based on the reaction force of the molten resin acting in the screw axis direction to perform the switching from injection (filling) to the holding pressure, and the screw position for ending the injection holding pressure process. The pressure-holding completion position SH set as a reference is set and stored.

Reference numeral 109 denotes a bus arbiter controller (hereinafter referred to as a BAC). The BAC 109 shares the CPU 108 for the NC and the CPU 110 for the PMC.
The buses of the RAM 103, the input circuit 104, and the output circuit 105 are connected,
The bus to be used is controlled by the BAC 109. Reference numeral 114 denotes a manual data input device with a CRT display device (hereinafter referred to as CRT / MDI) connected to the BAC 109 via the operator panel controller 112, and is operated by operating various operation keys such as soft keys and numeric keys. For example, the user can input various commands, set data in the setting memory section of the shared RAM 103, reset the data, and the like.
Reference numeral 102 denotes a RAM connected to the NC CPU 108 via a bus, which is used for temporary storage of data and the like.

FIG. 3 relates to an injection shaft of the injection molding machine, that is, an injection servomotor 2 for driving a screw 1 in an axial direction to perform an injection (holding pressure) operation, and attached to the injection servomotor 2. 1 shows a pulse coder 3 that detects the rotation of the servomotor 2 to detect a screw position, and omits other clamping shafts, screw rotation shafts, ejector shafts, and the like. Therefore, only the servo circuit 101 for the injection servomotor is shown in the NC device 100, and the servo circuits of the other axes are omitted. The servo circuit 101 is connected to the injection servomotor 2, and the output of the pulse coder 3 mounted on the servomotor 2 is input to the servo circuit 101. A torque limit value for limiting the output torque of the injection servomotor 2 is output from the output circuit 105 to the servo circuit 101, and is input to the torque limit circuit in the servo circuit 101.

The output from the pressure sensor 4 provided on the screw 1 is input to the input circuit 104 via the A / D converter 115,
At least every predetermined cycle during the injection holding pressure process, for example, by the process of the NC CPU 108 executed every pulse distribution cycle,
The output from the pressure sensor 4 is sequentially updated and stored in the storage area of the shared RAM 103 as the current injection pressure or the current holding pressure, and the value input as the screw position from the pulse coder 3 to the servo circuit 101 is stored. Are sequentially updated and stored in the storage area of the shared RAM 103 by the same processing as described above. Incidentally, the screw position in the present embodiment, the origin is set in the screw tip direction,
It is indicated by a coordinate system in which the screw retreat direction is a positive value.

In the configuration as described above, the NC device 100
The PMC CPU 110 performs sequence control according to the NC program for controlling each operation of the injection molding machine stored in 3 and the parameters such as various molding conditions stored in the setting memory section and the sequence program stored in the ROM 113. Meanwhile, the CPU 108 for NC drives the injection molding machine by distributing pulses to the servo circuits of each axis of the injection molding machine via the servo interface 107 to drive and control the servo motors of each axis.

Hereinafter, the outline of the injection process executed by the PMC CPU 110 by detecting a mold clamping completion signal input from the NC CPU 108 to the PMC CPU 110 at the time when the mold clamping process which is a process before the injection pressure holding process is completed. Referring to FIGS. 1 and 2, two embodiments of the present invention will be described.

In the embodiment shown in the flowchart of FIG.
The PMC CPU 110 that has detected the mold clamping completion signal from the CPU 108,
First, an injection start signal is output to the NC CPU 108 so that the NC CPU 108
Start of pulse distribution to the injection servomotor 2 by the above, that is, movement of the screw for injection is permitted (step S1).
01), the torque limit value PI for defining the upper limit of the injection pressure set and stored in the setting memory section of the shared RAM 103 is read once, and the servo circuit 10 is output via the BAC 103 and the output circuit 105.
Set the torque limit circuit in 1 (switch S10
2).

Next, the CPU 108 for the NC which is detected through the pulse coder 3
The current position SA of the screw 1 which is updated and stored in the storage area of the shared RAM 103 is read by the processing of the predetermined period (step S103), and the current position SA of the screw 1 is
Whether or not the injection holding pressure switching position ST set and stored in the setting memory unit 103 has been reached, that is, the value of the screw current position SA becomes equal to or less than the value of the injection holding pressure switching position ST. Is determined (step S10
4) If SA> ST and the current screw position SA has not reached the injection holding pressure switching position ST, step S is performed again.
The flow returns to 103, and the loop-shaped processing composed of step S103 and step S104 is repeatedly executed until SA ≦ ST, and waits until the screw current position SA reaches the injection holding pressure switching position ST.

While repeatedly executing the loop-like processing composed of steps S103 and S104, in step S103, SA ≦
If it is determined that the screw current position SA has reached the injection holding pressure switching position ST, the PMC CPU 110
Once reads the torque limit value PH for specifying the upper limit of the holding pressure stored in the setting memory section of the shared RAM 103, and resets the torque limit value in the servo circuit 101 via the BAC 103 and the output circuit 105. (Step S105) The timer TH is set to the allowable pressure continuation time, and the timer TH is set.
To start monitoring the elapsed time after the shift to the pressure holding (step S106).

Next, the current screw position SA is read from the shared RAM 103 (step S107), and whether or not the current screw position SA has reached the pressure-holding completion position SH set and stored in the setting memory section of the shared RAM 103, that is, Position SA
Is determined to be equal to or less than the value of the pressure holding completion position SH (step S108), and SA is determined.
> SH and the current screw position SA is the pressure-holding completion position S
If it has not reached H, it is further determined whether or not the set time of the timer TH started in step S106 has elapsed, ie,
It is determined whether the elapsed time after the shift to the holding pressure has reached the allowable holding time of the holding pressure (step S109). If the set time of the timer TH has not elapsed, the process returns to step S107 again, and if it is determined in step S108 that SA ≦ SH,
Alternatively, until it is determined in step S109 that the set time of the timer TH has elapsed, a loop-like process including steps S107 to S109 is repeatedly executed.

While step S107 to step S109 repeatedly execute the loop-like processing, SA in step S108
If it is determined that ≦ SH, the screw 1 driven in the axial direction within the range of the holding pressure specified by the torque limit value PH is continuously operated within the allowable holding time of the holding pressure. PM means that the mold cavity is filled with a predetermined amount of resin by moving to the pressure-holding completion position SH, and PM
The C CPU 110 immediately ends the processing of the injection pressure-holding step, and shifts to the next step, that is, the processing of the measuring step.

On the other hand, if it is determined in step S109 that the set time of the timer TH has elapsed while the loop-shaped process composed of steps S107 to S109 is repeatedly executed, the value specified by the torque limit value PH is maintained. This indicates that even if the screw 1 is driven in the axial direction at the maximum value of the pressure and pressure for the duration of the dwelling, the screw 1 cannot be moved to the dwelling completion position SH. Since it is impossible to fill the mold cavity with a predetermined amount of resin even if the process is continued, the PMC CPU 110 immediately terminates the process of the injection and pressure holding process and shifts to the process of the measuring process.

As described above, in this embodiment, if the screw 1 is driven in the axial direction within the range of the holding pressure specified by the torque limit value PH, the screw 1 is moved to the pressure holding completion position. Since the injection pressure-holding step is immediately terminated at the stage of moving to SH (step S108), the filling amount of the resin into the mold cavity is determined only by the moving amount of the screw 1, and the change in the viscosity of the resin is caused. Regardless of the amount of resin filled in the mold cavity, the amount of resin filled in the mold cavity can always be kept constant. Is possible.

Also, for some reason, the screw 1
Movement of the screw 1 is stopped, and the screw 1 is placed at the pressure-holding completion position SH
Even if it is not possible to move to the maximum holding pressure specified by the torque limit value PH, the holding pressure is executed for the allowable holding time of the holding pressure (step S1).
09) At least, it is guaranteed to obtain a molded product equal to or more than the conventional method of controlling the pressure-holding step by pressure and time.

In the embodiment shown in the flowchart of FIG. 2, the CPU for PMC which has detected the mold clamping completion signal from the CPU for NC 108
110 first outputs an injection start signal to the NC CPU 108 to
The CPU 108 permits the screw movement for injection (step S201), sets the timer TI to an allowable injection continuation time, starts the timer, and starts monitoring the elapsed time after the start of injection (step S202). ),share
The torque limit value PI for defining the upper limit of the injection pressure is temporarily read from the RAM 103 and set in the torque limit circuit in the servo circuit 101 via the BAC 103 and the output circuit 105 (step S203).

Next, the shared RAM 103 is detected by the pressure sensor 4 via the A / D converter 115 and is processed by the NC CPU 108 at predetermined intervals.
Injection pressure current value PA updated and stored in the storage area
Is read (step S204), and whether or not the current value PA of the injection pressure has reached the injection holding pressure switching pressure PT set and stored in the setting memory unit of the shared RAM 103, that is, the value of the current value PA of the injection pressure Is determined to be equal to or greater than the value of the injection holding pressure switching pressure PT (step
S205), if PA <PT and the current injection pressure value PA has not reached the injection holding pressure switching pressure PT, step S202.
It is determined whether or not the set time of the timer TI started in step has elapsed, that is, whether or not the elapsed time after the start of injection has reached the allowable duration of injection (step S206). If the set time of the timer TI has not elapsed, the current position SA of the screw 1 is read from the shared RAM 103 (step S20).
7), whether or not the screw current position SA has reached the pressure-holding completion position SH, that is, whether or not the value of the screw current position SA is equal to or less than the value of the pressure-holding completion position SH. Is determined (step S208), and if SA> SH and the screw current position SA has not reached the pressure-holding completion position SH, the process returns to step S204 again, and step S205 is performed.
In steps S204 to S208, it is determined whether or not PA ≧ PT in step S206, whether the set time of the timer TI has elapsed in step S206, or whether SA ≦ SH in step S208. The loop-like process is repeatedly executed.

While the loop-like processing composed of steps S204 to S208 is repeatedly executed, PA
If it is determined that ≧ PT, the screw 1
Means that the ideal injection operation in which the current value PA of the injection pressure reaches the injection holding pressure switching pressure PT during the injection movement is performed, and it is determined in step S206 that the set time of the timer TI has elapsed. If this is done, it means that the present value PA of the injection pressure has not reached the injection holding pressure switching pressure PT even if the elapsed time after the start of the injection has reached the allowable duration of the injection. Since there is room to move up to the holding pressure operation after rounding up, the PMC CPU 110
In step 9, the timer TH is set to a durable time for holding pressure, the timer is started, and the monitoring of the elapsed time after shifting to holding pressure is started, and the upper limit of the holding pressure is defined from the shared RAM 103. The torque limit value PH of the servo circuit 101 is once read and reset in the torque limit circuit in the servo circuit 101 via the BAC 103 and the output circuit 105 (step S210).

Next, the screw current position SA is read from the shared RAM 103 (step S211), and it is determined whether or not the screw current position SA has reached the pressure-holding completion position SH (step S21).
2) If the screw current position SA has not reached the pressure-holding completion position SH, it is further determined whether or not the set time of the timer TH started in step S209 has elapsed, that is, the elapsed time after shifting to the pressure-holding state. It is determined whether or not the dwell time has been reached (step S213). If the set time of the timer TH has not elapsed, the process returns to step S211 again, and it is determined whether SA ≦ SH is determined in step S212, or until it is determined in step S213 that the set time of the timer TH has elapsed. During step S211 to step S2
The loop-like processing composed of 13 is repeatedly executed.

While the loop-shaped processing composed of steps S211 to S213 is repeatedly executed, SA in step S212 is executed.
When it is determined that ≦ SH, the screw 1 driven in the axial direction within the range of the holding pressure specified by the torque limit value PH is normally set within the allowable holding time of the holding pressure. It means that the mold cavity is filled with a predetermined amount of resin by moving to the pressure-holding completion position SH without delay, and the PMC CPU 110 immediately terminates the processing of the injection pressure-holding step, and the next step, that is, The process proceeds to the measurement process.

On the other hand, if it is determined in step S213 that the set time of the timer TH has elapsed while the loop-shaped processing composed of steps S211 to S213 is repeatedly executed, the value specified by the torque limit value PH is retained. This indicates that even if the screw 1 is driven in the axial direction at the maximum value of the pressure and pressure for the duration of the dwelling, the screw 1 cannot be moved to the dwelling completion position SH. Since it is impossible to fill the mold cavity with a predetermined amount of resin even if the process is continued, the PMC CPU 110 immediately terminates the process of the injection and pressure holding process and shifts to the process of the measuring process.

Further, when it is determined in the process of step S208 that the value of the screw current position SA is equal to or less than the value of the pressure-holding completion position SH, the screw 1 is moved during the injection movement. The screw 1 moves to the pressure holding completion position SH at a stage where the current value PA of the injection pressure does not reach the injection holding pressure switching pressure PT and before the elapsed time after the start of the injection reaches the allowable continuation time of the injection. It usually means trouble such as insufficient weighing. In this case, there is no time to round up the injection operation and shift to the pressure holding operation, so the PMC CPU 110 immediately ends the processing of the injection pressure holding step. The same situation may occur when the viscosity of the molten resin is extremely low or when there is an inconvenience in the mold parting line, but the current injection pressure PA increases. Even if this is not done, the injection pressure-holding step is terminated when the screw 1 has moved to the pressure-holding completion position SH, so that accidents such as injection of molten resin can be prevented beforehand.

According to these embodiments, it is easy to keep the amount of the resin filled in the mold cavity constant. However, in order to obtain a more stable molded product, when setting the pressure-holding completion position SH, condition setting is required. It is desirable to set an ideal pressure-holding completion position with reference to data and the like at the time of molding a non-defective product, and if the viscosity of the molten resin is expected to increase, set the timer TH. It is preferable to set a longer dwell time of the dwelling pressure so that the screw 1 can surely move to the dwelling completion position SH within the durable time.

Advantageous Effects of the Invention The present invention is characterized in that when the screw of the injection molding machine reaches a preset pressure-holding completion position within the set pressure-holding time, the pressure-holding step is terminated, so that the resin The filling amount is determined only by the moving amount of the screw, and the amount of the resin filled in the mold cavity can be kept constant regardless of the change in the viscosity of the resin. It is possible to realize a high-speed molding cycle without continuing a meaningless dwelling operation. In addition, even if the screw does not reach the set pressure-holding completion position for some reason, the injection pressure-holding process is terminated when the set pressure-holding time has been reached. It will not be long.

[Brief description of the drawings]

FIG. 1 is a flowchart showing an outline of an injection (holding pressure) process of one embodiment of the present invention, FIG. 2 is a flowchart showing an outline of an injection (holding pressure) process of another embodiment of the present invention, and FIG. FIG. 1 is a block diagram showing an electric injection molding machine according to one embodiment of the present invention and a main part of a control system of the injection molding machine. 1 ... screw, 2 ... servomotor for injection, 3 ...
Pulse coder (screw position detecting means), 4 ... Pressure sensor, 100 ... Numeric control device (Control device of injection molding machine), 101 ... Servo circuit, 102,106 RAM, 103 ... Shared RAM, 104 ... Input Circuit, 105 Output circuit, 107 Servo interface, 108 Microprocessor for numerical control, 109 Bus arbiter controller, 110
Programmable machine controller, 111,113 …… ROM,
114 …… Manual data input device with CRT display.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Keno Ueguchi 3580 Kobaba, Oshino-mura, Oshino-mura, Minamitsuru-gun, Yamanashi Pref. No. 3580 Kobaba FANUC CORPORATION Product Development Laboratory (56) References JP-A-62-127221 (JP, A) JP-A-63-17020 (JP, A) JP-A-62-18233 (JP, A)

Claims (3)

(57) [Claims] In the injection pressure-holding step, when the screw position reaches a set pressure-holding completion position before reaching a set pressure-holding time, or before the screw position reaches the set pressure-holding completion position. The method of controlling the injection pressure-holding step of the injection molding machine, wherein the injection pressure-holding step is terminated when either one of the times when the pressure-holding time is reached is satisfied. 2. In the injection pressure-holding step, the elapsed time after the shift to the pressure-holding step is measured to measure the pressure-holding time, the screw position is detected, and the screw position is detected before the measured time reaches the set time. The injection pressure-holding step is performed when either the pressure reaches the set pressure-holding completed position or when the measurement time reaches the set time before the screw position reaches the set pressure-holding completed position. The method for controlling an injection pressure-holding step of an injection molding machine, characterized by terminating the process. 3. A timer for measuring a dwell time, a screw position detecting means for detecting a screw position, and a screw for determining whether the screw position detected by the screw position detecting means has reached a set dwell completion position. Position determining means, and pressure-holding time completion determining means for determining whether the timer has timed the set pressure-holding time, and the screw position determining means determines that the screw position has reached the set pressure-holding completed position. An injection molding machine characterized by terminating the injection pressure-holding step when it is determined by the pressure-holding time completion determining means that the timer has counted the set pressure-holding time. Injection holding pressure process control device.