JPH0459325A - Cold starting prevention method of injection molding machine - Google Patents

Abstract

PURPOSE:To prevent damage or a trouble of each part of an injection molding machine by preventing cold starting, by a method wherein a positional deviation of an injection screw is detected and a binding state of a screw is confirmed. CONSTITUTION:CPU 22 for PMC is read in a positional deviation of an injection screw 1 through an error register of a servocircuit 27 and whether or not the absolute value of the positional deviation exceeds a range of the allowable maximum value of a positional deviation which is established and stored beforehand in common RAM29 is discriminated. In the case where it is discriminated that the absolute value of the positional deviation of the screw 1 exceeds the allowable maximum value before detection of the lapse of an established fixed time of a timer, it means that a movement of the injection screw 1 is hindered because of the reason why melting of resin is incomplete. Therefore, the CPU for the PMC suspends distribution of the pulse to a servocircuit 27 and a fixed time to wait the melting of the resin is set to a timer. Then a low speed backward movement command is put out by setting the fixed time to detect the positional deviation to the timer and positional deviation detecting treatment is executed repeatedly.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a method for preventing cold startup of an injection molding machine.

Conventional technology If the injection screw is driven with strong force while the injection screw and cylinder are still stuck together due to solidified residual resin, excessive stress will be applied to each part of the injection molding machine, resulting in damage or malfunction. Therefore, when starting the injection molding operation, it is necessary to sufficiently melt the resin in the cylinder so that the injection screw can move freely.

As a method to prevent cold start, prior to the start of injection molding operation, power is applied to the cylinder heater in advance, a cold start warning light is turned on, and the temperature detected by the cylinder temperature detection means is When the temperature reaches the set temperature range, the cold start prevention timer is activated, and the warning light that was turned on when the heater was turned on continues to be lit until the timer setting time has elapsed, giving the operator the warning that the cylinder It was common to indicate that the temperature was low and to urge caution during operation. Normally, the set temperature range that serves as a guideline for activating the cold start prevention timer is set within ±10% of the target value, which is the optimum temperature for melting the resin. The set time is set by assuming the time from when the cylinder temperature detecting means detects the set temperature range until the actual temperature inside the cylinder reaches the target value, and also taking into account a certain degree of safety factor.

Problems to be Solved by the Invention However, since the time from when the cylinder temperature detection means detects the set temperature range until the cylinder's actual temperature reaches the target value is affected by environmental factors such as temperature and humidity, there is a certain degree of safety factor. Even if you set the cold start prevention timer in anticipation of this, there is no guarantee that the actual temperature of the cylinder will necessarily reach the target value once the timer setting time has elapsed, and the resin may remain insufficiently melted. In some cases, the injection screw is driven by

In addition, proper temperature measurement may not be possible due to failure of the cylinder temperature detection means itself, and if the screw is driven with strong force when the cylinder temperature is considerably low, normal injection molding operations may not be possible. Otherwise, unreasonable stress may be applied to various parts of the injection molding machine, resulting in damage or malfunction.In particular, if the tip of the injection screw remains fixed to the cylinder due to solidified residual resin, the rotation of the screw may Doing so may lead to serious accidents such as breakage of the tip of the screw, which is vulnerable to torsion.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for preventing cold startup of an injection molding machine that can eliminate the drawbacks of these conventional techniques and reliably protect each part of the injection molding machine from damage or failure due to cold startup. It is in.

Means for Solving the Problems The cold start prevention method of the present invention starts timing when the temperature detected by the cylinder temperature detection means reaches a set temperature range, and outputs a slow backward command with a minute torque to perform injection. If the positional deviation of the injection screw exceeds the set predetermined value within a predetermined clocking time, the driving of the injection screw will be stopped. The above object has been achieved by allowing injection molding operation unless a predetermined value is exceeded.

Also, when the temperature detected by the cylinder temperature detection means reaches the set temperature range, the timer is activated and a slow backward command is output with a minute torque to start driving the injection screw, and the timer detects a predetermined time. Every time the positional deviation of the injection screw exceeds a predetermined value, the injection screw stops driving, waits for a predetermined period of time, starts timing again, and outputs a slow backward command with a minute torque to drive the injection screw. The driving operation may be repeatedly performed, and the injection molding operation may be enabled if the positional deviation of the injection screw does not exceed a predetermined value even after the timer has counted a predetermined time.

When the temperature detected by the working cylinder temperature detecting means reaches the set temperature range, timing is started, and a slow backward command is output with a minute torque to drive the injection screw.

If the position deviation of the injection screw exceeds a predetermined value within a predetermined time period, the injection screw will stop driving, and if the position deviation exceeds the predetermined value even after the predetermined time period has elapsed. Enables injection molding operations.

Therefore, if the positional deviation of the injection screw exceeds a predetermined value within a predetermined time period, in other words, the movement of the injection screw is restricted due to reasons such as the injection screw being stuck to the cylinder due to residual resin. Even if the injection screw does not follow the movement command and the positional deviation increases, the injection screw will not be driven with strong force.
Damage or failure of various parts of the injection molding machine due to cold startup is reliably prevented.

In addition, the timer is activated to output a slow backward command with minute torque to start driving the injection screw, and each time the position deviation of the injection screw exceeds a preset value until the timer detects a predetermined time, Stop driving the injection screw, wait for a predetermined period of time, start timing again, output a slow backward command with a minute torque, repeatedly execute the driving operation of the injection screw, and the timer measures the predetermined period of time. By enabling the injection molding operation unless the positional deviation of the injection screw exceeds a predetermined value, the injection molding operation is automatically permitted when the inhibiting factor that restricts the movement of the injection screw is removed. Ru.

Example Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 2 is a block diagram of essential parts of an injection molding machine according to an embodiment of the present invention.

In Fig. 2, 1 is an injection screw, 2 is a cylinder, 3 is a servo motor that drives the injection screw 1 in the axial direction, and 4 detects the rotation of the servo motor 3 to detect the current position of the injection screw 1. This is a pulse noder for detection. The cylinder 2 is divided into a plurality of heating zones, each heating zone is equipped with band heaters B1 to Bn, and each band heater B1 to Bn is connected to the power source 6 via switches 7-1 to 7-n, The cylinder 2 is heated. In addition, each heating zone includes temperature sensor sections S1 to S of the temperature converter 5.
n is arranged, and constitutes cylinder temperature detection means for detecting the temperature of each heating zone.

Reference numeral 20 denotes a numerical control device (hereinafter referred to as an NC device) that controls the injection molding machine, and the NC device 20 includes a microprocessor for NC (hereinafter referred to as CPU for NC) 21 and a c-pu for a programmable machine controller. (below,
PMC CPU) 22,
Connected to the PU 22 are a ROM 23 that stores sequence programs and the like for controlling sequence operations of the injection molding machine, and a RAM 24 that is used for temporary storage of data.

The NC CPU 21 includes a ROM 25 that stores a management program that controls the injection molding machine as a whole, and a servo circuit that drives and controls the servo motors of each axis for injection, clamp, injection screw rotation, ejector, etc. They are connected via a servo interface 26. In addition,
In Figure 2, the injection servo motor 3. Only the servo circuit 27 of the servo motor 3 is shown. In addition, 29 is a non-volatile shared R consisting of bubble memory and CMOS memory.
AM is a memory section that stores NC programs, etc. that control each operation of the injection molding machine, and various setting values.

It has a setting memory section that stores parameters and macro variables.

30 is a bus arbiter controller (hereinafter referred to as BAC), and the BAC 30 includes a CPU 21 for NC and a PMC.
CPU22. Shared RAM 29° input circuit 31. Each bus of the output circuit 32 is connected, and the bus to be used is controlled by the BAC 30. Further, 34 is a manual data input device (hereinafter referred to as CRT/MDI) with a CR7 display device connected to the BAC 30 via the operator panel controller 33. It is possible to input commands and setting data. Note that 28 is a RAM connected to the NC CPU 21 via a bus and used for temporary storage of data.

The output circuit 32 is connected to the servo circuit 27 and outputs a torque limit value that limits the output torque of the injection servo motor 3, and also connects to the switches 7-1 to 7-.
n to turn the switches 7-1 to 7-n on and off, and connect the power supply 6 to the band heaters B1 to Bn to turn them on.
It is supposed to be controlled off. It is also connected to the temperature converter 5, so that the channel of the temperature sensor section can be specified.

Further, the output of the temperature converter 5 is input to the input circuit 31 .

In the above configuration, the NC device 20
NC that controls each operation of the injection molding machine stored in M29
While the PMC CPU 22 performs sequence control based on the program and parameters such as various molding conditions stored in the setting memory section and the sequence program stored in the ROM 23, the NC CPU 21 controls the servo circuits for each axis of the injection molding machine. The injection molding machine is controlled by distributing pulses to the injection molding machine via the servo interface 26.

FIG. 3 is a block diagram of an example of the temperature converter 5, which includes six temperature sensor sections S1 to S6.

In Fig. 3, 51-1 to 51-6 are temperature sensor parts S1 to S.
A bridge cold junction compensation circuit for thermocouples 6 and 6, and the output voltage from the circuit is connected to voltage/frequency converters 52-1 to 52-.
6, and is sequentially connected to a counter 54 via a multiplexer 53. The counter 54 counts the outputs from the voltage/frequency converters 52-1 to 52-6 and converts the detected temperature into a digital quantity. There is. 55 is a microprocessor which outputs the detected temperature read from the counter 54 via a latch 56;
First, it reads the detected temperature from the counter 54, outputs to the latch 56 the channel code CH corresponding to the temperature sensor section S1 to S6 that sent out the detected temperature, and also outputs the read detected temperature data TD to the latch 56. . After these data are output and held in the latch 56, the ready signal READY is output, and after a predetermined period of time, the ready signal READY is turned off and the counter 56 outputs the ready signal READY.
The detected temperature data from the next temperature sensor sections S1 to S6 read from 4 and the channel code representing the temperature sensor sections S1 to S6 are output to the latch 56, and the ready signal R is outputted again.
Outputs EADY. Thereafter, the above-described processing is performed at predetermined intervals, and the temperatures detected by the temperature sensor units S1 to S6 are transferred to the multiplexer 53. The detected temperature data from the temperature sensor sections S1 to S6 is sequentially received through the counter 54 and received by the latch 56, and then sent out in a circular manner. Then, in order to indicate which temperature sensor section S1 to S6 the temperature data TD that is being output at that time comes from,
A channel code CH is output at the same time, and this channel code CH represents a temperature sensor section. For example, let the channel code CH=1° be the temperature sensor part S1, and the channel code CH=2 be the temperature sensor part S2, and hereafter, the temperature sensor part 33. S4. 35. For S6, each corresponds to a channel code CH=3.4.5°6,
Sequentially, this channel code CH becomes 1. 2. 3...
. . 6, 1.2, . . . are sequentially circulated and output, and the temperature data TD detected by the channel of the temperature sensor section is also output at the same time.

Note that 57 is a buffer that constitutes an input circuit, and when the request signal REQ and channel code CH' from the output circuit 32 on the NC device 120 side are input, the microprocessor 55 responds to the input channel code CH'. Read the detected temperature from the temperature sensor and close the latch 5.
6 to the input circuit 31 on the Nc device 20 side.

Before starting the injection molding operation by the injection molding machine, the operator first installs each band heater B1 to Bn heating temperature TS, ~
Set TS. In addition, in the case of the example, the heating temperature TS
, ~TS, the set temperature width TS, . . . ~TS.・ is −10 for the target heating temperature TS, ~TS,
Automatically set as a percentage.

Thereafter, the NC device 20 closes the switches 7-1 to 7-n to start raising the temperature of the band heaters B1 to Bn, and
22 starts the "cold start prevention process" as shown in FIG.

At the initial stage when the "cold start prevention process" is started, each part of the cylinder 2 heated by the band heaters B1 to Bn has not reached the set temperature range T S , ...T S , , so the PMC CPU 22 , First, CRT/MDI
In step S1), a warning message "cold start prohibited" is displayed on the CR7 display screen of 34 to warn the operator that the temperature rise of cylinder 2 is insufficient. In step S1), the temperature rise incomplete flag F is initialized and the channel code is Step S2. Step S3), Step S
A loop temperature detection process consisting of steps 4 to S8 is started.

That is, the PMC CPU 22 sends the channel code CH' corresponding to the index i to the request signal RE at predetermined intervals.
output to the temperature converter 5 via the output circuit 32 along with Q,
The temperature data TD of the channel code CH' corresponding to the index i is read from the temperature converter 5 via the input circuit 31 (step S4), and the temperature data TD is the set temperature set corresponding to this heating zone. In step S5), it is determined whether the set temperature width TS, , has been reached.
If the temperature has not reached , set the heating incomplete flag F,
It is remembered that there remains a heating zone that has not reached the set temperature range, and the index 1 is incremented in step S6. In step S7), the temperature detection process in steps S4 to S8 is repeatedly executed until it is determined in the process in step S8 that the value of the index i has reached the value of the number n of band heaters.

Each time the temperature detection process ends, the PMC CPU 22
Whether or not the heating incomplete flag F is set, that is,
It is determined whether or not there remains a heating zone that has not reached the set temperature range in the cylinder 2 (step S9), and if there remains a heating zone that has not reached the set temperature range, the heating incomplete flag F is initialized and the channel Step S2. Set the index i indicating the code to 1. Step S3), the temperature detection process is repeatedly executed.

Then, when all of the heating zones in the cylinder 2 reach the set temperature range and the determination result in step S9 becomes true,
The PMC CPU 22 sets the cold start prevention time Tw to the timer.
1 and start (step 510), power is continuously applied to each of the band heaters Bl-Bn, and the actual internal temperature of each part of the heating zone in the cylinder 2 reaches the target value TSI of the heating temperature. The system enters a standby state in which it waits for the next step (step 511).

Under normal conditions, if heating is continued for the cold start prevention time Twl after all of the heating zones have reached the set temperature range, the actual internal temperature of each part of the heating zone in cylinder 2 will reach the target temperature increase temperature TS. However, since the temperature rise of cylinder 2 is affected by environmental factors such as temperature and humidity, there is no guarantee that the actual temperature of the cylinder will reach the target value when the timer setting time has elapsed. Temperature sensor section S1-S
6 etc., it may be difficult to appropriately detect the temperature.

Therefore, the PMC CPU 22 applies a minute torque limit value T m l to the torque limit circuit of the injection servo circuit 27 via the output circuit 32 . Step 51
2) Set a predetermined time TW2 for position deviation detection in the timer and start it (step 513), and output a low-speed retraction command to the servo circuit 27 of the injection servo motor 3 to retract the injection screw 1 at a slow speed. , starts distributing pulses at very low speed (step 514). The commanded retreat position of the injection screw 1 based on the low-speed retreat command and the current position of the injection screw 1 detected by feedback from the pulse noder 4 are input to the servo circuit 27 of the injection servo motor 3, and the injection screw The positional deviation Sd of 1 is detected as the value of the error register in the servo circuit 27.

The PMC CPU 22 reads the position deviation Sd of the injection screw 1 from the error register of the servo circuit 27 (step 515), and the absolute value l5d1 of the position deviation is the shared RA.
Maximum permissible positional deviation value SS preset and stored in M29
It is determined whether the range is exceeded (step 81).
6) Since the servo circuit 27 performs pulse distribution at a minute speed, the resin is not completely melted and the injection screw 1
Even in a case where the movement of is restricted, 1sdl>Ss does not immediately hold. Therefore, step S
At predetermined intervals until the elapse of the predetermined time TW2 set by the timer is detected in step 17, or until it is determined in step 816 that the absolute value 18dl of the positional deviation of the screw 1 exceeds the allowable maximum value Ss. Step 315
The positional deviation detection process from step 317 is repeatedly executed.

The absolute value lSd of the positional deviation of the screw 1 reaches the maximum allowable value Ss before the elapse of the timer set predetermined time Tw2 is detected.
If it is determined that the injection screw 1 has exceeded the limit, it means that the injection screw 1 is being prevented from moving due to incomplete melting of the resin, etc., so the PMC CPU 22 moves to step S18 and starts the servo circuit. 27, a predetermined time Tw3 for waiting for melting of the resin is set and started on a timer, and the timer waits for a predetermined time (Step S19. Step 520). Next, the process moves to step S13, where a predetermined time Tw2 for detecting positional deviation is set and started in the timer, and after a low speed backward command is output in the process of step S14, steps S15 to S
17 is repeatedly executed.

If the resin melts while repeatedly performing this process while increasing the temperature of the cylinder 2, the restraint on the injection screw 1 is removed and the screw 1 is moved toward the commanded retreat position. Absolute value of position deviation +s
Since di is less than or equal to the allowable maximum value Ss of positional deviation, the determination result in step S16 in the positional deviation detection process is always true, and the PMC CPU 22 performs step S21 at the stage when it detects the elapse of the predetermined time T w 2 set in the timer. The pulse distribution to the servo circuit 27 is stopped, and the maximum injection pressure T m is applied to the torque limit circuit of the servo circuit 27.
a, to enable normal injection molding operation that requires strong force to drive screw 1, and also to enable CRT/
The "cold start prohibited" warning message is canceled from the CRT display screen of the MDI 34 to notify the operator that injection molding operation is possible (step 522).
).

Note that the value of the error register may be reset at the stage where pulse distribution is stopped in the process of step S18.

In addition, since it is a waste of time to repeatedly perform such a process when the resin does not melt due to inappropriate settings of the heating temperature TS or the set temperature width TS, the cooling is performed in step S11. If the value of the position deviation Sd does not decrease even after a certain period of time has elapsed after the inter-start prevention time Tvl has elapsed, or if the screw 1 gradually retreats leaving a position deviation equal to or greater than the maximum allowable value Ss. If the retraction limit has been reached, the setting is assumed to be inappropriate and a message is displayed on the CRT/MDI 34 (7) CRT display screen, and "cold start prevention processing" is automatically performed. It may also be configured to end the process. However, the maximum allowable value Ss
The phenomenon in which the screen 1 gradually retreats and reaches the retreat limit while leaving the above positional deviation can be avoided by alternately outputting the low-speed backward command and the low-speed forward command in the process of step S14.

Above, an embodiment has been described in which the torque limit is automatically released to enable injection molding operation when the injection screw 1 becomes able to move freely. It may also be entered manually. For example, after setting the torque limit T m l n in the process of step S12 of the embodiment shown in FIG. After operating the backward minute movement key and detecting the key operation by the operator, a predetermined time TW2 for position deviation detection is set and started in the timer in the process of step S13, and the PMC CPU 22 performs the steps from step S15 onwards. You can have the process run automatically. In this case, since the low-speed retreat command for the injection screw 1 is input by the operator, step S
The processes from step S19 to step S20 are not necessarily necessary,
After stopping the output of the low-speed reverse command in the process of step S18, the system may enter a standby state in which it waits for the operator to operate the minute movement key. The waiting time for the resin to melt is determined by the operator's will. Furthermore, when the operator manually inputs a low-speed retreat command, it is assumed that the injection screw 1 may be rotated (extrude) due to an erroneous operation, so the steps in the embodiment shown in FIG. In the process corresponding to step 312, a small torque limit should also be set in the servo circuit for screw rotation to prohibit rotation of the screw 1, which is susceptible to torsion.

However, whether the rotational driving force is transmitted to the injection screw 1 at a stage where the resin is not sufficiently melted and the screw 1 is damaged is a matter of setting the torque limit, and theoretically, the It is possible to detect the molten state of the resin by the positional deviation during rotation of the screw 1 instead of the retraction.

Effects of the Invention The cold start prevention method of the present invention prevents cold start by detecting the positional deviation of the injection screw and confirming the locked state of the screw. Strong driving force is not applied in this state, and each part of the injection molding machine can be reliably protected from damage or failure due to cold startup.

[Brief explanation of drawings]

Fig. 1 is a flowchart showing an outline of "cold start prevention processing" in one embodiment of the present invention, Fig. 2 is a block diagram showing the main parts of an injection molding machine of the same embodiment, and Fig. 3 is a block diagram showing the main parts of the injection molding machine of the same embodiment. It is a block diagram showing a temperature converter of an injection molding machine. 1...Screw, 2...Cylinder, B1~Bn・
...Band heater, S1-Sn...Temperature sensor section, 5
...Temperature converter, 6...Power supply, 7-1 to 7-n...
・Switch, 20...NC device. Figure Figure

Claims (2)

[Claims] (1) When the temperature detected by the cylinder temperature detection means reaches the set temperature range, it starts timing and outputs a slow backward command with a minute torque to drive the injection screw,
If the positional deviation of the injection screw exceeds a predetermined value within a predetermined clocked time, the driving of the injection screw is stopped, but if the positional deviation exceeds the predetermined value even after the predetermined clocked time, A method for preventing cold startup of an injection molding machine, characterized by enabling injection molding operation. (2) When the temperature detected by the cylinder temperature detection means reaches the set temperature range, the timer is activated and a slow backward command is output with a minute torque to start driving the injection screw, and the timer detects a predetermined time. Every time the positional deviation of the injection screw exceeds a predetermined value, the injection screw stops driving, waits for a predetermined period of time, starts timing again, and outputs a slow backward command with a minute torque to start the injection. A cooling system for an injection molding machine, characterized in that the screw driving operation is repeatedly executed and the injection molding operation is enabled if the positional deviation of the injection screw does not exceed a predetermined value even if a timer measures the predetermined time. How to prevent intermittent startup.