JPH06226787A - Nozzle touch method - Google Patents

Abstract

PURPOSE:To prevent a touching force of a nozzle of an injection molding machine from becoming excess by dividing an operation of a nozzle touching unit to be driven by a servo motor into a touching operation, a maintaining operation and a releasing operation, and specifying touching forces of the nozzle to a mold in the touching and maintaining operations. CONSTITUTION:A servomotor 16 is managed by a numerical controller NC of an injection molding machine. A touch maintaining operation is executed simultaneously with a molding cycle operation. A touching operation is an operation from bringing an end of a nozzle of of an injection unit 2 into contact with a mold 5 up to confirming the nozzle touch completion after a continuation of a predetermined time of a predetermined touching force FT. The force FT of the nozzle with the mold 5 is a minimum force F0 of a range for preventing leakage of resin in the touching operation and the size of addition of a force FR balanced with a reaction force to be received by the unit 2 and the F0 in the touch maintaining operation. Thus, it prevents an excess touching force from operating at a stationary board 4 and prevents leakage of resin at the time of a cycle operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nozzle touch unit for an injection molding machine.

[0002]

2. Description of the Related Art In an injection molding machine, a mold clamping unit 1 and an injection unit 2 are connected to a nozzle touch unit 3 as shown in FIG. 1 in preparation for purging work, replacement of a cylinder assembly, or injection molding by a sprue break system.
The nozzle 6 at the tip of the injection unit can be brought into contact (touch operation) or separated (touch release operation) from the die 5 attached to the die plate 4 of the die clamping unit 1. There is.

The nozzle 6 is in contact with the mold 5 when the molten resin is injected into the mold 5 and at the time of measuring, and the reaction force received by the injection unit 2 by the injection pressure and the back pressure at the time of measuring ( It is pressed with a predetermined force F _T (touch force) so as to counter the load).

The structure of the nozzle touch unit 3 in the electric injection molding machine (FIG. 1) is composed of a general motor 7, a ball screw / nut mechanism 8, an elastic body such as a spring 9, and a brake 1.
0 and a proximity switch 11 for detecting the touch completion position are combined, and the touch force F _T is driven by the motor 7 to operate the ball screw / nut mechanism, the injection unit 2 is advanced, and the tip of the nozzle 6 is moved. The spring 9 is brought into contact with the die 5, and further, the motor 7 is driven to compress the spring 9 to a position where the proximity switch 11 sends a touch completion signal. This force is maintained by actuating the brake 10 and maintaining the position of the ball screw / nut mechanism 8.

Touch force F exerted in this way
_T is substantially constant in the injection molding process, and is set to be large so as to be able to counter the maximum reaction force (generated during injection / pressure holding) that the injection unit 2 receives.

However, the reaction force is generated in the injection molding process in each of the steps of injection, pressure holding and metering, and in the steps other than these, such as mold opening / closing, ejection and cooling, a resin having low viscosity is molded. In this case, it is sufficient to provide a touch force that prevents resin leakage. It is the fixed platen 4 that imparts a touch force of a magnitude capable of counteracting the maximum reaction force even in the steps of mold opening / closing, ejection, and cooling.
Not only causes the mold plate to fall but also impairs the parallelism of the mold plate, which has a bad effect such as damage to the mold and burrs on the molded product.

This is the same during each of the steps of injection, pressure holding and metering that require a large touch force, and an excessive touch force F _T adversely affects the parallelism of the mold board to some extent. There is.

In an injection molding machine using a fluid pressure such as air pressure or hydraulic pressure as a drive source, it is easy to increase the touch force F _T according to the increase or decrease of the injection pressure by using a common drive source. However, in the method using the fluid pressure, the control characteristics tend to be deteriorated due to instability of the fluid pressure and characteristic changes due to temperature changes of the medium. Also, the injection pressure and the holding pressure
The touch force F _T is as small as 2 to 3 t with respect to 0 to 20 _t ,
It is difficult to control precisely.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a nozzle touch method capable of preventing an excessive touch force F _T in an injection molding machine.

[0010]

A motor M for driving a nozzle touch unit is a servomotor and is under the control of a numerical controller provided in an injection molding machine. The operation of the nozzle touch unit is classified into touch operation, touch maintaining operation, and touch release operation.

In the touch operation, the touch force F _{T of the} nozzle with respect to the mold is set to the minimum force F ₀ within the range in which resin leakage can be prevented. In the touch maintaining operation, the force F _R that balances the touch force F _{T of the} nozzle on the mold with the reaction force received by the injection unit.
To the above-mentioned minimum force F ₀ .

[0012]

The structure in which the touch force F _{T is set} to the minimum force F ₀ during the touch operation prevents an excessive touch force from acting on the fixed board during the touch operation. Touch force F _T during touch maintenance
Has a minimum force F ₀ , which prevents the occurrence of resin leakage in each step of mold opening / closing, ejection and cooling in cycle operation.

Further, the structure in which the touch force F _T has a force F _R that balances the reaction force received by the injection unit during the touch maintaining operation prevents an excessive touch force from acting on the fixed plate during the cycle operation.

[0014]

FIG. 2 shows an essential part of an electric injection molding machine, in which an injection unit 2 is arranged so as to face a mold clamping unit 1, and the injection unit 2 connects both units 1 and 2. The nozzle touch unit 3 can be moved forward and backward. The fixed platen 4 of the mold clamping unit 1 is attached with the fixed side of the mold 5.

In the injection unit 2 of FIG. 2, the tip of the nozzle 6 is retracted to point A to release the nozzle touch, and the tip of the nozzle 6 is separated from the mold 5. Nozzle 6
A screw 13 is movably arranged in the front-rear direction inside a cylinder 12 having a tip attached thereto, and a load cell as a load sensor 14 is attached to the base of the screw 13. The load sensor 14 is a force acting on the screw 13, that is,
Injection unit 2 based on injection pressure or back pressure during measurement
The reaction force (load) received by is detected.

Reference numeral 15 is a servomotor for measurement, reference numeral 1
Reference numeral 6 denotes an injection servo motor, which is under the control of a numerical control device (NC device) 100 provided in each injection molding machine.

The nozzle touch unit 3 includes a nozzle touch motor M, a ball screw / nut mechanism 8 and a brake 10. The motor M is a servomotor under the control of the NC device 16. And the motor M
The ball screw / nut mechanism 8 is driven by this, and the injection unit 2 moves forward and backward. The brake 10 is provided for emergency stop.

The NC device 100 (FIG. 3) has a microprocessor (CPU) 101 for NC and a CPU 102 for programmable machine controller (PMC), and the CPU 101 for NC controls the injection molding machine as a whole. A ROM 107 which stores a management program for controlling a servo circuit 105 for driving and controlling various servo motors such as a motor M for injection, clamping, screw rotation, ejector, or nozzle touch is connected via a servo interface 104. Note that FIG. 3 shows only the servo circuit for the motor M. The RAM 108 is bus-connected to the NC CPU 101 and is used for arithmetic processing and primary storage of data.

The PMC CPU 102 is connected with a ROM 109 storing a sequence program for controlling the sequence operation of the injection molding machine, a PMC RAM 110 used for primary storage of arithmetic and data, and an A / D converter 114. There is. The A / D converter 114 converts the output of the load sensor 14 from an analog signal into a digital signal and transmits it to the PMC CPU 102.

CPU 101 for NC, CPU 10 for PMC
2 is bus-coupled to a bus arbiter controller (BAC) 103, which has a nonvolatile shared RAM 111 composed of a bubble memory or a CMOS memory, an input circuit (DI) 112 connected to various sensors of the injection molding machine, Output circuit 11 connected to various actuators of injection molding machine
3 (DO) is bus-coupled, and the bus used by the BAC 103 is controlled.

Reference numeral 116 is a manual data input device (CRT / MDI) with a CRT display device, which is connected to the BAC 103 via an operator panel controller 115. By using the input device 116, various setting screens and work menus are displayed on the CRT display screen, and various operation keys (soft keys, ten keys, etc.) are operated to input various setting data and display various setting screens. You can choose.

The shared RAM 111 has a CRT / MDI 11
The NC program input by 6 or the like is stored, and various molding conditions regarding injection, pressure holding, mold opening / closing, weighing, and nozzle touch set by the input device 116 are stored. For the nozzle touch, touch release completion position A in FIG. 2, the forward speed deceleration position B of the injection unit 2, in addition to the forward target position D of the touch position C and Reriri injection unit 2, the torque limit value T _A, various Standby times τ ₀ , τ ₁ and output value P of load sensor 14
And a conversion formula T _P = f (P) + T _A for calculating the torque value T _P required for the motor M with respect to the minimum force F ₀ are stored. The torque component f (P) corresponds to the touch force balanced with the reaction force received by the injection unit 2 due to the injection pressure or the back pressure.

Other components of the injection molding machine and NC device 10
The exchange of signals inside 0 is the same as the known one, and thus detailed description thereof will be omitted.

In the operation of the injection molding machine, the CPU for NC
101 performs pulse distribution via the servo interface 104 to the servo circuit 105 of each servo motor based on the NC program stored in the shared RAM 111 and various molding conditions to perform NC control of each servo motor, and
The PMC CPU 102 sequence-controls the injection molding machine based on the sequence program stored in the ROM 109.

In the injection molding process, the nozzle touch unit 3
The nozzle touch operation and the molding cycle operation by the injection unit 2 and the mold clamping unit 1 are performed (FIG. 4). The nozzle touch operation includes a touch operation, a touch maintaining operation, and a touch releasing operation. The touch maintenance operation is performed simultaneously with the molding cycle operation. Touch actuation
The injection unit 2 is advanced toward point D (FIG. 2), the tip of the nozzle is brought into contact with the die 5 (point C), and a predetermined touch force F is applied.
It is the operation until it is confirmed that the nozzle touch is completed when _T continues for a predetermined time τ. The movement start point of the injection unit 2 is a release position (point A) in which the tip of the nozzle 6 is separated from the mold 5 by a predetermined distance. In addition, the forward speed of the injection unit 2 may be reduced at point B on the way to protect the mold.

The touch maintaining operation maintains the nozzle touch to prevent resin leakage while the injection unit 2 is performing the molding cycle operation, and minimizes the touch force F _T to the reaction force received by the injection unit 2. This is an operation in which the force F ₀ is applied. The touch release operation is an operation of retracting the injection unit 2 from the point C where the tip of the nozzle 6 is in contact with the mold 5 to the original point A.

The molding cycle operation is an operation which is executed by sequentially circulating the mold closing process, the injection process, the pressure holding process, the measuring / cooling process, the mold opening process and the ejecting process until the molding of a predetermined quantity is completed. is there.

The nozzle touch operation will be described with reference to the flow charts of FIGS. These flows are executed as task processing at every processing cycle of the PMC CPU 102. Since the molding cycle operation is the same as the conventional one, its explanation is omitted.

The PMC CPU 102 first starts the touch operation shown in FIG. 5 at a proper time when various conditions are satisfied with the operation of the injection molding machine. [Touch Operation] In steps 1 to 3, the flag f determines which stage the nozzle touch operation is in. The flag f = 1 indicates the first stage, f = 1 indicates the first stage, f = 2 indicates the second stage, and f = 3 indicates the third stage. Since this is the first time, the routine proceeds to steps 4 and 5, where the timer a is started and the motor M is driven to advance the injection unit 2 toward point D. Motor M
From NC CPU 101 to servo interface 1
The pulse amount required to reach the point D is supplied to the servo circuit 105 via 04. In this state, the torque control section in the servo circuit is instructed with a torque value sufficient to start the injection unit 2 by overcoming its inertia.

The read time t _a (Step 6), determines whether a predetermined time has elapsed tau ₀ set (step 7).
If it has not elapsed, the process proceeds to step 8 and the flag f =
The processing of this time is ended as 1. Since the timer a is started and the advance of the injection unit 2 is started, the state of the first stage is reached. This is the end of the process. Practically, τ ₀ is about 1 second.

The next time, the process proceeds from step 1 since the start in the state of stage 1 Step 2, Step 6, already read the time t _a timer a that has started. If τ ₀ or less, the process of this time is ended with the flag f = 1, and next time the process proceeds from step 2 to step 6 again.

When the time t _a exceeds τ ₀ , the first stage ends, the process moves from step 7 to step 9, and the torque T of the motor M is limited to T _A. This is PMC
CPU 102 reads the set value T _A from shared RAM 111, and the servo circuit 10 is read via NC CPU 101.
5 to the torque control unit. This limit value T
_A is sufficient for overcoming the friction of the movement of the injection unit 2 that has started to move, and for the motor M to bring the nozzle 6 into contact with the die 5 with the minimum force F ₀ . The minimum force F ₀ is such a force that the molten resin inside the cylinder 12 does not leak from the touch surface with the mold 5, and it is actually about 0.5 t although it varies depending on the type of resin.

Next, in order to detect the contact state between the nozzle 6 and the die 5, the torque T of the motor M is read in step 10 and compared with the above limit value T _{A in} step 11. If they are not equal, the process proceeds to step 12 and flag f
= 2, the processing of this time is ended. Since the torque limit of the motor M is set to T _A , the state of the second stage is reached.

Next time, since the stage 2 is started, the process proceeds from step 1 to step 2, step 3 and step 10, and the torque T of the motor M is read. If the torque T is not equal to the limit value T _A , f
= 2, the processing of this time is ended, and the processing is started again from step 10 next time.

When the torque T of the motor M becomes equal to the limit value T _A , the third stage is started, the timer b is made a star (step 13), and the time t _b is read (step 1).
4) This time t _b is compared with τ ₁ (step 1)
5). τ ₁ is practically 1 to 2 seconds. Time t _b
Does not exceed τ ₁ , the flag f = 3 is set and the current processing ends.

Next time, we will start in stage 3 so
The process proceeds from step 1 to step 2, step 3, and then step 14, and starts by reading the time t _b . Then, if the time t _b does not exceed τ ₁ , f = 3
The processing of this time is ended as it is, and step 14 is performed again next time.
Start with.

When the time t _b exceeds τ ₁ , it is determined that the nozzle 6 cannot advance, that is, the nozzle touch is completed, and the process proceeds to step 17, where the PMC CPU 102 completes the touch. Signal to RAM
It is stored in 110. Then, the timers a and b are reset (step 18), and the flag f = 0 is set to prepare for the next touch operation, and the current touch operation is ended.

Even if the touch operation is completed, the servo circuit 10
5 does not actually reach the tip of the nozzle D
Since the pulse distribution for moving to the point is performed, the motor M is driven in the direction of advancing the injection unit 2, and the contact between the nozzle 6 and the mold 5 is continued. And
The touch force F _T is the limit value T of the torque T of the motor M.
It is the minimum force F ₀ because it is limited to _A. The touch completion signal is used as a confirmation signal for starting the molding cycle operation by the mold clamping unit 1 and the injection unit 2 and a confirmation signal for switching the nozzle touch operation to the touch maintaining operation.

[Touch maintenance operation] PMC CPU 102
Confirms the touch completion signal and switches the touch operation of the nozzle touch unit 3 to the touch maintaining operation. At the same time, the injection molding machine is operated in the molding cycle to drive the mold clamping unit 1 and the injection unit 2 including the ejection mechanism. In the molding cycle operation, as shown in FIG. 4, the mold closing process to the ejecting process are sequentially circulated, and the tip of the nozzle 6 is kept in contact with the mold 5 during this period. However, the touch force F _{T at} that time is changed so as not to become excessive according to the flow of FIG.

That is, in the touch maintaining operation, PM
The CPU 102 for C first reads the output value P of the load sensor 14 of the injection unit 2 (step 1), then calculates the torque T _P that the motor M should currently exert, and commands this (step 2). Ends the process. The next cycle is processed similarly. F (P) in the conversion formula is ^{f (P) = πd 2/} 4 × p [d ... nozzle hole diameter, p ... injection pressure, back pressure] in this example. However, a conversion formula obtained from detailed simulations or experiments may be used.

In this process, with respect to the nozzle position, the torque of the motor M rises to eliminate the position deviation in the error register of the servo circuit 105 because the nozzle tip always stays at the C point before this in response to the movement command to the D point. _Create a situation where T is limited by the torque limit value T _lim . That is, the tip of the nozzle 6 maintains the touch with the die 5, and the touch force F _T is equal to the force when the motor M operates with the torque T _P. The size thereof is a size (F _R ) that opposes a reaction force received by the injection unit 2 and the like by the injection pressure and the back pressure during the operation of the molding cycle (F _R ), and does not cause resin leakage even at the minimum (F ₀ ). Is.

When the magnitude of the touch force F _T in the touch maintaining operation is shown as an example according to the step of the molding cycle operation, it is 0.5 t in the mold closing step in which neither injection pressure nor back pressure acts.
(Minimum force F ₀ ), 0.8 to 2 t in the injection process, 2-1 t in the pressure holding process, 0.5 to 1 t in the measuring process, 0.8 to 0.5 t in the cooling process, and the mold opening and ejection process. It is about 0.5t. The magnitude of the touch force F _T depends on the time or the screw 1 during the injection process, the pressure holding process, and the measuring process.
The change greatly depends on the position of 3.

[Touch Release Operation] When a predetermined number of molding cycles are achieved, the molding cycle operation of the injection unit 2 ends, so the PMC CPU 102, which confirms this, ends the touch maintaining operation of the nozzle touch unit 3, Switch the nozzle touch operation to the touch release operation. The touch release operation is processed according to the flow of FIG. 7. That is, first, in step 1, it is determined whether the flag f = 0. If f = 0, it means that the touch release operation is in the beginning, so the process proceeds to step 2.
Send back command to point. In step 3, it is determined whether the point A has been reached, and if it has not reached point A, in step 4 the flag f
After setting = 1, the processing of this time is ended. During this time, the injection unit 2 continues to retreat toward point A.

Next time, since the flag f = 1, the process shifts from step 1 to step 3 to determine again whether the point A has been reached.
If not, this process is repeated every cycle until it arrives. Eventually, the signal from the limit switch P
When the arrival at the point A is confirmed by the arrival signal received by the MC CPU 102, the process proceeds from step 3 to step 5, and the touch completion signal is stored in the RAM 110 (step 5). Then, the flag f = 0 is set, and this processing ends. As described above, the nozzle touch operation that executes the present invention ends (referred to as the first embodiment).

As described above, in the nozzle touch operation in which the present invention is executed, the touch force F _T is always the minimum force F ₀ or more, and the injection unit 2 is driven by the injection pressure or the back pressure (F during the measuring process). Since the force F _R that balances with the reaction force received does not exceed the magnitude of the above-mentioned minimum force F ₀ , the force that the stationary platen 4 must support is minimized.

FIG. 8 is a flow chart of the touch operation relating to the second embodiment. As shown by the chain line in FIG. 2, the nozzle touch unit 3 is provided with the proximity switch 17, and in the same configuration as the first embodiment, the nozzle is When the tip of 6 reaches the position B immediately before contacting the mold 5, the PMC CPU
102 is configured to be detected.

Point B is a position where the forward speed of the injection unit 2 is reduced to protect the mold. This position after other words, if limiting the torque T of the motor M to T = T _A, a large force to the stationary platen 4 unnecessarily during nozzle touch does not act. Therefore, the timer a in the flow of FIG.
It is unnecessary, in the flow of FIG. 8, after reaching the point B (step 5), to speed the slow injection unit 2 (set value) torque T of the motor M (step 7) T = T _A
I am trying. The other points are not particularly different from those of the first embodiment.

In FIG. 9, the nozzle touch unit 3 is provided with a spring 9 for applying a touch force, a proximity switch 17 for detecting the B point, and a proximity switch 18 for detecting the touch completion.
Regarding the touch operation, the forward speed of the injection unit 2 is made slow at the point B, and the touch force F _T is applied by the elastic force of the spring 9 compressed to the touch completion position. This touch force F _T is the minimum force F ₀ and corresponds to the torque T = T _A of the motor M.

FIG. 10 shows the nozzle touch unit 3 of FIG.
In the flowchart of the touch operation relating to the third embodiment executed in step 1, after the moving speed is set to be slow (step 6), the injection unit 2 waits until it moves forward and reaches the touch completion position (step 7). When the completion of touch is confirmed by the signal from the proximity switch 18, the PMC CPU 102 reads the torque T of the motor M at that time (step 9), and commands this as the torque limit value T _lim of the motor M (step 10). ). Therefore, the timer b in the second embodiment is also unnecessary.

Other than that, there is no particular difference from the case of the second embodiment. Since the torque limit value T _lim is substantially the torque value T _A corresponding to the minimum force F ₀ , in the touch maintaining operation subsequent to the touch operation, the spring 9 is further compressed forward from the touch completion position, It will oppose the load received by the injection unit 2.

The above is an embodiment, and the present invention is not limited to the specific configurations shown and described. In the touch maintaining operation, the force F _R balanced with the reaction force received by the injection unit 2 is calculated from the output value P of the load sensor (step 2), but the injection process of the molding cycle operation by the injection unit 2 or the like is performed. If these values are preset in order to control the injection pressure, the holding pressure, or the back pressure in the pressure holding process or the measuring process, these set values are read out and used for the above conversion. You can also In that case, the flow of touch maintenance operation is C for PMC.
The PU 102 may not be executed every processing cycle of the PU 102 but may be executed every time these values are switched.

[0052]

Since an unnecessarily large touch force does not act on the fixed platen, the fixed platen does not fall down and the parallelism of the mold plate is less likely to change.

[Brief description of drawings]

FIG. 1 shows a main part of an injection molding machine (conventional example).

FIG. 2 is a main part of an injection molding machine (first embodiment).

FIG. 3 is a configuration of an NC device.

FIG. 4 is a block diagram of a nozzle touch operation.

FIG. 5 is a flow chart of a touch operation (first embodiment).

FIG. 6 is a flowchart of a touch maintaining operation (first embodiment).

FIG. 7 is a flow of a touch release operation (first embodiment).

FIG. 8 is a flow chart of a touch operation (second embodiment).

FIG. 9 is a main part of an injection molding machine (third embodiment).

FIG. 10 is a flow chart of touch operation (third embodiment).

[Explanation of symbols]

 1 Clamping unit 2 Injection unit 3 Nozzle touch unit 4 Fixed plate 5 Mold 6 Nozzle 7 Motor (conventional example) 8 Ball screw / nut mechanism 9 Spring 10 Brake 11 Proximity switch (touch completion position) 12 Cylinder 13 Cylinder 14 Load sensor 15 Servomotor for weighing 16 Servomotor for injection 17 Proximity switch (point B position)

Claims (1)

[Claims] 1. A motor M for driving a nozzle touch unit is a servomotor, which is placed under the control of a numerical controller provided in an injection molding machine, and the operation of the nozzle touch unit is a touch operation, a molding cycle of an injection unit or the like. The operation is divided into a touch maintaining operation and a touch releasing operation corresponding to the operation, and the nozzle touch force F _T with respect to the mold is set to the minimum force F ₀ within the range capable of preventing resin leakage in the touch operation, and the injection unit receives the touch maintaining operation. A nozzle touch method, wherein the force is equal to the reaction force F _R and the minimum force F ₀ is added.