JP2623162B2 - Injection molding machine nozzle touch method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a nozzle touch method for an injection molding machine.

2. Description of the Related Art As a mechanism for moving an injection unit to perform a nozzle touch operation, a gear motor or a servomotor moves the injection unit forward through a drive mechanism such as a chain or a ball screw, and a nozzle position at the tip of a cylinder is used as a proximity switch. The brake is applied to the motor when the contact between the nozzle and the mold sprue is detected, and the nozzle touch force is held by the elastic energy of the spring interposed between the injection unit and the drive mechanism. Is known.

In a configuration using a servo motor as a drive source, usually, a first nozzle touch at the start of a molding operation is performed by operating a jog feed switch or the like that drives and controls an injection unit. In a sprue break during a molding operation, The injection unit is driven and controlled by a control device that sets the retreat position and the moving speed of the injection unit at the time of the spre break, and manages the approach / separation operation of the nozzle.

However, when a mold with a non-standard sprue is attached to the fixed platen or when the nozzle of the cylinder is replaced, the mold touch position with respect to the fixed platen changes variously, The proximity switch and the like for detecting is located on the fixed platen side and does not necessarily have sufficient detection accuracy, so the amount of deformation of the spring that holds the nozzle touch force also changes variously,
It is difficult to secure a constant nozzle touch force.

In addition, since there is a time delay from when the motor driving the injection unit starts to start and reaches the set number of revolutions, when the retreat distance of the injection unit at the time of the spre break is set to be short, There is no guarantee that the movement speed of the injection unit will reach the set speed during the movement process. Therefore, it is also difficult to maintain a constant impact force at the time of nozzle contact.

In addition, in order to improve the cycle of the molding operation, it is desirable to speed up the spre-break operation to some extent.However, if the moving speed of the injection unit is increased, the impact at the time of touching the nozzle increases, so that the mold or the nozzle The disadvantage is that the exhaustion of the device becomes severe. Particularly, in a configuration in which a spring is interposed between the injection unit and the driving mechanism, since there is a degree of freedom of movement between the injection unit and the driving mechanism, a motor or a driving mechanism is required to position the nozzle at the nozzle touch position. It is difficult to apply a sufficient static force to the injection unit itself even if the
There is a disadvantage that a strong impact acts upon contact with the nozzle.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate these drawbacks of the prior art, secure a constant nozzle touch force, and further reduce the impact force at the time of nozzle contact to perform a high-speed sprue break operation. It is an object of the present invention to provide a method for touching a nozzle of an injection molding machine that can perform the method.

Means for Solving the Problems The upper limit of the output torque of the servomotor is limited to a torque corresponding to the nozzle touch force, the servomotor is driven, the injection unit is advanced, and the tip of the nozzle is brought into contact with the mold sprue.

Also, at least one or more speed switching positions are set,
Each time the forward-moving injection unit reaches the speed switching position, the moving speed of the injection unit is sequentially switched to low speed, and when the injection unit reaches the final speed switching position, the upper limit of the output torque of the servo motor corresponds to the nozzle touch force The nozzle tip is brought into contact with the mold sprue.

Furthermore, after once positioning the advancing injection unit at the final speed switching position, the upper limit of the output torque of the servomotor is limited to a torque corresponding to the nozzle touch force, and the servomotor is driven again to advance the injection unit. The tip of the nozzle is brought into contact with the mold sprue.

After the tip of the nozzle is brought into contact with the mold sprue, the servomotor is braked when the positional deviation between the movement command position and the current position exceeds a set value to maintain the nozzle touch force.

Operation Since the servomotor is driven by limiting the upper limit of the output torque of the servomotor to the torque corresponding to the nozzle touch force, the contact force of the nozzle tip against the mold sprue, that is,
The nozzle touch force is kept constant.

At least one or more speed switching positions are set, and the moving speed of the injection unit at the time of nozzle contact is low by successively switching the moving speed of the injection unit to a low speed every time the advancing injection unit reaches the speed switching position. And the careless impact is reduced.

When moving forward, the injection unit is once positioned at the final speed switching position and decelerated, the upper limit of the output torque is limited to the torque corresponding to the nozzle touch force, and the servomotor is driven again to bring the nozzle tip into contact with the mold sprue. By doing so, the moving speed of the injection unit at the time of nozzle contact is reliably reduced, and careless impact is appropriately mitigated.

Since the servomotor is braked when the positional deviation between the movement command position and the current position exceeds the set value, it is necessary to accurately detect nozzle contact and maintain the nozzle touch force. Can be.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a nozzle touch mechanism of an electric injection molding machine according to one embodiment for carrying out a nozzle touch method of the present invention, and a main part of a control device of the electric injection molding machine.

In the figure, reference numeral 1 denotes a base frame serving as a body of an electric injection molding machine, reference numeral 2 denotes a fixed platen, reference numeral 3 denotes an injection unit, and an injection cylinder 5 to which a nozzle 4 is mounted is fixed to the injection unit 3. ing.

The fixed platen 2 having the through hole 6 for nozzle insertion is firmly fixed on the base frame 1, and the injection unit 3 is slidably fitted on the base frame 1 so as to be movable along the injection axis. A speed reducer 7 is fixed to a lower portion of the base frame 1, and a ball screw 8 serving as a rotation output shaft of the speed reducer 7 is screwed into a ball nut 9 provided integrally with a lower portion of the injection unit 3. . An output shaft 11 of a servo motor 10 serving as a drive source of the injection unit 3 is connected to an input shaft of the reduction gear 7, and a brake device 12 for mechanically fixing the output shaft 11 of the servo motor 10 is provided.

Reference numeral 100 denotes a control device for controlling the electric injection molding machine. The control device 100 includes a microprocessor for numerical control (hereinafter, referred to as an NC CPU) 108 and a microprocessor for a programmable machine controller (hereinafter, PMC).
The PMC CPU 110 is used for a ROM 113 storing a sequence program for controlling a sequence operation of the injection molding machine, and for temporarily storing data.
The RAM 106 is connected. The CPU 111 for the NC has a ROM 111 storing a management program for controlling the entire injection molding machine,
Also, a servo circuit for driving and controlling a servomotor of each axis for the injection unit 3, for direct movement of the screw, for clamping, for rotating the screw, for the ejector, and the like is connected via the servo interface 107. However, in FIG. 1, only the servo motor 10 for the injection unit and the servo circuit 101 of the servo motor 10 are shown.

Reference numeral 105 denotes a non-volatile shared RAM composed of a valve memory and a CMOS memory, a memory section for storing an NC program for controlling various operations of the injection molding machine, and various setting values, parameters, and macro variables relating to molding conditions and the like. And a setting memory unit for storing Reference numeral 109 denotes a bus arbiter controller (hereinafter referred to as a BAC). The BAC 109 includes an NC CPU 108 and a PMC CPU 110, a shared RAM 105, an input circuit 104, and an output circuit 103.
Are connected, and the bus to be used is controlled by the BAC 109. Reference numeral 114 denotes a manual data input device (hereinafter referred to as CRT / MDI) with a CRT display device connected to the BAC 109 via the operator panel controller 112. The CRT / MDI displays various setting screens and work menus on the CRT display screen. By operating operation keys (soft keys, numeric keys, etc.), various setting data can be input and a setting screen can be selected. 102 is the CPU for NC
A RAM connected to the bus 108 is used for temporary storage of data and the like.

The servo motor 10 for the injection unit 3 is provided with a pulse coder that detects the rotation of the servo motor 10 and detects the amount of movement of the injection unit 3 with respect to the nozzle 4. The drive control output is connected to the servomotor 10, while the feedback pulse from the pulse coder is connected to the servo circuit 101. An error register for detecting a position deviation between the current movement command position and the current position of the injection unit 3 by subtracting the feedback pulse from the distribution pulse input at predetermined intervals via the servo interface 107. And a current position register for positively calculating the feedback pulse and storing the current position of the nozzle 4. Also, the servo motor 10 is provided in the servo circuit 101.
A torque limit circuit that limits the upper limit value of the output torque to is provided, and the torque limit value is set according to a command from the output circuit 103. The brake device 12 has an output circuit 103
The output shaft 11 of the servomotor 10 is mechanically fixed or released in response to an ON / OFF command from the controller.

The description of the servo circuits for each axis such as for direct operation of the screw, for the clamping, for the rotation of the screw, and for the ejector will be omitted.

In the above configuration, the control device 100
The PMC CPU 110 performs sequence control with the NC program for controlling each operation of the injection molding machine stored in 105, the parameters of various molding conditions stored in the setting memory unit, and the sequence program stored in the ROM 113. The NC CPU 108 distributes pulses to servo circuits of each axis of the injection molding machine via the servo interface 107, and controls the driving of the injection molding machine.

In the nozzle touch method of this embodiment, in addition to the normal molding conditions, a speed switching position set for switching the forward speed of the injection unit 3 and a moving section divided by the speed switching position The set moving speed of the injection unit 3, the upper limit value (hereinafter referred to as the torque limit value) of the output torque of the servo motor 10 set for each moving section, and the completion of the nozzle touch operation are detected. The set value ε is set and stored in the shared RAM 105 in advance. Table 1 shows the relationship between the set values, taking as an example the case where the speed switching position is set in two steps.

For the sake of explanation, the coordinate system is defined by a straight line along the injection axis of the cylinder 5, and the coordinate value indicating the position of the injection unit 3 is represented by the tip position of the nozzle 4. Therefore, the tip position of the nozzle 4 and the current position of the injection unit 3 have the same value. Further, the direction in which the nozzle 4 moves toward the fixed platen 6 is defined as a positive movement direction, and the coordinate origin is set at the retreat limit position where the nozzle 4 is farthest from the fixed platen 6 (see FIG. 1).

In Table 1, the torque limit value PR ₂ is an upper limit value of the output torque set when the tip of the nozzle 4 reaches the _second speed switching position P ₂ which is the final speed switching position, that is, the nozzle touch force. Is the torque limit value corresponding to. After the tip of the nozzle 4 comes into contact with the mold sprue, the speed switching position P ₃ is further subjected to pulse distribution to the servo circuit 101 to drive the servo motor 10, and the nozzle touch force equal to the torque limit value PR ₂ Is output, and is not a substantial speed switching position. Accordingly, the final target value P ₃ of the movement command is set to the movable platen toward exceeds the maximum value of the nozzle touch position varies by the influence of such sprue and nozzle exchange, the speed of the final speed switching position P ₂ and the first stage switching position P ₁ is set to the origin side of the coordinate system so as not to exceed the minimum value of the nozzle touch position varies (see FIG. 1). Usually, not set torque limit for movement section which is divided by the speed switching position P ₁ and the coordinate origin of the first stage. Further, for convenience of drive control described later, it is desirable speed switching position P ₁ of the first stage is to be set to a fixed platen 6 nearer retracted position of the nozzle 4 tip during sprue break, usually in Table 1, V ₁ > V ₂ >
V ₃ and PR _1> relation of PR ₂ is established. In addition, the value of the set value ε is such that the output torque of the servo motor 10 is the torque limit value.
It is set larger than the value of the error register when reaching the PR _2.

FIG. 3 is a flowchart showing an outline of a program for the nozzle touch process stored in the ROM 111.
It is started by a nozzle touch command from the CPU 110 or a nozzle touch command from a manual switch (not shown) provided in the injection molding machine main body.

The NC CPU 108 that has received the nozzle touch command first shares
Speed switching positions P ₁ and P ₂ set in RAM 105 and final target position P
₃ and the moving speeds V ₁ , V ₂ , V set for each moving section
₃ and the torque limit values PR ₁ , PR ₂ , and the set value ε are read and stored in the RAM 102 (step S 1), and an injection unit movement command is output to the servo circuit 101 for the servo motor 10 to start pulse distribution processing. (Step S2). However, the target position of the movement command in step S2 is the final speed switching position P ₂
, And the movement speed is V _1. No torque limit is set.

Since a torque limit for limiting the output torque is not set in the servo circuit 101, the servo motor 10 starts driving with a strong torque, and strongly drives the injection unit 3 through the reduction gear 7, the ball screw 8, and the ball nut 9. accelerated, towards the injection unit 3 in the sprue break position or any retracted position to the final speed switching position P _2, as shown in Figure 2, movement section to be divided by the speed switching position P ₁ and the coordinate origin moving at a high moving speed V ₁ corresponding to. However, FIG. 2 shows that the initial position of the injection unit 3 is at the coordinate origin.

NC for CPU108 movement to the start of the injection unit 3, a current position storage register sequentially reads the stored value P _N, the nozzle 4 the tip of the current position P _N is the speed switching position P of the first stage ₁ of the servo circuit 101 It is determined whether or not has reached (step S3),
If not reached, it causes a constant speed moves the injection unit 3 at the moving speed V ₁ of the this state.

Nozzle 4 current position P _N is the speed switching position of the first stage of the tip P ₁
Is reached, then the NC CPU 108
Is a low-speed moving speed V ₂ corresponding to a moving section in which the moving speed of the injection unit 3 is divided by the first-stage speed switching position P ₁ and the final speed switching position P ₂ by switching the speed setting override value. and sets change, the torque limit value PR ₁ corresponding to the movement section is set to the torque limit circuit of a servo circuit 101 (step S4), and the speed switching position P ₁ of the first stage to the final speed switching position P ₂ towards causes a constant speed moves the injection unit 3 at a slower speed V ₂ (see Figure 2).

The pulse distribution processing of movement commands output in step S2 is completed and the current position of the nozzle 4 the tip has reached the final speed switching position P ₂ (step S5), and as shown in Figure 2, injection unit 3 stops temporarily.

Since the final speed switching position P ₂ is set to the origin side of the coordinate system so as not to exceed the minimum value of the nozzle touch position varies, at the stage of positioning the final speed switching position P ₂ has been completed, in FIG. 2 as shown, the position of the nozzle 4 tip is located in the coordinate origin closer than the true nozzle touch position P _X,
The tip of the nozzle 4 does not contact the mold sprue.

After positioning the injection unit 3 to the final speed switching position P _2, for NC CPU 108 further corresponds to a movement section that is divided a moving speed of the injection unit 3 by the final speed switching position P ₂ and the final target position P ₃ while reset to the low speed of the moving speed V _3,
Reconfigure the torque limit value PR ₂ corresponding to the nozzle touch force to the torque limit circuit of a servo circuit 101, starts the final target position move command output to again pulse distribution processing to the servo circuit 101 to the P ₃ and the movement target and (step S6), and the final target position P ₃ to the injection unit 3 from the final speed switching position P2
Is moved at a low speed with a force corresponding to the nozzle touch force (see FIG. 2).

The injection unit 3 moves forward gradually to bring the tip of the nozzle 4 into contact with the end face of the mold sprue. However, since the movement is at a low speed, the impact when the nozzle is touched is small. Although the tip of the nozzle 4 is forward of the injection unit 3 and abuts against the end surface of the mold sprue is inhibited, the moving command to the servo circuit 101 is set to the final target position P ₃ to the servo circuit 101 pulses The distribution processing is continuously executed, and the deviation between the sum of the distribution pulses input to the servo circuit 101 at predetermined intervals and the feedback pulse, the speed, and the difference between the current command position and the current position of the injection unit 3 are described. The value of the error register for detecting the positional deviation is gradually increased.

NC CP that started pulse distribution processing in step S6
The U108 reads the position deviation from the error register of the servo circuit 101, and sequentially determines whether or not the position deviation has reached the set value ε. If not, the pulse distribution process is continued (step S108). S7).

During this time, the position deviation of the error register gradually increases,
While the drive current of the servo motor 10 increases the tip of the nozzle 4 is pressed against the mold sprue in gradually strong force, the upper limit of the output torque is restricted by the torque limit value PR ₂ set in the torque limit circuit since the final nozzle touch force does not become _more torque limit value PR.

When it is detected that the position deviation value of the error register further increases and reaches the set value ε, the NC CPU 1
08, the mold sprue abuts regarded as the nozzle touch operation is completed at a predetermined nozzle touch force the tip of the nozzle 4 corresponding to the torque limit value PR _2, brake system 12
And the output shaft 11 of the servo motor 10 is mechanically fixed, the movement of the injection unit 3 is inhibited, and the nozzle 4
The nozzle touch force between the tip and the mold sprue is maintained (step S8). The value of the set value ε is set to be larger than the value of the error register when the output torque of the servo motor 10 reaches the torque limit value PR2, so that the stage before the output torque of the servo motor 10 reaches PR ₂ There is no inadvertent feed stop, and
Since the upper limit value immediately output torque at the stage where the output torque reaches the PR ₂ is restricted, it is possible to always maintain a constant contact force without causing excess or deficiency in the nozzle touch force.

The NC CPU 108 that activated the brake device is a servo circuit.
Following the positional deviation accumulated in the error register 101, the torque output to the servo motor 10 is stopped, and the nozzle touch processing is terminated (step S9). The nozzle touch force in the injection holding pressure process is held by the rigidity and elastic force of the ball screw 8 and the drive mechanism components to which the tension is applied in the axial direction. During a break, the operation of the brake device 12 is released and the servo motor 10 is released.
Is driven in the reverse direction to retract the injection unit 3 to a desired sprue break position, and a nozzle touch operation similar to that described above is repeatedly executed by a second nozzle touch operation.

In the present embodiment, since the moving speed and the torque limit value are individually set for each moving section divided at the speed switching position, the injection unit 3 is moved at a high speed in the first moving section to perform nozzle touch. While reducing the required time, the moving speed of the injection unit 3 is reduced in a short moving section divided by a final speed switching position set before the nozzle touch position to reduce the impact at the time of nozzle contact. Therefore, even if the spre-break operation is accelerated to shorten the molding time, no inadvertent impact occurs when the nozzle is touched, and a high-speed and stable injection molding operation can be performed. The speed switching position may be set in multiple stages.

Further, since the pressure accumulating means such as a spring is not used to hold the nozzle touch force, the structure is simple, and the deceleration and positioning operation of the drive mechanism are directly transmitted to the injection unit 3, so that the speed reduction and the positioning can be performed. In addition, it is possible to prevent an accident in which only the injection unit 3 pops out by inertia and the tip of the nozzle 4 comes into contact with the mold sprue.

Moreover, those in the nozzle 4 tip final target position P ₃ is the tip mold sprue nozzle 4 from being set to the movable platen toward exceeds the maximum value of the nozzle touch position varies by the influence of such sprue and nozzle exchange The injection unit 3 can be reliably advanced until it touches, and at the stage where the completion of the nozzle touch is determined by the value of the positional deviation, the output torque of the servo motor 10 reliably reaches the torque limit PR ₂ corresponding to the nozzle touch force. because equal, it is possible to even if the true nozzle touch position P _X varied with sprue and replacement of the nozzle to always ensure a constant nozzle touch force. Instead of detecting the position deviation in the process of step S7 and confirming the completion of the nozzle touch,
A pressure sensor is provided between the ball screw 8 and the ball nut 9 to detect the actual pressure between the nozzle 4 and the mold sprue, and when the pressure reaches a set pressure, it is determined that the nozzle touch is completed. May be.

Further, since after once stopping the injection unit 3 at the stage where the tip of the nozzle 4 has reached the final speed switching position P ₂ to re-drive the servo motor 10 so that to perform the nozzle touch, terminal velocity switching position P ₂ change retracted position of the injection unit at the time of the previous set speed changes and sprue break does not affect at all the motion during nozzle contact, impact during nozzle abutment always constant. It is not always necessary to stop the injection unit 3 at the stage of reaching the final speed switching position P _2,
The torque limit value at the stage of pulse distribution to the final speed switching position P ₂ is performed and PR _2, the final target position P at the moving speed V ₃
Pulse distribution of up to _three movement commands may be performed.

Effect of the Invention The nozzle touch method of the present invention drives the servomotor by limiting the upper limit value of the output torque of the servomotor to a torque corresponding to the nozzle touch force. No pressure accumulating means is required, the configuration is simple, and the nozzle touch force does not change due to the change of the nozzle touch position, so that the contact force of the nozzle tip against the mold sprue is always maintained at a constant value. Can be.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a main part of a nozzle touch mechanism of an electric injection molding machine and a control device of the electric injection molding machine according to one embodiment for carrying out the nozzle touch method of the present invention, and FIG. Principle of operation showing an example nozzle touching method, third
FIG. 5 is a flowchart showing an outline of a nozzle touch process by the control device of the electric injection molding machine of the embodiment. DESCRIPTION OF SYMBOLS 1 ... Base frame, 2 ... Fixed platen, 3 ... Injection unit, 4 ... Nozzle, 5 ... Injection cylinder, 6 ...
… Through-hole, 7… reduction gear, 8… ball screw,
9: Ball nut, 10: Servo motor, 11: Output shaft, 12: Brake device, 100: Control device, 101: Servo circuit, 102: RAM, 103: Output circuit, 104: Input circuit, 105: Shared RAM, 106: RAM, 107: Servo interface, 108: Microprocessor for numerical control, 109: Bus arbiter controller, 110: Microprocessor for programmable machine controller,
111… ROM, 112… Operator panel controller, 1
13… ROM, 114… Manual data input device with CRT display.

Claims (4)

(57) [Claims] In a nozzle touch method for performing a nozzle touch operation by controlling a servo motor for moving an injection unit along an injection axis by a control device, an upper limit value of an output torque of the servo motor corresponds to a nozzle touch force. A nozzle touch method for an injection molding machine, characterized in that the servomotor is driven with torque limited, and the injection unit is advanced to bring the nozzle tip into contact with a mold sprue. 2. A nozzle touch method for performing a nozzle touch operation by driving and controlling a servo motor for moving an injection unit along an injection axis by a control device, wherein at least one or more speed switching positions are set, and the injection proceeds forward. Every time the unit reaches the speed switching position, the moving speed of the injection unit is sequentially switched to low speed, and when the injection unit reaches the final speed switching position, the upper limit of the output torque of the servo motor is changed to the torque corresponding to the nozzle touch force. A nozzle touch method for an injection molding machine, wherein the servomotor is driven with a restriction, and a nozzle tip is brought into contact with a mold sprue. 3. After the injection unit that is moving forward is once positioned at the final speed switching position, the upper limit of the output torque of the servomotor is limited to a torque corresponding to the nozzle touch force, and the servomotor is driven to drive the injection unit. 3. The nozzle touch method for an injection molding machine according to claim 2, wherein the nozzle tip is brought into contact with the mold sprue by moving forward. 4. An injection unit is advanced to bring a nozzle tip into contact with a mold sprue, and a servomotor is braked when a positional deviation between a movement command position and a current position exceeds a set value. 4. A nozzle touch method for an injection molding machine according to claim 1, wherein the touch force is maintained.