JPS63102917A - Injection controlling apparatus - Google Patents

Abstract

PURPOSE:To mold a molding without burrs with automatic measuring, by controlling the displacement of the parting face of a mold and the plasticizing measuring position of a screw by means of a specific sensor set on the mold. CONSTITUTION:A detecting device 8 with a displacement sensor is set on a mold 7 to detect the displacement 8 of parting faces of molds 6 and 7. deltaD is a displacement of the parting face in a state where no clamping force is applied just after the molds 6 and 7 are closed. By clamping the mold (a), the displacement of the parting face decreases and reaches the min. value deltaE. Then, a resin pressure in a molding cavity 20 acts to open the molds 6 and 7 in the injection filling period (f) and the displacement of the parting face thereby begins to increase and reaches a displacement deltaC. At this point, it is switched to the injection dwelling period (h), where a servo valve 38 is worked to make the displacement of the parting face to be constant value deltaS and an injection is controlled. The parting face does not thereby open and no burr occurs.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an injection control device that automatically adjusts the screw metering position of an injection molding machine.

(Prior Art) FIG. 7 shows an outline of a conventional injection molding machine and its control circuit diagram.

In FIG. 7, 1 is a mold clamping cylinder, 2 is a mold clamping ram inside the cylinder, 3 is a tie bar connecting the mold clamping cylinder 1 and the fixed mold platen 5, and 4 is supported by the tie bar 3 so as to be movable back and forth. It is also a movable mold board connected to the mold clamping ram 2.

6 is a movable mold attached to the movable mold platen 4, 107 is a fixed mold attached to the fixed mold platen 5, and 20 is a molded product cavity.

Further, by sending pressure oil from the hydraulic pressure inflow source 90 to the hydraulic motor 18 via the switching valve 91, the screw 14 connected to the hydraulic motor 18 is rotated. And the raw resin is
It is supplied from a hopper (not shown) to the right side of the screw 14 in the cylinder 13 in the figure, and is melted and plasticized by heating by a heater (not shown) and rotation of the screw 14 driven by a hydraulic motor 18, and then sent to the front of the screw 14. It is stored as molten resin 12.

On the other hand, by sending pressure oil from the hydraulic inflow source 34 through the servo valve 38 to the illustrated side of the injection cylinder, the screw 14 is advanced to the left in the drawing via the injection ram 16 and the bearing box 17, and the screw The molten resin 12 at the tip of 14 is injected into the molded product cavity 20. In the figure, 130 is a controller, 19 is a position sensor, 31.32 is an oil pressure sensor, 33 is an oil pressure inflow source for the mold clamping cylinder 1, 35.37 is a relief valve, and 36 is a switching valve.

The amount of molten resin 12 stored in front of the screw 14 is
It must be necessary and sufficient to fill the molded product cavity 20 and at the same time compensate for the cooling shrinkage of the molten resin within the cavity 20.

If the amount of the molten resin 12 is insufficient, short shots and sink marks may occur, resulting in poor molding. Moreover, if the amount is too large, the molded product cavity 20 will be overfilled, causing cracks.

The amount of the molten resin 12 is determined by the operator setting the screw position at which melting and plasticization by rotation of the screw 14 is stopped, that is, the metering position, and when the screw position detected by the position sensor 19 reaches the set value, the switching valve is activated. 91 to the neutral position to cut off the pressure oil to the hydraulic motor 18 and stop plasticization. However, since the measurement position has to be set by trial and error, it may take time to determine the appropriate setting value, or the amount of molten resin 12 may be too large, causing flakes and damaging the mold. do. Therefore, setting the weighing position is a troublesome task that requires the driver to use his/her nerves.

(Problem to be Solved by the Invention) In other words, according to the conventional method, the operator has to set the measuring position for melting and plasticizing by trial and error, which takes time and effort to optimize the measuring position. Alternatively, there is a problem in that too much metering may result in formation of molding chips and damage to the mold.

The present invention aims to solve these problems and provide an injection control device that automatically optimizes the melting and plasticizing metering position without causing molding flash.

(Means for Solving the Problems) Therefore, the present invention provides a detection means provided on the parting surface of a mold to detect the displacement of the parting surface when the mold is closed, and a value detected by the detection means and a target value. It has a control means that compares the values and controls the displacement of the mold parting surface during injection to a target value, and also has a screw stroke position detection means, and the most advanced screw position during injection detected by the detection means is a constant target. The injection side 'a device is characterized in that it has a correction means for correcting the screw metering position by the amount of deviation from the value, and this is used as a means for solving the above-mentioned problem.

More specifically, in the present invention, the displacement of the mold parting surface at low mold clamping force immediately after the mold is closed is stored as a reference point, and the displacement of the mold parting surface is prevented from returning to the reference point during injection. At the same time, the screw metering position is automatically corrected by the amount that the most advanced screw position during injection deviates from a fixed target value.

(Function) In this way, the mold parting surface displacement at low mold clamping force immediately after the mold is closed is used as the reference point, and injection control is performed so that the mold parting surface displacement does not return to the reference point.
There is no risk that the mold parting surface will open during injection.

On the other hand, since the screw metering position is automatically corrected by the amount that the most advanced screw position deviates from the constant target value, the most advanced screw position is brought closer to the constant target value every shot, thereby optimizing the metering position.

(Example) Hereinafter, typical examples to which the present invention is applied will be described in detail with reference to the drawings.

Embodiments of the present invention are shown in FIGS. 1 to 6. Fig. 1 shows an overview of the injection molding machine and its control circuit, Fig. 2 shows an enlarged sectional view of the part in which the parting surface displacement detection device, which is the main component of the present invention, is incorporated, and Fig. 3 shows the controller. Figure 4 shows the main circuit for parting surface displacement control, Figure 4 shows a change graph of parting surface displacement, Figure 5 shows the control circuit for controller screw metering position correction, and Figure 6 shows a flowchart for screw metering position correction. .

In FIG. 1, the parts other than the mold 7, the parting surface displacement detection device 8, which will be described later, the lead wire 21a, which will also be described later, and the controller 30 are the same as the conventional device shown in FIG. The explanation of the parts will be omitted.

Next, the main part of the present invention, which is indicated by A in FIG. 1, will be explained in detail.
As shown in the figure, 6p is a parting surface of the movable mold 6, 7p is a parting surface of the stationary mold 7, and 21 is a displacement sensor, which is fitted into a sleeve 22. For installation, the sleeve 22 has shoulders 22 on its outer periphery at the large diameter part and the small diameter part.
The small diameter side of one end is fixed to the stationary mold 7, and the other end has a rubber pad 23 attached to the large diameter side to prevent the sleeve 22 from coming off. The dimensions are such that the rubber pad 23 is slightly compressed when the mold is closed.

Further, 24 is a set screw, which is used to prevent the displacement sensor 21 from coming off from the sleeve 22. 2
1a is a lead wire of the displacement sensor 21, which is guided to the outside of the mold and connected to the controller 30 shown in FIG. For installation, the sleeve 22 is press-fitted into, for example, the stationary mold 7, and the shoulder 22a of the sleeve 22 is firmly attached to the mold 7. However, during use, this shoulder 2
If the tightness of the sleeve 2a loosens, it will cause an error in the gap measurement, so to prevent this, when the mold is closed, the sleeve 22 is always mounted so that it is pressed against the shoulder 22a side by the rubber pad 23. There is.

In FIG. 3, 31 is the same oil pressure sensor as shown in FIG. 1, and 21 is the same displacement sensor as shown in FIG. 50 is mold clamping oil pressure p for switching from injection filling to injection holding pressure;
51 is the mold clamping oil pressure p which gives the target value of the injection holding pressure.
This is the setting device for number 3.

40 and 41 are amplifiers. Reference numeral 70 denotes a signal line which is output as a signal (ON) by the comparator 55 when the mold clamping oil pressure is equal to or higher than the switching setting value for injection holding pressure (pkpc).

60 is a memory device in which the signal from the signal line 70 changes from OFF to OFF.
The parting surface displacement manual force δ from the signal line 65 when the switch is not switched to N is stored, and the value δC at that time is output to the signal line 75. This δ. The value is cleared from 80 to 0 when a reset signal is input.

Similarly, 71 is a signal line which outputs a signal (O
N), at that time, the memory 61 stores the parting surface displacement manual force δ from the signal line 66, and transmits the value δ, to the signal line 7.
6, and holds the value of δ while no reset signal is input from 81. Note that the reset signals from 80 and 81 are input at the start of every cycle of injection molding (at the start of mold closing). Further, the parting surface displacement δ is always outputted from the signal line 42.

On the other hand, in FIG. 5, numeral 19 is the same position sensor as shown in FIG. 1, and detects the position of the screw 14, which moves back and forth integrally with the bearing box 17. Reference numeral 82 denotes an amplifier, whose output X is the screw position, and the signal is inputted to the microcomputer 88 through a signal line 83. The microcomputer 88 also has a signal line 84 that is ON during injection.
During other operations, an OFF signal is input, and from another signal line 85, an ON signal is input during plasticization by screw rotation, and an OFF signal is input during other operations. According to the flowchart in FIG. 6, an ON signal is output to the signal line 86 when the plasticization measurement is completed, and an OFF signal is output during other operations.

In FIG. 6, xo is the target value for the most advanced screw position, and is initially given a constant value a. XF is the target value of the most retracted screw position during plasticization, that is, the metering position, and first, the maximum screw stroke value as the molding machine specifications or an arbitrary value is given as b. As shown in the flowchart of the same figure, let the most advanced screw position of each injection be X, and △X
=Xo−x, and set X and +ΔX as new x.

Next, to explain the operation of the above embodiment, in FIG. 1, the switching valve 36 directs the pressure oil from the hydraulic inflow source 33 to the mold closing side (left side in the figure) or the mold opening side (left side in the figure) of the mold clamping cylinder 1. right side) and supply it. That is, when the solenoid a is energized, the pressure oil from the hydraulic inflow source 33 flows to the left side of the mold clamping cylinder 1, causing the mold clamping ram 2, and therefore the movable mold platen 4 and the movable mold 6 connected thereto, to the right side. move towards
Perform mold closing action. Conversely, when solenoid b is energized, pressure oil from the hydraulic inflow source 33 flows to the right side of the mold clamping cylinder 1, moves the mold clamping ram 2, movable mold platen 4, and movable mold 6 to the left, and opens the mold. performs an action. Also, solenoid a
, b In the neutral position where neither is excited, the mold closing side,
When the mold is opened, both sides of the oil are opened to the tank.

When the mold closing operation is performed by energizing the solenoid a as described above, after the mold is closed, the mold clamping pressure rises to the set pressure of the relief valve 35 and is maintained. Further, the injection operation is performed after the mold clamping pressure has increased sufficiently.

Next, explaining the injection operation, by sending pressure oil from the hydraulic inflow source 34 through the servo valve 38 to the illustrated side of the injection cylinder 15, the screw 14 is moved to the left side of the figure via the injection ram 16 and bearing box 17. The screw is moved forward, and the molten resin 12 at the tip of the screw 14 is injected into the molded product cavity 20. Note that the relief valve 37 is a safety valve that provides relief when the oil pressure increases too much.

Further, the parting surface displacement detecting device 8 detects the gap δ in FIG. 2. That is, in Figure 2,
The displacement sensor 21 generates an output (voltage or current) proportional to the gap δ through the lead wire 21a. Now, in FIG. 1, the displacement detected by the parting surface displacement detection device 8 (gap δ in FIG. 2) is sent to the controller 30, and the controller 30 uses the circuit shown in FIG. Performs injection control.

In FIG. 4, the graphs of mold clamping oil pressure and parting surface displacement have a common time axis, and in both graphs, the same alphabetical symbol with a suffix of 1.2 represents the same point in time. In the same figure, δD is the parting surface displacement immediately after each of the molds 6 and 7 is closed, and when no clamping force is applied. Further, in the mold clamping pressurization section a, the parting surface displacement represented by the gap δ in FIG. 2 decreases and reaches the minimum value δ, due to compressive deformation of the mold due to the increase in the parting surface bearing pressure.

Subsequently, in the injection filling section f, the molded product cavity 20
Since the resin pressure acts in the direction of opening the mold, the compressive deformation decreases and the parting surface displacement begins to increase.
displacement δ. At the 0 point, which is reached, the process switches to the injection and holding pressure section. In the section, the hydraulic pressure acting on the injection cylinder 16 is controlled by the servo valve 38 in FIG. 1 so that the parting surface displacement is maintained at δ (a constant value).

The above δ. If and δ are smaller than the initial displacement δゎ, the parting surface is not open and no paris occurs.

On the contrary, δ. Alternatively, if δS becomes larger than δD, the parting surface will open, and there is a risk that the molten resin in the cavity 20 will flow out onto the parting surface and become flaky. Therefore, δ0<δ. It must be set so that δ and <δ.

By the circuit shown in FIG. 3, the mold clamping oil pressure pc for injection holding pressure switching shown in FIG. 1) c
and p, respectively (point C,, C2 and point St,
S2 corresponds to each), and the parting surface displacement at that time is δ, respectively. and δ.

Next, in the injection filling section f, the parting surface displacement δ is δ. When it reaches (corresponds to point C), it switches to the injection holding pressure section. During the injection pressure holding period, the injection hydraulic circuit controls the parting surface displacement δ to maintain it at δ (constant value) as described above.

That is, instead of setting δゎ and 63, set pc and p, and δ from pc and δ from ps.

are automatically calculated.

The maximum mold clamping pressure p□ is set with a setting device (not shown) and the value is known, so it is sure that Q<p, , <pE, and O<p
p and p can be set so that s<1)E. Therefore, δE〈δ,〈δD, and δ,〈δ,kuδ. becomes. δ. , δ.

are both smaller than δ, so the parting surface does not open and no paris occurs.

On the other hand, in the measurement correction circuit shown in Figs. 5 and 6, the difference between the target value x0 and the actual value Since the position Xr is corrected, the screw most advanced position approaches the target value x0, and the screw plasticization metering is optimized.

(Effects of the Invention) As described above in detail, according to the present invention, the displacement of the parting surface is controlled so that the parting surface does not open during injection, so no paris occurs, and on the other hand, the screw is adjusted at every shot. Since the measuring position of the screw plasticizer is changed to compensate for the difference between the target value and the actual value of the forward position, the operator does not have to set the measuring position of the screw plasticizer at all, and it is possible to safely and without causing damage. Weighing can be reliably optimized. That is, the troublesome work of setting and adjusting the measuring position for screw plasticization becomes unnecessary.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of an injection molding machine and its control circuit showing an embodiment of the present invention, Fig. 2 is an enlarged view of part A in Fig. 1, and Fig. 3 is a parting surface of a controller applied to the present invention. The main circuit diagram for displacement control, Fig. 4 is a graph showing changes over time in mold clamping oil pressure and parting surface displacement, Fig. 5 is a control circuit diagram for screw metering position correction of the controller of the present invention, and Fig. 6 is a graph showing changes over time in mold clamping oil pressure and parting surface displacement. FIG. 7 is a flowchart of screw metering position correction, and is a schematic diagram of a conventional injection molding machine and its control circuit. Explanation of main parts of the figure 6, 'l--Mold 8--Parting surface displacement detection device 14--Screw 19- Screw position sensor

Claims (1)

[Claims] A detection means is provided on the parting surface of the mold to detect the displacement of the parting surface when the mold is closed, and a value detected by the detection means is compared with a target value to target the displacement of the mold parting surface during injection. It has a control means for value control, a screw stroke position detection means, and a correction means for correcting the screw metering position by the amount that the most advanced screw position at the time of injection detected by the detection means deviates from a constant target value. An injection control device comprising: