JPS6242818A - Injection-controlling device - Google Patents

Abstract

PURPOSE:To surely prevent flashes from developing by a method wherein a mold clamping oil pressure, under which the changing-over from filling during injection to dwelling during injection is performed, is set within a range corresponding to the range of the displacement of a mold parting face so as to change over to the dwelling during injection by means of the set displacement of the mold parting face. CONSTITUTION:A displacement-detecting device of the parting face 8 is used to detect a gap (delta) or a displacement sensor 21 sends an output in proportion to the gap (delta) through a lead wire 21a. A mold clamping oil pressure PC under which the changing- over to dwelling during injection is performed is set. In addition, the displacement deltaC of the parting face at the time when mold clamping pressure P reaches PC within the rising range (a) of mold clamping pressure is memorized. When the displacement (delta) of the parting face reaches deltaC in the filling section (f) during injection, the section (f) is changed over to the dwelling section (h) during injection. Further, because the maximum mold clamping oil pressure PE is set at a setter so as to set PC to satisfy the condition of O<PC<PE, the relation of deltaE<deltaC<deltaD is also satisfied. Because the relation of deltaC<deltaD is kept, no opening of the parting faces occurs and consequently no flashes develop.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an injection holding pressure switching control device using mold parting surface displacement, which can be applied to injection molding machines, die casting machines, etc.

(Prior Art) Fig. 5 shows an overview of a conventional injection molding machine and its control circuit diagram. FIG. 6 shows a graph of controlled variables by the same control circuit.

In FIG. 5, l is a mold clamping cylinder, 2 is a mold clamping ram inside the cylinder l, 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 side mold attached to the movable mold board 4;
107 is a stationary side mold attached to the stationary mold board 5, and 20 is a molded product cavity.

Further, the raw resin is supplied from a hopper (not shown) to the right side of the line 95140 in the cylinder 13 in the figure, and is melted and plasticized by heating by a heater (not shown) and rotation of the screw j4 driven by the hydraulic motor 8, and then transferred to the front of the screw 14. and stored as molten resin 12.

On the other hand, by sending pressure oil from the hydraulic inflow source 34 to the illustrated side of the injection cylinder via the servo valve 38, the screw 14 is advanced to the left in the figure via the injection ram 16 and the bearing box 17. The molten resin I2 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, 35.37 is an IJ valve, and 36 is a switching valve.

Next, in FIG. 6, Po is the injection oil pressure of the injection cylinder 15, which is the detected value of the oil pressure sensor 32. VF is screw 1
The forward speed of 4 is commonly referred to as the injection speed. t is time, I, T1. ITJ and IV indicate the injection section. Usually, the injection speed VF is changed as shown in ■ to ■ to prevent molding defects and improve quality. Further, in the section (2), a constant injection hydraulic pressure is applied to compensate for the cooling shrinkage of the molten resin in the molded product cavity 2o during injection holding. Furthermore, I,
The sections 1 and 2 may be set based on the screw position detected by the screw position sensor 19 instead of time.

Target control is performed as shown in the solid line graph in FIG.

The dotted line graph shows the dependent variable value portion of each solid line.

Pmax is the set value of the relief valve 37. The amount of injected oil is controlled by the servo valve shown in Figure 5 so that in each section from I to ■, VP (constant value part) as shown, and in the section ■, Po (constant value) as shown in the figure. Control.

However, in this conventional example, an overshoot of the injection oil pressure as shown by arrow B in Fig. 6 occurs, and even if the injection holding oil pressure Po in section (■) is constant, the oil temperature, machine temperature, mold temperature, resin temperature, etc. are constant. As a result, the important resin pressure inside the mold cavity may vary.

Furthermore, due to condition fluctuations or incorrect setting of conditions, the resin pressure inside the cavity may overcome the mold clamping force and push the parting surface of the mold open, causing molten resin to overflow into the opened gap and causing cracks. In injection molding, once a break occurs, it tends to become a habit and can also damage the mold. As described above, in the conventional example, variables that are directly connected to Paris are not detected and controlled, and therefore Paris cannot be reliably prevented.

(Problems to be Solved by the Invention) As mentioned above, conventional injection control devices often have the problem of forming flashes on the mold parting surface, damaging the mold. Measures were taken to solve the problems and reliably prevent the occurrence of Paris.

(Means for Solving the Problems) For this reason, the present invention sets the switching point from injection filling to injection holding pressure using the mold clamping oil pressure or mold clamping force within the mold clamping pressure increase section,
The mold parting surface displacement δC corresponding to this mold clamping oil pressure or mold clamping force is automatically detected and stored, and during injection filling, when the mold parting surface displacement reaches δC, the switch is made to injection holding pressure. This structure is used as a means to solve problems.

(Function) In the above configuration, the switching to injection holding is performed by the set mold clamping oil pressure or mold clamping force, and the parting surface displacement corresponding to the set value is automatically detected and stored when the mold clamping pressure is increased, and the injection filling is performed. When the parting surface displacement reaches the above memorized value, the injection holding mode is switched.

(Example) An example of the present invention will be described below with reference to the drawings. Figures 1 to 3 show an example of the present invention, Figure 1 shows an outline of an injection molding machine and its control circuit, and Figure 2 shows an outline of an injection molding machine and its control circuit. 3 is an enlarged sectional view of a part in which a parting surface displacement detection device, which is the main part of the present invention, is incorporated, and FIG. 3 shows the main circuit of the controller of the present invention.

In FIG. 1, a mold 7, a parting surface displacement detection device 8, which will be described later, and a lead wire 21, which will also be described later. Since the components other than a and the controller 30 are the same as the conventional device shown in FIG. 5, the explanation of these same components will be omitted.

Next, to explain in detail the part indicated by A in Fig. 1, which is the main part of the present invention, the details of the part indicated by A are shown in Fig. 2, and 6P is the parting surface of the movable mold; 7P is a stationary mold parting surface, and 21 is a displacement sensor, which is fitted into the sleeve 22. For installation, the sleeve 22 has shoulders 22a on its outer periphery at the large diameter part and the small diameter part.
One end of the small-diameter side is fixed to the stationary mold 7, and the other end is attached to the large-diameter side with a rubber pad 23 attached to prevent the sleeve 22 from coming off, as shown in Figure 1. The dimensions are such that the rubber pad 23 is slightly compressed when the mold is closed.

24 is a set screw, and the displacement sensor 21 is attached to the mounting sleeve 2.
This is to prevent you from getting out of 2. 21a 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.

The sleeve 22 is press-fitted, for example, into the stationary mold 7, and the shoulder portion 22a of the sleeve 22 is firmly attached to the mold 7. However, during use, this shoulder 22
If the adhesion of a becomes loose, it will cause an error in the gap measurement, so
To prevent this, when the mold is closed, the sleeve 22 is always pressed against the shoulder 22a by the rubber pad 23.

In FIG. 3, 31 is the same oil pressure sensor as shown in FIG. 1, 21 is the same displacement sensor as shown in FIG. 2, and 40
is a setting device for mold clamping oil pressure Pa for switching from injection filling to injection holding pressure.

41 and 42 are amplifiers, 43 and 44 are comparators, and 47 is a signal line. In the figure, when the mold clamping oil pressure P≧PaO, a signal is output (ON) from the comparator 43. 45 is a memory device that stores the parting surface displacement force δ from the signal line 46 when the signal from the comparator 43 switches from OFF to ON, and stores the parting surface displacement force δ at that time.
Outputs 0 to the signal line 48. The direct line of this δ0 is the signal line 47
There is no change while the signal from
When switched to FF', it is cleared to O. A signal 49 is turned on only during the injection process, and the comparator 44 operates only when the signal 49 is turned on. 50 is a switching signal from injection filling to injection holding pressure, which is output (ON) from the comparator 44 when the signal 49 is ON and δ≧δ0.

Next, to explain the operation of the above embodiment, in FIG. 1, the switching well 36 transfers the pressure oil from the hydraulic inflow source 33 to the mold closing cylinder 1 (on the left side of the figure) or the mold opening side (on the left side of the figure). (on the right side of the figure). 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 I, causing the mold clamping ram 2, and therefore the movable mold platen 4 and the movable mold 6 connected thereto, to the right side. Method: Move and perform the mold closing action. On the contrary, solenoid 1]
When energized, the 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 performs the mold opening operation. In addition, in the neutral position where neither solenoids a nor b are energized,
Oil on both the mold closing side and the mold opening side are open 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 held there.

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 through the injection ram I6 and the 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 wires 2 + and a. Now, in FIG. 1, the displacement detected by the parting surface displacement detection device 8 (gap δ in FIG. 2) is calculated by the controller 3.
0, and the controller 30 performs injection control as shown in FIG. 4 using the circuit shown in FIG.

Now, to explain Fig. 4, the graphs of mold clamping pressure and parting surface displacement have a common time axis, and the same point in time is indicated in both graphs by the same alphabenoto symbol with subscripts 1 and 2 respectively. represent. In the same figure, δ1 is the parting surface displacement immediately after each of the molds 6 and 7 is closed, and when no clamping force is applied. In addition, in the mold clamping pressure increase section a, the parting surface displacement represented by the gap δ in Fig. 2 decreases, and the minimum value δ
reach ya. The bend at point 02 indicates that the mold clamping pressure is sufficient. At point 02 (corresponding to point G on the mold clamping pressure graph), the hydraulic pressure inflows into the oil solution in time to maintain the mold clamping. This is because the amount of oil in 33 is reduced.

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.
The maximum displacement δC is reached at point C, where the injection and holding pressure section is switched.

In the section, the resin pressure decreases as the resin inside the cavity 20 cools, so the compressive deformation increases again.
Therefore, the parting surface displacement (gap δ) decreases again.

The maximum displacement δ0 is the initial displacement δ. If it is smaller, the parting surface is not open and no paris will occur.

On the contrary, δ. is δ. (If the parting surface becomes thicker, 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, the parting at the switching point C from the injection filling section to the injection holding section The surface displacement δ. must be set so that δ.<δ0.

The circuit shown in FIG. 3 sets the mold clamping pressure Pc for switching the injection holding pressure shown in FIG.
When reaching 7111''-Pc (points C1 and q correspond), the parting surface displacement at that time is stored as δ. 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 and holding pressure section. That is, instead of setting δC, Pc is set,
δC is automatically calculated from Pc. Further, the maximum mold clamping oil pressure Pg is also set by a setting device not shown, and since its value is known, Pc can be set so as to always satisfy O<PC<P8, so that δ8<δ. 〈δ0
The relationship will also be satisfied. In this way, δ0〈δ,
Since this relationship is maintained, the parting surface will not open and no cracks will occur.

On the other hand, if δ0 is too close to δ8, there is a risk of switching from injection filling to injection holding pressure before the molded product cavity is sufficiently filled. Since it corresponds to ~δ0, it is easy to set the mold clamping oil pressure Pc for injection holding pressure switching to be sufficiently smaller than the maximum mold clamping oil pressure P8 (for example, half of P8), so that δ0 and 9 are not close to each other. It can be done.

In addition, when detecting the parting surface displacement δ, errors occur due to the influence of temperature and other environments, but in this device, in every cycle of injection molding, the parting surface displacement δ corresponding to the set mold clamping pressure Pc for switching injection holding pressure is detected. Since the parting surface displacement δC is detected and used, the error affects only within one cycle, and the injection holding pressure switching control based on the parting surface displacement has good accuracy. Incidentally, since the mold clamping oil pressure and the mold clamping force are in a proportional relationship, it is possible to easily change the above example to use the mold clamping force in place of the mold clamping oil pressure by incorporating a conversion circuit therefor.

(Effects of the Invention) As described above in detail, according to the present invention, injection can be performed within the range of 0 to maximum mold clamping oil pressure (or maximum mold clamping force) corresponding to the mold parting surface displacement range during mold clamping. Switching from filling to injection holding pressure The mold clamping oil pressure (or mold clamping force) is set, and the mold parting surface displacement at that setting value causes the switch to injection holding pressure. In addition, automatic detection of mold parting surface displacement, which is compatible with the mold clamping oil pressure (or mold clamping force) set above, is used for each injection molding process. By performing the process every cycle, the influence of errors in detecting displacement of the mold parting surface can be sufficiently eliminated, thereby ensuring the accuracy of injection holding pressure switching control.

[Brief explanation of the drawing]

Fig. 1 is a side view of an injection molding machine showing an embodiment of the present invention and a schematic diagram of its control circuit, Fig. 2 is an enlarged view of part A in Fig. 1, and Fig. 3 is the main circuit of the controller of the present invention. Figure 4 is a diagram showing the relationship between mold clamping pressure increase and elapsed time during injection, mold clamping oil pressure, and parting surface displacement. Figure 5 is a side view of a conventional injection molding machine and an overview of its control circuit. 6 are diagrams showing changes in injection control variables in the prior art. Description of main parts of diagram

Claims (1)

[Claims] The switching point from injection filling to injection holding pressure is set by the mold clamping oil pressure or mold clamping force in the mold clamping pressure increase section, and the mold parting surface displacement δ_0 corresponding to this mold clamping oil pressure or mold clamping force is automatically set. An injection control device characterized by detecting and storing the detection and switching to injection holding pressure when the mold parting surface displacement reaches δ_0 during injection filling.