JPH0767610B2 - Injection molding method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for controlling the position of a cylinder piston of a cylinder device in a molding machine such as a die casting machine,
In particular, the present invention relates to a method of controlling the position of the cylinder piston of an injection cylinder and a pressurizing cylinder of an injection molding machine or a die casting machine that injects and fills a material into a mold to control the mold opening.

[Prior Art] FIG. 2 and FIG. 3 are longitudinal sectional views showing a main part of a die-casting machine for molding a disc wheel, and FIG.
~ (E) is a diagram showing a molding process, and Fig. 2 (f) is a second diagram.
FIG. 3D is an enlarged view of part A of FIG. 3D, and FIG. 3 is a block diagram showing the overall configuration. As shown in the figure, the upper mold 33, the lower mold 35 that can be opened and closed in the vertical direction, and the four cores 34 that can move in the horizontal direction are combined and clamped from the vertical direction in the drawing by a mold clamping mechanism (not shown). Then, in the cavity 38 formed thereby, the molten metal 37 in the injection sleeve 39 is injected by the action of an injection cylinder (not shown) into the injection plunger 36 and the plunger tip 36 that integrally operates with the injection plunger 36.
Fill with the ascending action of a.

FIG. 2 (a) shows a state in which the injection sleeve 39 containing the molten metal 37 is brought into contact with the lower mold 35 and the runners of the injection sleeve 39 and the cavity 38 are connected, and FIG. 2 (b) shows The injection plunger 36 is lifted so that the molten metal 37 becomes the gate portion 38 of the cavity 38.
indicates a state of reaching a, and generally, for example, JP-A-63
As shown in Japanese Patent Publication No. 40659, thereafter, the rising speed of the injection plunger 36 is reduced so that the molten metal 37 is gently injected into the cavity 38 without scattering. Normal,
This timing is detected by detecting the position of the injection plunger 36 with a limit switch (not shown) or the like, and at the same time, a cooling timer for "mold opening" described later is started. FIG. 2 (c) shows a state in which the molten metal 37 is completely filled in the cavity 38, and is obtained by detecting that the working pressure of the injection cylinder (not shown) exceeds a predetermined pressure value. After a lapse of a predetermined time (pressurization time lag) from the completion of filling of 37, the solenoid 23 of the direction switching valve 23 shown in FIG.
By exciting a, the pressure plunger 40 attached to the cylinder piston 32 of the pressure cylinder 31 is projected into the cavity 38, and the molten metal 37 in the cavity 38 is added, as shown in FIG. 2 (d). The pressurizing action is performed so as to match the shrinkage allowance (solidification shrinkage) accompanying the cooling of the molten metal 37.
In FIG. 3, 5 is a pump, 4 is a motor for driving the pump 5, and 7 is a tank, which constitutes a pressure source for driving the pressurizing cylinder 31. As shown in FIGS. 2D and 2F, in the final stage of pressurization, the pressurizing plunger 40 is lowered to the position of the gate portion 38a of the cavity 38 (gate seal position). That is, the pressure plunger 40 having a diameter slightly smaller than that of the gate portion 38a and having a narrow gap d between the inner peripheral surface of the gate portion 38a is lowered to the gate seal position to form a thin molten metal solidified product 41. Then, when the cooling timer described above is completed, the clamp by the mold clamping mechanism and the pressurization by the injection plunger 36 are released, and as shown in FIG. By performing the mold opening operation between the mold 33 and the core 34 and the lower mold 35, a thin portion 41 formed between the molded product 42 and the biscuit 43.
Is easily disconnected (hereinafter, the operation performed by the completion of the timing of these cooling timers is generically referred to as "mold opening").

[Problems to be Solved by the Present Invention] At this time, the operation of the pressure plunger 40 is performed from the time when the operation is started, for example, as the applicants have previously proposed in Japanese Patent Application No. 63-244552. That cavity over time
The best method is to control the history of the protrusion stroke amount into the 38 so as to follow a predetermined target locus. The reason is that the pressurizing plunger 40 and the upper die 33 change in size due to the amount of heat from the molten metal 37, but the state is not uniform due to the difference in the thermal expansion coefficient and the cooling state of the two, so simply By simply controlling the operating pressure of the pressure plunger 40, that is, the feeder force,
This is because the stroke behavior of the pressure plunger 40 is not uniform due to external factors such as changes in frictional resistance and insertion of molten metal, so that the above-described feeder action is not stable.

When controlling the protrusion stroke amount of the pressure plunger 40 so as to follow a predetermined target locus, first, the pressure plunger 40 is set with reference to the time t from the operation start time (t = 0) of the pressure plunger 40. The moving stroke amount st of the 40 into the cavity 38 is predetermined in the model unit 9 as a target locus. Deviation amount e between the moving stroke amount st that is the target locus and the actual moving stroke amount stb of the cylinder piston 32 detected by the position detector 3, that is, the pressurizing plunger 40.
(E = st-stb) is obtained by the deviation detection unit 10, the deviation amount e is received, the gain setting unit 8 appropriately processes it, and a predetermined output signal v corresponding thereto is output to the driver 12. The driver 12 outputs the output signal p in accordance with the magnitude of the output signal v from the gain setting section 8 to adjust the pressure adjusting valve 6 to control the pressure P of the pressure source. The model controller 9, the deviation detector 10, and the gain controller 8 include a feedback controller 11
Are configured.

By changing the working pressure that drives the pressure plunger 40 according to the deviation e between the target locus st and the actual movement stroke amount stb of the pressure plunger 40 in this way, the movement stroke amount of the pressure plunger 40 with respect to time is changed. However, since the follow-up control is performed so as to follow the target locus, it is possible to eliminate the factors of unstable operation such as the fluctuation of the sliding resistance of the pressure plunger 40 described above. In addition, since it is possible to simultaneously achieve reliable lowering of the pressure plunger 40 to the gate seal position shown in FIG. 2 (d), it is easy to open the die from the thin portion 41 that has been formed. The disc wheel, which is a molded product, is prevented from being distorted.

In such a technical background, in the conventional method in which the cooling timer is started from the middle of injection (FIG. 2 (b)) and the mold is opened upon completion of the cooling timer, the cooling is set in the model section 9 described above. The cooling timer must be set to a value that includes all the required time of the target trajectory. However, in order to adjust the molding conditions, (1) changing the rising speed of the injection plunger 36 and the plunger tip 36a from FIG. 2 (b) on and after starting the cooling timer, and (2) changing the pressurizing plunger 40 The predetermined working pressure value of the injection cylinder for detecting the completion of the filling of the molten metal 37 that determines the operation start point is changed, and (3) the pressurization time lag that starts the timing from the completion of the filling of the molten metal 37 is changed, (4) The cooling timer must be readjusted every time the target locus of the feedback controller 11 for controlling the operation of the pressurizing plunger 40 is changed, and the operation is very troublesome.

[Means for Solving the Problem] The moving stroke amount of the cylinder piston is predetermined as a target locus with respect to time, and the deviation amount between the moving stroke amount of the cylinder piston and the actual moving stroke amount is set as the target locus. Accordingly, by changing the cylinder chamber pressure that operates the cylinder piston, when the movement stroke amount of the cylinder piston is controlled to follow, the mold opening is performed based on time or when the movement stroke amount of the cylinder piston reaches a predetermined value. I issued a command.

[Operation] By performing the above means, the mold opening command depends only on the target locus of the feedback controller 11, and therefore, even if the adjustments of the items (1) to (4) described in the above problems are performed,
There is no place to reset each time.

When the time or the movement stroke amount of the cylinder piston reaches a predetermined value, the mold opening command is issued by taking the cooling time of the cast-molded product into consideration, the mold opening command is performed, and the mold is opened from the mold when the moving stroke amount of the cylinder piston reaches a predetermined value. Remove the molded product.

[Example] An explanation will be given according to FIG. It should be noted that elements having the same functions as those in the description of FIG.

The signal v processed and output through the model unit 9, the deviation detection unit 10 and the gain setting unit 8 is output to the driver 12. The mold opening commander 14 is programmed, for example, as shown in FIG. 4, receives the time t or the moving stroke st from the model unit 9, and receives the preset time t1 or the moving stroke st1. When the above is reached, the mold opening command vo is output to the controller (not shown). Here, the time t1 preset in the mold opening command device 14, or the movement stroke st1 is generally a value that covers the entire range of the target trajectory, that is, it takes the maximum value of the setting. For example, in the case where the mold opening command is given earlier and the pressure plunger 40 is operated in synchronization with the mold opening operation, the size may be smaller than that. In addition, the model part 9,
The deviation detection unit 10, the gain setting unit 8 and the mold opening command unit 14 constitute a feedback controller 15.

Now, as in Figs. 2 and 3, the upper mold 33, which can be opened and closed vertically,
The lower mold 35 and the four cores 34 that can move in the horizontal direction are combined, and clamped from the vertical direction in the drawing by a mold clamping mechanism (not shown), and in the cavity 38 formed thereby,
The molten metal 37 in the injection sleeve 39 is filled by the rising action of the injection plunger 36 and the plunger tip 36a that operates integrally with the injection plunger 36 by the action of an injection cylinder (not shown) (the molten metal 37 in the cavity 38 is shown in the figure. Filled state). After a lapse of a predetermined time (pressurization time lag) from the time when the filling of the molten metal 37 is completed, the pressure plunger 40 attached to the cylinder piston 32 of the pressure cylinder 31 is excited by exciting the solenoid 23a of the direction switching valve 23. The molten metal 37 is projected into the cavity 38 and the molten metal 37 in the cavity 38 is pressurized so that the molten metal 37 has a function of feeding in proportion to the shrinkage allowance (solidification shrinkage) accompanying cooling of the molten metal 37. The operation of the pressure plunger 40 is performed by the feedback controller 15 as described above.
It is configured to follow the st. At this time, in the feedback controller 15, the time t from the model unit 9 or the movement stroke st is output to the mold opening commander 14 together, and the preset time is set as shown in FIG. It is determined whether or not t1 or the movement stroke st1 or more. If the judgment condition is satisfied, a mold opening command vo is output to a controller (not shown) to release the clamp by the mold clamping mechanism and the pressure applied by the injection plunger 36, and the upper mold 33 and the core 34 and the lower mold 34. The mold is opened between the molds 35, and the thin portion formed by cutting is taken out to take out a molded product.

[Effects of the Invention] In the present invention, since the above is performed, the timing involved in the mold opening command is
Since it is determined only by the operating condition of the pressure plunger, complicated adjustment work becomes unnecessary.

[Brief description of drawings]

FIG. 1 is a block diagram showing one embodiment of an apparatus for carrying out the method of the present invention, and FIGS. 2 (a) to (e) show the operation sequence in one example of a conventional apparatus similar to the present invention. Fig. 2 (f) is a longitudinal sectional view, Fig. 2 (d) is an enlarged view of a part of Fig. 2 (d), Fig. 3 is a block diagram showing an example of the same conventional device as Fig. 2 (a) to (e), FIG. 4 is a flow diagram showing a part of the control state in the present invention. 3 ... Position detector, 6 ... Output adjustment valve, 8 ... Gain setting section, 9 ... Model section, 10 ... Deviation detection section, 11,15 ... Feedback controller, 12 ... Driver, 14 ... … Mold open commander, 31 …… Pressure cylinder, 33 …… Upper mold, 34 …… Core, 35 …… Lower mold, 36 …… Injection plunger, 37 …… Molten metal, 38 …… Cavity, 39 …… Injection sleeve, 40 ... Pressure plunger.

Claims (1)

[Claims] 1. A cylinder device for injecting, filling, and pressurizing a molding material into a mold is used, and a moving stroke amount of a cylinder piston is predetermined as a target locus with respect to time. Depending on the deviation amount between the movement stroke amount of the cylinder piston and the actual movement stroke amount,
When controlling the movement stroke amount of the cylinder piston by changing the cylinder chamber pressure that operates the cylinder piston, the mold is set based on time or when the movement stroke amount of the cylinder piston reaches a predetermined value. On the other hand, an injection molding method characterized in that a mold opening command is output.