JPS6260624A - Injection compression molding method for straight-hydraulic mold clamping system - Google Patents

Abstract

PURPOSE:To secure accuracy of a molded article in the direction of the thickness of the same, by a method wherein injection of resin is performed by interposing a spacer between partings of a mold, the spacer is shifted and eliminated from a space between molds at the time of slackening of the mold when the mold is opened slightly through pressure based on the injection of the resin and the resin filling in a cavity is compressed by performing secondary mold clamping. CONSTITUTION:Primary mold clamping of molds 1, 2 is performed by advancing and actuating the movable mold 2 by a cylinder 3 under an interposed state of a spacer 4. The inside of a cavity 1a of the molds 1, 2 clamped primarily is filled with molten resin 8 by injecting the same. In this instance, although an injection screw 7 begins an injection action at a point (c) lagging timewise slightly from a point (b) and the injection action is completed at a point (e), as the mold 2 becomes a slackened state wherein the mold is opened slightly through pressure of injection of the resin at a point (d) anterior to the point (e) a little timewise at this time, the spacer 4 is shifted and eliminated through a space between the molds 1, 2 during mold slackening time (t). The resin 8 filled out the cavity is made to compress by performing secondary clamping of the molds 1, 2 after shifting and breaking away of the spacer 4.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a direct pressure mold clamping injection compression molding method that is mainly used when molding plastic products with high dimensional accuracy.

[Conventional technology and its problems]

There are various methods for injection compression molding, but the most commonly used method is the direct pressure mold clamping method, which can be realized with a little modification to the injection molding machine of the mark. This is an injection compression molding method (method using a mold clamping device).

This injection compression molding method using the direct pressure mold clamping method includes a primary clamping process of a molding die, an injection process in which molten resin is injected and filled into the cavity of the primary clamped mold, and a The molded product is molded through three steps: a compression step in which the mold is secondary clamped and the resin filled in the cavity is compressed; this creates a high pressure inside the cavity that cannot be obtained with injection pressure alone, and also reduces the flow of molten resin. This method is often used as a molding method for molding plastic products with high dimensional accuracy because the molecular orientation (internal stress) that sometimes occurs is removed and the cavity shape can be accurately transferred.

However, this direct pressure mold clamping injection compression molding method
The timing of transition from resin injection to secondary mold clamping is determined by detecting the slight amount of mold opening due to resin injection, and the primary mold clamping stroke of the movable mold is controlled by limit switch signals, so it moves every stroke. Dimensional variations occur, and as a result, the dimensions of the molded product in the thickness direction are distorted.
There was a drawback that it was not possible to obtain molded products with high precision.

[Objective of the Invention] The object of the present invention is to solve the above-mentioned problems of the injection compression molding method using the direct pressure mold clamping method (variations in the primary mold clamping stroke), and to ensure accuracy in the thickness direction of the molded product. The aim is to provide an injection compression molding method using a direct pressure mold clamping method.

[Summary of the Invention] In order to achieve the above object, the injection compression molding method using the direct pressure mold clamping method of the present invention involves interposing a spacer between the mold parts prior to primary mold clamping, and molding the spacer with a spacer. The accurate primary mold clamping stroke of the movable mold is determined by mold clamping intervention between the spacers, and whether molten resin is injected into the cavity in the primary mold clamping state with this spacer intervention, or by the pressure of this resin injection. The spacer sandwiched between the molds is moved and separated from between the molds by utilizing the time when the molds are slightly opened (mold loosening time);
The present invention is characterized in that after the spacer is removed, the mold is secondary clamped to compress the resin filling the cavity.

[Embodiments of the invention]

Hereinafter, the injection compression molding method using the direct pressure mold clamping method of the present invention will be specifically explained with reference to the drawings. Figure 1 is an operation diagram of an injection compression molding machine using a direct pressure mold clamping method (a diagram showing the operation of the movable mold and injection screw in relation to time and stroke)
FIG. 2 is an explanatory diagram showing the primary clamping state of the molding mold and the state of resin injection into the cavity. In the figure, 1 is a fixed mold, 2 is a hydraulic cylinder 3 A movable mold to be clamped, 4 a spacer for determining the accurate primary mold clamping stroke of the movable mold 2, 5 a fluid pressure cylinder, solenoid, etc. for moving and separating the spacer 4 from between the molds 1 and 2. Reference numeral 6 indicates a limit switch for detecting the movement and separation of the spacer 4, and 7 indicates an injection screw for injecting and filling the molten resin 8 into the cavity la of the fixed mold 1 as shown in FIG.

The spacer 4 is placed at the front clamping position of the fixed mold 1 between the mold parts so that it is sandwiched between the molds 1 and 2 as shown in FIG. 2 during the primary clamping of the movable mold 2. As shown in Fig. 1, they are interposed and moved outward from the mold by a drive device 5. Therefore, depending on the size of the molds 1 and 2, there are two pieces on the top and bottom, or two on the top and bottom, or on the left and right sides. Changes will be made as appropriate, such as arranging 4 pieces.

Next, the injection compression molding method of the present invention will be explained in order of steps.

(1) Preparation process (pre-process of primary mold clamping) Spacer 4 for determining the accurate primary clamping state and loaf of the movable mold 2 prior to primary clamping of the molding molds 1 and 2
is interposed between the mold partings as shown in FIG.

(2) Primary mold clamping process With the spacer 4 interposed, the movable mold 2 is moved forward by the cylinder 3, and the molds 1 and 2 are primarily clamped. In this case, the movable mold 2 moves from point a shown in FIG. 1 to point b (moves the primary mold clamping stroke l shown in FIG. The mold is closed by sandwiching it (primary mold clamping completed).

(3) Injection step and spacer removal step Molten resin 8 is injected into the cavity Ia of the primary mold-clamped molds 1 and 2 to fill it as shown in FIG.

In this case, the injection screw 7 enters the injection operation at point C, which is slightly delayed from point b, and completes the injection operation at point e, but at this time, the mold 2 is at the end of the resin opening/1 injection. At point 6, which is a little earlier than point e, the mold is loosened due to the pressure of resin injection.Use this loosening to remove the spacer 4 from the front 11 within the mold loosening time. Move and remove from between molds 1 and 2.

(4) Compression step by secondary mold clamping After the spacer 4 is moved and removed, the molds 1 and 2 are secondary clamped to compress the cavity filling resin 8. That is, when the spacer 4 is moved and removed by the driving device 5, the limit switch 6 is activated, and the mold clamping cylinder 3 is moved forward again by this switch detection signal to enter the secondary mold clamping state.
The cavity filling resin 3 is continued to be compressed from point f to point g. At this time, the injection screw 7 retreats from point e to point h and waits for the next injection operation at this point h.

(5) Mold opening process During the compression process from point f to point g, the cavity filling resin 8 (molded product) is cooled and solidified, so after this molding is completed, the mold 2 is opened from point g by the operation of cylinder 3. It retreats to point i, and the opening of molds 1 and 2 is completed.

〔Effect of the invention〕

Since the injection compression molding method using the direct pressure mold clamping method of the present invention is as described above, it is possible to prevent variations in the primary mold clamping stroke with the spacer and to ensure accuracy in the thickness direction of the molded product. It's cold.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram showing an injection compression molding machine using a direct pressure mold clamping method in relation to an operation diagram (a diagram showing the operation of the movable mold and injection screw in relation to time and stroke). The figure is an explanatory diagram showing the state of primary clamping of the molding die and the state of resin injection into the cavity. DESCRIPTION OF SYMBOLS 1... Fixed mold, 1a... Cavity, 2... Movable mold, 3... Hydraulic cylinder, 4... Spacer, 5
... Spacer drive device, 6... Limit switch,
7... Injection foam, Ryu, 8... Molten forged resin.

Claims (1)

[Claims] The primary clamping process of the molding die, the injection process of injecting and filling the molten resin into the cavity of the primary clamped mold, and the secondary clamping of the mold after filling the resin into the cavity to fill the cavity. In a direct pressure mold clamping injection compression molding method in which a molded product is molded through three steps, including a compression process in which resin is compressed, an accurate primary mold clamping stroke of a movable mold is determined prior to the primary mold clamping of the mold. A spacer is inserted between the mold partings, and the spacer is sandwiched between the molds by primary mold clamping, and resin is injected into the cavity.The pressure of this resin injection causes the mold to open slightly. An injection compression molding method using a direct pressure mold clamping method, characterized in that the spacer is moved and removed from between the molds when the mold loosens, and after the spacer is removed, the mold is secondary clamped to compress the resin filling the cavity.