JPS5950503B2 - injection molding method - Google Patents

Description

Detailed Description of the Invention The present invention relates to an injection molding method in which injection molding is performed by switching the injection pressure in two stages, which can prevent the occurrence of molding during injection, and can also eliminate defective losses due to variations in filling amount. The purpose is to provide an injection molding method.

In conventional injection molding, the injection molding pressure is constant, and the amount of filling is kept to the minimum necessary to prevent burrs, thereby reducing the occurrence of blemishes.

However, the problem was that variations in the amount of filling resulted in increased occurrence of chipping and blurring of the molded product, causing defects.

In order to eliminate such drawbacks, Japanese Patent Application Laid-Open No. 50-1267
In No. 58, the injection speed and injection pressure are controlled as shown in FIGS. 7a and 7b.

In other words, when molding the molding material with an injection molding machine, the screw or plunger that fills the molding material is injected at high speed and high pressure during the injection process until the resin is filled with an amount close to the volume of the sprue runner of the mold. The speed and pressure are reduced at the screw or plunger position corresponding to a part of the sprue runner being filled with the forming material, and the runner dividing surface is closed with solidified forming material, and then the predetermined pressure and speed are increased to fill the mold cavity. Immediately before completing the filling of the molding material into the mold cavity, the speed and pressure are once lowered below the predetermined pressure and speed to complete the filling, and then the pressure is reduced to the predetermined pressure or higher than the predetermined pressure. It is designed to be held for a certain period of time.

However, in such conventional examples, it is very difficult to set the time required for the pressure to rise above a predetermined pressure after lowering the pressure/speed (this varies depending on the temperature, molding material, and injection pressure), and If the pressure was increased above the level, there was a possibility that the excess material would come out.

The present invention has been made in view of the above points, and will be explained below with reference to the drawings.

FIG. 1 shows an apparatus for carrying out the method of the present invention, in which 1 is a mold on the cavity side, 2 is a mold on the core side, 3 is an ejector bin, 4 is a molded product, 5 is a molten molding material, and 6 is a cylinder. ,
7 is a hydraulic cylinder, 8 is an injection screw, 9 is a limit switch for changing injection pressure, 10 is a limit switch for stopping filling, 11 is an injection switching valve, 12 is a flow rate adjustment valve,
13 is a first stage injection pressure regulating valve such as an IJ IJ-F valve, 14 is a second stage injection regulating valve such as a relief valve,
15 is a second stage injection regulating valve such as a remote control valve.

Further, FIGS. 2a and 2l) are views showing the air bleed part, and there is an air bleed hole 1 between the ejector bin 3 and the hole 16.
7 is provided, and the air vent hole 17 is communicated with the air vent 18.

Also, Figure 3 is a chart diagram for injection molding, and Pl is injection molding 1.
Next pressure, P2 is secondary injection pressure, L is total injection stroke amount, Ll is primary injection pressure stroke (P1 stroke),
L2 is the injection secondary pressure stroke (P2 stroke), L
3 is the total injection secondary pressure stroke, L4 is the remaining injection amount stroke (cushion amount), H is the total injection time, and Hl is the injection 1
Next pressure time (P1 time), H2 is injection secondary pressure time (P
2 hours), H3 is the retention time.

Next, the method of the present invention will be explained using the above-mentioned apparatus.

First, the molding conditions are determined using a conventional molding method, and the filling of the molding material is set.

At this time, increase the weight of the one-piece molded product by 2 to 4%.

Also, set the injection pressure switching position.

In other words, a stroke of 4 to 5% of the total injection stroke L is taken from the injection completion position (set the filling amount to 94 to 85% with the volume control), and the injection pressure switching limit switch 9 is activated at that position. Set to .

Also adjust the injection pressure. Pl is adjusted by the first stage injection pressure regulating valve 13, and P2 is set below the mold clamping pressure.

How to set P2 is the injection pressure switching limit switch 9.
When the second stage injection pressure regulating valve 14 operates, the required pressure P is increased.
Set to 2.

Furthermore, the injection speed is set by the flow rate of the flow rate regulating valve 12.

Therefore, from the first stage injection pressure regulating valve 13, the hydraulic cylinder 7
When a hydraulic pressure of Pl is applied, the molten molding material 5 is injected by the injection screw 8, and is filled into the cavities, runners, sprues, and gates of the molds 1 and 2 under the pressure of Pl.

When 94% to 85% of the total filling amount is filled, stroke amount of Ll When the injection screw 8 moves, the injection pressure switching limit switch 9 is activated, the injection switching valve 11 is switched, and the hydraulic cylinder 7 is set to the second stage. A pressure of P2 is applied from the injection pressure regulating valve 14, and the molten molding material 5 is injected into the molds 1 and 2 at a pressure of P2.

After being filled with a stroke amount of L2 at a pressure of P2, the remaining amount is injected by a stroke amount of L4 during a holding time of H3, and the molded product 4 is molded.

In addition, in the above explanation, the first stage injection was set to 85% to 94% of the volume before filling was completed, as shown in the table below.
If it is less than 5%, the molded product will become blurred and cannot be injected, and if it is more than 94%, burrs will occur.

However, with four molded products, the per-boost amount is 131 g (total stroke amount 75 m/m).

As described above, in the present invention, injection is performed at a pressure lower than the mold clamping pressure before the injection is completed, so there is no rise in the parting surface of the mold, and the pressure is maintained at normal pressure in the range of 85% to 94% before the filling is completed. The first stage of injection is carried out at Furthermore, since the pressure is simply switched from normal pressure to below the mold clamping pressure, the device settings are extremely simple.

Moreover, since the present invention is stable, mold opening is eliminated, the dimensions of the molded product are stabilized, damage to the mold parting surface due to burrs is eliminated, and the molding cycle is shortened.

Further, in the second aspect of the present invention, since the amount of molding material filled is increased by 2 to 4%, insufficient filling due to variations in the amount of filling is eliminated.

The present invention will be explained in more detail below using examples.

<Example 1> ■) Molding machine Matsuda ■-100B used ME system nozzle 2) Mold (a) Circuit breaker and cover 4-hole mold used
.

(b) Runner diameter φ4mm (c) Sprueless mold Sprue length 9mm diameter, φ8 3) Molding method The injection pressure is controlled in two stages to shorten the injection time, allowing injection in the conventional injection special injection time. In order to eliminate this, the pressure is lowered before the injection is completed, and the pressure is controlled by switching the solenoid valve with a signal from a limit switch and controlling the pressure by operating the second stage of the relief valve. As shown in the figure.

Here, each symbol is the same as in the previous explanation.

4) Molding material Use CY-9310-30 5) Molding conditions As shown in the table below.

(2) Appearance of the molded product (when the deformation condition P2 is 20 kg/cm□G), as shown in Figure 5a.

Here, 5 is a molded product, a is a burr, and C is a gas unevenness.

Also, P2 is 25 kg/cm2G ~ 40kg/cm2
In the case of G, as shown in Figure 5, P2 is 80 kg.
/cm□G, the result is as shown in FIG. 5C.

<Example 2> 1) Sample molding conditions Material - CY9310 (30) Mold temperature - Fixed part 190°C Movable part - 190°C Cylinder temperature - Front part 80°C Rear 40°C Temperature controller - 100°C Curing time - 38 seconds Injection pressure holding time - 10 seconds Mold clamping pressure car 130 kg/cm2 Injection pressure car 30 kg/cm2 130 kg/cm2 or more Two types of samples differing only in injection pressure were used.

2) Testing method A force of F was applied to the molded product 5 using an air micro universal testing machine as shown in FIG.

Tests were conducted for model numbers 11 to 14.

<Example 3> 1) Molding conditions: 1: General injection mold temperature 175°C/Acceptable, solid Cylinder temperature 70°C/Pre-40°C/Post-injection pressure 140kg/cm2 Mold clamping pressure 140kg/cn12 Curing time 80 Second material CY9310 7f&,,2: Two-stage injection pressure control method Molding mold temperature 175℃/OK, solid Cylinder temperature 70℃/front 40℃/post injection pressure 35kg/cm□ Mold clamping pressure 140kg/c1112 Curing time 80 Second material CY9310

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an example of an apparatus for carrying out the method of the present invention, Fig. 2a, 1) is a sectional view and side view showing the air bleed part of the same, and Fig. 3 is a chart for forming the same. Figure 4 is a chart explaining the molding of Example 1, Figure 5 a, l), and c are explanatory diagrams showing the external appearance of the molded product of Example 1, Figure 6 is the same as above. FIG. 7a is a perspective view showing the test method of Example 2. 1) is a chart diagram of a conventional example.

Claims (1)

[Claims] 1. The first stage injection is performed at normal pressure to a range of 85% to 94% before filling is completed, and then the second stage injection is performed at a pressure below the mold clamping pressure. injection molding method. 2. Perform the first injection at normal pressure to a range of 85% to 94% before filling is completed, and then perform the second injection at a pressure below the mold clamping pressure. ~4
Injection molding method characterized by making % extra.