JP3127391B2 - Pre-plastic injection molding machine and control method therefor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pre-plastic injection molding machine having an injection device and a plasticizing device separately, and a control method thereof.

[0002]

2. Description of the Related Art Conventionally, a prepra-type injection molding machine having an injection device and a plasticizing device separately is disclosed in, for example, Japanese Patent Application Laid-Open No. Hei 8-25.
No. 437.

[0003] This kind of pre-plastic injection molding machine basically comprises an injection device having an injection cylinder having an injection plunger therein and a plasticizing device having a heating cylinder having a plasticizing screw therein. The inside and the front end of the injection cylinder are connected to each other by a resin supply passage, and the supply port 50e of the resin supply passage 51 facing the inside of the injection cylinder 50 is connected to the front of the inner peripheral surface of the injection cylinder 50 as shown in FIG. It was open at the upper end.

In such a plastic injection molding machine, when a molding material (pellet) is supplied to a rear portion of a heating cylinder in a plasticizing apparatus, the molding material is plasticized by a rotating plasticizing screw and a heating cylinder. The plasticized resin L is supplied through the resin supply passage 51 from the supply port 50e to the front of the injection plunger 52 in the injection cylinder 50. As a result, the injection plunger 52 is retracted, the metering is performed, and when the injection plunger 52 is advanced by the end of the metering, the resin L is injected and filled into the mold cavity.

[0005]

However, in the above-described conventional pre-plastic injection molding machine, since the resin L supplied from the plasticizing device is supplied to the tip end of the injection cylinder 50, the resin L is supplied immediately before the injection plunger 52. The existing resin L is pushed back together with the injection plunger 52 to the rear of the injection cylinder 50 by the newly supplied resin L, and remains in the injection cylinder 50 for a long time, so that the resins L having different heat histories are mixed. There were problems such as dripping and resin burning. Moreover, as is apparent from FIG. 6, when the cushion amount increases, the amount of the resin L remaining in the injection cylinder 50 increases accordingly, so that even if a large cushion amount is required, the set cushion amount is There was a problem that a high quality and stable molded product could not be obtained without compromising.

The present invention has been made to solve the problems existing in the prior art, and eliminates a long-term residual resin in an injection cylinder and eliminates the mixture of resins having different heat histories and the burning of the resin. In addition, an object of the present invention is to provide a pre-plastic injection molding machine capable of obtaining a high-quality and stable molded product by setting an optimal cushion amount according to the type of a resin or a mold, and a control method thereof.

[0007]

Means and embodiments of the present invention A plastic injection molding machine 1 according to the present invention comprises an injection device 2 having an injection cylinder 4 having an injection plunger 3 built therein, and an injection plunger 3 in the injection cylinder 4. A plasticizing device 5 having a heating cylinder 7 having a plasticizing screw 6 for supplying the resin L in the front, and in particular, increasing the inner diameter Df of the front portion 4f of the inner peripheral surface 4i of the injection cylinder 4 by increasing the inner diameter Df. A stepped surface 8 is formed on the inner peripheral surface 4i, and a resin supply passage 9 inclined so that the resin L supplied into the injection cylinder 4 from the plasticizing device 5 hits the stepped surface 8 is formed. And In this case, according to the preferred embodiment, the resin supply passage 9 facing the inside of the injection cylinder 4 is constituted by a plurality of branch passages 9a, 9b, 9c, and each of the branch passages 9a. They can be arranged at predetermined intervals.

Further, the control method of the pre-plastic injection molding machine according to the present invention uses such a pre-plastic injection molding machine 1, and particularly, the leading edge of the injection plunger 3 at the most advanced position Pf (injection completion position). The position of the injection plunger 3 is controlled so that the portion 3s is located forward of the rear edge 10r of the supply port 10 of the resin supply passage 9 opening into the injection cylinder 4. In this case, according to the preferred embodiment, the position of the injection plunger 3 is controlled such that the leading edge 3s at the most advanced position Pf is located between the rear edge 10r and the front edge 10f of the supply port 10. It is desirable.

By controlling the leading edge 3s of the injection plunger 3 at the most advanced position Pf so as to be located forward of the rear edge 10r of the supply port 10, the inside of the injection cylinder 4 from the supply port 10 can be controlled. Is supplied to the stepped surface 8 and moves along the stepped surface 8 in the initial stage of supply, so that the newly supplied resin L enters behind the remaining resin L. As a result, the remaining resin L is injected and filled into the mold cavity in the next injection step, and long-term residual resin L is eliminated. Further, since the inner diameter of the inner peripheral surface 4i in front of the step surface 8 is Df, a gap corresponding to the step surface 8 is formed between the injection plunger 3 and the inner peripheral surface 4i. Therefore, since the supply port 10 is not closed by the existence of the injection plunger 3, an arbitrary cushion amount can be set by stopping the injection plunger 3 at an arbitrary most advanced position Pf.

[0010]

Next, preferred embodiments according to the present invention will be described in detail with reference to the drawings.

First, an overall schematic configuration of a pre-plastic injection molding machine 1 according to the present embodiment will be described with reference to FIG.

In FIG. 4, a pre-plastic injection molding machine 1 includes an injection device 2 and a plasticizing device 5. The injection device 2 includes an injection cylinder 4, and the injection cylinder 4 incorporates the injection plunger 3. The injection cylinder 4 has an injection nozzle 21 at the front end and a plunger drive unit (not shown) for moving the injection plunger 3 forward or backward at the rear end.
On the other hand, the plasticizing device 5 includes a heating cylinder 7, and the heating cylinder 7 incorporates the plasticizing screw 6. In addition, a screw driving section (not shown) for rotating the plasticizing screw 6 and a hopper (not shown) for supplying a molding material into the heating cylinder 7 are provided at a rear portion of the heating cylinder 7. The inside of the front end of the heating cylinder 7 and the inside of the front end of the injection cylinder 4 are connected to each other through a resin supply passage 9. 22 are heaters mounted on the outer peripheral surfaces of the injection cylinder 4 and the heating cylinder 7.

Next, the main structure of the present invention in the pre-plastic injection molding machine 1 will be described with reference to FIGS.

First, as shown in FIG. 1, the inner peripheral surface 4i of the injection cylinder 4 increases the inner diameter Df of the front part 4f, thereby
A step surface 8 is formed on the inner peripheral surface 4i. In this case, the axial length of the inner peripheral surface 4i formed by the inner diameter Df can be arbitrarily selected. Further, it is desirable that the step surface 8 is formed at right angles to the inner peripheral surface 4i.

On the other hand, the resin supply passage 9 is provided such that the resin L supplied from the plasticizing device 5 hits the step surface 8.
Therefore, the supply port 10 of the resin supply passage 9 facing the inside of the injection cylinder 4 is opened before the step surface 8, and the resin supply passage 9 communicating with the supply port 10, particularly, the resin supply passage located on the injection cylinder 4 side. A part 9 p of the passage 9 is inclined in a direction in which the supplied resin L hits the step surface 8. The resin supply passage 9 may be a single resin supply passage 9 as shown in FIGS. 1 and 2, or a plurality (three in the embodiment) of branch passage portions 9a and 9b as shown in FIG. , 9c, and the branch passage portions 9a, 9b, 9c may be arranged at equal intervals in the circumferential direction of the injection cylinder 4. With such a configuration, the resin L remaining for a long time can be more reliably eliminated.

Next, such a pre-plastic injection molding machine 1
The control method according to the present embodiment including the operation of FIG.
This will be described with reference to FIG.

Now, it is assumed that the injection step is completed by moving the injection plunger 3 to the most advanced position Pf. This state is shown in FIG.

In this case, a plunger driving unit (not shown) provided in the injection device 2 is configured to move the injection plunger 3 to the most advanced position Pf.
Control to stop. That is, the most advanced position Pf of the injection plunger 3 is set to the leading edge 3 of the injection plunger 3.
s is set in advance as a target value so that s is located between the rear edge 10r and the front edge 10f of the supply port 10, and when the injection process ends, the injection plunger 3 stops at the most advanced position Pf. Thus, the position control for the injection plunger 3 is performed. Therefore, when the stop position of the injection plunger 3 is deviated from the most advanced position Pf during the adjustment operation, the operator can automatically correct the position by pressing a switch or the like. Also, during automatic operation, the injection plunger 3
When the stop position is continuously deviated from the most forward position Pf, an abnormality alarm is issued.

On the other hand, a molding material (pellet) is supplied from a hopper (not shown) provided in the plasticizing device 5 into the heating cylinder 7. As a result, the molding material is plasticized by the rotating plasticizing screw 6 and the heating cylinder 7, and the plasticized resin L passes through the resin supply passage 9 from the supply port 10 to the injection cylinder 4.
Is supplied in front of the injection plunger 3.

At this time, the resin L supplied from the supply port 10
Moves in the direction of arrow F shown in FIG. That is, the step surface 8
And moves along the step surface 8 in the initial stage of supply, so that the newly supplied resin L enters behind the remaining resin L. As a result, the remaining resin L is injected and filled into the mold cavity in the next injection step,
The long-term residue of the resin L is eliminated. Further, since the inner diameter of the inner peripheral surface 4i in front of the step surface 8 is Df, a gap corresponding to the step surface 8 is formed between the injection plunger 3 and the inner peripheral surface 4i. Therefore, since the supply port 10 is not closed by the existence of the injection plunger 3, an arbitrary cushion amount can be set by stopping the injection plunger 3 at an arbitrary most advanced position Pf.

Then, the resin L is supplied from the supply port 10 to the injection cylinder 4.
When the injection plunger 3 is retracted, the injection plunger 3 is retracted, the measurement is performed, and when the injection plunger 3 is advanced by the end of the measurement, the resin L is injected into the mold cavity through the injection nozzle 21. Is done.

The embodiment has been described in detail above.
The present invention is not limited to such an embodiment,
The configuration, shape, quantity, method, and the like of the details can be arbitrarily changed without departing from the gist of the present invention.

For example, the most advanced position P of the injection plunger 3
f is the front edge 1 of the supply port 10.
Control located ahead of 0f may be performed. Also,
The step surface 8 may be provided on the injection plunger 3 if necessary, and such modifications are included in the equivalent scope of the present invention.

[0024]

As described above, in the pre-plastic injection molding machine according to the present invention, the inner diameter of the front portion of the inner peripheral surface of the injection cylinder is increased to form a step surface on the inner peripheral surface, and the plasticizing device is used. A resin supply passage which is inclined so that the resin supplied from inside to the injection cylinder hits the stepped surface, and the control method according to the present invention uses the prepra-type injection molding machine, and controls the injection plunger. The position of the injection plunger is controlled so that the leading edge at the forward position is located ahead of the rear edge of the supply port of the resin supply passage opening into the injection cylinder. It works.

By eliminating the long-term residual resin in the injection cylinder, it is possible to eliminate the mixture of resins having different thermal histories and the burning of the resin.

By setting an optimal cushion amount according to the type of resin or mold, a high-quality and stable molded product can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional side view of a main part of a pre-plastic injection molding machine according to the present embodiment,

FIG. 2 is a sectional view taken along line AA in FIG.

FIG. 3 is an operation explanatory view of a main part of the pre-plastic injection molding machine,

FIG. 4 is an overall schematic configuration diagram of the pre-plastic injection molding machine;

FIG. 5 is a configuration diagram showing a modified example of a resin supply passage in the pre-plastic injection molding machine;

FIG. 6 is a cross-sectional side view of a main part of a pre-plastic injection molding machine according to a conventional technique;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pre-plastic injection molding machine 2 Injection apparatus 3 Injection plunger 3s Tip edge part 4 Injection cylinder 4i Inner peripheral surface 4f Front part 5 Plasticizing device 6 Plasticizing screw 7 Heating cylinder 8 Step surface 9 Resin supply passage 9a ... Branch passage 10 Supply port 10r Rear edge 10f Front edge L Resin Df Inner diameter Pf Most advanced position

Claims (4)

(57) [Claims] 1. A pre-plasticizer comprising: an injection device having an injection cylinder having a built-in injection plunger; and a plasticizing device having a heating cylinder having a built-in plasticizing screw for supplying a resin in front of the injection plunger in the injection cylinder. In the injection molding machine, the inner diameter of the front portion of the inner peripheral surface of the injection cylinder is increased to form a stepped surface on the inner peripheral surface, and the resin supplied from the plasticizing device into the injection cylinder is supplied to the stepped portion. A pre-plastic injection molding machine characterized by forming a resin supply passage inclined so as to hit a surface. 2. The resin supply passage facing the inside of the injection cylinder has a plurality of branch passages, and the branch passages are arranged at predetermined intervals in a circumferential direction of the injection cylinder. The pre-plastic injection molding machine according to claim 1. 3. An injection device having an injection cylinder having a built-in injection plunger, and a plasticizing device having a heating cylinder having a built-in plasticizing screw for supplying a resin in front of the injection plunger in the injection cylinder, Increasing the inside diameter of the front part of the inner peripheral surface of the injection cylinder to form a step surface on the inner peripheral surface, and inclining so that the resin supplied from the plasticizing device into the injection cylinder hits the step surface. In controlling the pre-plasticization injection molding machine having the resin supply passage formed, the leading edge portion of the injection plunger at the most advanced position is closer to the rear edge of the supply port of the resin supply passage opening into the injection cylinder. Controlling the position of the injection plunger so that the injection plunger is also located forward. 4. The position control of the injection plunger is performed so that the leading edge at the most advanced position is located between a rear edge and a front edge of the supply port. 4. The control method of the prepra injection molding machine according to 3.