JPH0631784A - Accurate injection molding method - Google Patents

Abstract

PURPOSE:To enhance an accuracy in molding an article by a method wherein a molten resin to be charged into a plurality of cavities in a mold by injection is weighed by an accurate amount to ensure a molten resin charging balance. CONSTITUTION:While a resin charged in cavities of a mold in a previous injection molding cycle is cooled, a resin to be used in a next injection molding cycle is supplied from a single plasticizing cylinder 3 to two injection plunger devices A, B while being weighed for every device. After the melt resin is supplied to the devices A, B respectively by a predetermined amount, the devices A, B are actuated at the same time to charge the molten resin into the cavities provided for every device in the mold.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding method,
In particular, it relates to a precision injection molding method for obtaining a molded product, such as an optical component, which requires precision molding.

[0002]

BACKGROUND ART In an injection molding method using a pre-plastic injection molding machine including a plasticizing section having a plasticizing cylinder and the like, and an injection section having a plunger and the like, a molten resin made in the plasticizing section is supplied to the injection section. Molten resin is injected and filled from the injection section into the cavity in the mold, and a molded product is obtained by cooling and solidifying the molten resin. If this molded product is a precision molded product that does not have thermal distortion, such as an optical component, the mold in which the molten resin is injected and filled in the cavity is temperature-controlled, and the molten resin is cooled under this temperature control. It

[0003]

When a molten resin is cooled while controlling the temperature of the mold to obtain a precision molded product, it is necessary to wait until the molten resin becomes a precision molded product at a temperature at which it can be taken out. Since it takes a long time, one injection molding cycle becomes long and the production efficiency decreases.
In order to solve such a problem, a large number of cavities are formed in the mold, and the molten resin injected from the injection part of the injection molding machine is diverted and filled in these cavities,
It is conceivable to produce a large number of molded products by one injection molding cycle.

However, it is difficult to accurately fill each cavity with a predetermined amount of molten resin injected from the injection portion of the injection molding machine, and it is impossible to secure a filling balance of the molten resin. In a precision molded product such as an optical component, the amount of the molten resin filled in the cavity has a great influence on the molding accuracy of the molded product, and therefore the amount of the molten resin filled in the cavity must be accurate.

In the conventional injection molding method, when it is attempted to produce a plurality of molded products in one injection molding cycle, it is impossible to fill the plurality of cavities in the mold with the molten resin in an accurate amount. It was not possible to make the molding accuracy of the molded product sufficiently high to the extent required due to the variation of.

An object of the present invention is to enable a plurality of molded articles to be produced in one injection molding cycle, and to fill a plurality of cavities in a mold with a precise amount of molten resin to secure a filling balance. Accordingly, it is an object of the present invention to provide a precision injection molding method that enables the molding accuracy of a molded product to be sufficiently high.

[0007]

According to a first aspect of the present invention, there is provided a precision injection molding method which comprises one plasticizing cylinder forming a plasticizing section and a plurality of injection plunger units forming the injection section. It was carried out using the injection molding machines connected in parallel, and during the cooling of the molten resin injected and filled in the cavity in the mold in the previous injection molding cycle, one molten resin to be used in the next injection molding cycle The plasticizing cylinder supplies a plurality of injection plunger units while measuring each of these units, and after a predetermined amount of molten resin has been supplied to these injection plunger units, all the injection plunger units are activated at the same time. Allows the molten resin to be taken out of the molded product by the previous injection molding cycle and be put into the cavity provided for each injection plunger unit in the mold. It is characterized in that and filling.

In the above, the operation of supplying a predetermined amount of molten resin from one plasticizing cylinder to the plurality of injection plunger units is performed even if the molten resin is sequentially supplied to these injection plunger units. Alternatively, the molten resin may be simultaneously supplied to all the injection plunger units.

In the precision injection molding method according to the second aspect of the present invention, in the first aspect of the present invention, a metering stop is provided for each injection plunger unit in a resin supply passage in which a plurality of injection plunger units are connected in parallel to one plasticizing cylinder. It is characterized in that a predetermined amount of molten resin is sequentially supplied to a plurality of injection plunger units by providing valves and sequentially opening and closing these metering stop valves.

[0010]

In the first aspect of the present invention, the molten resin is supplied from one plasticizing cylinder to a plurality of injection plunger units while being metered for each of these units, and the predetermined amount supplied to these injection plunger units. Since the molten resin of is injected and filled into the cavity provided for each injection plunger unit in the mold, the amount of molten resin filled in these cavities becomes an accurate predetermined amount, and the filling balance of the molten resin is secured. Therefore, the molding accuracy of each molded product molded in one injection molding cycle is high.

The operation of supplying the molten resin from one plasticizing cylinder to the plurality of injection plunger units while measuring the molten resin is performed by cooling the molten resin injected and filled in the cavity in the mold in the previous injection molding cycle. This cooling work is performed while controlling the temperature of the mold because it is performed in the inside.Therefore, even if the working time is long, this long working time can be used to transfer the molten resin to multiple injection plunger units. It is possible to perform the work of supplying while measuring, and achieve the work efficiency.

Further, in the second aspect of the present invention, a predetermined amount of molten resin is sequentially supplied to the plurality of injection plunger units by sequentially opening and closing the metering stop valve provided for each injection plunger unit. Therefore, the metering stop valve serves as a means for measuring and supplying a predetermined amount of molten resin to each injection plunger unit, and switches and supplies the molten resin from one injection plunger unit to another injection plunger unit. The metering stop valve performs two tasks.

[0013]

An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a plan view of an injection molding machine used for carrying out the precision injection molding method according to this embodiment, and FIGS. 2 and 3 are sectional views taken along the line II-II and line III-III in FIG. Is.

This injection molding machine is a pre-plastic type having a plasticizing section 1 and an injection section 2. As shown in FIG. 2, the plasticizing part 1 is composed of a plasticizing cylinder 3 and the like, and the injection part 2 is composed of a plunger 9 and the like. This plunger 9
2 are provided in the front-back direction of the paper surface of FIG. 2, and therefore, the injection unit 2 is provided with two injection plunger units A and B including a plunger 9 and the like as shown in FIG. , B have the same structure.

As shown in FIG. 2, a screw 4 is rotatably housed inside the plasticizing cylinder 3 of the plasticizing section 1, and the screw 4 is rotated by a hydraulic motor 5. Further, a hopper 6 is provided in the plasticizing cylinder 3, and a resin as a material is supplied from the hopper 6 into the plasticizing cylinder 3.

A plunger block 7 which is a main body of the injection section 2 and is a common member of the injection plunger units A and B is coupled to the tip of the plasticizing cylinder 3, and the plunger block 7 extends vertically. Passage 8
Is formed, and the plunger passage 8 is provided for each of the injection plunger units A and B. A plunger 9 is vertically movably inserted into the plunger passage 8, and a chamber above the plunger passage 8 serving as a plunger guide serves as a resin filling chamber filled with the molten resin supplied from the plasticizing portion 1. There is. An injection cylinder 10 is provided below the plunger block 7, a plunger 9 is connected to a piston 11 in the injection cylinder 10, and the piston 9 moves the plunger 9 up and down. A nozzle 13 having an injection passage 12 communicating with the plunger passage 8 is provided on the upper portion of the plunger block 7.

The inside of the plasticizing cylinder 3 has a resin supply passage 14
This resin supply path 1 communicates with the plunger path 8 via
4 is the passages 14A and 14B in the plunger block 7.
And a passage 14C formed in the valve block 15 attached to the plunger block 7 and connecting the passages 14A and 14B. The passage 14C is opened and closed by the metering stop valve 16. A reciprocating piston 18 in a cylinder 17 is connected to the metering stop valve 16.

Another valve block 19 is attached to the plunger block 7, and a passage 20B formed in the valve block 19 is a passage 20 in the plunger block 7.
A passage 20A, 20B connected to A forms a staying resin discharge passage 20 communicating with the plunger passage 8, and the end portion of the discharge passage 20 is a discharge port 20C opened on the outer surface of the valve block 19. ing. The passage 20B is opened and closed by a staying resin discharge valve 21.
1, a piston 23 in a cylinder 22 is connected, and the reciprocating motion of the piston 23 opens and closes the discharge valve 21. Further, the passage 20A of the staying resin discharge passage 20 is formed by the resin supply passage 1
4 is below the passage 14B, the plunger passage 8
Connected with.

A moving member 24 is fixed to the lower end of the plunger 9 protruding from the plunger block 7, and moves together with the plunger 9. This moving member 24 is attached to a non-moving member (not shown), for example, a magnetic type or an optical type. And the like, and the retracted position of the plunger 9 by the movement of the moving member 24 with respect to the position scale 25, in other words, from the resin supply passage 14 to the plunger passage 8.
It is possible to measure the amount of molten resin supplied to and accumulated in. Therefore, the moving member 24 and the position scale 25
By these, the measuring means 26 for measuring the amount of resin is constituted.

In the above, the plunger 9, injection cylinder 10, nozzle 13, metering stop valve 16, cylinder 17, valve block 19, stagnant resin discharge valve 2
1, the cylinder 22 and the like are injection plunger units A and B
2 are provided corresponding to the number (see FIGS. 1 and 3).
reference). The number of the plasticizing cylinders 3 of the plasticizing part 1 is one, and the resin supply passage 14 for communicating the inside of the plasticizing cylinder 3 with the plunger passages 8 of the two injection plunger units A and B is as shown in FIG. As shown in 3, one passage 14A
And branch passages 14D and 14E that connect the two passages 14C with each other. The inside of the plasticizing cylinder 3 and the plunger passages 8 of the injection plunger units A and B are connected in parallel by these branch passages 14D and 14E. Thus, the resin supply passage 14 is provided with a metering stop valve 16 for each of the injection plunger units A and B.

The mold 33 shown in FIG. 2 is provided with two sprue bushes corresponding to the number of nozzles 13, and the cavity inside the mold 33 communicating with these sprue bushes is an injection plunger unit. It is provided for each of A and B, and one or two molded products are molded by the molten resin injected from one injection plunger unit. Further, the mold 33 is provided with a temperature control circuit for circulating a fluid such as water for controlling the temperature of the mold 33.

Next, the operation will be described. In the precision injection method according to this embodiment, the mold 3 is used in the previous injection molding cycle.
The molten resin injected and filled into the cavity inside the mold 3
By controlling the temperature of the mold 33 by the flow of the fluid to the temperature control circuit of 3, while gradually cooling and solidifying over time, one molten resin used in the next injection molding cycle is plasticized. It is supplied from the cylinder 3 while being metered into the plunger passages 8 of the two injection plunger units A and B, and these injection plunger units A and B are filled with a predetermined amount of molten resin.

Explaining this concretely, the resin of the material charged from the hopper 6 is kneaded in the plasticizing cylinder 3 by the rotation of the screw 4, and is plasticized by the heater provided in the plasticizing cylinder 3. As a result, it becomes molten resin. At this time, the hydraulic pressure of the port 27 of the cylinder 17 of the injection plunger unit A is released, and
Port 27 of cylinder 17 of injection plunger unit B
The hydraulic pressure is supplied to. Therefore, the metering stop valve 16 of the injection plunger unit B is closed. Therefore, the molten resin extruded from the inside of the plasticizing cylinder 3 into the passage 14A of the resin supply passage 14 by the rotation of the screw 4 does not flow to the injection plunger unit B side, but flows into the branch passage 14D shown in FIG. The metering stove valve 16 of the injection plunger unit A is opened by the pressure of the resin, and the molten resin flows into the plunger unit passage 8 which is the resin filling chamber of this unit A.

The hydraulic pressure is supplied to the port 29 of the cylinder 22 of the injection plunger unit A for a certain period of time after the screw 4 of the plasticizing cylinder 3 starts to rotate, so that the accumulated resin discharge valve 21 of the unit A is opened for a certain period of time. There is. Therefore, the molten resin that has flowed into the plunger unit passage 8 of the unit A retains the retained resin that was left without being injected into the clearance 30 between the plunger passage 8 and the plunger 9 in the previous injection molding cycle. The resin is pushed out to the resin discharge path 20 and the accumulated resin is discharged. Therefore, the retained resin that causes the resin burn due to the plunger 9 remaining in the reciprocating plunger passage 8 is discharged from the injection plunger unit A by the new molten resin used in the next injection molding cycle. To be done.

At this time, the injection plunger unit A
Since the back pressure by the hydraulic pressure is supplied to the port 28 of the injection cylinder 10, the plunger 9 does not descend.

After the elapse of the predetermined time, that is, after all the stagnant resin stagnant in the clearance 30 is discharged, hydraulic pressure is supplied to the port 31 of the cylinder 22 of the injection plunger unit A, whereby the stagnant resin discharge valve 21. Closes. Since the molten resin is still supplied from the plasticizing cylinder 3 to the plunger passage 8 after this, the plunger 9 is lowered by the pressure of the molten resin accumulated in the plunger passage 8 against the back pressure from the port 28, and the plunger 9 The lowering amount of the molten resin, in other words, the amount of the molten resin accumulated in the plunger passage 8 as the resin filling chamber is constantly detected by the measuring means 26, and when this amount reaches a predetermined amount, the measuring means 2
A signal from 6 supplies hydraulic pressure to the port 27 of the cylinder 17 of the injection plunger unit A, which causes the metering stop valve 16 of the unit A to close.

As a result, the plunger passage 8 of the injection plunger unit A is filled with a predetermined amount of molten resin.

Cylinder 17 of injection plunger unit A
At the same time that the oil pressure is supplied to the port 27 of the injection plunger unit B, the oil pressure acting on the port 27 of the cylinder 17 of the injection plunger unit B is released by a signal from the measuring means 26 of the unit A. Therefore, from the plasticizing cylinder 3 to the resin supply path 1
4, the metering stop valve 16 of the injection plunger unit B is opened by the pressure of the molten resin flowing into the branch passage 14E shown in FIG. 3, and the molten resin flows into the plunger passage 8 of this unit B. Thereafter, similar to the case of the injection plunger unit A, a predetermined amount of molten resin is supplied and filled in the plunger passage 8 of the unit B.

As described above, the injection plunger unit A,
When the molten resin is supplied to the plunger passage 8 of B, the nozzles 13 of these units A and B are in contact with the sprue bush of the mold 33, and the gate cutter or the sprue cutter provided in the mold 33 is Since it is closed, the molten resin supplied to the plunger passage 8 does not leak from the tip of the nozzle 33.

As described above, after the predetermined amount of molten resin is supplied to the plunger passages 8 of the injection plunger units A and B, the cavity in the mold 33 is injected and filled in the previous injection molding cycle. After the molded product formed by cooling and solidifying the molten resin is taken out from the mold 33, the injection cylinder 1 of the injection plunger units A and B
A high pressure is supplied to the port 28 of 0, whereby the plungers 8 of these units A and B are simultaneously raised. Therefore, the molten resin extruded from the plunger passages 8 of the units A and B is stored in the mold 33.
Each cavity is injection-filled. Then, the molten resin is gradually cooled under the temperature control by the flow of the fluid to the temperature control circuit provided in the mold 33.

According to this embodiment described above, the molten resin from one plasticizing cylinder 3 is unitized in the plunger passages 8 of the injection plunger units A and B provided in the injection section 2 of the injection molding machine. The units A and B are supplied while being measured, and the units A and B are filled with a predetermined amount of molten resin, and then the units A and B are simultaneously operated so that the units A and B are provided in the mold 33. Since the molten resin is injected and filled in each cavity, the amount of molten resin filled in each cavity is more than that in the case where the molten resin is injected and filled from one injection plunger unit into multiple cavities. Can be set to an accurate predetermined amount, and the molten resin filling balance can be secured. Therefore, a plurality of molded products can be produced in one injection molding cycle, and the molding precision of these molded products can be improved.

The predetermined amount of the molten resin is supplied to the injection plunger units A and B while the molten resin injected into the cavity in the mold in the previous injection molding cycle is cooled and solidified. Since this cooling and solidifying step takes a long time when the molded product is an optical component, for example, this working time can be effectively used to supply a predetermined amount of the molten resin to the units A and B. As a result, work efficiency can be improved.

Further, the metering stop valve 16 provided for each of the injection plunger units A and B is sequentially opened and closed to supply a predetermined amount of molten resin to these units A and B in order, so that the metering stop valve 16 is Units A and B
It also serves as a means for supplying a predetermined amount of molten resin and also serves as a switching means for supplying the molten resin by switching from one unit to the other unit, which makes the structure of the injection molding machine simple. And reduction of the number of parts can be achieved.

Further, in this embodiment, as described above, the residual resin of the previous injection molding cycle, which was left in the clearance 30 between the plunger passage 8 and the plunger 9, is discharged, and then the plungers of the units A and B are discharged. Since the molten resin is supplied to the passage 8, the cavity inside the mold 33 is not filled with the stagnant resin that causes the generation of resin burn.
A molded product of good quality can be obtained.

In the embodiment described above, the metering stop valves 16 of the injection plunger units A and B were opened and closed in order. However, these metering stop valves 16 are simultaneously opened by the pressure of the molten resin, and the respective units A and B are opened. Each time B is filled with a predetermined amount of molten resin, these measuring stop valves 16 may be closed by a signal from the measuring means 26 of the units A and B.

Further, the metering stop valve 1 of the above embodiment
Although 6 is a piston type, it may be a rotary valve type, for example, and the structure of the metering stop valve is not limited to that of the above embodiment.

In the above embodiment, the plunger passage 8
Although the discharge valve 21 for discharging the residual resin remaining in the clearance 30 between the plunger 9 and the plunger 9 is provided, the discharge valve 21 may be omitted.

Further, although the number of the injection plunger units is two in the above embodiment, the number is not limited to two and may be three or more.

[0039]

According to the present invention, the molten resin is supplied from one plasticizing cylinder to a plurality of injection plunger units while being metered for each unit, and a predetermined amount of the molten resin is supplied to these units. After that, all the units are operated at the same time to inject the molten resin into the cavity provided for each injection plunger unit in the mold, so the amount of molten resin filled in these cavities Can be made to be an accurate predetermined amount, and while the number of molded products obtained in one injection molding cycle can be increased, the molding accuracy of these molded products can be made high by securing the filling balance of the molten resin. The specified amount of molten resin is supplied to the plunger unit while the molten resin injected into the cavity in the mold in the previous injection molding cycle is being cooled. It is therefore possible to enhance the working efficiency.

Further, a metering stop valve is provided for each injection plunger unit in the resin supply path that connects the plasticizing cylinder and the plurality of injection plunger units in parallel, and these valves are opened and closed in sequence so that the injection plunger units are in turn. Since a predetermined amount of molten resin is supplied to the unit, the metering stop valve is a unit for sequentially supplying a predetermined amount of molten resin to each unit,
It also serves as a means for switching and supplying the molten resin from one unit to another unit, and the structure of the injection molding machine can be simplified accordingly.

[Brief description of drawings]

FIG. 1 is a plan view of an injection molding machine used to carry out a method according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line II-II in FIG.

3 is a sectional view taken along line III-III in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Plasticizing part 2 Injection part 3 Plasticizing cylinder 4 Screw 8 Plunger passage 9 Plunger 10 Injection cylinder 13 Nozzle 14 Resin supply path 16 Measuring stop valve 21 Retained resin discharge valve 26 Measuring means 33 Mold A, B Injection plunger unit

Claims (2)

[Claims] 1. While cooling the molten resin injected and filled in the cavity in the mold in the previous injection molding cycle, the molten resin used in the next injection molding cycle is one plasticizing cylinder of the injection molding machine. Is supplied to the plurality of injection plunger units connected in parallel to this plasticizing cylinder while being metered for each of these units, and after a predetermined amount of molten resin is supplied to these injection plunger units, all of the above injections are made. The plunger units are simultaneously operated, whereby the molten resin is taken out of the molded product by the previous injection molding cycle, and is injected and filled into the cavity provided for each of the injection plunger units in the mold. Precision injection molding method. 2. A metering stop valve is provided for each of the injection plunger units in a resin supply path connecting the plurality of injection plunger units in parallel to the one plasticizing cylinder, and these metering stop valves are sequentially opened and closed. The precision injection molding method according to claim 1, wherein a predetermined amount of molten resin is sequentially supplied to the plurality of injection plunger units by performing the above.