JPH0270407A - Molding die - Google Patents

Abstract

PURPOSE:To form a plastic optical part of high accuracy at low cost by shaping a heat medium flow channel in a simple disk shape. CONSTITUTION:A temperature control heat medium in a tank 16 is heated up to the temperature set in a controller by a heater in the tank 16. The heated temperature control medium is sucked in negative pressure by a pump 17 through a molding die 1. That is, the temperature control heat medium coming out of the tank 16 passes through a hose 15 and proceeds to a medium inlet plate 7b. Then the same passes through a medium outlet plate 6b and the center of an adapter plate 5b, and is transferred from a central flow channel 23b of a flow channel block 4b to a disk-shaped channel 19b. The temperature control medium is expanded in a concentric shape in the disk-shaped flow channel 19b. The temperature control medium expanded fully inside the disk-shaped flow channel 19b flows into a cylindrical flow channel 20b. Then, the temperature control medium is transferred to a flow channel 24 of the medium outlet plate 6b through a through-hole 21 of the adapter 5b. Then, the same is sucked from a hose 15 into the pump 17 and returned to the tank 16 again. A molding die is heated up to the molding starting temperature by said action.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a mold for molding plastic optical parts such as plastic lenses, and particularly to a mold structure suitable for high-precision plastic parts.

[Conventional technology]

When molding high-precision optical parts such as plastic lenses, if the temperature of the mold surface that shapes the optical surface is uneven, a difference in material density will occur in the molded product, causing shrinkage during cooling. Due to the difference in degree, deformations such as torsion and warpage occur in the molded product. Therefore, it is necessary to keep the temperature of the mold surface uniform.

When heating and cooling during the molding process, in order to shorten the molding cycle and equalize the temperature, it is necessary to use a large flow rate of heat medium.
It is desirable to pass it near the mold surface that shapes the optical surface.

When the heat medium flow path approaches the mold surface, the flow path shape affects the temperature distribution on the mold surface. In the case of plastic lenses and disks, their shape must maintain rotational symmetry. Therefore, the shape of the heat medium flow path must also be close to rotationally symmetrical.

In view of the above, a molding die having a concentric heat medium flow path structure as described in Japanese Patent Application Laid-Open No. 57-187211 has been proposed.

[Problem to be solved by the invention]

The above conventional technology had the following problems: 61) No consideration was given to mold processing costs. In other words, the structure of the concentric heat medium flow path becomes complicated, and processing time is required. This resulted in higher mold processing costs, which in turn led to an increase in the price of the molded product.

2) In a concentric underground flow path, the cross-sectional area of the flow path is only about 1/2 of the cross-sectional area of the mold surface, even if it is large.

In this case, heat conduction is different between the channel portion and the non-channel portion, resulting in a temperature distribution. Further, the flow path shape cannot be completely rotationally symmetrical.

Therefore, the precision of the molded product deteriorates.

An object of the present invention is to eliminate the above-mentioned drawbacks and to realize a high-precision plastic optical component at low cost.

[Means to solve the problem]

The above object is achieved by making the heat medium flow path shape into a simple disk shape.

However, a new problem arises when the flow path is shaped like a disk, but the following solution was used.

1) Install reinforcing supports at several locations in the disc-shaped channel in contact with the mold entry side having an optical surface.

2) A material with low thermal conductivity and high strength is used as the reinforcing support.

[Effect]

In the disk-shaped flow path, the center is the inlet and the periphery is the outlet, so that the heat medium flowing out from the center spreads concentrically and moves toward the outlet from the outer periphery. Therefore, all positions equidistant from the center have the same temperature. As a result, all positions equidistant from the center of the molded product have the same amount of shrinkage. That is, the molded product can maintain a rotationally symmetrical shape.

Furthermore, since the disk-shaped channel has only an inlet and an outlet structure, the disk shape itself does not require any special processing, and therefore mold processing time can be shortened.

Since the heat medium flow path is provided near the mold surface, in the case of a disk-shaped flow path, the wall thickness of the mold insert piece becomes thinner and the strength deteriorates. However, high-strength reinforcing supports provided at several locations can prevent the mold pieces from deforming due to resin pressure.

Since the reinforcing support is made of a material with low thermal conductivity, it is possible to prevent the occurrence of temperature distribution that occurs in the case of concentric underground channels.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 4.

FIG. 1 is a sectional view of a molding die according to an embodiment of the present invention.

The molding die 1 includes a fixed frame 2a, a movable frame 2b, and a lens 11.
A fixed input piece 3a, a movable human piece 3b, flow path blocks 4a, 4b, adapter plates 5a, 5b, medium inlet plates 6a, 6b, medium outlet plates 7a, 7b, pressure plate 8. It is composed of a hydraulic cylinder 9. Inside the mold r is a sprue 1 that connects the molding machine (not shown) and the cavity 10.
2, a runner 13, and a gate 14 are present. Also, a fixed insert piece 3a, a movable insert piece 3b, and a flow path block 4a.

4b, a heat medium flow path is provided. A flow path passing through the center of each flow path block 4a, 4b is connected to each medium inlet plate 6a, 6.
b is connected to a tank 16 by a hose 15.

In addition, the flow paths provided between each flow path block 4a, 4b, fixed input piece 3a, and movable input piece 3b are connected to each medium outlet plate 6a, 6.
b is connected to a pump 17 through a hose 15.

A tank 16 and a pump 17 are also connected. Further, the hydraulic cylinder 9 is connected to a hydraulic pump 18.

FIG. 2 is an enlarged sectional view of the vicinity of the movable insert piece 3b of the mold shown in FIG. The movable inserting piece 3b has a concave shape on the side opposite to the optical surface. This concave bottom surface 3b1 and the channel block 4
b are arranged at regular intervals. Here, the space 19b formed by the mold inserting piece bottom surface 3b1 and the channel block 4b becomes a disk-shaped channel as shown in FIG.

Further, the concave inner surface 3b2 of the movable inserting piece 3b and the outer surface of the flow path block 4b are arranged with a constant interval.

The space 20b formed here becomes a cylindrical flow path. The cylindrical channel 20b further communicates with the medium inlet plate 6b via the adapter plate 5b. The adapter plate 5b has several through holes 21b as shown in FIG. The medium inlet plate 6b has a flow path 24 structure in which the flow paths formed by the through holes 21b are combined into one.

Reinforcing supports 22 are arranged at several locations in the disc-shaped flow path 19b1 and the cylindrical flow path 20b. This reinforcing support 22
is made of a material with high strength and low thermal conductivity.

The operation of the molding die configured as above will be explained. Note that the operation of the temperature regulating medium will be explained only on the movable side, but the same applies to the fixed side.

A heater (not shown) in the tank 16 causes the tank 16 to
The temperature regulating medium inside the chamber is heated to a temperature set in a controller (not shown). The heated temperature regulating medium is drawn through the molding die 1 by the pump 17 under negative pressure. That is, the temperature regulating medium leaving the tank 16 passes through the hose 15 and advances to the medium inlet plate 7b. The temperature control medium then spreads concentrically within the 6-disc-shaped channel 19b that passes through the center of the medium outlet plate 6b and the adapter plate 5b and is sent from the center channel 23b of the channel block 4b to the disc-shaped channel 19b. go. The temperature regulating medium that has spread all the way inside the disc-shaped channel 19b is the cylindrical channel 2.
Flows into 0b. Thereafter, the temperature regulating medium moves to the flow path 24 of the medium outlet plate 6b via the through hole 21 of the adapter 5b. Then, it is sucked into the pump 17 through the hose 15 and returns to the tank 16 again. This operation heats the mold to the molding start temperature. Here, the rotational symmetry of the temperature of the optical surface of the movable inserting piece 3b is very excellent.

Next, molten resin is injected from a mold 4i (not shown) and filled into the cavity 10 via the sprue 12, runner 13, and gate 14. Thereafter, the hydraulic cylinder 9 is advanced by the hydraulic pump 18 to compress the molded product 11 via the pressure plate 8. At the same time, the temperature regulating medium in the tank 16 is cooled to a predetermined temperature, and the temperature regulating medium is sent to the disk-shaped channel 19b1 and the cylindrical channel 20b by the same operation as described above. Even at this point, the temperature regulating medium spreads in a perfect concentric circle, so the rotational symmetry of the temperature is excellent.

400 to 100 to the movable entry piece 3b during injection and compression.
Although a pressure of 0 kg/cd was applied, no deformation occurred because ceramic was used as the reinforcing support 22.

When cooling is completed, the molded product is taken out and the temperature control medium is heated again to return to its initial state.

The molded product taken out has high precision with excellent rotational symmetry.

The input piece 3b and the adapter plate 5b, the adapter plate 5b and the flow path block 4b, the adapter plate 5b and the medium outlet plate 6b, and the medium outlet plate 6b and the medium inlet plate 7b can be easily brought into close contact with each other by silver soldering. There is no need to worry about leaks.

In this example, the temperature control medium was heated and cooled when heating and cooling the mold, but it is also possible to install multiple tanks, set the temperature control medium in each tank at a different temperature, and change the switching or mixing ratio. I can't stand it.

Furthermore, although the present embodiment uses a heating-cooling temperature pattern, it may be a constant temperature or a more complicated temperature pattern. Furthermore, although this example deals with injection compression molding,
There is no problem with injection molding or compression molding.

By creating a structure in which the flow moves from the central flow path to the disk-shaped flow path and then to the cylindrical-shaped flow path as described above, it was possible to improve the rotational symmetry of the mold temperature and improve the precision of the molded product.

Further, by adopting the structure of the present invention, there is no need to process complicated concentric circular flow channels, and machining of simply planes and circles is sufficient, so that the machining time can be shortened. In other words, the cost of mold processing became cheaper, which in turn led to a reduction in the cost of molded products.

〔Effect of the invention〕

As described above, according to the present invention, by making the heat medium flow path into a disk shape, the rotational symmetry of the mold temperature can be reduced to 1/2 that of the conventional one.
The accuracy was more than doubled. Also,
The disk-shaped flow path made it possible to simplify the flow path shape and reduce mold processing costs.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a molding die according to an embodiment of the present invention, and FIG. 2 is an enlarged cross-sectional view of the main parts of the molding die shown in FIG. 1. Figure 3 is a view taken along the line I-1 in Figure 2, and Figure 4 is a view of n in Figure 2.
-N line arrow view. 1... Molding mold, 3a, 3b... Fixed, movable insert piece,
6... Medium outlet plate, 7... Medium inlet plate, 19...
Disk-shaped channel, 20... Cylindrical channel, 23... Center channel.謬I/Do/7 Figure No. 1

Claims (1)

[Claims] 1. The surface of the mold inserting piece that shapes the optical surface opposite to the optical surface and the flow path block having a flow path for the heat medium in the center are arranged at a constant interval, and the mold A molding die characterized in that a disc-shaped space sandwiched between the surface of the input piece opposite to the optical surface and the flow path block is used as a heat medium flow path.