JPH0464418A - Mold - Google Patents

Abstract

PURPOSE:To contrive shortening of a molding cycle and controlling of injection pressure by improving a quality of a molded product, by a method wherein a heat insulation layer by a heat insulation member, a heating layer by an electric conductive member and a protective film layer by a wear-resistant part are provided respectively on the inside of a cavity of a mold by a strengthened member, the top of the heat insulation layer and the top of the heating layer. CONSTITUTION:At the time of performance of injection molding by making use of molds 1, 2, heating layers 6, 7 comprised of an electric conductive member are set up at almost the same temperature as a heating and deformation temperature of a molding material by applying fixed voltage to the heating layers 6, 7 by control circuits 10, 11. Since temperatures of the heating layers 6, 7 are raised in a moment by the impression of the voltage, this becomes effective for shortening of a molding cycle. Since heat insulation layers 4, 5 are interposed among the heating layers 6, 7 and molds 1, 2, electric leakage is feared little and, moreover, the heating layers 6, 7 are kept at a uniform temperature without transfer of heat to the molds 1, 2. Further, protective film layers, 8, 9 by a wear-resistant member are provided on the top of the heating layers 6, 7.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a mold for molding, and is used for injection molding, compression molding, and thermoforming of resin.

(Prior Art) In the injection molding method, usually heated and molten resin is press-fitted into a mold whose temperature is lower than that of the resin, and the mold is further cooled to solidify the resin and mold the resin.

In injection molding, the viscosity of the molten resin increases in the lower temperature parts of the mold, resulting in poor fluidity, so in order to completely fill the mold cavity with resin, a high pressure (e.g. -1600 atmospheres) is required. It is necessary to press-fit it at high pressure and hold it at high pressure for a certain period of time.

It would be ideal if the temperature inside the mold could be maintained at the same temperature as the resin from the start of the shot to the time the cavity is filled, and after filling, the resin could be solidified and molded by rapid cooling, but in reality, the heat capacity of the mold The reality is that it is not possible to rapidly heat and cool only the inner surface of the mold.

Therefore, as disclosed in Japanese Unexamined Patent Publication No. 174624/1984, a molding die has been proposed in which a heating means is provided at or near the surface facing the molding space (cavity) of the mold.

(Problems to be Solved by the Invention) Although the conventional technology described in the above-mentioned publication is recognized to have some usefulness, such as being able to improve the quality of molded products and shorten the molding cycle, it is difficult to use copper as a conductive film for electrical heating. Because it has a so-called two-layer structure in which foil is used and an insulating layer made of ceramic is provided between the conductive film and the mold, there is a problem that the conductive film is easily damaged due to wear due to repeated injection molding. there were.

The present invention provides a molding die in which a heating means is provided at or near the surface facing a molding space (cavity), including a heat insulating layer,
By adopting a so-called three-layer structure consisting of a heating layer and a protective film layer, while maintaining the usefulness of the conventional technology mentioned above, it has improved wear resistance and is highly durable even after repeated injection molding. It is an object of the present invention to provide a molding die that can reduce the pressure to, for example, 200 atmospheres or less.

(Means for Solving the Problem) The present invention takes the following technical means to achieve the above-mentioned object.

In other words, the present invention includes a heat insulating layer 45 made of an insulating material on the inner surface of the cavity 3 of the molds 1 and 2 made of a strength member, a heating layer 6 and 7 made of a conductive material on the upper surface of the heat insulating layer 4. Protective film layers 8 and 9 made of wear-resistant materials are provided on the upper surface of the heating layer 6.7.

(Embodiments and Operations) Hereinafter, embodiments and operations of the present invention will be described with reference to the drawings.

The first figure shows a cross-sectional perspective view of a mold that goes into an injection molding machine, in which a first mold 1 and a second mold 2 are provided for injection molding, and the first and second molds 1 The cavity 3 is defined by .2.

The base materials of the first and second molds 1 and 2 are soft steel, CrMo steel,
It is made of a strong material such as tool steel, and a spool (not shown) is communicated with the cavity 3 to which an injection nozzle is connected.

A heat insulating layer 4.5 made of an insulating material is provided on the inner surface of the cavity 3, and a heating layer 6 made of a conductive material is provided on the upper surface of the heat insulating layer 4,5.
7, and a protective film layer 8.9 made of a wear-resistant material is provided on the upper surface of the heating layers 6, 7, and a control circuit 10.9 is provided on the heating layer 6.7. II is connected so that a predetermined voltage can be applied.

In FIG. 2, the heat insulating layers 4 and 5 include glass powder,
Ceramics such as zirconia and alumina are used, and the layer thickness is several 100 μm.

Specifically, when using glass powder, baking and
It is provided by enamel, and when it is made of zirconia, it is sprayed,
It is provided by HIP treatment after thermal spraying, and when thermal spraying is used, it can have a porous structure. In the case of alumina, it is provided by sputtering or thermal spraying means. Note that when zirconia is used, it has a low thermal conductivity and a coefficient of thermal expansion close to that of steel, and when alumina is used, it can be made to have high hardness.

As the heating layer 6.7, N1-P, nichrome, TiN,
A conductive material with low electrical resistance such as TiC is used, and the number of
It is provided with a layer thickness of 0 μm to 100 μm.

Specifically, Ni-P is provided by electroless coating, nichrome is provided by HIP bonding, and TiN and TiC are provided by physical vapor deposition (
PVD), chemical vapor deposition (CVD) 5-20μm
It is provided with a layer thickness of .

When using an algal membrane or sheet of other ductile metal material as the heating layer, the heating layer can be provided with a predetermined thickness by explosive bonding.

As the protective MN8.9, Cr, TiN, and TiC, which are wear-resistant members having better thermal conductivity than the heat insulating layers 4 and 5 and higher electrical resistance than the heating layers 6 and 7, are used, and the hloumO layer It is provided with a thickness.

Specifically, in the case of Cr, electrolytic plating means or T
For iN and TiC, PVD and CVD are used.

Note that when TiN or TiC is used as the protective film layers 8 and 9, the heating layers 6 and 7 are made of Ni-P, nichrome, or the like other than TiN or TiC.

When performing injection molding using the molds 1 and 2 configured as described above, a predetermined voltage is applied by the control circuit 10.11, and the heating layers 6 and 7 made of conductive members are
is set to a temperature equal to -the heating deformation temperature of the molding material. This voltage application causes the temperature of heating N6 and N7 to rise instantaneously, which is effective in shortening the molding cycle. Also,
Since the heat insulating layers 4 and 5 are interposed between the heating layers 6 and 7 and the molds 1.2, there is little risk of electrical leakage (in addition, the heating layers 6 and 7 do not transfer heat to the molds 1 and 2). It will not be taken away (it will maintain a uniform temperature).

Furthermore, by providing the protective film layers 8 and 9 made of wear-resistant materials on the upper surfaces of the heating layers 6 and 7, damage to the heating layers 6 and 7 due to wear is prevented even if injection molding is repeatedly performed.

Next, let's talk about injection molding cycle time.
Injection start time t1, injection end time t2, cooling start time t
3. Injection molding is performed with cooling end time t4 and molded product removal time t5 as one cycle.

Between the time t1 and t2, thermoplastic material is injected into the cavity 3 from the injection nozzle via the spool.

At this time, the molten molding material is filled into the first and second molds 1 and 2 without losing heat due to the surfaces of the cavity 3, that is, the heating layers 6 and 7 which are in a heat-generating state. In this way, by setting the temperatures of the molds 1 and 2 to a low level while setting only the surface temperature of the cavity 3 to a high level, the unbalance of molding shrinkage is eliminated and a high-quality molded product can be obtained.At time t2 , the control circuit 10.11 releases the voltage application to the heating layer 6.7.At this time, since the heating layers 6 and 7 have a smaller heat capacity than the whole of the molds 1 and 2, they are set in advance to the solidification temperature of the molding material. mold 1,
2 means -, etc. The temperature drops instantly to 7.

Between time t3 and t4, the thermoplastic material injected into the molds 1 and 2 is cooled and solidified within the cavity 3 to form a molded product.

Between time t4 and t5, the molds 1 and 2 are opened to take out the molded product, and then the control circuit 1011 applies voltage to the heating layer 6.7 again to heat the cavity 3.
Raise the surface temperature and repeat the above operation.

By instantaneously raising and lowering the surface temperature of the cavity 3 in this way, it is possible to shorten the molding cycle. Furthermore, by raising the surface of the cavity 3 to the melting temperature of the molding material between the injection start time and the injection end time, the molding shrinkage of the thermoplastic material can be kept in balance and a high-quality molded product can be obtained. can.

Referring to Figure 3, the base material of molds 1 and 2 and the heat insulating layer 4.5
By making the interfaces between the heat insulating layers 4, 5 and the heating layers 6, 7, and the interfaces between the heating layers 6, 7 and the protective film layers 8, 9 into graded composition materials over all or part of the layers. A means for preventing peeling and cracking due to differences in thermal expansion is disclosed.

Figure 4 shows the means for energizing the heating layer (control circuit)
Another example is shown in which the upper mold 1 is insulated with N4
, a heating layer 6 and a protective layer 8 are illustrated.

The control circuit 10 shown in FIG. 4 includes electrodes 10A, 1. OB
In this case, it is preferable to provide a temperature controller 10D to measure the temperature at a certain point in the mold l for each section using a thermocouple 10ε, and locally control the heating power from the Cyrisk IOC. This enables temperature control.

In addition, in order to check and improve the uniform heating of the inner surface of the mold, molds 1 and 2 are opened, heated with electricity through the Cyrisk IOC, and the temperature distribution on the inner surface (surface) is measured using a scanning infrared thermometer. Monitor with electrode 10A.

10B mounting arrangement can also be optimized.

FIG. 5 shows a more desirable example of a graded composition material.

That is, the molds 1 and 2 made of strength members and the heat insulating layer 4.5
Steel materials,
On the surfaces of the molds 1 and 2 made of a strong material such as CrMo@,
Insulating layers 4 and 5 made of zirconia, preferably partially stabilized zirconia, are provided as insulating members.

In this case, the heat insulating layers 4 and 5 are coated with copper powder 10
0% by weight of the first layer 4A, 5A, 75% by weight of fA powder, the second layer 48.5B of 25% by weight of zirconia, and 50% by weight of steel powder.
% by weight and third layers 4C and 5B of 50% by weight of zirconia,
Fourth layer 4D, 5 of 25% steel powder and 75% zirconia by weight
D and fifth layers 4E and 5E of zirconia 100% by weight, and the thickness of the fifth layers 4E and 5E is 50 to 20 μm.
The thickness of the other first to fourth layers is 10 to 30 μm, which improves workability.

As for the method of thermal spraying, it is preferable to use low-pressure plasma spraying, which produces fewer pores.
IP processing is desirable.

In addition, in the part facing the cavity 3 side of the molds 1 and 2,
It is free to provide cooling medium passages, etc.

(Effects of the Invention) The present invention is as described above, and according to the present invention, a molding metal with high durability is produced while improving the quality of molded products, shortening the molding cycle, and suppressing injection pressure. We can provide the mold.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention; FIG. 1 is a cross-sectional perspective view showing a mold of an injection molding machine, FIG. 2 is an enlarged view of section A in FIG. 1, and FIG. 3 is an alternative embodiment of FIG. 2. Enlarged view showing an example, Figure 4 is the first
A sectional view showing the other side of the figure, and FIG. 5 is an enlarged view showing another example of FIG. 3. L2... 1st and 2nd mold, 3... Cavity, 4, 5
... Heat insulation layer, 6, 7 ... Heating layer, 8, 9 ... Protective film layer. 1st

Claims (1)

[Claims] (1) Cavities of molds (1) and (2) by strength members (
3) A heat insulating layer (4) (5) made of an insulating material is provided on the inner surface, and a heating layer (6) made of a conductive material is provided on the upper surface of the heat insulating layer (4) (5).
) (7); and protective film layers (8) and (9) made of a wear-resistant material are provided on the upper surfaces of the heating layers (6) and (7).