JPH02158316A - Mold for injection molding - Google Patents

Abstract

PURPOSE:To obtain a mold having a high heat speed capable of being heated to high temperature in a short time through high frequency conductive heating by heat-treating the magnetism being existed in an iron metal and an electroless nickel-phosphorus plated layer. CONSTITUTION:It is constituted with an iron metal and electroless nickel- phosphorus plated layer, wherein the phosphorus contained rate of the electroless nickel-phosphorus plating is made 8-13%, and the heat treating condition is to be at the temperature of 200-350 deg.C for one hour or three hours. For instance, the manufacture of a mold comprising an iron metal layer 100 and metal plated layer 110 is such that the configuration work of cavity configuration of a molded product is carried out on the surface of the iron metal. In the metal plating liquid contained phosphorus, an electroless nickel-phosphorus layer 110 is metal-plated on the cavity surface. After forming the metal plated layer, a heat treatment is conducted within an atmospheric constant temperature bath.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a mold used for injection molding, and more particularly to a mold heated by a high frequency induction heating method.

[Prior art to the invention]

Conventionally, heating a mold using high-frequency heating and performing injection molding involves having an oscillating electrode and a cooling channel inside the mold, and an external oscillator as described in Japanese Patent Application Laid-open No. 50-45039. It is configured to have a cooling water pump, and when filling with resin, the mold is instantaneously heated by an oscillating electrode installed in the mold, and after filling is completed, the oscillation is stopped, and the cooling water pump supplies cooling water to the mold. A method has been proposed in which the resin is poured, cooled, and solidified.

Furthermore, JP-A No. 58-40504 discloses that when injection molding a thermoplastic resin, the surface of the mold on which the surface of the injection molded product is to be formed is preheated by high frequency induction to a temperature higher than the heating deformation temperature of the thermoplastic resin. An injection molding method for injection molding has been proposed.

Mold materials include cast and rolled steel materials such as rolled steel (SS), carbon steel for machine structures (SS, 5CK), tool steel (SK, 5KS), high speed steel (SNC), and chrome-molybdenum steel. Or, heat treatment. Then, a mold is formed by cutting and finishing assembly.

The above-mentioned iron-based mold material is suitable for heating a mold by the above-mentioned high frequency induction heating method.

In addition to the iron-based materials mentioned above, there are materials such as copper-based, aluminum-based, and phosphor bronze as mold materials.

[Problem to be solved by the invention]

High molding precision for optical parts, etc. (Molded products that require high precision, such as lenses and Fresnel lenses, require surface finish precision and shape precision of lens curvature.In the case of lenses, molded products that are injected into the mold cavity After the injection is completed, the injected resin cools and solidifies as the mold cools, forming a lens shape.At this time, if the cooling temperature of the mold is not properly controlled, whiskers may appear on the lens surface and the lens shape may deteriorate. Mainly, the shape of the lens curvature cannot be made as desired.

In the case of the Fresnel lens shown in FIG. 9 as well, unless the temperature of the mold is appropriately controlled, the acute angle portion at the tip of the apex portion 100A will not be formed.

If the mold is heated by high-frequency induction heating, the mold can be heated to a high temperature within a short time. When the above-mentioned iron-based material is used as the mold material, heating by the high-frequency induction heating can be efficiently performed.

However, the above-mentioned iron-based materials, especially the steel base materials that are frequently used these days, have difficulties in machinability. In other words, since the material is super hard, the cavity surface must be cut to create a curved surface while maintaining a high-precision surface roughness, or a Fresnel shape can be formed on the cavity surface, especially in the case of a Fresnel lens, to form micrometer-sized irregularities. That is difficult.

In order to form fine irregularities on the cavity surface, mold materials with good workability are preferred, and the aforementioned copper-based or aluminum-based materials are suitable; cannot use any means.

The present invention makes it possible to cut a fine shape on the cavity surface, and also enables heating using a high-frequency induction heating method to make it easier for the molten resin injected into the cavity to be injected into the fine irregularities inside the cavity. The purpose is to propose a new mold.

Another object of the present invention is to improve the productivity of molded products, such as optical parts such as lenses and Fresnel lenses, which require high accuracy in molding surface roughness. Mirror cutting was not possible with the previously used molds mainly made of steel.

The present invention improves the transfer rate of fine shapes of molded products by creating a composition that can mirror-finish the surface layer of the cavity of the mold, and also forms the mold by heating the surface layer of the cavity at a high temperature in a short period of time using high-frequency induction heating means at the base of the mold. We propose a mold that can shorten the cycle and improve productivity per hour.

Table 1 shows the specularity (surface roughness accuracy) and mold heating rate by high-frequency heating means when carbon steel (345C) is used as conventional example (1) and phosphor bronze is used as conventional example (2). As shown in the table, the heating rate for carbon steel is 22℃/sec.
Although it is fast, mirror finishing is impossible.

Also, phosphor bronze can be mirror-finished, but the heating rate is 3℃.
/SeC, both of which are unsuitable as mold materials.

The present invention proposes a mold that can be mirror-finished and can be heated at high speed by high-frequency induction heating means for molding optical components.

[Means to solve the problem]

In the mold according to the present invention, the base of the mold is made of an iron-based metal, and an electroless nickel-phosphorus plating layer is formed on the surface of the iron-based metal base.

The present invention focuses on the characteristics of a composition that combines nickel N1 and phosphorus P1 or nickel N], phosphorus P, and cobalt CO,
Heating is performed by high-frequency induction due to the magnetism of nickel Ni and cobalt Co, and an amorphous structure of the composition of nickel Ni and phosphorus P is formed on the mold surface.

[Effect]

The composition of nickel N1 containing phosphorus P becomes amorphous, and the mold surface can be mirror-finished by mirror cutting using a diamond cutting tool, and the mold cavity can be formed by high-frequency induction heating due to the magnetism of nickel Ni or cobalt Co. The temperature of the surface layer can be raised in a short time.

[Explanation of Examples]

FIG. 1 is a block diagram of an injection molding apparatus using a mold according to the present invention which will be described later, FIG. 2 is a temperature curve diagram of the mold, and FIG. 3 is a timing chart of each unit constituting the apparatus.

In the figure, reference numeral 1 indicates the main body of the injection molding machine, which includes a stationary mold 2A having a cavity (not shown) for forming a molded product, a movable mold 213, and a mold plate 4A supporting the mold. 4B, a moving guide member 6, a hopper 8, an injection cylinder IO, a driving means 12 for opening and closing the mold, and the like.

14 is a temperature regulator for adjusting the temperature of the mold;
4 is connected to a cooling medium flow path (not shown) in the molds 2A and 2B via a pipe 14A, so that the cooling medium can be circulated by a pump (not shown).

Reference numeral 18 denotes a high-frequency induction heating means, which includes a high-frequency induction control section 18A, a coil section 18B, a support member 18C that supports the coil section 18B, and drives the support member forward and backward in the direction indicated by the arrow. It is composed of a moving means 18D.

20A and 20B are temperature detection sensors, which are embedded in appropriate positions of the mold to detect the temperature of the cavity surface of the mold and output a detection signal, and the detection signal is sent to the lead wire 22A. The temperature is inputted to the temperature detection means 22 via the temperature detection means 22.

Reference numeral 24 indicates a molded product take-out means, and the means 24 takes out the molded product molded by the automatic handler l' 24A.

26 is a controller that controls the entire molding apparatus.

[First Example of Mold] FIG. 3 shows a mold composed of an iron-based metal layer 100 and a plating layer 110. 555C was used as the iron-based metal. FIG. 4 shows the manufacturing process of the mold of the first embodiment.

First, the surface of the iron-based metal 355C is processed into the shape of a cavity of a molded product (a). The surface roughness accuracy Rmax is processed to be 1 μm or less. After that, the electroless nickel-phosphorus plating layer 110 is coated in a plating solution with a phosphorus content of 11%.
Plate the cavity surface of 355C to a thickness of 00 μm (b). After the plating layer was formed, heat treatment was performed at a temperature of 250° C. for 2 hours in an atmospheric constant temperature bath (c). After the heat treatment, a cavity surface was formed by mirror cutting a 50 μm deep chevron groove using a precision lathe using a diamond tool. The surface roughness accuracy of the cavity surface is Rm a x 0, 01μm
The following accuracy was maintained (d).

The mold according to the first embodiment is mounted on the molding apparatus shown in FIG. 1, and a temperature sensor is installed in the mold.

The space interval between the heating coil 1.6B of the high-frequency induction heating means 16 and the mold cavity surface was set to 2 mm, and the high-frequency output was 8.2 Kw at t and the frequency was 132.
KHz oscillation operation is performed, and the aforementioned temperature sensor 20A.
When the output of 0B was measured by the temperature controller 22, the surface temperature of the cavity surface was instantaneously heated from 55° C. to 244° C. in 9.5 seconds. The heating rate of the mold in this example was 20° C. per second. Table 1 shows this embodiment and the conventional example (1
) and (2) in terms of specularity and heating rate, the mold of this example is superior in both aspects.

Table 2 shows a comparison between the mold of the first example having a phosphorus content of 11% and other comparative examples. In Comparative Example 1, a mold material with a phosphorus content of 4% and heat treated at 250° C. for 2 hours was diamond-cut, and the surface roughness accuracy was limited to 0° and 15 μm. The heating rate by high-frequency heating was 21° C./sec, but this is not suitable for mold materials that require a high degree of surface roughness accuracy for optical parts and the like.

Comparative example 2 is the data of a mold material heat-treated at 400°C for 2 hours with a content of 11%, and comparative example 3 is the data of a mold material with a content of 14% and heat treated at 250°C.
Data for a molded material heat-treated for 2 hours is shown.

As can be understood from the comparative data in Table 2, increasing the phosphorus content (increasing the phosphorus content makes it possible to improve specularity.Also, although nickel itself has magnetism, its specularity is low, and nickel containing phosphorus Since the plating layer has an amorphous composition, it has good mirror machinability, and when heat treated, it becomes magnetized depending on the heat treatment conditions, so high frequency heating can be performed efficiently.

As a result of repeated various experimental studies, the phosphorus content was reduced to 8.
% to within 13%, and heat treatment temperature from 2000C to 3
The mold material formed by heat treatment at 50°C for 1 to 3 hours has a surface roughness of less than 0.01 μm when cutting the plating layer, and high-frequency induction heating It was found that a heating rate of 20'C/sec or more was obtained by this method.

Table 3 shows data when a Fresnel lens was molded using the mold shown in the first embodiment.

Next, the operation of the apparatus shown in FIG. 1 will be explained with reference to FIG. By the molding start operation (not shown) of the controller 26, the movable mold 2B that is in the initial mold opening position starts moving in the direction of closing the mold, and the movable mold 2B is brought into contact with the fixed mold 2A at a predetermined position. When the movable mold 2B reaches the first position where the distance is maintained, the movable mold 2B stops moving.

When the movable mold 2B reaches the first position and stops, a signal P for controlling the high frequency induction heating means 16 is output from the controller 26. In response to the control signal P, the moving means 16D moves the heating coil 18B, which had been evacuated outside the opening/closing movement area of the molds 2A and 2B, to enter between the moving mold 2B and the fixed mold. Start. Heating coil 18B
V is a position facing a cavity surface (not shown) of the mold, and stops when it reaches a position suitable for heating the cavity surface. As the heating coil 18B is stopped, the high frequency induction control section 16A outputs 8.2Kwatt,
High-frequency oscillation with a frequency of 132 KHz is performed, and the high-frequency oscillation is transmitted to the heating coil 18B, and the molds 2A and 2B are heated by a known high-frequency induction heating operation, and the temperature reaches the point at which the oscillation starts, as shown in FIG. Temperature t at t1
The temperature rises along the curve a from A to the peak temperature tB.

A signal P for operating the temperature regulator 14 is sent from the control unit 26.
2 is activated, and the temperature regulator 14 is activated during the initial operation of the molding start-up operation of the controller. The temperature regulator 14 adjusts the temperature of the cooling medium in a storage tank (not shown) to a predetermined temperature of 80° C., and at the same time operates a pump (not shown) to move the cooling medium into the flow path 14. A cooling medium is circulated through A into the stationary mold and the movable mold. While the cooling medium circulates within the mold, the temperature of the mold cavity rapidly rises to 244° C., the peak temperature tB shown in FIG. 2, due to high frequency induced oscillation by the heating coil 16B. The temperature of the mold is detected by sensors 2OA and 20B installed in each mold, and the detection signal is input to the temperature detection means 22.

The temperature detection means 22 has a sensor that detects the peak temperature tB24.
When 4° C. is detected, an oscillation stop signal is sent to the high frequency oscillation control section 16A, and at the same time, the heating coil 16B is evacuated by the moving means 16D.

Simultaneously with the completion of retraction of the heating coil 16B, the movable mold 2B is closed by the mold driving means 12, and a mold clamping operation is performed.

When the mold clamping operation is completed, the mold is ready for injection of the resin material (polycarbonate), but it takes the time shown in Figure 2 from the time when the heating coil stops oscillating to the completion of the mold clamping operation. There is a time lapse Δt1 from t2 to time t3. During this elapsed time Δt, the temperature of the mold is (tB-t o) -244-160=84℃
However, one of the features of this device is instantaneous heating by high-frequency induction heating and cooling operation using a cooling medium during the heating, so that the injection temperature t is lowered from the peak temperature tB - 244°C. The temperature drop curve up to -160°C always forms a constant curve, and the injection temperature t.

The temperature of 160° C. remains constant throughout the injection molding cycle.

The control unit 26 operates the injection cylinder 10, and the molten resin material in the hopper 8 is injected into the mold cavity through a gate (not shown). After a predetermined amount of the resin material is injected, the mold is cooled along a temperature curve C, and the molten resin inside the cavity solidifies along the cavity shape to form a molded product.

After that, the mold temperature is set to a temperature tD-11,00 suitable for mold release.
When it descends to C, a mold opening signal is sent from the control section 26 to the mold driving means 12, and the movable mold 2B moves. When the mold opening is completed, the molded product ejecting means 24 is activated and the auto hunt 2 is activated.
4A, the molded product is taken out, molding is completed, and one cycle of molding is completed.

If the above-mentioned molded product is a Fresnel lens as shown in Figure 9, the molten resin material injected into the cavity should spread to every corner of the cavity that forms the acute angle part of the lens, so that no voids are created. To achieve this, it is necessary to set the mold temperature to a high temperature to promote the fluidity of the resin, and at the same time, no matter how many times the molding cycle is repeated, the temperature shown in Fig. Although it is necessary to maintain the curve, the present invention has obtained sufficiently satisfactory results using the above-mentioned molding method.

The material of the mold of the comparative example shown in Table 3 is S K D 61, and as can be understood from Table 3, the molding cycle of the mold of the comparative example shown in the first example is shorter than that of the comparative example. could be significantly shortened.

FIGS. 8A and 8B are schematic diagrams showing the molding results of molded products according to the molding method according to the present invention and the comparative example described above based on the data in Table 1.

The molded product shown in FIG. 8A-B above shows an enlarged view of the cross section of a Fresnel lens, and FIG. 8B shows the molding method of the prior art. Curled up. On the other hand, FIG. 8A shows the molding method of the present invention, in which the apex angle is accurately acute and the tip is not rounded.

In the case of a Fresnel lens, the incident light Xl + X2... needs to be refracted at the lens surface and focused at one point on the optical axis. In the embodiment of the present invention, as shown in FIG. 4A, the light incident on the vertex is refracted accurately, so each incident light can be focused on one point, and the image called a ghost of the image is eliminated. No blurring occurs. On the other hand, in the case of the prior art, as shown in Figure 8B, the refraction angle of the light incident on the apex portion becomes smaller due to the blurring of the apex angle, and the incident light is focused at a point on the optical axis. This results in ghosting and blurring of the image.

There is a method shown in FIG. 10 as a guideline for measuring the molding accuracy of Fresnel lenses.

The ratio of the height h actually obtained by molding to the designed height H from the bottom of the Fresnel lens to the top corner h/
It can be said that the larger H is, the higher the molding accuracy is.

According to this method, the value was about 70% in the case of the prior art, but in the case of the above-mentioned Examples 1 and 2 of the present invention, a very high value of 98 to 99% could be obtained.

[Second Example of Mold] This example provides a mold material in which a cobalt layer is formed on an electroless plating layer. FIG. 5 is a diagram showing the structure of the mold material of this example. In the figure, 100 is an iron-based metal, 120 is an electroless nickel-phosphorus plating layer, and 130 is a cobalt vapor deposition layer deposited on the plating layer. 55 as iron-based metals
Using 5C, shape processing is performed in the same manner as in the first embodiment, and an electroless nickel-phosphorus plating layer 120 with a phosphorus content of 11% is formed to a thickness of 100 μm, followed by heat treatment at 2508C for 2 hours. Thereafter, a chevron-shaped groove with a depth of 50 μm was mirror-finished, and then cobalt was deposited to a thickness of 2 μm on the mirror-finished surface by an ion blating method.

The mold made as described above is mounted on the apparatus shown in FIG. 1,
When the high frequency induction heating means was operated at an output of 8.2 Kwatt and a frequency of 132 KHz to heat the mold, the mold surface temperature rose from 55° C. to 245° C. in 8 seconds. The heating rate of the mold in this example was 24° C./sec. In addition, the accuracy of the surface roughness of the cobalt vapor deposited layer described in 1. is Rm
a x 0 was 01 μm.

The mold of Example 2 was molded to form a Fresnel lens under the conditions of Example 2 in Table 3 to obtain the data shown in the table. As a result, the molding cycle had a cycle time of 58±2 seconds.

As a result of the confirmation experiment of this example, the cobalt content ranges from 2% to 1%.
2 in the range of 0% and the phosphorus content in the range of 4% to 10%.
The molds subjected to heat treatment at a temperature of 00° C. to 350° C. for 1 hour to 3 hours secured the data shown in Example (2) of Table 1.

[Third Embodiment of Mold] FIG. 6 shows the structure of a mold material according to a third embodiment. In the figure, 100 is an iron-based metal 555C, 120 is an electroless nickel-phosphorus plating layer, and 140 is a hard chrome plating layer. Using iron-based metal 555C, the first
Shaping was carried out in the same manner as in the example, and an electroless nickel-phosphorus plating layer with a phosphorus content of 10% was formed to a thickness of 100 μm, and heat treatment was performed at a temperature of 2008C for 2 hours. A heart chrome plating layer 140 having a thickness of 3 μm was formed on the nickel-phosphorus plating layer to form a mold.

When the mold of the third embodiment was mounted on the molding machine shown in the first diagram and a temperature test of the mold was performed, the output was OKwatt.

The temperature was measured by operating the high frequency dielectric heating means at a frequency of 132 KHz. As a result, 550 in 8 seconds
It was confirmed that the temperature rose from C to 198C. The specularity of this mold had a surface roughness accuracy of Rmaxo, 01 lt m.

[Fourth embodiment of mold] FIG. 7 shows a fourth embodiment. In the figure, 200 is the base of a mold made of a copper alloy, and 210 is an electroless nickel-phosphorus plating layer. The surface roughness accuracy of copper alloy is Rmax
Finish to 2μm. An electroless nickel-phosphorus plating layer with a 11% phosphorus content is formed on the surface of a copper alloy to a thickness of 1 mm, and a 50 μm deep chevron groove is machined by mirror cutting. At this time, the roughness was RmaxO, 01 μm. This mold was installed in the molding machine shown in the first figure, and the output was 30Kwatt.
When the high-frequency induction heating means was operated at a frequency of 420 KHz, the mold surface was heated from 55°C to 20°C in 10 seconds.
Heated to 0°C.

The base of the mold in the fourth embodiment is made of a non-magnetic copper alloy that is not an iron-based metal, and by forming an electroless plating layer on the surface of the copper alloy, the plating layer is made amorphous and the mold surface is It was possible to ensure the specularity of the shape processing, and to raise the temperature of the mold by oscillating at a high output of 30 Kwatts and 420 KHz for heating.

〔Effect of the invention〕

According to the present invention, the magnetism of iron-based metals and electroless nickel
By heat-treating the phosphor plating layer to obtain a mold material with a specular surface, it was possible to obtain a mold that can reach high temperatures in a short time using high-frequency induction heating. . By using the mold of the present invention, it was possible to form a cavity with excellent surface roughness accuracy and a finely uneven shape, thereby improving the molding accuracy of optical components and the like.

In addition, due to the magnetism of the iron-based metal and the resistance value of the iron-based metal during high-frequency induction heating, it is possible to heat the iron-based metal to a high temperature in a short time, thereby shortening the molding cycle shown in the second diagram, which improves productivity. I was able to improve.

Part 1 table No. table Table 2

[Brief explanation of the drawing]

FIG. 1 is an apparatus configuration diagram of a molding machine using a mold according to the present invention. Figure 2 is a temperature curve diagram. 3 to 4 (a), (b), (c), and (d) show the first embodiment, and FIG. 3 is an explanatory diagram of the structure of the mold, and FIG. b), (c), and (d) are mold manufacturing process diagrams. FIG. 5 is an explanatory diagram of the structure of the mold of the second embodiment. FIG. 6 is an explanatory diagram of the structure of the mold of the third embodiment. FIG. 7 is an explanatory diagram of the structure of the mold of the fourth embodiment. FIG. 8A-B is an explanatory diagram of a Fresnel lens. FIG. 9 is a configuration diagram of a Fresnel lens. FIG. 10 is an explanatory diagram of a Fresnel lens. 2A, 2B... Mold 16, 16A, 16B, ], 6 C, 16D... High frequency induction heating means 100, iron-based metal

Claims (2)

[Claims] (1) Composed of iron-based metal and electroless nickel-phosphorus plating layer, the phosphorus content of the electroless nickel-phosphorus plating is 8%.
13%, and the heat treatment conditions are 1 hour to 3 hours at a temperature of 200° C. to 350° C. (2) Consisting of an iron-based metal, an electroless nickel-phosphorus plating layer, and a cobalt layer, the phosphorus content of the electroless nickel-phosphorus plating layer is in the range of 4% to 10%, and the cobalt content is 2%. 10%, and is heat treated at a temperature of 200°C to 350°C for 1 to 3 hours.