JPS5925645B2 - Method for manufacturing molds by electroforming - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a mold by electroforming, which is improved so as to improve manufacturing accuracy.

BACKGROUND ART Recently, molds with cavities made of nickel electroforming, for example, have been provided as molds for molding molded products that require dimensional accuracy or molded products with complex shapes. The cavity produced in this way is usually integrated into a mold to form a mold, but in the past, for example, a mold was made by pouring molten zinc alloy into the back side of the cavity, or a mold made of steel was used. A recess is formed on the surface of a mold material by copying the cavity as a model, the cavity is fitted into the recess, and the two are connected by bolting. However, when manufacturing molds by pouring zinc alloy, the cavity itself is heated to about 400℃, which is the thermal composition deformation temperature of the nickel electroformed product (430℃).
℃ to 450℃), there is a drawback that the dimensional accuracy and electrodeposited physical properties deteriorate considerably due to thermal deformation, and when forming recesses by copying, it takes a long time for copying. When fitting the concave portion after copying into the cavity, there is a large amount of finishing margin and it takes a long time to fit the pattern, which has the disadvantage of lengthening the manufacturing time and increasing the cost of labor.
The present invention has been made in view of the above-mentioned circumstances, and it is possible to obtain a mold with very good dimensional accuracy (b') without deteriorating the dimensional accuracy of the cavity due to thermal deformation. Manufacture of molds by electroforming process, which eliminates the need for copy processing, reduces mold matching time, shortens production time overall, and significantly reduces production costs. The purpose is to provide a method.

Hereinafter, an embodiment in which the present invention is applied to a mold used for injection molding of plastic will be described with reference to the drawings.

That is, a mold for injection molding usually consists of a pair of upper and lower molds that are divided into upper and lower halves at a parting line, and the upper mold 1 will be explained below. Second
In the figure, 2 is a mother mold for electroforming formed into an uneven shape opposite to that of the cavity 3. This is a conductive material or a non-conductive material with conductive processing applied to the surface of the mother mold 2. The cavity 3 is manufactured by electroforming nickel to a predetermined thickness by electroforming. Cavity 3 after electroforming is the mother mold 2
Without releasing the undercut part 3a from the mold, for example, nickel is welded to the undercut part 3a on the outer surface by metal spraying and overlaid B4 into a shape that can be cut out (see Fig. 2a), and then the cavity 3 is
A reinforcing layer 5 is formed by welding a predetermined thickness of nickel over the entire outer surface of the reinforcing layer 5 by metal spraying (see Fig. 2b).
. After the metal spraying has been completed, a thin layer of copper or a copper alloy, for example, is electrodeposited on the outer surface of the reinforcing layer 5 of the cavity 3 by electroforming. First, a female mold 6 is formed from plaster using the cavity 3 that has been electrodeposited with copper or copper metal as a prototype (
Further, a male mold 7 is formed using this female mold 6 as a prototype (see FIG. 2 d). 8 is a mold manufactured by casting iron, aluminum, brass, etc. using this male mold 7 as a prototype, and a recess 9 having a shape that substantially matches the outer surface of the cavity 3 is formed on one side of the mold. (See Figure 2e)
.

Now, this mold 8 is made to match the outer shape of the cavity 3 by electro-discharge machining the concave portion 9 using the cavity 3 on which the electrodeposition of copper or copper alloy ◇ or the like as described above has been completed as a mass. In this case, when the mold 8 is cooled to room temperature after casting, it shrinks at a predetermined rate and the recess 9 becomes slightly smaller than the outer shape of the cavity 3. .5~1r
m) is obtained. In addition, the reinforcing layer 5 of the cavity 3 described above
The material of the thin electrodeposited layer to be electrodeposited on the outer surface of the mold 8 may be selected from a material suitable for use as an electrode when electrical discharge machining is performed on the recess 9 of the mold 8. You can choose. Now, the outer surface of the cavity 3 whose concave part 9 of the mold 8 has been finished by electric discharge machining is electrodeposited in a thin layer with a soft filler material mainly composed of tin and lead by electroforming, and the electrodeposition is completed. The rear mother mold 2 is released from the cavity 3, and the cavity 3 is fitted into the recess 9 of the mold 8. Because the recess 9 becomes slightly larger (5/1000 to 1/100 rfm) than the outer shape of the cavity 3 due to the electrical discharge machining described above, the thickness of the electrodeposited layer of soft brazing material is set to 5/1000 to 1/100? If it is set within the range b, it becomes possible to tightly fit the cavity 3 into the recess 9. The mold 8 into which the cavity 3 is fitted is heated in a heating furnace at, for example, 250° C. to 300° C. for a predetermined period of time, and then cooled to room temperature outside the heating furnace. Then, the soft brazing material layer on the outer surface of the cavity 3 is first melted and then solidified, and the cavity 3 and the mold 8 are bonded together by brazing. In this case, the heating temperature in the heating furnace is set appropriately according to the material of the soft brazing material, and the flux necessary for brazing is applied to the outer surface of the cavity 3 or to the recess before fitting the cavity 3 into the recess 9. All you have to do is apply it to 9 and count it. In addition, in FIG. 1, reference numeral 10 denotes a holding member as an appropriate fixing means fixed to the mold 8 with bolts 11.
The claw portion 10a of this is pressed into contact with the engagement groove 12 of the cavity 3, thereby increasing the degree of coupling between the cavity 3 and the mold 8.

The presser member 10 is a concave portion 1 formed on the surface of the mold 7.
3, so that it does not protrude beyond the parting line. Further, the engagement groove 12 and the recess 13 may be formed in the cavity 3 and the mold 8, respectively, by machining before the cavity 3 is fitted into the recess 8. In the above embodiment, the cavity 3 is connected to the recess 9 of the mold 8.
Brazing with a soft brazing material is used as a fixing means to bind the
Although both are used together with the presser member 11 fixed with bolts 11, the bonding strength required for both may vary depending on the material of the plastic to be molded, the molding temperature, or the molding method. On the other hand, if very high bonding strength is not required, it is sufficient to use one of the fixing means.

When brazing is used to connect the cavity 3 and the recess 9 of the mold 8, local distortion in the cavity 3 can be prevented as much as possible compared to when only bolts are tightened. The dimensional accuracy of can be further improved.

In this case, the heating temperature of cavity 3 for brazing is about 250°C to 300°C, which is sufficiently lower than the thermal composition deformation temperature of nickel electroformed products (430°C to 450°C), so brazing The thermal deformation of the cavity 3 is negligible and does not affect the dimensional accuracy of the mold and the electrodeposition properties at all. Furthermore, in this case, since the entire outer surface of the cavity 3 is brazed to the recess 9 of the mold 8, the cavity 3 and the mold 8 are bonded together even though the strength of the soft brazing material itself is relatively weak.
The strength of the bond can be equal to or higher than that of bolt tightening. By the way, when the cavity 3 and the mold 8 are bonded together by brazing, the method of attaching a soft brazing material to the cavity 3 by electrodeposition in advance has been explained as an example. Brazing does not necessarily have to be done by this method, and any commonly used brazing may be used. For example, the mold 8 is immersed in a bath containing melted soft brazing material, and the outer surface including the recess 9 is brazed. It is also possible to attach a soft brazing material, and in short, it is sufficient to select the material as appropriate.
According to the present invention, since the mold is manufactured by casting using the cavity filled with the undercut as a model, there is no need to copy the mold. Finishing allowance suitable for electric discharge machining (approximately 0.
5 to 1), the time required for second discharge machining is also short, and the machining time is significantly shortened overall. As an example, if the master mold is semi-cylindrical with a length of about 30 cm and a radius of about 8 cm, it takes 10 hours to copy the mold using the conventional method, and the finishing margin of the recess is about 3 to 30 minutes when copying. 5m
The remaining 7 to 8 hours are required for electrical discharge machining, but in the method of the present invention, the finishing margin for the concave portion of the mold is approximately 1 mm, so the cavity and mold can be matched in just 2 to 3 hours of electrical discharge machining. .

Furthermore, since the cavity is not heated to high temperatures unlike the conventional structure in which molds are manufactured by pouring zinc alloy, the dimensional accuracy of the cavity does not deteriorate at all due to thermal deformation, resulting in a mold with excellent dimensional accuracy. Can make molds.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and FIG. 1 is a longitudinal sectional view, and FIGS. 2 a to 2e are longitudinal sectional views showing the manufacturing process of the upper mold. In the drawings, 1 is an upper mold, 2 is a mother mold, 3 is a cavity, 5 is a reinforcing layer, 8 is a mold, and 9 is a recess.

Claims (1)

[Scope of Claims] 1. A step of manufacturing a cavity by depositing metal on the surface of a mother mold by electroforming, and depositing metal on an undercut portion of the outer peripheral surface of the cavity by metal spraying. and filling the undercut portion to make the outer peripheral surface of the cavity into a shape that can be cut out, and using the cavity that has been overlaid to be cut out in the above step as a model, a mold having a recess corresponding to the cavity is created. A step of manufacturing by casting, a step of matching the molds by electrical discharge machining using the cavity, which is overlaid so that the recess of the mold can be removed, as a master, and a step of mold matching the recess of the mold after the mold matching. A method for producing a mold by electroforming, which comprises the steps of fitting the removably built-up cavity body and bonding the two together using a suitable fixing means. 2. The step of bonding the mold and the mold-cuttable cavity is to form a soft brazing material layer on one side of the mold, fit the cavity into the recess of the mold, and then heat the mold in a heating furnace. 2. The method of manufacturing a mold by electroforming according to claim 1, wherein the molds are integrated by brazing by heating within the mold. 3. Molding by electroforming according to claim 2, characterized in that the soft brazing material layer is formed by electroforming on the outer surface of a removable overlay cavity. Mold manufacturing method.