JPH04151207A - Manufacture of zinc alloy mold - Google Patents

Abstract

PURPOSE:To bury pinholes and sink voids generated on a precision cast skin and prevent them from being transferred to the surface of a molded product by forming a flame spray coated film of zinc or zinc alloy on a section constituting the molded product surface of a mold. CONSTITUTION:Pinholes and sink voids on a cast skin section of a precision cast mold surface are crushed by the blast treatment, and a matrix is activated and then a zinc or a zinc alloy uniform film is formed by the usual flame spray coating to bury the pinholes and sink voids. A uniform film is formed on the precision cast skin by said arrangement, and after that, defects such as pinholes and sink voids are not recognized on a finished surface to form a good finished skin, and also the surface of a molded section is provided with the good skin. Also, an aluminum or aluminum alloy flame spray coated film is formed on a section to form the molded surface of a mold, and an anodized film is formed and the mold surface is hardened after the finishing process to bury the pinholes and sink voids generate on the finished surface.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention uses a zinc-based alloy to create a mold made of a zinc-based alloy that can be used to manufacture molds for forming metals, ceramics, paper, foods, etc. This relates to a manufacturing method.

(Conventional technology) Molds are often used for molding mass-produced products, but the need for such molds is increasing toward high-mix, low-volume production. On the other hand, if molded parts are manufactured by cutting the parts themselves without using molding molds, the costs will be enormous, and the products that make up the parts themselves will be expensive, making the product less competitive and less competitive. Sometimes it becomes impossible to convert. Therefore, if you consider the cost of each part, you may be able to use a mold to produce it even in small quantities. There was a need to reduce it.

One example is the use of molds made of zinc-based alloys, which are relatively inexpensive to manufacture. In particular, molds made of zinc-based alloys are being used in large quantities by precision casting, which has been significantly developed in recent years. On the contrary, zinc-based alloys have low hardness and deformation due to wear, so the use of prototype molds was limited to small-volume production molds.

(Problem to be solved by the invention) Since zinc-based alloy precision casting molds are low melting point alloys when compared to other mold materials, they are easy to melt and cast, and can be used in sand molds, plaster molds, molds, etc. It can be cast easily and is easy to use for precision casting. It also has good machinability and grindability, and has low processing costs. Furthermore, it can be repaired by welding, can accommodate design changes, can be used repeatedly by remelting the base metal, and has higher thermal conductivity than steel.
It has many advantages, including lower manufacturing costs compared to steel mold materials, and 40% lower manufacturing costs than molds made from other mold materials.
It is said that molds can be made at ~50% of the cost, and in particular, molds manufactured by precision casting can shorten the cutting process, and are used as prototype molds and small-scale production molds for resin molded products. However, zinc-based alloy materials have lower hardness than other mold materials (H3 = 100), so they are prone to roughness and deformation due to wear and the like, making them unsuitable for mass production molds.

However, in precision casting, the surface of the molded product or casting skin is used as the mold surface with little polishing, and this may be one of the factors contributing to the cost reduction of molds. It is recognized that a hole has occurred. Therefore, in order to remove these pinholes, unless the pinholes are removed by polishing or welding to fill them, the pinholes and cavities will be transferred to the surface of the molded product. Ru. This hinders the reduction in finishing costs due to good transferability and good surface roughness formed by precision casting, and there is a problem in that the characteristics of the precision casting mold cannot be sufficiently compressed.

Furthermore, zinc-based alloys can be machined from cast blocks,
It is made by precision casting, and since it is basically a cast material, it may have cavities or pinholes. For this reason, when a mold is machined from a cast material block, the occurrence of these cavities and pinholes is observed on the cut and finished surface, and these are also transferred to the product surface.

The present invention easily fills pinholes and cavities that occur on the casting surface, which is the surface of the molded product of zinc-based alloy precision casting molds that can be manufactured at low cost, and also makes good use of the transferability of precision casting. To achieve this, by forming a sprayed layer of zinc or zinc-based alloy on the surface of the precision-cast mold, it fills in the pinholes and cavities that occur on the precision-casting skin and improves the quality of the molded product. The purpose is to prevent it from being transferred to the surface.

In addition, the present invention forms a thermally sprayed coating of aluminum or aluminum alloy that is easy to cut and polish on the surface of a zinc-based alloy mold, and at the same time fills the shrinkage cavities and pinholes that occur on the surface of the mold. After finishing, by forming an anodized film (hard alumite treatment) on the core part, it smoothes the forming surface of the molded part and hardens at the same time. This project aims to utilize zinc-based alloy molds, which were previously limited to molding products, as molds for medium and large-scale production.

(Means for Solving the Problems) For this reason, the present invention forms a sprayed coating of zinc or a zinc-based alloy on the part constituting the surface of the molded product of a zinc-based alloy mold to improve the surface of the molded product of the mold. It was designed to form
This is a means to solve problems.

The present invention also provides a method for forming a thermally sprayed coating of aluminum or an aluminum alloy on the surface of a molded product of a zinc-based alloy mold, and after final surface forming such as polishing and texturing, the thermally sprayed aluminum or aluminum An anodic oxide film is formed on the surface of an aluminum alloy film, and this is used as a means to solve the problem.

(Function) The present invention uses a blasting process to crush the pinholes and cavities on the casting surface of a precision-cast mold, and also coats the base material uniformly with zinc or zinc-based alloy by a normal thermal spraying method after activation. By forming a protective film, it fills in pinholes and cavities. In addition, the coating formed by the thermal spraying method has a uniform coating thickness, and a uniform coating is formed on the precision casting surface, so subsequent polishing etc. can be completed in the same process and with the same number of man-hours as finishing the precision casting surface. The finished surface has no defects such as pinholes or cavities.
A good finished surface is obtained, and the surface of the molded part has a good surface with no pinholes or cavities observed.

These surfaces can also be textured,
The finished surface on which the sprayed coating is formed is completely the same as the base material of the zinc-based alloy, and it is possible to obtain the same surface formability as that of the zinc-based alloy.

Further, the present invention is to form a thermally sprayed coating of aluminum or an aluminum alloy on the portion that will become the molding surface of the mold, and to harden the mold surface by forming an anodic oxide film after finishing. Since the mold surface is covered with an aluminum or aluminum alloy film that has good workability, it is possible to fill in the pinholes and cavities that occur on the machined surface, reducing the increase in processing costs.

The aluminum or aluminum alloy thermal spraying method used here is not particularly limited as long as it is a normal thermal spraying method, or a thermal spraying method that generates as few pores as possible in the sprayed coating may be used.

Further, the thermal spraying process can be handled by a thermal spraying process used for normal surface treatment. Various methods have been proposed for anodic oxide film treatment, and it is difficult to know which method is best to use. Surface roughness or fineness is required.

In this way, by forming an anodic oxide film on the aluminum and aluminum alloy thermal spray coating used for boat fishing on the molded product forming surface of the mold, the zinc-based alloy material has a low hardness and is therefore resistant. By forming an anodic oxide film with poor abrasion resistance, which could only be used for simple molds, prototype molds, and small-scale production molds due to wear and deformation, or hardness,
There will be less wear and deformation during use, and molds for medium and high volume production can be manufactured at low cost and in a short lead time.

(Example) Hereinafter, the present invention will be explained in detail with reference to the following examples.

Example 1 In Example 1, a mold for molding motorcycle parts for molding ABS resin will be described. This mold is a mold for resin injection molding, which is made so that a pair of right-hand and left-hand symmetrical shapes are molded in one mold.

Now, after manufacturing using normal precision casting using zinc-based alloy material, parts other than the resin molded parts were finished by machining. After that, the surface of the right specification part that will become the molded product was finished, and the finished surface had a diameter of 0.1 to 0.8 mm and a depth of 0.1 to 0
．． It was observed that the shrinkage of about 3 mm was caused by concave portions, which were thought to be nests, or at a density of about 1 piece/ad. Therefore, the mold surface of the right specification part was left as is, and the recess was filled with TIG welding using a zinc base metal made of the same material as the mold material, and then finished by polishing. As a result of a detailed observation of the casting surface, which is the surface of the molded product in the one-pressure part, it was found that there were concave areas similar to the surface of the right part. Therefore, we decided to form a thermal spray coating on the surface of the molded product for the left specification part.

However, since molded parts are exposed to the human eye on both sides, we decided to form a thermal spray coating on the surfaces of both the movable and fixed molded parts.

First, the movable Y part and the fixed mold part are degreased with a solvent, and then the parts other than the molded part and the surface are masked with cloth tape coated with adhesive. Thereafter, blasting, preheating, and then thermal spraying were performed in the usual thermal spraying process. For blasting, the alumina grid material is blasted with compressed air using a suction blasting machine.
The part to be thermally sprayed was blasted with kg/alG. At this time, the blasting is done so that the nests and pinholes are crushed. Immediately after that 100-1
Preheat to 20℃ and spray.

Currently, many thermal spraying methods have been developed for thermal spraying, such as arc spraying, wire flame spraying, powder flame spraying, plasma spraying, high-velocity flame spraying, wire explosion spraying, and deflagration spraying. method may also be used. However, it is desirable to use a thermal spraying device that can produce a dense thermal sprayed coating without large pores remaining in the thermal sprayed coating.

In this example, a zinc material was uniformly sprayed to a thickness of 0.2 mm on the molding surface by arc spraying, and then the surface was finished. The thermal spraying conditions are preferably standard conditions for the thermal spraying material used by each thermal spraying device, or thermal spraying conditions that make the film denser.

The processed precision casting mold was completed by attaching necessary parts such as the base, cooling pipe, dowel pin, bushing, etc., and was installed in an injection molding machine and molded with the specified ABS resin. I was able to mold an ABS resin molded product with good specifications. Also, regarding the number of man-hours required for surface finishing the molded product, if we compare the process of polishing → weld build-up → polishing for the right model and the thermal spraying → polishing for the left model, the number of man-hours for the former is approximately %.
It was found that the present invention is a mold manufacturing method that is effective as a surface treatment for repairing pinholes and cavities that occur on the surface of precision casting molds.

Example 2 This Example 2 is a mold for molding a urethane resin using a measuring instrument/'% Uging. Initially, only a few prototypes were planned, and when they were made using a zinc-based alloy precision casting mold, recesses due to evacuation cavities were observed on the surface of the mold, which is the surface of the molded product.

Next, the urethane resin molded product was polished and used as a housing part to make a prototype measuring device.Afterwards, the design was changed, so the shape of the mold was changed by cutting and welding, and the prototype was made again. Since only a few prototypes were produced, the surface of the transfer part based on the concave shape of the mold surface was polished before use.

Due to this design change, the delivery date was delayed. Originally, we had planned to create a new mold using 325C material as a production mold, but due to the delay in delivery, the surface of the molded product was made from a zinc-based alloy mold that was created as a prototype mold. As in Example 1, a 0.2% zinc-based alloy was sprayed onto the part by the arc spraying method, and after polishing, it was used as a green prototype. Since the number of pieces to be molded was approximately 8,000, production was completed using this mold, and parts with commercial value or similar to the products manufactured using this mold could be created without making the actual mold.

In addition, with this method, a measuring device can be commercialized without creating a production mold, resulting in a mold manufacturing method that can significantly reduce costs (Table 1).

Table 1 Embodiment 3 The resin molding mold is used as a RIM molding molding mold, a vacuum molding mold, etc. In this Embodiment 3, an injection molding mold will be described.

In this example, in order to compare the performance of anodized film treatment,
A prototype mold for automobile parts was used.

This mold is made of urethane resin and has two symmetrical shapes, one for the right side and the other for the left side, in one mold. This mold was reused after the trial production was completed, and was manufactured using precision casting from a zinc-based alloy. The surface of the prototype molded product after polishing has a diameter of 0.1 to 0.5 mm.
Protrusions with a height of 0.1 to 0.3 mm were observed at a density of about 1 month/al. These protrusions are defects specific to precision casting molds made of zinc-based alloys. Pinholes and cavities occur on the mold surface during casting, and even if the precision casting zinc-based alloy is lightly polished, it remains on the mold surface skin. This is transferred to the surface of the molded resin product.

Since approximately 30 of these prototype molded products were required, the surface of the trial molded products was polished to remove pinholes and holes that had been transferred into protrusions before use. This mold is the surface of the movable side or the surface of the molded product, so in this test, we used this mold on the movable side, leaving the right side as it is, and coating the left side with the aluminum spraying + anodic oxide coating of the present invention. After processing, tests for practical use were conducted. The process involves removing all the bases, cooling pipes, dowel pins, bushings, etc. other than the main body zinc-based alloy attached to this mold, and closing the holes where the cooling pipes and dowel pins are installed with blind covers. Thereafter, it was degreased with an organic solvent to remove oil, mold release agent, etc.

After the degreasing process was completed, the parts other than the surface of the molded product shown on the left were masked with glass tape. The mold, which was masked except for the necessary parts, was blasted with a #320 mesh alumina blasting material at a pressure of 3 kgf/cofG of compressed air on the part that would become the surface of the molded product using a simple blaster. Immediately thereafter, aluminum was thermally sprayed to a thickness of about 0.2 mm.Although 99% or more aluminum material was used, an aluminum alloy material may also be used. The thermal spraying method used at this time was a wire arc thermal spraying method. In addition, thermal spraying methods such as powder flame spraying, high-velocity flame spraying, plasma spraying, etc. may be used, or a thermal spraying method with as few pores as possible is preferred. Further, the thermal spraying conditions may be the standard conditions of the system used.

Next, the masking was removed and the aluminum sprayed surface was polished to match the specifications on the right. A current-carrying electrode made of anodized film was attached to one end of the polished mold. Then, except for a part of the current-carrying electrode and the exposed aluminum part, it was masked with acid-resistant tape. Next, the approximate surface area for forming the anodic oxide film on the aluminum sprayed surface was measured.

The surface is degreased with an organic solvent, and then immersed in a 10% caustic soda aqueous solution at 60°C for 30 seconds to remove oxides that have formed on the aluminum spray coating. After treatment, the item is thoroughly washed with running water. Then, the product was immersed in 10 to 30% nitric acid to neutralize the alkali remaining on the surface of the product, and at the same time, the oxide adhering to the aluminum surface was dissolved and removed or rubbed off with a brush. Using the mold as an anode and a lead plate as a cathode, add some glycerin to a 20% H2SO4 aqueous solution and maintain the liquid temperature at 20 to 25 °C.
A direct current of 5 V and 3 Amp/drrf was applied for about 50 minutes to form an anodized film.

Electrolyte, voltage, current,
Various liquid temperature methods have been developed, or any method may be used as long as it forms a hard and dense anodic oxide film. After the anodic oxide film formation treatment, it was washed with running water, neutralized with a neutralizing agent, dried, and the masking blind cover etc. was removed. After that, the base that had been removed from the movable side, cooling pipes, dowel pins, bushings, etc. were assembled to form the mold for the movable side.

This mold was attached to an injection mold, and 5,000 shots of 20% glass fiber-containing PP resin were molded. This result is
Flow-like pattern wear was observed on the surface of the molded product of the right specification side cavity that was not anodized, but it was either transferred to the surface of the molded product or no abnormality was observed on the anodized product.

Example 4 A prototype was manufactured in the same manner as in Example 3, and the product was produced while being repaired by welding due to design changes.

A zinc-based alloy mold for the front panel of a room air conditioner was used. Originally, after the trial production was completed, we would produce a mass production mold by cutting out a 355C Hayashi block, but
The zinc-based alloy surface treatment method of the present invention was applied to a prototype mold because the schedule could not be met. The thermal spraying material used was an aluminum alloy containing 6% Si, and the mold surface was coated with 0.00% by wire flame spraying method. l5mm
After thermal spraying, an anodized film is formed using the sulfuric acid method to a thickness of A.
It was possible to mass produce about 30,000 pieces by molding BS resin (Table 2).

Table 2 (Effects of the Invention) As explained in detail above, according to the present invention, it is possible to fill in the concave portions caused by pinholes and cavities that occur on the casting surface of a zinc-based alloy precision casting mold at a low cost. It fully brings out the characteristics of precision casting, such as good transferability and surface roughness, making it possible to manufacture molds at low cost, and its industrial value is extremely large.

In addition, the present invention has the advantages of zinc-based alloy molds;
Although it has the advantage of being able to be manufactured in a short lead time, it prevents the wear that occurs due to the low hardness of zinc-based alloy molds, and its use is limited to prototype molds, simple molds, and small-lot production molds. Zinc-based alloy molds can be used for medium to high volume production.

Claims (2)

[Claims] (1) Zinc-based alloy metal manufacturing, characterized in that the surface of the molded product of the mold is formed by forming a sprayed coating of zinc or zinc-based alloy on the part that constitutes the surface of the molded product of the zinc-based alloy mold. Mold manufacturing method. (2) A thermally sprayed coating of aluminum or aluminum alloy is formed on the surface of the molded product of a zinc-based alloy mold, and after final surface forming processing such as polishing and texturing, the thermally sprayed aluminum or aluminum alloy coating is applied. A method for manufacturing a mold made of a zinc-based alloy, characterized by forming an anodized film on the surface of the mold.