Electroforming tooling achieves outstanding precision in terms of copying original shapes and designs, while porous electroforming utilizes such characteristics to provide minute pores 0.1 to 0.2 mm in diameter in the plating process, which enables the vacuum thermoforming of plastic parts using female molds. The size and density of pores (usually 3-5 pores per cm2) can be controlled based on the component, current density, and temperature of plating solutions, while the positions of pores can be controlled by applying materials having differing conductivity to the mold. However, details have yet to be disclosed. Porous electroforming and a number of its applied technologies have been patented inside and outside Japan. These methods of high quality, high productivity, and high cost effectiveness are widely used by domestic and overseas automakers for forming interior and exterior plastic parts.
Konan Tokushu Sangyo Co., Ltd. http://www.ktx.co.jp/goaisatu1.html
After being established in 1965, Konan Tokushu Sangyo Company was engaged in electroforming tooling for the metal parts or ornaments of family Buddhist altars kept in the home. The company successfully developed porous electroforming in 1982. By subsequently developing various electroforming tooling technologies, the company has positioned itself as an all-round manufacturer of mold production and tooling machines. Its business is quite wide-ranging, from highly skilled leather wrapping, tooling, and CAD/CAM design to high-precision processing and inspection in clean rooms.
Demonstration of vacuum thermosetting by using a porous electroforming mold. First, the mold is set inside a mini forming machine. Then it is covered by a plastic sheet and heated. Finally, the air is continuously purged to reveal the finished product shown in the photo
Denchu is a Japanese word for abbreviated electroforming tooling. In this process, an original mold is plated with nickel 3 to 5-mm thick, which is then removed like an eggshell to reveal a finished mold for plastic forming. Most plastic automotive parts such as dashboards, door trims (interior lining), and bumpers, are manufactured using electroformed molds. In particular, denchu methods are uniquely effective in forming what is called shibo (“squeeze wrapping”), that is, parts having a leather texture and stitch design that precisely reflect the original mold.
“Before, the only way to use such features was through the method of slash molding, which entails a troublesome procedure of scattering plastic powder on a heated mold to form material in the melting process.
From the standpoint of productivity, vacuum molding, in which a plastic material is formed after being heated and placed in a metal mold, followed by the continuous purging of air between the mold and plastic, is better. In order to reproduce even the minute designs of shibo, the electroforming mold must be female (or negative). By placing a plastic sheet over it, which is like covering with a lid, air cannot escape.”
Thus relates Mr. Noda who has dedicated 40 years to electroforming. The story goes back 20 years ago. One day, Mr. Noda saw a worker at the factory discarding a failed piece of denchu having 3 or 4-mm pores.
If bubbles form in an electrolytic plating solution, plating cannot be conducted on the area where the bubbles form, and this makes the surface rough (gasagasa in Japanese). The end product is gasa denchu (“rough-surfaced electroformed mold”), which is a totally rejected item.”
However, something clicked in Mr. Noda’s mind. It reminded him of an epoxy resin mold with small holes in it that he saw during a previous visit to Europe. “I asked the worker to retrieve the discarded gasa denchu from the bin,” he says, in order to “make the same thing once again.” And that’s what he did.
“I thought there would be some use in it by reproducing the same thing. Then I asked the worker if he could make these holes even smaller down to 0.1 mm, even if it took a whole year. He continued to study in addition to his regular work assignments. I later heard from him that he even built a small test bath at home and conducted nighttime testing.”
A year later, the worker successfully completed an electroforming mold with a number of 100-μm (0.1-mm) holes in it. Holding it against the light, one could see many small shining stars. Moreover, these holes have a hanging bell shape on the back.
This could be used for vacuum thermosetting tooling using female molds by completely venting out the air to bring the mold and plastic sheet into firm contact, while reproducing the minute designs of shibo. They lost no time in preparing a sample and offered it to Honda, a company well known for its enterprising spirit. Their response was disappointing. In fact, Honda had already developed an epoxy resin mold incorporating a ventilation design. That did not, however, force Mr. Noda to give up. Three months later, they again visited Honda with a complete door trim panel produced through electroforming tooling. Honda’s response was totally opposite of their last response. Around the same time, the durability of molds made of resin was becoming a major problem.
The world’s first technology known as “porous electroforming tooling” which is based on the idea of “many small holes” or “multi-micropores” has been adopted by a number of domestic automakers, thereby significantly contributing to improved automotive quality and productivity. Moreover, production costs were cut by 20% when compared to the troublesome method of slash molding, and energy consumption was reduced to an amazingly 1/12 of slash molding. Another advantage is that the materials used can be recycled and the products have been reduced in weight by 30%. All of these achievements have helped improve vehicle fuel consumption and recycling efficiency. The company is now known as “KTX” in the West, as well as all-round manufacturer of mold production and tooling machines.
“What is important in monodzukuri is first of all materializing an idea into a concrete form, and sticking to it with perseverance. The most challenging time for our company was during the oil crisis in 1973. We had no job orders for denchu and I had to work everyday cleaning the chairs in pachinko parlors just to earn income for daily wages to keep the business running. Despite that sacrifice, I saw to it that one worker?who has since retired?to remain in the company in order to continue the denchu business, since we couldn’t let the company go out of business.”
In fact, this former worker is the engineer who later achieved porous electroforming.
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