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April 1, 2002

9 Min Read
IMMC's Plant Tour: Molding magnesium's future

Many new molding machines have been added to MGP since we last visited in 1999, including five new 220-tonners, yet there still seems to be plenty of room.

Three years ago in the first issue of IMMC we introduced you to the world's first mass-production TXM plant, MG Precision Co. Ltd. (MGP). MGP is a wholly owned subsidiary of The Japan Steel Works Ltd., the world's first TXM injection molding machine builder. JSW originally created MGP in 1996 to convince potential customers that TXM was a viable process for making consumer electronics parts. Increasing demand for the parts MGP was molding convinced JSW to spin its offspring off as a separate profit center. Its decision has paid off-not just for JSW, but for the entire global TXM community.

That's because in addition to producing the key components used in many of today's leading-edge mobile consumer electronic products-everything from digital cameras to third-generation, Web-capable mobile phones with color video displays-MGP also serves as a testing ground for the latest types of TXM production systems JSW develops to reduce materials, molding, and labor costs, while improving good parts yield.

Working as one with JSW's Technology Development Center, MGP today is proving out many of the systems that will improve the productivity of its TXM customers tomorrow. Hot runner TXM, automated power lubricant dispensing, induction heating of barrels, and recycling are among the latest systems MGP is fine tuning. Meanwhile, by putting these newer technologies to work, MGP helps fund JSW's TXM R&D, as it continues to grow its own business.

MGP is remodeling its plant layout to improve flow and reduce waste. Secondary operations like tumbling, shot blasting, and machining have been moved away from the press.

As JSW's subsidiary magnesium custom molding operation, MGP proves out many of the new productivity-improving systems developed at JSW's Technology Development Center. Attendees of Thixomat's International Magnesium Conference toured MGP last year.

The attendees of Thixomat's 2001 International Magnesium Conference in Hiroshima were treated to a tour of MGP. IMM tagged along. Of course, there have been a few new changes at MGP since last summer. Let's tour.

Hot Running Mg

MGP is right next door to JSW's Technology Development Center, which is a good place to begin our tour. The center is used for plastics molding R&D, as well as magnesium molding. It's a glimpse of what's to come.

There is a Model JLM 220-MG JSW for instance, a 220-metric-ton TXM double toggle, demonstrating the application of hot runner tooling. As previously reported in IMMC, JSW has worked with Ju-Oh Inc. (Kanagawa-Ken, Japan) to make runnerless, magnesium alloy molding a reality.

Hot runners can speed cycle times in magnesium molding, just like they can in plastics molding. What's more, they have a significant impact on reducing the volume of costly material wasted in those huge magnesium sprues. Hot runners also can widen the projected areas of parts and allow for molds with higher cavitation, further improving productivity.

MG Precision Co., Hiroshima-City, Japan
Square footage: 21,528 (2000 sq m)
Annual sales: 1.6 billion Yen (approximately $11.9 million)
Markets served: Mobile electronics (mobile phones, video cameras, digital cameras, LCD projectors)
Parts produced: 300,000 parts/month
Materials used: AZ91D Mg alloy
No. of employees: 68, including part-time employees
Shifts worked: One shift/day, five days/week
Molding machines: 14, 75 to 850 tons, JSW
Secondary operations: CNC machining, shot blasting, tumbling, belt sanding, finishing, inspection
Internal moldmaking: Yes
Quality: ISO 14002, ISO 9002

The JLM220-MG in the testing area is running a two-cavity hot runner tool molding mobile phone housings with a shot weight of 43g. It would have weighed 125g if a conventional cold runner was used. With the hot runner the machine cycles at 18 seconds vs. 24 seconds running a cold runner tool.

Inmold Lube Job

Next we see a Model JLM450E-C5, an older-model JSW press. In fact, it was the first production TXM machine JSW ever built. It is seven years old and still runs well. The press is molding a 480g automotive oil pump body in 60-second cycles. It is also demonstrating JSW's new automated powder lubricant system, developed by JSW in conjunction with Hanano Corp. (Tokyo, Japan).

Lubricant (mold release in plastics molding lingo) must be applied to TXM mold faces after every shot, what with magnesium being as sticky as it is. Lubricants have traditionally been silicone liquids sprayed into open molds. JSW's new system dispenses dry powder lubricant on the cavity surface while the mold is closed. It is primarily for large, flat TXM parts because it would be difficult for the powder to be applied in small, intricately configured cavities.

Flash is reduced because there is no accumulation of the lubricant on the parting line. Cycle times are faster and gas emissions from the lubricant are reduced for a better working environment. Mold temperatures also are more consistent, and the powders eliminate misting and waste water.

Induction Heater Bands

The final magnesium molding demo in the Technology Development Center is of a new induction heating (IH) system designed to super-heat the barrel and thereby speed cycle time. A Model JLM650-MG, a 650-metric-tonner, is molding a laptop PC enclosure out of AZ91D. With a 540g shot for a product weighing in at 275g, the press is cycling at 28 seconds. Normally, with only conventional electric heaters, these parts would cycle at anywhere from 40 to 60 seconds.

IH uses an induction current in an alternating magnetic field to heat an electrically conductive material. In doing so, IH systems provide a higher power density and heat efficiency, and a more uniform heating profile than conventional electric barrel heaters. The hot runner system JSW developed with Ju-Oh is based on IH technology.

JSW is still testing its IH barrel heating system in hopes of increasing shot weights on parts run in smaller machines. Sources say IH heating will better stabilize magnesium alloy melting and metering in the barrel and extend heater life, while also reducing cycle times. No date has been announced for commercialization.

MGP, the first mass-production TXM molding facility, now runs the world's first mass-production TXM hot runner molds. This photo was taken when the plant was running mobile phone housings in two-cavity cold runner tooling. Material costs have been reduced by 50 percent using hot runners.

MGP has plans to further automate and isolate secondaries (shown in these four images) off the main shop floor, including degating, machining, tumbling, and shot blasting.

Mobile Phone Cell

Approaching MGP's building, it looks much the same as it did when we visited in 1999. Yet, inside, under its 3.4- to 5m-high ceiling with surrounding skylights and bright halogen lamps, it's a brand-new factory.

The plant itself is evolving into a lean manufacturing cell. There have been expansions in its molding capacity and the general layout of the shop floor has been altered to improve material and product flow while reducing waste. Among MGP's latest additions are five 220-tonners and one 150-ton machine. Most of its materials handling auxiliaries are from Matsui.

All secondaries will eventually be off the main floor in their own enclosed areas, so product can flow even more smoothly. Today, many of the secondary machining, shot blasting, and tumbling procedures have been moved away from the primaries, but some secondaries are still being carried out beside the press.

One of MGP's big 850-metric-ton JSWs is the first machine we see. It is running housings for an LCD projector in a single-cavity tool. Shot weight is 604.2g with a product weight of 315.8g. The press cycles at 56 seconds. It is impressive, but the next product family manufacturing cell we see blows us out of the water. It is the shape of things to come.

The molding machines in this area are mass-producing TXM mobile phone housings with the help of two floor-mounted, five-axis, articulated-arm robots. During the Thixomat-sponsored tour last year, cold runner molds were being used. Things have changed since then. Today, the 220-metric-ton molding machines in this area are running hot runner molds. This is the first TXM manufacturing system anywhere mass-producing parts with hot runner molds.

The robots remove the parts and automatically transfer them to a trimming press nearby. There are four 220-tonners in the cell. Today, three of them are robotized. The cell produces 3000 mobile phone enclosures every 18 hours.

These parts are buffed, polished, and CNC drilled before moving on to inspection. Since the conversion to hot runner molds, material costs have been reduced by 50 percent and molding costs by 22 percent. These molds, like all the molds at the factory, are produced by MGP at a separate facility in Hiroshima. Kazuo Kitamura, gm of JSW's Magnesium Process Equipment & Products Div., tells us the company is already thinking of building four-cavity hot runner molds.

Direct Recycling

Kitamura says JSW has already built its 230th TXM press and he is elated by the company making its first inroads into mainland China. He says the Chinese government is actively supporting the developments of magnesium mobile phone manufacturing, and JSW already has signed contracts with two companies there to deliver full production lines, including everything from molding presses to painting systems.

Fifteen molding machines were involved in the first round of orders late last year, from 220 to 850 tons, and 15 more are now being supplied. What's more, one customer plans to double its press capacity later this year. The new systems being developed by JSW and proven out in production by MGP will be part of the packages.

Leaving MGP, we can't help but notice drums of magnesium alloy chips sporting a label that reads JSW Thixalloy. As previously reported in IMMC, JSW has begun supplying its own materials, even to MGP.

Next to these drums are recycled AZ91D chips. MGP and JSW work closely with Nihon Sahmo, a materials supplier located in the Okayama prefecture, in its direct scrap recycling efforts.

Contact information
The Japan Steel Works Ltd.
Tokyo, Japan
Kazuo Kitamura
+81 (3) 3501 6164

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