Thinking outside the cut: a Silicon Valley manufacturer's survival strategy involves closer relationships with customers, and high speed machining is crucial to this. The shop pays particular attention to the process factors that affect high speed machining before the cut takes place

Modern Machine Shop, August, 2003 by Peter Zelinski

Manufacturers that used to be flush with work are now struggling, and the struggle is made even more difficult by the amount of manufacturing going to cheaper sources overseas.

That predicament of U.S. manufacturers in general is even more pronounced for the semiconductor industry associated with Silicon Valley. This is the sector served by FM Industries, a subsidiary of NGK in Fremont, California.

David Miller is FM Industries' president. He says he sees those overseas manufacturers continuing to close any gap in technology. "About the only defense is to increase efficiency and productivity," he says. For his company, that has meant not just acceleration but integration as well.

The company makes the guts, basically, for processing chambers used in semiconductor production. Assembly occurs in a clean room at the heart of the Fremont facility.

In response to declining demand for its product, the company searched for a way to increase its share of customers' business. The company asked itself this question: What if FM Industries could be relied on to produce not just internal assemblies but completed chamber modules instead?

That change would simplify customer supply chains.

It would also expand FM Industries' role as a source of vital technical expertise.

And the principal challenge, the company realized, lay not in the clean room but in the CNC machine shop.

Body Parts

That shop had to begin machining the bodies for these completed chambers.

These parts, hogged out of solid aluminum, are not only elaborate but also large. A typical chamber body occupies a volume 30 inches square by 14 inches thick. It has a variety of complex details that vary significantly from one chamber design to the next. To become an outsource chamber manufacturer, FM Industries needed its shop to produce these challenging parts not just economically, but also within the tight lead times that are typical of the semiconductor supply chain.

Step one was to get the right equipment. The company had no machines in house big enough to accommodate these parts. It purchased a Mazak Palletech cell including ten pallets and two CAT-50 taper, 50-hp machining centers capable of 15,000 rpm.

Step two was more difficult. The shop had to develop a process for using this equipment effectively.

When the first opportunity came to run a chamber body, the shop borrowed high speed machining techniques from its less powerful machines. The result failed to realize the new equipment's potential, says engineering director Mark Filice. The customer's deadline was met along with all of the other requirements, but it was clear to Mr. Filice and others that if the company would succeed as a chamber supplier, it was going to have to make chamber bodies in a fraction of the time this first part had required.

Part of what the shop learned is that a 50-taper machine may call for high speed machining techniques all its own. That insight sent the company down a path of fundamentally revising the process to achieve more efficient production. Kurt Sanfilippo, a recent hire for the company, joined this effort after it had already succeeded in cutting machining times in half. Now the Mazak cell manager, Mr. Sanfilippo is applying some 50-taper expertise of his own to put in place additional process improvements that are expected to remove two thirds of the processing time that still remains.

Much of this process engineering takes place outside the cut, he points out.

And within the cut, he says, the optimum machining is likely to occur below the top spindle speed. This is one potentially striking difference between higher-power and lower-power machines.

Speed Versus Volume

More important than the cutting speed is the metal removal rate. This is where Mr. Sanfilippo places his attention.

On a 40-taper machine, the most productive cutting is more likely to occur at the top rpm, he says. But on a 50-taper machine, particularly one with 50 hp, the highest metal removal rate may occur instead at a point along the power curve where horsepower remains high. While the shop generally does use the top rpm for finishing with 1-inch tools, the shop is more likely to run at 10,000 rpm when roughing or using larger tools. The lower speed lets the shop take advantage of much more spindle horsepower. Through strategic choices of tooling and tool paths during this high-power cutting, the shop is able to realize high feed rates that translate to a metal removal rate of 6 cubic inches per minute for every unit of spindle horsepower.

But removing so much material so quickly can place the quality of the part at risk. There is a danger of deformation as the material's internal stresses are relieved. Therefore, rather than concentrate too much machining in one place during high-power cutting, the shop is careful to have the cutter leave the workpiece frequently so that it can skip around between far-removed features of the part. Often the tool moves back and forth between opposing faces.

To make the tool move from place to place in this way involves heavy-handed manipulation of the CAM software's automatically generated tool paths. It also has implications for the way the work is held.