This technical information has been contributed by
Stanfordville Machine & Manufacturing Company

CNC Machine Shop Delivers Precision Parts on Short Lead Times

Precision CNC Machining

Powered by the productivity advantages of vertical and horizontal machining centers equipped with pallet systems, a specialist in CNC milling and turning can consistently reduce cycle times and manufacturing costs.

An enterprising machine shop in the northeastern region of the United States is regularly immersed in meeting the challenges of the semiconductor and other high-tech industries, including medical and aerospace. Stanfordville Machine & Manufacturing Company, located about an hour's drive north of New York City in Stanfordville, N.Y., manufactures a substantial array of parts for the semiconductor industry, including wafer rings, mask frames, sputtering fixtures, wafer handling equipment, inspection fixtures, and components for wafer chucks. Stanfordville Machine not only makes parts for the manufacturers of micro chips, but also for the OEMs that make manufacturing equipment for the chip makers.

"Most of these parts are small and have extremely tight tolerances," says Neal Johnsen, the vice president of sales for Stanfordville Machine. "We specialize in close tolerance, Just-in-Time parts, where there are stringent requirements for flatness, surface finishes, and perfectly clean parts."

Stanfordville Machine's biggest strength, according to Johnsen, is its ability to do medium production runs in a short lead time, usually two weeks or less. The company runs 24 hours a day to handle the requirements of the high-demand industries that it services. On two shifts, the equipment is worker-operated; on the third shift, the machines run unattended on less critical parts. Stanfordville derives much of its strength from 23 CNC machine tools, a sizable amount of equipment for a medium-sized shop. Its equipment cluster includes 14 vertical and horizontal machining centers (several are four-axis and one is five-axis) and nine multi-axis, standard, and Swiss-type turning centers. In addition, Stanfordville utilizes many different types of grinders, jig borers, hones, saws, deburring machines, and EDM machines.

In the last year, the company has purchased four new CNC machines. One is a Mori Seiki NH-4000, a three-pallet horizontal machining center. Two are multi-axis turning centers: a Mori Seiki ZT-1500YB and a Mori Seiki NL-1500; and the fourth machine is a Mori Seiki NV-5000 vertical machining center. The turning centers have twin turrets and live tooling, bar feeders, parts catchers, and chip conveyors, attachments that eliminate many secondary machining operations.

Stanfordville Machine is willing to attempt parts that many companies "no-quote" because of difficult tolerances and tough materials. "We're willing to raise the bar continuously on tolerances, surface finishes, and the small sizes of parts, and we'll take the time to do the engineering research to find the best way to produce a part," Johnsen explains.

A Full-Service CNC Job Shop

Stanfordville Machine operates out of a 30,000-sq-ft facility with two buildings. Neal's father, John Johnsen, started the company in 1975 and is still its president. Neal's brother, Peter, is vice president and general manager of the firm. His father started the business by buying out a metal stamping company that also did machining. The company is now a full-service, one-stop, CNC job shop with 42 full-time employees. Stanfordville specializes in CNC turning and milling, but also handles sheet metal fabrication and welding, wire and sinker EDM, a variety of grinding processes, and assembly work. The firm provides turnkey sub-assemblies for many of its customers that need fabricated and machined parts coupled together.

The firm's primary markets are parts for semiconductor, medical, and commercial and military aerospace equipment, as well as parts for instrumentation and packaging equipment. In the medical field, the machining company performs work for large companies that sell diagnostic and surgical equipment. In the military and aerospace field, the company makes parts for jet engines for commercial and military aircraft of all kinds, as well as for satellites, nuclear power plants, and optical equipment.

The contractor gets written vendor ratings quarterly from many of its clients, who grade the machining company's turnarounds and quality level for consistency. "Our average rating is usually about 95% for on-time delivery and quality, which is what they expect us to maintain," says Johnsen. "Our company is not yet ISO 9000 certified, although much of the work we do meets ISO guidelines. We hope to become certified in the near future."

In-House Tooling and Fixturing

Stanfordville designs and builds most of its own fixturing in-house, which gives the firm a decided edge over machining companies without toolmaking departments. The company has four toolmakers on staff, each with about 30 years of experience. Besides building fixtures, they also perform development work, much of it for prototypes.

High-end, precision fixtures allow Stanfordville to machine at very fast speeds, up to 14,000 rpm, and at feeds of up to 500 inches per minute. In addition, the company often uses high-pressure coolants that are delivered at 1,000 psi, which keeps the tool cooler and gets the chips out of the way more readily. In addition, it buys high-quality carbide tooling and helix end mills that are coated for aggressive machining.

Stanfordville Machine has a mechanical designer and three manufacturing engineers on staff. While the designer spends much of his time designing measuring tools for jet engines, the engineers design and engineer fixturing and tooling, and handle CAD/CAM programming for the CNC machining equipment. Stanfordville's engineers are willing to help an OEM design and engineer a part from a sketch, Johnsen says.

Meeting Challenges of the Semiconductor Industry

The company machines parts in a wide range of sizes. On its vertical machining centers, it can machine plate stock up to 4 feet x 8 feet; on turning centers, it can machine diameters ranging from about 0.030-inch up to 24 inches. Most of the semiconductor parts that it machines are very tiny. "One little part that we machine is 0.075-inch square, and has a 0.015-inch diameter hole drilled into it," Johnsen affirms. Stanfordville handles small to medium-sized production from one prototype to about 30,000 pieces.

The firm's ability to hold tolerances is also impressive. For a titanium part used in a wafer chuck for the semiconductor industry, for example, Stanfordville can hold a 0.218-inch bore, +/-0.0004-inch-0-inch, and a #8 surface finish on its turning centers. Its milling machines routinely hold tolerances of +/-0.0002-inch. Surface finishes down to light bands are vended out.

For such a high level of precision, a machining company must have a very extensive quality control (QC) department. Stanfordville Machine's QC department uses optical comparators, computer-controlled Coordinate Measuring System machines, electronic height gages, a Rockwell hardness tester, a profilometer, a benchtop super micrometer, and a variety of bore gages. Three full-time inspectors utilize this digitally-assisted equipment to inspect parts throughout various processes.

Stanfordville Machine handles almost any material available, including a wide variety of engineered plastics and metal alloys. Many of the plastic parts that it manufactures are for the semiconductor industry and incorporate engineered plastics with high temperature and high purity ratings, such as DuPont Teflon®, Vespel®, and Delrin®, VICTREX® PEEKTM, G-10, and polyvinylidene fluoride (PVDF). The company also machines a substantial amount of titanium, copper, 300 and 400 series stainless steel, aluminum, and Invar. It also handles machinable ceramics, which are very abrasive and prone to breakage.

One particularly challenging plastic part for the semiconductor industry was a Teflon part for a ceramic screening process. "We were using three vises for three different operations," says Johnsen. "We built a vacuum chuck that allowed us to do the same work in two operations. This cut the cost per part by about 30%."

Due to confidentiality requirements, Johnsen is hesitant to divulge the names of large corporations that he does business with. However, he willingly mentioned that the company has been doing business with one such client, IBM, for 25 years. "Our clients are all based in the U.S., but our parts are shipped all over the world," the sales director maintains.

The machining company has a semiconductor customer that it's been servicing during the past 20 years. "They were having trouble even finding someone that would do this part at all," says Johnsen. The part is a nozzle that requires a 0.0002-inch tolerance for bonding carbide rods to hardened tool steel in a parallel fashion. It requires several machining processes.

"I don't think anyone, besides our customer, knows how to make these parts, so I would call it proprietary technology that only our company is doing," Johnsen added. "We bought a new surface grinder and some special cutting tools, and were then able to lower the cost of the part by 20%."

Secondary processes, including deburring, polishing, tumbling, grinding, bead blasting, cleaning, and honing, are offered to complete a machined part. All of the finishing processes—plating, anodizing, hard—coating, and painting-are sent out. The company does, however, handle sheet metal fabrication and all types of welding in-house, mostly to make simple panels, frames, holders, and brackets for sub-assemblies.

Greater Productivity on CNC Machining Centers

For increased production, three vertical machining centers have pallet tables mounted to them. Operators will usually load both pallets, depending on the size of the run, and run them unattended for eight hours. This doubles table capacity and helps the machines achieve faster cycle times. Compressors that supply air to the machining centers are on timers, so they automatically shut off when the run is completed. All of the machines have tool breakage detectors that set off an alarm and shut off the equipment in case a tool breaks.

On one horizontal machining center that is capable of running at 500 inches per minute, Stanfordville Machine reduced the cost of an aluminum housing for a medical instrument by 35%. The company was able to decrease the cost per part because the machine runs so quickly, reducing cycle times. Feeds went from 300 inches per minute to 500 inches per minute; coolant pressure increased from 200 psi to 1000 psi; and tool speeds, from 10,000 rpm to 14,000 rpm.

One situation required a 30% reduction in cost for a part that Stanfordville had been producing for many years.

"Rather than lose the business to a competitor, we took the lean approach," says Johnsen. "We drew a value stream map and performed a Kaizen event and a cost study on the part, which had us analyzing all of the processes and costs that went into making the part." The company came to the conclusion that it needed to buy a new CNC turning center. Previously, the part had three CNC lathe operations and one CNC milling operation. But with its new Mori Seiki turning center, which does turning and milling, the company was able to complete the part in one operation and bring the cost of the part down by 30%, as required.

All things considered, Stanfordville Machine believes that it's been successful because it listens closely to its clients' needs and constantly brainstorms projects with staff members from every department. "With this approach, we generate a lot of ideas to come up with creative ways to best produce our customer's parts more cost-effectively," Johnsen summarizes.

Teflon®, Vespel®, and Delrin are registered trademarks of DuPont.

VICTREX® is a registered trademark of Victrex Manufacturing Limited. PEEKTM is a trademark of Victrex plc.

This technical information has been contributed by
Stanfordville Machine & Manufacturing Company

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