An Arnold Publication- Serving the Western Metalworking Industry Since 1981
Real-time SPC
A Global Contract Manufacturer Creates New Real-time SPC Software to Meet
Growing Customer Demands.
Story and photos by C. H. Bush, editor
Horizontal supervisor Ron Harris (l) and CNC machinist Derek Tran discuss the next project slated to be machined on the giant Niigata 130 horizontal machining center, shown in the background. The machine is one of five operated by the Newark Sanmina plant.
Sanmina-SCI, founded in Silicon Valley in 1980 as Sanmina, is a publicly traded company (NASDAQ) with global operations in 18 countries on four continents. One of the world’s largest EMS companies, with headquarters in San Jose, CA, Sanmina has approximately 45,000 employees and fiscal year 2010 revenues totaling $6.3 billion dollars.
Machinist Timothy Nguyen at the Dashboard of the Unified Quality System developed by Al Huber. The dashboard gives real-time SPC data during machining. He’s checking to get feedback on the process that’s running. If it drifts off spec, he can make adjustments before it’s too late.
Global Footprint
As a contract manufacturing source, the company provides customers with a global reach, offering full-service design, engineering, manufacturing, new product introduction and complete logistics and repair services, including inventory management, reverse and sustaining engineering, forward logistics, after-market solutions, information technology solutions and green programs.
Sanmina’s customers fall within a broad range of industries, including medical systems, communication networks, defense and aerospace, industrial, clean technology, enterprise computing and storage, multimedia and automotive. Sales are divided approximately 20% in the U.S., 20% in Latin America and Mexico, 10% in Europe, 30% in China, and 20% in the rest of Asia.
In order to avoid costly duplication of effort, Sanmina’s various divisions specialize in different “core competencies,” and then sub out to each other as required.
“At our Newark, CA plant, our core competency is large format machining,” says plant quality manager, Cathy Brake. “At this location we serve the semiconductor, LED, oil and aerospace industries. We operate six huge Niigata 130 mills and a lot of other large equipment, which, as you can imagine, requires special solutions to meet our customers’ quality control and reporting requirements. The larger the parts, the more challenging it is to find satisfactory systems to deliver the kind of quality data our customers require.”
Sanmina quality manager Cathy Brake (r) and CMM programmer Cliff Myint discuss inspection requirements for a project. In the background is a recently refurbished Stabilus gantry CMM.
Big Machines, Big QC
Just because the parts produced are huge (up to 120” X 88”), doesn’t mean tolerance standards are lowered. In fact, at Sanmina, it’s just the contrary.
“Our customer tolerances are very tight,” says Al Huber, Sr. NPI Engineer and close assistant to Cathy Brake. “But we don’t use their tolerances. We avoid problems by tightening their tolerances probably by a factor of five or more.”
“Of course, with big parts, normal inspection equipment, the kind you find in most shops, won’t work,” adds Brake. “So we operate a variety of CMMs and other equipment. For example, we currently have three CMMs, including a medium-size Mitutoyo BHN1015L, a Brown & Sharpe PFX 7.6.7, and a large Phoenix PHX20.15.12 gantry CMM recently refurbished by John Servin at HS&S Machine Tools and Metrology, Inc. John has worked with us for years, so whatever requirements or needs we have in metrology, he’s the first one that we call. He’s a distributor for Hexagon products.”
“We also use a Faro Arm portable CMM from time to time on the really large parts,” adds Huber, “and we recently bought a Leica Absolute Tracker AT401 portable CMM to inspect products too large for normal systems. Plus, we currently have an RFQ out for a large c, which will allow us to pull large parts under the CMM while they’re still on a pallet. No more lifting big parts onto a table.”
Demanding Inspection Reports
Sanmina’s customers are very demanding when it comes to final inspection reporting.
“Customers want us to track critical dimensions,” says Brake. “They may require as many as 80 or more critical dimensions to be tracked and reported on for statistical process control reasons. And, we understand the importance of those final inspection reports for certain customers in certain industries. But meeting requirements like that can be very demanding, since typically the data has to be collected and manually input. A process like that can really slow down deliveries, which is why we turned to Al Huber to solve the problem by developing an automated, real-time SPC data collection system. He wrote a program that uses a combination of Visual Basic and Excel. It works great.”
Sr. NPI engineer Al Huber uses a Leica Absolute Tracker AT401 portable CMM to check dimensions of a part too large for a normal CMM. The Leica allows extreme precision over ultra-long distances. It is powered by its own internal battery and is able to work in the most demanding environment, yet maintains a high level of precision and a very large work envelope.
Real-time SPC
Sanmina uses German-made M&L probes and Renishaw probes on their machines.
“I wrote the program to extract critical dimension data from the probes real time,” Huber explains. “The data is taken from the probes, loaded into a database and from there it can go into the reports for the customer.”
But the software is much more than a data collection system, he says.
“Some of the large parts we fabricate can cost more than $100,000,” he says. “Some of the smaller ones can be in the range of $25,000 each.”
“We can’t afford to scrap them,” Brake says, “so we’re monitoring the process in the machine. The software is
looking at all those data points, and it will alert the machinist if something drifts out of process requirements.”
“We’re measuring the parts as they’re being manufactured,” says Huber. “As soon as the tool pulls out of the spindle we load the probes and measure. The machine tools are accurate, but realistically with all things considered, we have to know what sigma levels we’re maintaining. Here we’re working to a thousandth or less at a sigma level of 2, which is extreme.”
“The manufacturing process drifts all the time,” Brake adds, “and if you’re working within plus or minus 5, you may not see it, but it’s still drifting. With Al’s system, even if we’re working with very tight tolerances, we can know immediately what’s happening. If the process drifts, the operator can react to it before it’s too late. Plus, we have a complete inspection report to give to our customer.”
Benefits of Real-time SPC
At its heart, SPC is about getting the most from processes and continually improving those processes to consistently deliver the best products possible.
“With real-time SPC we gain a lot of benefits,” Huber says. “First, work is qualified at the floor level in real time, which allows reduced loads to the quality department’s CMM inspection schedule. Truth is it’s almost impossible for the operator to take all 318 data points that we monitor. And, because the numbers are so small, you really can’t mechanically do it. The resolution is in microns.”
“Our systems utilize the Westinghouse Rule set together with other industry standards and proprietary statistical tests,” Huber continues, “so if a measurement value changes or there’s been a shift in our process sigma, various alarms are activated on the system’s operator dashboard to alert the machinists and prompt any adjustments or engineering responses that may be necessary. Our purpose is to predict before the fact. That the beauty of real-time SPC.”
“Other benefits are that the system prepares the required inspection documents automatically,” Brake adds. “That allows dramatic increases in accuracy, reductions in documentation costs, labor, and personnel. Throughput is increased through automation, especially during high production runs or when the work is very large in size, as are most of the parts we build.”
“One thing our customers appreciate,” Huber says, “is that we’re able to automatically upload resultant statistical process data to our proprietary network database. That allows us to offer to our customers, and their engineering/quality teams the ability to log in remotely ad-hoc and review their project’s process-performance at the manufacturing level in real time.”
Sanmina CNC machinist Long Vu inspects a large part just off a Niigata HN100C horizontal mill. The huge Sanmina plant employs 94 people operating some of the biggest machines available in the U.S.
Future of Quality
“Personally, I believe the real future in quality improvement lies in manufactures’ ability to use real-time SPC to constantly monitor and improve their processes,” Brake says. “We couldn’t buy Al’s system on the market, because it wasn’t available, which makes us unique and puts us at a competitive advantage.”
