 |
|
About PMF Feature Stories Coming Events Archives Search Links Forum Contact Us Classified Ads Home |
|
Machine Shop Makes Engineering Plastics its Bread and Butter Precision plastics machining
capabilities keeps California-based BY HARRY URBAN When the raw material is a plastic that is more expensive than most precious metals, the average machine shop might think twice about accepting an order to perform high tolerance machining and milling. But for Darmark Inc. in Poway, CA, working with sophisticated plastics is a key to survival. The 20-year-old company considers these plastics its "bread and butter" and just part of doing business with a portfolio of high-tech customers. Darmark's customer list includes firms from the semiconductor, aerospace and medical industries. According to Darmark President Mark Zavadil, most of the company's work is for the semiconductor industry, machining relatively small parts that require precision work, including tolerances of plus or minus 0.0001 inch. While metals like aluminum, stainless steel and titanium account for 70 percent of the workload, the remaining 30 percent, engineering plastics such as PEEK, Ertalyte, Delrin, Torlon and Vespel, are what distinguishes Darmark. A typical example of Darmark's precision plastics machining is in the hundreds of parts it manufactures for semiconductor testing machines. These machines are used to test semiconductors once they have been manufactured. For example, the semiconductors are subjected to temperature extremes in the testing machines. Among the parts Darmark makes for these highly sophisticated machines are the chip carriers on which the semiconductors travel while in the testing chambers. Darmark's customer's material specification for the chip carriers is Torlon, because of its resistance to expansion and contraction in temperature extremes and its insulating qualities, said Zavadil. Machining Parts Another recent semiconductor industry job at Darmark was the manufacture of parts for silicon wafer planerization machines. Planerization is an intermediate stage in the process of manufacturing silicon chips. In this application, Darmark machined Ertalyte and Delrin with Haas VF-0 vertical milling machines. According to Zavadil, these materials were chosen for their dimensional stability, wear resistance and machinability. Yet another plastics project involved the machining of white Delrin to make plastic parts for leg and knee braces. Zavadil said white Delrin was again chosen because of its stability and wear resistance. A majority of the projects machined at Darmark involve milling. All totaled, Darmark has 21 Haas VF-0 vertical milling machines. These 7,000-pound machines feature 20-inch X by 16-inch Y by 20-inch Z travels and a 7,500 rpm spindle. The VF-0 has a Haas-built controller which receives its instructions from Darmark's Gibbs CAD/CAM software. Zavadil said the Virtual Gibbs software was selected for its user-friendly attributes. Virtual Gibbs is a CAM system for both 3-axis milling and 2-axis turning applications. Its freeform interface lets users move seamlessly between geometry creation, solid modeling, toolpath creation, rendering and post processing, Zavadil said. Rendering of the cut part shows users exactly what the part looks like before taking the file to the machine, he added. Darmark's tooling list also includes: nine Supermax vertical machining centers, 11 Lagun FTV-2 vertical mills, an Okuma Cadet turning center, two Puma 8HS turning centers, two Puma 6HS turning centers, a Puma 350 12-inch CNC lathe, a 40-inch Cutking lathe, a 40-inch Nardini lathe and two Citizen screw machines. Rebuilding Darmark's recent move into its brand new 28,000-square-foot facility near San Diego &emdash; where they are working virtually around the clock with 110 employees &emdash; is also a clear indication of its prosperity. Darmark was founded in a garage by Darwin Zavadil in 1978. The company grew steadily as a job shop enjoying the boom in California's economy by focusing on aerospace and computer equipment accounts. However, in the early '90s Darmark had placed too much of its business with a computer equipment manufacturer that went belly up. In 1994, Darmark was forced into survival mode &emdash; looking for new customers. It was then that Darwin Zavadil turned the company over to his son, Mark, and Martin Drake, both of whom had worked for the company since their teenage years. The two young men proceeded to change the company's fortunes. Focusing on quality and timely delivery and not afraid to adapt the newest technology, Darmark has more than rebuilt itself. Old contacts came back to Darmark with fresh business and the company made it a point to focus on diversity. Mark Zavadil said he places Darmark in the top 5 percent of American machine shops because of its capabilities. "A lot of shops won't touch plastics because they're not familiar with them and don't want to take a risk &emdash; the material is often two to three times the cost of manufacturing." He pointed out that costs of Vespel and Torlon are sometimes 10 to 15 times higher than comparable metals. To avoid making errors on the expensive plastics, Darmark performs dry runs of programs on less expensive plastics materials. Because of the extreme tolerances required for parts such as those Darmark manufactures for computer chip testing machines, the company relies heavily on its plastics supplier for technical guidance. Zavadil said he works closely with DSM, which manufactures Torlon, PEEK, Ertalyte and other materials, to keep up with the latest industry news, availability of materials, and, most importantly, questions regarding material specification and customer requirements. Quality Focus A RAM Optical Instrumentation (ROI) measurement system is used to ensure tolerances are kept. The ROI is a computer-controlled, video-based measurement and inspection system. It is calibrated to measure tolerances up to one-half of one ten-millionth of an inch. The ROI system will run off of a DXF file to assure that the part being inspected matches the programmed toolpath. Other equipment in the inspection department includes: a Mitutoyo TM toolmakers microscope, a Microview 2000 optical comparator, two 12-inch electronic height gauges, one 18-inch electronic height gauge, and a 12-inch Mitutoyo Height Master. Darmark uses JobBoss shop management software to monitor and enable production flow. When PM&F visited Darmark, the company was in the midst of converting to 100 percent bar coding throughout its entire process. "With JobBoss we are able to tell exactly what's going on with a job at any given time. Jobs are entered into the company's Novell network incorporating JobBoss, which then generates a bar-coded route sheet. The route sheet tags along with the order throughout its production cycle all the way to inspection and shipping. At each station, whether milling or deburring etc., the employee knows exactly what needs to be done because all information is relayed though the bar-coded route sheet. Conversely the front office can track its jobs and knows exactly where they are and what is happening to them," Zavadil said. Darmark is in the process of preparing for ISO 9002 certification. "Right now we're in the documentation process," Zavadil said. Some, but not a lot, of Darmark's customers are asking for ISO certification. "We're trying to stay ahead of the curve by being ISO certified now," he added. Precision machining capabilities, quality control and the aggressive pursuit of challenging jobs are also keeping Darmark ahead of the curve.
|
||||