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The Search Engineer finds solutions to all your questions, problems, and dilemmas. Occasionally, he could be wrong. But he doubts it.
By Design News Staff -- Design News, June 2, 2003
Howdy Partner: I need a process to apply a low-resistance circuit to clear polycarbonate that can accept surface-mounted components. Any ideas?—M.B. in Dallas, TX
Hey y'all: We've got a couple of issues with producing circuits on clear polycarbonate. If your part is molded, then you will need to metallize the part, such as electroless/electrolytic copper and dry processes like vacuum metallization and sputtering. The electroless process requires roughening of the surface by either mechanical or chemical means. The vacuum metallization and sputtering provide thin films with good adhesion of the metal if you need to go through subsequent electroplating operations. The circuits can be defined by laser removal of the thin film or through printed circuit techniques. But be forewarned—attaching surface mount components may be a problem. PC doesn't have sufficient temperature resistance to survive standard reflow soldering. Another option is adhesive-backed copper foil tape, either bare or tin-plated—3M, Chomerics, and other brands are available. Foil can be die cut to your needs. Adhesives have to be at least as temperature resistant as polycarbonate.
Dear Search Engineer: We manufacture power tools and would like to injection mold a soft-feel grip onto a cylindrical aluminum housing. The soft grip needs to be chemical-, oil-, and sweat-resistant.—A.B. in Dayton, OH
Dear A.B.: One possible solution is to consider putting a polyurethane coating over magnesium and chromating the metal part before molding to give it a bond.
Dear Search Engineer: I have an application that calls for a 1.5-inch duplex pair ball bearing with a 10-lb preload, Teflon® separators, and a friction requirement of 0.3 inch-oz. We expect about 500,000 cycles over 10 years of life, mostly oscillations of ±15° and ±180° at 2 to 150°/sec speed. We are already using a small amount of oil, but find that the amount of friction is still largely driven by the presence of the oil. I have been asked to see if operating a bearing of this size with no lubrication would work. What sort of problems might I expect?—F. S. in Raleigh, NC
Dear F.S.: Balzers offers a tungsten carbide carbon PVD coating that is very lubrious even in a dry mode. Check out their website at www.balzers.com for further information.
Another two cents: An astute reader, Tom A., suggests another method of determining position on a linear vertically mounted track up to 50-ft long (DN 04.07.03 issue). He writes that cable-type position transducers can be reliable for measurements up to and exceeding 50 ft. Check out the engineering guide at http://spaceagecontrol.com/s054b.htm. You can also check out displacement measurement tips at http://spaceagecontrol.com/reqsub.htm. And keep these e-mails coming.
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