Cast from toughened epoxy resin, the cartridge housing for the film drive mechanism of the Q2000 Optimark system is produced by RESIN SYSTEMS with tolerances as tight as +/-.001″.
Cast Epoxy Housing for Laser Print Mechanism Ensures Proper Alignment and Tracking in Production Line Marking Applications
MARKEM Corporation of Keene, New Hampshire, manufactures the industry’s most extensive line of in-plant marking and decorating equipment. Best known for the systems and supplies it provides to the electronics industry, MARKEM also offers a broad range of systems for other industries, including packaging, textiles, apparel, food processing, and pharmaceuticals.
One of the newest systems from MARKEM is the programmable, digitally-controlled Q2000 Optimark laser marking system, which performs high-speed, high-quality film printing on integrated circuit packages. It uses a combination of a focused laser beam and a film drive mechanism to deposit opaque dry ink impressions precisely and crisply onto the surface of IC packages.
Obtaining a Rugged, Lightweight, Dimensionally Stable Housing Quickly and Economically . . . in Production Quantities
A critical part of the Q2000 Optimark System is the cartridge housing for the film drive mechanism. “In designing the system,” explains David Georgis, Senior Production Engineer at MARKEM, “we needed a housing that was dimensionally stable to ensure proper tracking of the film mechanism and accurate alignment of the laser optics. The housing also must be sufficiently lightweight and rugged to withstand repeated handling by system operators, who regularly unlock and remove it to replace the film that conveys the ink supply. As the housing mounts externally, it is always visible, so, cosmetics are important too.”
Because of comparatively low-volume production requirements — not high enough to justify the cost of plastic injection molding — MARKEM considered several alternatives for manufacturing the housing: aluminum machined from block, cast Nylatron, and cast liquid resin.
“Working with aluminum had significant limitations,” notes Georgis. “An aluminum housing would weigh up to 60% more — and would also cost more to produce — than a comparable housing made of plastic.”
Machining aluminum also posed technical problems. “The complex geometry would have meant segmenting the housing into two parts which would need to be machined and assembled,” says Georgis. “Cast Nylatron was not competitive due to tooling costs and unit cost, and was not pursued beyond initial inquiries.”
Meeting and Exceeding Requirements with a Cast Epoxy Housing
Liquid resin casting offered a way to overcome the difficulties noted earlier and to produce the desired housing quickly, efficiently and economically. MARKEM had previously worked with RESIN SYSTEMS CORPORATION to produce cast liquid resin parts for other marking systems. Although those parts were smaller and less complex than the Q2000 film drive housing, MARKEM approached RESIN SYSTEMS to determine if the same process was applicable to larger parts.
Engineers from both companies consulted with each other and adjusted the housing design to make it more readily manufacturable by liquid resin casting. According to Stuart McCord, RESIN SYSTEMS’ Engineering Manager, “The design team considered various materials including a urethane elastomer, a filled urethane, and epoxy. We settled upon a toughened epoxy because of its superior handling characteristics, suitability for casting into complex shapes, durability, minimal shrink factor, and its ability to withstand moderate heat.”
Next RESIN SYSTEMS produced the required machined-aluminum tooling for molding the housing against a very tight deadline (“Within six weeks,” says McCord). Upon completion of the tooling, it took only another two days to cast the first housing, perform required secondary CNC machining and make delivery to MARKEM.
“The resultant quality and precision of the cast resin housing was so good — with tolerances as tight as +/-0.001″– that production could begin immediately,” Georgis recounts. “In fact, within a week after receiving the first housing from Resin Systems, we installed it on a Q2000 system and shipped the system directly to a customer.”