A fast cost-effective route to rapid prototypes of electronics enclosures is a process developed in Europe that combines CAD with CNC machining and fabrication of sheets of shielded plastic. The process is growing rapidly for lots of 50 to 200, in part, because of its low costs compared to making injection molds. The most commonly used materials are flame-retardant ABS and other styrenic alloys.
Printed circuit boards are attached with snap-on, screw-in or other fastening options. Prototypes can typically be produced in three to 21 days. It's most economical to produce square housings with flat sides with this process, but it is possible to make curved to complex shapes. One other drawback, compared to injection molding, is the need for greater tolerances. Tolerances on feature alignment and product dimensions are ±.008 inch or .2 mm, according to Clickfold Plastics CEO and Founder Patrick Oltmanns. Maximum size is about 20 x 15 x 15 inch.
More Parts Per Sheet
Plastronic Enclosures of Piscataway, NJ, has installed new, larger processing machines that yield improved economics. We can get parts to customers quickly because we use four-feet-by-eight-feet sheets, which means shorter production cycles, says President Daniel L. Cucchiara. Plastronic's roots go back to 1993 when it became the first U.S. company to design and manufacture tool-less enclosures. PEI says its approach, called Digital Design and Manufacturing, includes unique developments in Pro-E that allow more contours, radii and complexity. We're finding that the volumes are increasing, says Cucchiara. Five years ago, the norms would have been between 25 and 100. Now, 250 to 500 is becoming more the average. The growth in competition is helping spur growth, he says. Average design time for enclosures is four to six hours. PEI focuses on UL-certified materials, such as ABS/PVC.
How It's Done
Step 1. Design the enclosure starting from a dimensioned drawing or CAD file showing electronic components oriented in space.
Step 2. Generate CNC code that drives machining and bending operations.
Step 3. Machine sheet for openings, vents and recesses.
Step 4. Cut individual pieces from sheet.
Step 5. Prepare joint and edge details on routing machines.
Step 6. Score the sheet with bending cuts on a custom table saw.
Step 7. Bend the pieces in a computerized thermal bending machine.
Step 8. Heat stake metal inserts into bosses. Install bosses into machined recesses in the sheet.
Step 9. Assemble the pieces using a solvent-bonding process.
Step 10. Perform secondary operations such as painting, EMI shielding and latch or hinge installations.
Doubling Floor Space
ClickFold Plastics of Charlotte, NC, is doubling production floor space due to a more than doubling in backlog growth over the last six months. One example is a cover for connector housings, says CEO and Founder Patrick Oltmanns. The part is pretty large, so the mold would be expensive. Yet, the part is simple. It's a perfect candidate for plastics fabrication. ClickFold has a lot of business in medical enclosures, which typically have runs of less than 10,000. ClickFold also sees strong growth in demand for enclosures that were previously made from sheet metal. For the same amount of money, they can get a box that weighs less and they don't have to worry about painting, says Oltmanns.
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