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Volume Two, Number Four
Rotomolding fans - this issue offers new information to help design engineers, product managers and others use plastics. Email me with questions and comments. If you need to leave the newsletter, see the end for instructions.
Now boldly mold!
For more information, contact Meese Orbitron Dunne Co., American Rotational Molding Group; 16404 Knott Ave., La Mirada, CA 90638; Phone: 888.724.1228; Fax: 877.904.1670; www.modroto.com.
Why Your Resin May Not Be What It Used To Be
Scan the pricing tables for resins in any of the major magazines, and realize pricing is based on the idea that PE is PE and PP is PP whether it comes from Exxon, Borealis, Nova or any other supplier. But experienced molders know that many resins listed as identical on the charts will perform very differently from each other once placed in the mold.
Be careful when switching resin suppliers and molders just to cut a few pennies off the cost. Differences in melt flow, stiffness and other properties may upset your process. In molding housings, for example, we had designed the parts around geometry that demanded flow only in certain areas. A Mobil resin filled the part well for years even to the point we fine-tuned the design to capitalize on the resin’s characteristics.
But another resin substituted by Exxon after the Mobil acquisition had slightly different flow characteristics and stiffness. It was similar enough to be labeled the same material but different enough that many of the cost-efficiencies we had created around the original resin went out the window.
Thanks to our size, volume and track record, we are now working with Nova’s new line of rotational molding resins. And thanks to Nova for their commitment to the industry.
For more on this, see here.
YOU, TOO, CAN DESIGN FOR ROTOMOLDING (#4 In A Series)
Savvy product developers can enhance their designs with a limitless number of textures, dimples, letters and other 3-d tactics. Permanent warnings, symbols, logos and nearly any other type of raised or dimpled shape can be applied during rotational molding by adjusting the mold using any of these processes:
Acid etching - leathery, stone and other looks may be achieved by etching the surface of the mold with hydrofluoric acid. Effective in parts that need to withstand bending and handling.
Shot peening - to add raised shapes in a pattern or random dispersion, pressurized steel balls are literally shot onto the aluminum casting.
Engraving – for letters and numbers for consumer warnings, warranty terms, serial numbers, codes and other permanent, virtually tamper-proof information, engraving is done directly on the mold itself.
In many cases, using these processes eliminates the need for some secondary operations and permits faster overall production rates.
For projects where secondary operations were eliminated or reduced, see a p-o-p display here and E.T. here.
Get an estimate on your next project at http://www.modroto.com/cgi-bin/request.
For a free brochure, call 800.772.7659 or go to http://www.modroto.com/cgi-bin/request.
Adventures In Rotomolding is published by Meese Orbitron Dunne Co., Saddle Brook, NJ, www.modroto.com; 800.829.3230. Copyright 2004 Meese, Inc. May not be reprinted without permission. Please feel free to pass along to other engineers and colleagues.
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