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Thermoforming Technology

Ren Shape Molds Support Fast Production

Vantage Tool and Engineering (VTE) of Fort Wayne, IN, is redefining the concept of rapid manufacturing by working on a two-day, art-to-part turnaround time for many projects.

The company uses CAD/CAM technology, high-speed mills and easy-to-machine Ren Shape 450 boards from Vantico Inc., Ren Shape Tooling Systems, in East Lansing, MI.

VTE cuts Ren Shape 450 boards on a 3-axis mill to produce thermoform molds in half the time required for machining metal tools.
Typical Project Profile

The majority of VTE’s thermoforming projects call for molding food trays, bowls and other highly contoured containers in quantities of up to 5,000. The materials formed include polypropylene, polystyrene, PVC and polyethylene. The Ren Shape 450 board has worked well for quickly cutting prototype tooling that can be used for up to 500 cycles.

“Our toolmakers have the equipment and expertise to mill aluminum, but we can cut a Ren Shape mold in half the time needed to machine metal. The board helps us significantly reduce delivery times and costs on initial parts while hard tooling is being made,” says Sam Geiger, general manager at VTE. “The completed Ren Shape prototype molds also generate trays and bowls with a production-quality surface and intricate detail.”

Moldmaking

After VTE receives the data for a part or designs a container based on client requirements, the CAD file is downloaded to the CAM program which adds cutter and toolpaths. At the same time, VTE moldmakers begin building up a machinable block by laminating Ren Shape 450 boards together. Individual boards measuring 16 inches by 60 inches by 4 inches are bonded together using Ren Weld 103 adhesive. After the block is built up, the pieces are clamped for 48 hours until the adhesive cures.

“The key to good adhesion between board pieces is accurate measuring and weighing of the adhesive components,” Geiger says. “Once the boards are joined properly, the bondlines are really tough. In fact, during testing we’ve found that the board shears before the bondline breaks.”

To cut a mold cavity, the Ren Shape 450 block is installed in one of VTE’s high-speed, 3-axis mills. Machining typically begins with a 1/2-inch depth of cut followed by 1-inch and then 11/2-inch cuts to produce the deep cavities that characterize many of the traps and containers formed by VTE. Two-flute, hardened steel ball-end mills are used to machine the board at 3,500 rpm and 120 ipm for roughing. The finishing cuts are made with a 1/4-inch tapered, fluted-end mills at 4,500 to 5,000 RPM and 150 to 160 IPM using a 0.007-inch stepover to produce mold surfaces that require no secondary finishing.

Completed molds exhibit the strength and thermal properties needed to withstand numerous thermoforming cycles, including a glass transition temperature of 205F, shore hardness of 65D and tensile strength of 2,300 psi.

Forming Parts

In order to mold a container, the machined Ren Shape tool is mounted in a standard base and installed in the thermoforming machine. A plastic sheet is inserted in a frame over the mold, heated until soft and then formed into the mold cavity. The completed container is demolded immediately and preparations to produce another part are made.

“Thin-walled parts, run at temperatures up to 450F, are typically the most difficult to form because the Ren Shape molds hold the heat. When we’re running multiple parts, heat build-up has the potential to damage mold surfaces. To prevent this, we reduce the cycle time to allow the heat to dissipate,” says Geiger. “(But the) Ren Shape boards meet our needs for an easy-to-handle, durable moldmaking material for initial part production.”

For more information on Ren Shape, contact Vantico at (517) 35105899 or visit www.vantico.com

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Plastics Machining & Fabricating
P: (847) 634-4347
F: (847) 634-4379
EMAIL:
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P.O. BOX 1400
LINCOLNSHIRE
ILLINOIS 60069