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August 11, 1998

4 Min Read
Rapid tools for prototypes and beyond

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A composite tooling board was machined in 8.5 hours vs. the 58 hours required for an equivalent QC-7 aluminum mold. The resulting mold insert ran 100 visor parts in 20 percent glass-filled PP, complete with deep ribbed sections and other intricate details. Other composite board molds produced 250 dimensionally accurate visor bracket caps from PP, ABS, and PC resins yet required only 2.25 hours to machine.

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Like most relatively new technologies, rapid tooling (as well as prototyping) is taking a roller-coaster ride toward full-scale acceptance. Wohlers Assoc., a Fort Collins, CO-based consulting firm that tracks the market, recently reported that while sales of RP systems totaled more than 1000 units for 1997, the industry revenue clocked in at about 8 per-cent growth vs. 43 percent for the previous year. Is it time to lower expectations for RP?

Hardly. This technology holds such promise for both design and tooling functions that most industry experts are predicting growth, albeit uneven, for the future. Several developments unveiled at SME's recent Rapid Prototyping and Manufacturing show in Dearborn, MI give credence to these claims. Here are a few of the highlights.

Composite Tooling Board for Prototype Molds
Wouldn't it be great if toolmakers could machine prototype and short-run molds right on a high-speed milling machine at speeds 80 percent faster than aluminum? That was the thought behind a research partnership between JCI-Prince (Holland, MI) and Ciba Specialty Chemicals (East Lansing, MI). Together, the partners developed an aluminum-filled thermoset composite board that can be machined in hours rather than days or weeks, eliminates the need for stereolithography pattern masters, and requires no secondary finishing. Patents are pending on the Cibatool-Express material, but the board is now commercially available at a price equivalent to cast aluminum (about 25 to 30 cents/cu inch).

To prove the technology, Prince and Ciba ran several projects comparing the composite board to QC-7 aluminum. Unlike aluminum, the composite inserts need no secondary finishing or surface treatment. Using high-speed machining equipment, composite board tools were produced in 15 to 20 percent of the time required for aluminum, yet part quality and dimensional accuracy were identical. Molding parameters, including melt temperatures, are also similar with one caveat: The composite tools require slightly longer cycle times for cooling. As for durability, the tools have been able to mold 250 parts at the upper limit. Further testing, say the partners, will help determine the maximum life of these tools.

New Materials for Rapid Tools
At 3D Systems, the emphasis is on application-specific materials. Originally, the company's three SLA systems ran three general-purpose resins. Now, the line has been expanded to include 11 different resins targeted specifically for prototypes, tooling, and automotive underhood testing. One of the newer materials, SL5220, gives toolmakers the high-heat resistance they need along with dimensional accuracies within .001 to .003 inch.

Introduced several years ago, DTM's RapidTool process promised near-net-shape mold inserts using the company's line of metal powders and its Sinterstation equipment. When it became clear the materials required further development, DTM went back to the drawing board. That exercise spawned the next generation of RapidTool materials (now commercially available)-copper-polyamide and RapidSteel 2.0.

Kevin McAlea, marketing vice president, remarks both products offer improvements over original materials. RapidSteel 2.0, for instance, requires less finishing time than its predecessor because the particle size is smaller. The new formula also reduces total shrinkage from 4 percent to .2 percent. Copper-polyamide, a composite material, requires no furnace process and can handle several hundred parts using such materials as PE, PP, and ABS.

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XMD mold design software from Cornerstone Technologies promises to cut 30 to 70 percent of design time by offering a knowledge-based system that creates fully associative 2-D and 3-D drawings from wireframe, surface, or solid part data.

Software Cuts Mold Design Time
Although mold design software doesn't traditionally fall under the category of rapid manufacturing, its aim is the same-namely, to decrease the amount of time needed to produce a prototype or production mold. One such package, Expert Mold Designer (XMD) from Cornerstone Technologies, works seamlessly with Cadkey to help automate mold design by creating 2-D and 3-D drawings based on a 3-D model. It contains a parting line editor, proposes plate sizes, generates mold components, and draws four standard views of the mold.

The software also targets some repetitive, time-consuming tasks and reduces them to a mere click of the mouse. To illustrate, Cornerstone found many moldmakers were spending 3 to 4 hours just to create a manual bill of materials. With XMD, the process takes just 30 seconds and requires no retyping and no proofreading for errors. Results are then output onto a spreadsheet for use by the purchasing department.

Contact information
Cornerstone Technologies
Windsor, ON
Vince Shepley
Phone: (519) 250-8850
Fax: (519) 250-0006

DTM Corp.
Austin, TX
Kevin McAlea
Phone: (512) 339-2922
Fax: (512) 339-0634
Website: www.dtm-corp.com

Ciba Specialty Chemicals
East Lansing, MI
Phone: (800) 759-7165
Fax: (517) 351-6255

3D Systems
Valencia, CA
Merv Rutledge
Phone: (805) 257-4800
Fax: (805) 257-5800
Website: www.3dsystems.com


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