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3D CAD takes design from part to mold to assembly.

It's not that unusual these days for molders to use 3D solid modeling for part design. But Value Plastics, an injection molder in Fort Collins, Colo., has taken solid modeling a step further by applying it not just to the parts themselves but also to the mold and customized part-assembly equipment.

Value specializes in molding barbed fittings for fluid control. About 60% of the 50 million parts the company makes a year go into medical equipment. The remainder can be found in applications as diverse as Harley Davidson motorcycles and dispensers for toilet-bowl cleanser. Made from nylon, polypropylene, or polycarbonate, the fittings are small enough to be inserted into tubes with diameters of 1/16 to 1/4 in.


One of the biggest challenges in designing these parts is the barb, which holds the fitting in place. Chief engineer Bruce Williams explains that Value's barb poses some particular tooling design challenges. "We don't put a mold parting line on the conical section of the barb, where it could create a potential leak path," Williams says. Instead, Value uses slides and core inserts to make the barbs without creating this parting line. "Our barb contacts the tube around its full circumference," Williams adds.

While this barb design may cut the likelihood of a leak, it also means that Value faces mold-design difficulties and sacrifices cavitation: A barbed fitting with a parting line on its conical section would typically run in an eight-cavity tool with four slides, while Value's design runs in a four-cavity tool that has a more complex arrangement of slides and inserts.

Until two years ago, Value used a 2D CAD package to design its parts and tools. Today, more than half of the 10 or more new tools that Value designs yearly are designed entirely on a 3D CAD system from Solid Edge of Huntsville, Ala. Williams explains that the ease of visualization - especially when checking mold-action clearances - sold Value's engineering staff on 3D CAD. "The ability to see the mold open and closed, and to see the slides in both the in and out positions, lets us find and solve problems on screen," says Williams.


Value didn't stop with part and tooling design when it embraced 3D solids. The company also used Solid Edge to design a pneumatic tube-setting machine for its customers. The machine automatically inserts the molded fittings into the tubes.

The ability to visualize the tube-setting machine's 50 individual components as solids enabled engineers to fine-tune their designs as they created the CAD models for these components. Then, as the components were "assembled" on screen, potential clearance problems were spotted and fixed. "With the better visualization that solid-modeling provides, we could see things about the individual components, such as the need for a radius, that we might not have noticed working in 2D," says Williams.


About the time its engineering department made the decision to go with solid modeling, Value Plastics also became a "paperless" company. The Solid Edge CAD software helps because its Windows-based software eases the transfer of CAD models to other Windows applications such as word processors and page-layout programs.

This ability to transfer CAD data electronically has proven to be a time saver for the design engineering department, which produces electronic drawings not just for its own use but for the quality-control, production, shipping, and tooling departments. Rather than creating several different drawings for every design, the engineers now create one solid model and spin off different drawing versions as needed by Value's other departments. If the original model is changed, all related drawings are updated automatically, saving hours of drawing time. And rather than plotting drawings and delivering them to the various departments, engineers simply place them in a Microsoft Access database from which others download them.
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Article Details
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Title Annotation:three-dimensional computer-aided design
Author:Ogando, Joseph
Publication:Plastics Technology
Geographic Code:1USA
Date:Feb 1, 1998
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