SUBTRACTIVE / RECONFIGURABLE PIN TOOLING FOR COMPOSITES

 COMPRESSION MOLDING & THERMOFORMING

Jim D. Gray & Associates, Inc.

Supporting O.E.M.’s since 1977

SUBTRACTIVE PIN TOOLING™
Surface Generation in the U.K. developed an approach called Subtractive Pin Tooling™ (SPT™) to build molds that use a grid of rectangular "pins" mounted on threaded rods. Their height can be adjusted to form a rough net-shape surface. The pins are clamped and held in place by a bolster while the working mold surface is roughed and finished with traditional milling equipment. Molds made this way are useful in about a dozen operations including composite manufacturing, superplastic forming, vacuum forming, and pattern making.

 

"Subtractive Pin Tooling™ shrinks lead times and costs associated with large and short-run component manufacturing by creating the front face of the tool, as opposed to an entire solid mold insert," says Jim Gray of Jim D. Gray & Assoc. Inc., the North American distributor for Subtractive Pin Tooling™ in Richardson, Texas. "Pins can be of plastic, metal, ceramic, and even wood. Graphite could be used to make a large electrode and we've even proposed pins of Inconel for a high-temperature application."

 

According to the company, SPT™ tools slash cost and lead times by up to 90%, and it cuts time to market by 35% for large components. And ROIs are projected in six to 18 months.

 

"This approach allows rapid design iterations by adding material, removing it, or both. Over 90% of the mold can be reused in future projects. We suggest saving the model, not its mold. And the system can economically produce one part," says Gray.

 

"It's imperative that the first mold be made as quickly and cheaply as possible," adds Gray. "Tooling is only an asset while it is being used. So for low-volume work, it is essential to have a reusable tool. When the surface on the tool is no longer useful, pin heights can be adjusted and re-cut for new parts." Gray adds that Subtractive Pin Tooling™ also lets users verify assemblies, manufacture one-off's, and produce several prototypes from the same mold to assess competing designs.

 

Subtractive Pin Tooling™ performance is governed by how closely the pins can produce the near-net shape of the required geometry. In most cases, composite SPT™ tools are more stable than conventional steel tools.

For ductile materials, machining parameters can be set to blend away the pin-to-pin joint, usually less than 50 m. And when necessary, a temporary bond along the pin boundary may be used to create a "single" surface.
Machine DesignMachine Design celebrates 75 yearsCAD model surfaces of a final part appear under the white wire-frame blocks that represent the pins. A computer program reads the CAD file and adjusts the blocks accordingly. In a partially processed model (right) the CAD surface has been roughed into the ceramic pins.

CAD model surfaces of a final part appear under the white wire-frame blocks that represent the pins. A computer program reads the CAD file and adjusts the blocks accordingly.

 

In a partially processed model the CAD surface has been roughed into the ceramic pins
A mold of steel pins is taking shape. Two-inch2 pins compose most of the surface, but larger 4 in.3 pins are visible to the left.

A mold of steel pins is taking shape. 2-inch pins compose most of the surface, but larger 4 in.3 pins are visible to the left.

 
The rectangular pins in a Surface Generation machine are being adjusted for height. Afterwards, a clamp holds the pins tightly together for roughing and surface finishing, often on the same machine. This Subtractive Pin Tooling reduces lead times and costs for large molds by up to 90%.

The rectangular pins in a Surface Generation machine are being adjusted for height. Afterwards, a clamp holds the pins tightly together for roughing and surface finishing, often on the same machine.

 

This Subtractive Pin Tooling reduces lead times and costs for large molds by up to 90%.

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