A new rapid tooling system capable of producing stamping and die-casting tools turned up at this week's Hannover Fair. Tucked away in a booth dedicated to the winners of the 2007 Swiss Technology Awards, this new process from Tschopp Technical Engineering GmbH creates the tools from stacked layers of steel sheet. Like most rapid tooling systems, Tschopp's Metal Laminated Object Manufacturing process (LOM) starts out by dividing a 3D CAD model of the tooling component that will be manufactured into a set of slices. The process then uses the sliced CAD data to drive a CO2 laser that cuts out the individual slices from thin sheets of steel. Next, these layers are hand stacked before undergoing an operation that joins the steel laminations into a semi-finished tool.
Depending on the type of tool to be made, the layers are bonded in one of two ways. For most stamping tools, the layers of steel have a thin (4 to 6 micron) coating of epoxy adhesive. Once the laser-cut layers are stacked, the entire pile goes into a press, which adhesively bonds the layers together permanently. Aluminum die casting tools are also built up from layers of steel, but these have to be brazed together due to the temperatures and pressures generated in die-casting.
The entire tooling process using Metal LOM typically takes about two weeks. And the biggest tool created to date is a 5.5 ton stamping tool that measures 1,300 x 800 x 700 mm.
Tschopp’s Metal LOM system isn't the only LOM method around. Paper-based systems for rapid prototyping and even another metal rapid tooling system have been around for years. But Andreas Lehmann, chief technology officer of Tschopp’s start-up LOM division, notes that previous metal-based LOM systems did not rely on epoxy coated steel.
Tschopp has another twist on LOM in its ability to take turn prototype LOM tools into production tools. In metal LOM components, the edges of the laminations form many of the component surfaces, leaving a stepped effect that wouldn't be acceptable on most production tools. Lehmann says that the Tschopp process “masks” these rough surfaces by pressing a thin layer of steel over the rough surface left by the lamination edges. “With this method, we can transform the prototype tool into a production tool,” says Lehmann, who notes that some prototypes may also require small amount of machining to tweak the final tool surfaces and features.
Tschopp, which won a 2007 Swiss Technology Award for its Metal LOM process, has over the past year delivered a LOM stamping tool to Daimler Chrysler for evaluation, Lehmann says. And he's looking for other development partners in both U.S. and Europe.