Swiss injection toolmaker Georg Kaufmann Formenbau AG is using a new way to fabricate steel molds for prototype parts, as well as small-lot runs, within eight to 12 weeks.
Kaufmann uses the LOM process, which stands for laminated object manufacturing. It starts with epoxy-coated steel sheet. Once the company has the final three-dimensional CAD files of the two mold cavity halves, it uses a special software to generate a layer structure at a right angle to the mold parting line. The thickness of each slice corresponds to the gauge of the steel sheet.
Corresponding core and cavity slices are cut by a laser from the same sheet, and they remain interconnected by thin webs, which maintain tight tolerances. Each numbered section is cleaned and deburred. The slices are then stacked in the proper sequence and clamped with spring-loaded tie rods. The resulting stack is heated slowly in a special furnace for several hours. The steel and epoxy layers will fuse tightly together and bond into a solid mass.
After the stack cools down, Kaufmann removes the tie rods and severs the web links between the core and the cavity. The company does additional machining, and mold grinding before assembling the final mold.
After the grinding step, the layer structure is no longer visible, according to the company in Busslingen, Switzerland.
Kaufmann said one benefit of LOM is that holes for the tie rods, guide bars, slides and ejector pins can be produced during the laser cutting process. Also, the company can add large cooling channels that follow the surface of the mold, thanks to the multilayer structure.
Kaufmann Formenbau said it has obtained the exclusive right to use the LOM process to make injection molds.
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