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March 1, 2001

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A New Way to Make A Mold, Breaks The Mold

March, 2001

Moldmaking:

A New Way to Make A Mold,Breaks The Mold

0301pn-6.jpgD-M-ECo., working with a technology developed at MIT and the ProMetal Div. ofExtrude Hone Corp., has literally broken the mold on how molds can be madefaster and with greater design freedom. D-M-E and ProMetal have adaptedstereolithography techniques to print, layer by layer, powdered tool steelin a binder matrix to form prototype and short-run molds.

The process is called MoldFusion and D-M-E says that with this processit is possible to create near net shape three-dimensional structures from3-D CAD models. It also enables the creation of internal features and geometriesthat cannot be created with conventional mold-making techniques.

MoldFusion is an additive process that allows more design freedom thanthe typical machining or subtractive process and it can be accomplishedusing CNC equipment. According to D-M-E, the benefits of the process are: 

  • Rapid creation of production tooling for prototypes or short runs

  • Off-loading of low-value rough machining time on high-complexity jobs

  • Cycle time reductions of 20 to 35% through conformal cooling water lines

  • Improved part dimension control with advanced cooling designs

  • Thermal insulation of areas of mold temperature difference

  • Dynamic cycling of mold temperature with the injection molding cycle

The ProMetal 3-D process prints successive 2-D 'slices' through depositionof powder tool steel in a matrix, building layer-by-layer to near net shape.The 'green' part is then loaded into a sintering furnace that fuses a toolsteel skeleton and burns off the binder. A second furnace cycle infiltratesthe part with molten bronze via capillary action and brings it to fulldensity.

The near net shape part is then ready for final machining. All finishingprocesses are possible with a MoldFusion product and coatings to enhancewear and chemical resistance can be used as well.

The process can be used to create tools up to 12 in. in length and widthand up to 10 in. in height. The process is said to be particularly suitedto conformal cooling of mold inserts. It allows designers to create internalwater lines and water jacket features that conform to the shape of moldgeometries without the limitations associated with conventional machiningmethods. Greater control of cooling design allows for improved molded partquality, even with thick wall sections or thick/thin wall combinations.

Complex geometric control also makes MoldFusion effective for StructuralMass Reduction (SMR), the substitution of solid metal mass with structuralmold sections. Truss or honeycomb sections can be built into mold componentsto improve thermal isolation and reduce tool weight.

Combining SMR with selective heating and cooling of the mold duringthe injection molding process results in Dynamic Thermal Cycling, whichis said to allow for the molding of more complex designs, longer flow lengthsand improved part finish.

D-M-E Co.
Madison Heights, MI

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