How We Work
Tooling provides a mold cavity that compliments the finished part and is similar to that used in plastic injection molding including slides for three-dimensional features and multiple cavities for higher production quantities. Modern machinery such as EDM, Vertical Machining centers (5 axis), other Computerized Numerically Controlled machines are used to make tools. The expertise lies in designing and manufacturing the tools so accurately that we get right product at first try.
Mixing at selected temperatures combines micron sized metal powders with a multiple component thermoplastic binder system that enables the molten material to flow into the tool cavity. The mixture is called feed-stock and this feed-stock is used as the raw material for injection molding machine.
Molding occurs in conventional but automatic plastic injection molding machines using controlled conditions of pressure, temperature, and speeds.The feedstock is fed into the injection molding machines where heaters melt the binder to a toothpaste-like consistency and push it into the mold. The resulting part, once cooled, is ejected from the mold. Runners and gates are removed at this time so that that material can be recycled. These parts are the GREEN PARTS, handled with utmost care.
Stripping / de-binding
Stripping or de-binding is the removal of some binder from the part to permit sintering, achieved in two stages. The first stage is carried out either thermally or chemically,depending on the material process. The Green part is approximately 20% bigger than the finished parts will be. The second stage is a low temperature vacuum furnace specially manufactured for de-binding. Metabuild employs both technologies and each use is dependent of the product being produced. The resulting debound part is referred to as a “brown part.” Some of the binder is still left in the component after de-binding, so that the granules do not scatter and the part maintains its geometry. This remaining binder is called the back-up material.
The brown part is placed in a furnace and heated to within 85% of the metal’s melting temperature. The remaining binder is removed and the metal particles fuse together, shrinking to form a solid metal part that is nearly full dense (as compared to wrought density) and meets the desired design specifications.The original shape of the molded part is preserved during sintering and final part dimensional tolerances are closely held as the whole process is carried out in vacuum. The sintered metal component can then be further processed through machining, plating, heat treating, polishing, etc., if necessary, similar to that of a machined part.
Secondary processes if required
Metal Injection Molding (MIM) allows for secondary operations to be performed on metal parts when features cannot be made net shape.
Even with post-manufacturing work, MIM is usually quicker and more cost effective than machining or casting processes.
Metabuild has a full complement of machining capabilities for refining components that require extremely tight tolerances. Our state-of-the-art equipment includes fully-automated CNC machining centers and CNC electrical discharge machining (EDM).
Finishing may be required to remove certain injection molding features such as gate marks,
ejector pin marks, or parting lines. It may also be possible to remove these features in the as molded state.
Welding and Brazing :
Welding and brazing can be conducted on the sintered metal parts as readily as on cast and wrought metal parts.
Surface Finishing :
Metabuild’s turnkey solutions include many types of surface finishing services such as electro-polishing to improve a part’s appearance or performance.
Plating can be applied to the sintered metal surfaces in essentially the same way as for cast and wrought surfaces. Even the simple zinc plating we offers 100 hours salt spray test.