Injection molding is the most common manufacturing technology for large-scale production of plastic parts. By mixing metal powder with a binder, the advantages of the technology can also be utilized for metal components. The binder wets the metal powder particles and permits to mold them without heating the metal to its melting point. Afterwards, the binder is removed while the metal powder is sintered and compressed.
By using various different metal powders, there is little restriction as to the choice of the specific alloy. Part weight, however, is limited to within 0.1 and 200 grams. Therefore, the process is particularly suitable for very small parts in high volumes.
The raw materials of the metal alloy are processed to powder form.
The metal powder is mixed with the binder to feedstock.
The feedstock is metered into an injection molding machine, where it is plasticized by help of band heaters.
The plasticized compound is injected into the closed mold by axial forward motion of the screw.
The part cools in the mold, thereby gaining its dimensional stability, while pressure is maintained to compensate the shrinkage of the material.
After cooling, the mold opens and the green part is ejected.
The binder needed for molding is removed, resulting in a porous brown part of very low strength.
Only the sintering step gives the component its final properties. The powder particles coalesce and solidify at a temperature close to the material's melting point.
E.g. deburring, polishing, coating, etc.