The goal of Project FabMX is to design and build an affordable, open-hardware 3d printer capable of producing metal objects.
FabMX is part of MakerTools.
The Process
We want to build a "metal pellet fused deposition modelling" system. What does that mean? The material to be used is MIM (metal injection molding) feedstock. This is a metal powder / plastic mixture with a very high percentage of metal (>95%) and can be bought in the form of pellets. In a conventional MIM procress, these pellets will be heated up until the plastic (a thermoplastic) gets soft and then gets pressed into a mold that gives the object its shape, just like with (non-metal) injection molding.
To get a metal object, further processing steps are needed:
- First the plastic has to be removed from the "green" part, this is called "debinding". There are several debinding systems, usually this is done thermically (in a debinding oven) or chemically, e.g. by putting the part in an acetone bath.
- The result of the debinding step is a very brittle "brown" part. This now has to be sintered in a sintering oven. The temperature needed depends on the used metal, for stainless steel it is around 1300°C.
To turn this process into one suitable for 3d printing, the first step (injection molding) is replaced by an FDM/FFF style 3d printer, but one with a pellet extruder suited for taking MIM feedstock. The resulting 3d printed "green" parts are then debindered and sintered just like in metal injection molding.
