3-D printing technology can also make things out of metal. As I understand it, the process involves fusing powdered metal into a solid shape.
I have seen sintered titanium, used in jewelry. Not very impressive: rough and brittle.
Can an engineer chime in, here? Has this process been improved?
Sintered metal has been around for a long time. Carbide cutting tools and certain wear parts are made from powdered metal mixed with a binder. In essense the mixture gets baked and finish-ground, often with diamond grinding wheels.
With 3-D printing you could make the “pre-forms” very rapidly. I think that for the near-future your still looking at needing a tool shop to grind the semi-finished part coming off the 3D Printer.
While metal, the finished part is far from solid and is relatively porous and not all that strong in tension or torsion. One could look to conventional powdered metal fabrication for some help here. Powdered metal parts have been around a lot longer than 3-D printing. Compacting the powder in a die yields a "green part" which has almost no strength. Green parts are "sintered" by heating in a hydrogen atmosphere to just under the melting point of the metal used. The 3-D part is at about the same strength at this point as the more conventional PM part.
The PM part undergoes some slight shrinkage when sintering and may be brought to final dimensional form by re-striking it in a finishing die, forging the final part to finished dimension, increasing it's density and strength.
For the highest strength parts you may take the re-forged part and pass it thru a furnace in contact with a small copper block. Furnace temperature should be just above the melting point of copper with a reducing (hydrogen) atmosphere. The copper melts and capillary attraction draws the liquid copper into the porous PM part where upon cooling it brazes the powdered matrix into one solid piece.
The copper infiltration procedure could be adapted to add final strength to 3-D powdered parts to produce a stronger, near net shape part.
As an alternative I would look for plastic that could be used in the 3-D process yet remain soluble in a suitable solvent (styrene and acetone for instance). Post printing you cement on some gates and vents (made of styrene rod stock using acetone as a glue), Coating your model part with refractory plaster by dipping the model into the plaster which should be about like thick cream. Then inspect for air bubbles which should be popped with gentle blowing. Then use something like a tea strainer to dust the coated model with tiny glass beads (craft shop?? or bead blasting shop) and let air dry. Repeat five times to build up a shell. When dry dissolve the pattern with the solvent. Support your dry plaster pattern in a bed of dry sand with the vents and gates facing up. Preheat the pattern to red heat and pour anything you can melt. When cooled and the plaster removed you will have a solid metal part that can hold dimensional tolerances of +/- 0.001" per inch. This form of casting technology dates back to the bronze age and was lately used by Saturn to turn styrene pellets into engine blocks.
Regards,
GtG