Binder jetting prints a liquid binder into a bed of powder to glue the particles together layer by layer, producing a fragile green part that is then debound and sintered in a furnace. No laser, no melt pool and no supports, which makes it fast and cheap per part. The furnace stage is what makes it different from every other metal process, because the part shrinks substantially and predictably.
The two stage process
The printing stage is quick and can fill the whole build box with parts, since nothing has to be attached to a plate. The green parts are then cured, depowdered and sintered, where the binder burns out and the metal particles fuse. That furnace cycle takes many hours and is where density, dimensions and properties are actually decided.
Shrinkage is a design input
Parts shrink by a substantial and geometry dependent percentage during sintering, so the printed part is scaled up and the shrinkage compensated. Uneven sections shrink unevenly, large flat spans sag, and heavy parts can slump under their own weight, so setters and support furniture are used in the furnace. Designing for sintering is a different discipline from designing for laser melting.
Where it beats laser powder bed
Throughput, because the whole build volume can be packed and no laser has to trace every cross section. Cost per part in quantity. No support structures to remove. Better surface on downward faces. Materials that are difficult to laser melt, including some that are routine in metal injection moulding, are often straightforward here.
Where it loses
Dimensional accuracy on large or asymmetric parts, because sintering distortion is hard to control. Full density, which usually needs infiltration or additional processing. Very fine features. And any application where a qualified laser powder bed process already exists, since requalifying a new route is expensive.
Questions people ask about binder jetting
Is binder jetting the same as laser powder bed fusion?
No. Binder jetting glues powder and sinters it in a furnace afterwards. Laser powder bed fusion melts the powder in the machine. The two produce different accuracy, different density and very different economics.
How much do parts shrink?
A substantial and material dependent amount, compensated by scaling the printed geometry. The important point is that shrinkage is uneven on uneven parts, which is what limits accuracy.
Does binder jetting need supports?
No. The surrounding loose powder supports the green part, which is one of its main advantages. Furnace furniture may still be needed to stop sagging during sintering.
Which materials are available?
Stainless steels and tool steels are the common industrial set, with other metals, ceramics and sand for casting moulds also in use. The list is narrower than for laser processes on some alloys and wider on others.