Mechanical engineer here.

Metal clays have been around for a while. Physical properties depend greatly on the base metal used and the temperature and environment in which the clay is fired.

Compared to "regular" metal, the clays will be significantly weaker, especially in tensile or shear loading. Not so much under compression.

So what about firing process for the printer? The video don't show the finishing process. Is this heating table?

> The device prints with a commercially available jewelry product known as "precious metal clay." This material is a pre-mixed emulsion of metal particles in a water soluble organic binder. When heated in a kiln (600˚C-900˚C) the binder burns away as the metal particles fuse together.

process is the same as for firing metal clay objects you might make by hand in a jewelry studio. Let it dry, program kiln to the specs given with the clay, and fire for 2 hours.

would they exceed 5000 psi in compression? and what drives the cost up? I noticed they have a steel clay. Is that real (ish) steel and could it be made for under $5 per pound (as a bulk material)?

The process is expensive because it's a very low volume product and it's a heterogenous mixture that needs to be stored and processed without separating, rather than an alloy. It has been possible to print with metal clay for a very long time, with every paste extrusion setup made so far, the major problem is material cost and firing. I don't expect an object made with metal clay to handle 5000psi in compression, but it might be possible with some clever geometry. The major issue with metal clay is that is behaves like clay in many ways, severely limiting geometry that can be fired without breaking. You can think of it as very high viscosity solder paste.

True, I don't think anybody will be printing toaster ovens this way. The plastic/elastic properties of metal does make metal parts printed this way quite different in performance from parts printed in plastic. Not to mention the temp. ratings. Purity stamp for silver PMC after firing is 99.9%

Steel clays need to be fired in an oxygen-free environment or you'll have major oxidation problems. I don't realistically see this ever becoming a thing.

>5000 psi

Possibly. Again, it depends on the metal you use. With the right steel or aluminum alloy I could imagine seeing something on this order.

Have been working with a pottery studio that does quite a bit of reduced-firing for special types of glazes. The clays that require low-oxygen to be fired can be embedded in special types of activated charcoal & reducing agents within the kiln. We've had some excellent results with bronze, have yet to try iron & steel. The firing instructions on those clays are similar to the bronze, however.