The quest for a promising metal printer continues... ultrasonic consolidation

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Ok, so you may have heard of ultrasonic welding. Basically two metal surfaced are rubbed against each other at ultrasonic frequencies, and amplitudes in the 10-20 micron range, under high pressures (it was ~1500-1800 newtons under a roller but not apparent what the area under said roller effectively was, the length of the roller can probably be found in those docs).

So what Ultrasonic consolidation, as a printing process, is, is you take a layer of metal foil, apply to a layer beneath it, and roll a vibrating sonotrode over it to weld it to the substrate. It might seem this "weld" is not very strong. However it can be 100% or more (due to changes in microstructure (crystalline structure) of the material caused by the rapid heating and cooling) the strength of the bulk material of the foil.

In other words 100% strength.

So that's how you add a layer of metal, the foil is usually bauot 150 microns thick. Then you machine each layer, or every couple of layers, with a normal mill. Net result, a custom full strength, fairly low internal stress object "grows" upwards.

There are some problems, obviously the object being printed needs to support the ~1600 newton load being placed on it during the consolidation process. Secondly, as explained in the second document I linked to, the build object has to not wiggle too much or there ends up bing insufficient/no relative motion between the new foil and the layer beneath, so no frictoin=no welding. This implies the need for a certain rigidity/stiffness .

Lastly, leaders. You know, overhands that have to, when building from the bottom up, start in mid-air. Clearly you need a support material of some sort.

So suppose you basically fill every voxel that isn't filled with metal with some support material as you go along. It could be applied with a reprap like extruder head. Sometimes you will want the support material to be flush with the top surface of the build object (top layer). In that case, machine down everything with the mill.

One of the main requirements here would be a good support material. Suppose the build material is Aluminum alloy. It has to be : rigid/stiff (similar to Aluminum) and reasonably strong (enough to stand the pressure from UC without cracking or deforming much), you can weld the Al foil to it ultrasonically (probably not a hard req to meet), soluble in some solvent or otherwise easily removed from hard to reach places, resistant to maybe 300 deg C, or maybe more. Because the metal zone where the welding is done still gets hot, about 50% of the melting temperature of the metal, and it will be right close by. And chemically compatible withthe build material. Preferrably low viscosity during deposition.

Hm. Ideas on what material might fill this spec?

Imagine for a second the build process and results... suppose the support material was transparent (somehow)... the print process completes, and whatever desired full strength, hgih quality, pretty accurate parts are embedded in a block of this (water soluble?) support material... Simply dissolve the material and retrieve your parts :-). It would be awesome. The economic impact of this sort of thing could be enormous; replacement mechanical parts, odd fasteners and brackets, custom parts for custom machines could all be made with it.

I visited a company in the USA some years ago that were doing this, I forget the name now but they had a cnc miller with the ultrasonics and a tape roll of alluminium, with machining between layers, I think they found an application in military stuff, but for mould making and the like it was not competative.
mesh and fibre optic cable can be embeded into blocks which is interesting.

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Random Precision

yeah, I think the first doc uses said company's machine. They don't use support material though. That is the main innovation we need. Plus cheaper and way smaller.

The support material allows us to get around the 1:1 height:width ratio and also to start leaders which their machine cannot do.

It sure would be a good start to get access to one of those machines though. Hey If they're not competitive I wonder if there are any laying around out there not being used? Man that would be a flying start to get a project to develop such a printer off the ground. We could start experimenting with support materials right away!