1922 additive manufacturing weld-buildup on cast iron

Glancing historical reference, not developed.

There are powder-based processes. A lot of these were the first metal 3D printing processes officially called 3D printing. Professor Eagar and I were talking about how additive manufacturing has been around for eighty years or so if you consider just welding one layer on top of another. But from the perspective of this new 3D printing industry, it really started with laser powder bed about twenty years ago, out of a lot of research in Germany with lasers and powdered metals. Then there are companies like Desktop Metal, also based in Burlington — they're neighbors, with a lot of ties to MIT — doing things with binder and metal powder. And there are some niche processes that use large rods of metal doing friction stir welding, basically spinning rods to generate heat to melt the metal in contact with the substrate. And there's ultrasonic sheet welding, basically binding whole layers on top of one another.

*Welding Journal* 1922 article showing weld bead buildup on cast iron, presented as the earliest modern example of metal additive manufacturing. Tom notes cracks at the edges.

So what's the history of additive manufacturing? I found in the Welding Journal of 1922 this additive manufactured part, where people were laying weld beads down on cast iron. There are little cracks on either side of this thing, but they were essentially building up pads and doing additive manufacturing. So that's the earliest modern example. Can anyone think of an earlier example of additive manufacturing?