3D Printing Metal from Rust

It seems backwards, but engineers from Northwestern University have made 3D printing metal easier (and eventually cheaper) by adding extra production steps to the procedure. (Paper available in PDF).

Laser sintering works by laying down a thin layer of metal powder and then hitting it with a strong enough laser to sinter the particles together. (Sintering sticks the grains together without getting the metal hot enough to melt it.) The rapid local heating and cooling required to build up 3D objects expands and cools the metal, and can result in stresses inside the resulting object.

The Northwestern team still lays down layers of powder, but glues the layers together with a quick-drying polymer instead of fusing them with a laser. Once the full model is printed, they then sinter it in one piece in an oven.

3D-printed copper lattice. Credit: Ramille Shah and David Dunand

The advantages of adding this extra step are higher printing speed — squirting the liquid out of syringe heads can be faster than fusing metal particles with a laser — and increased structural integrity because the whole model is heated and cooled at one time. A fringe benefit is that the model is still a bit flexible before firing, opening up possibilities for printing a flat model and then bending it into shape before sintering.

And if that weren’t enough, the team figured that they’d add a third step to the procedure to allow it to be used with rust (iron oxide) as the starting powder. They print the rust and polymer model, then un-rust the iron using hydrogen, and then fire it as before. Why rust? Do you know anything cheaper to use as a raw material?

What do you think? The basic idea may even be DIYable — glue metal particles together and heat them up enough to stick. Not in my microwave oven, though. We’d love to see a more energy-efficient 3D metal printer.

Thanks to [Joe] for the tip!

New 3D Printing Techniques at AMUG 2015

Sometimes there’s a lot of perks to working for a cutting edge tech company while also being a writer here at Hackaday. This week I had the opportunity to attend AMUG 2015 — the Additive Manufacturing User Group conference in Jacksonville, Florida.

I saw companies big and small, checked out the newest techniques like metal printing and mold making, and met a ton of interesting people. Join me after the break for the rundown and a video summary of my experience.

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Printing In Metal with a MIG Welder

Whenever the question of metal 3D printers comes up, someone always chimes in that a MIG welder connected to a normal 3D printer would work great. A bit of research would tell this person that’s already been done, but some confirmation and replication is nice. A few students at TU Delft University strapped a welder to a normal, off-the-shelf 3D printer and made a few simple shapes.

This project builds on the work of [Joshua Pearce] et al. at Michigan Tech where an MIG welder and delta bot was used to lay down rather complex shapes on a metal plate substrate. The team at TU Delft used a cartesian bot – a Prusa i3 – for their replication because of the sheer mass of moving a metal build plate, firebricks, and welder around.

In the first few prints on their machine, the team was able to lay down enough metal to build a vertical wall. It’s not much, and to turn this into a finished part would require some machining, but these are only the beginning steps of what could become a legitimate way of creating metal parts. Video below.

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THP Entry: An Affordable Metal 3D Printer

metalFor years now, people have been trying to develop an affordable, RepRap-derived 3D printer that will create objects in metal. There has been a lot of work with crazy devices like high-powered lasers, and electron beams, but so far no one has yet developed a machine that can print metal objects easily, cheaply and safely. For The Hackaday Prize, [Sagar] is taking a different tack for his metal 3D printer: he’s extruding low temperature alloys just like a normal 3D printer would extrude plastic.

[Sagar]’s printer is pretty much a carbon copy of one of the many ‘plastic-only’ 3D printers out there, the only change being in the extruder and hot end. As a material, he’s using an alloy of 95.8% tin, 4% copper, and 0.2% silver in a 3mm diameter spool. This alloy melts at 235° C, about the same temperature as the ABS plastic these printers normally use.

The only real problems with this build are the extruder and nozzle. [Sagar] is milling his own nozzle and hot end out of stainless steel; a challenging bit of machining, but still within the realm of a hobbyist. He has some doubts about the RepRap derived plastic geared extruder being able to handle metal, so he’s also looking at designing a new version and milling that out of stainless as well.

It’s an awesome project, and we hope we’ll be seeing some updates to the project shortly. While a 3D printer that produces objects out of a low temperature alloy won’t be building rocket engines any time soon, it could be a great way to fabricate some reasonably high-strength parts at home.

SpaceWrencherThe project featured in this post is an entry in The Hackaday Prize. Build something awesome and win a trip to space or hundreds of other prizes.