Dec 11, 2014 | By Alec

Even though 3D printing has finally starting making a name for itself as a consumer technology, it is still almost entirely a plastic affair. Virtually all 3D printers owned by private makers are plastic extrusion printers relying on FDM technology. While these are being used to create wonderful and creative goods, their plastic nature somewhat limits the potential of these printers.

Metal printing, on the other hand, does have the innovative strength to challenge and change every aspect of manufacturing. But limited material options, absurdly expensive equipment and high production costs mean that it is still almost entirely an industrial technology. While aerospace industries are doing wonderful things with that technology, it will be years before that technology becomes affordable for everyday makers. And while plastic printing technology has a wonderful open-source development platform, there just isn't anything similar for metal printing.

But there is some light at the end of the tunnel. For an engineering team from the Michigan Technological University – Led by Joshua Pearce, Associate Professor of Materials Science and Engineering – has been working on an open-source 3D metal printer for some time now. While it will be some time before their metal printing endeavours can be emulated in our own homes (garages, rather than desktops I think), they have made some interesting technological breakthroughs that could make metal printing far more affordable than ever. Their printing technology could cost as little as $1500 to set up yourself.

Their cost-cutting solution? Gas metal arc welding technology. Unlike the extremely expensive laser-based sintering and melting technologies, this manufacturing technology welds layers of metal 'filament' together with a gas welder, controlled with an open-source microcontroller. Essentially, it combines a commercial gas welder (like those often used on construction sites) with a RepRap deltabot setup. While most objects produced by welding technology have a limited print resolution and a poor surface finish, their 'Microwelding' setup has so far 'exhibited excellent dimensional control and finer surface finish resulting from the small - diameter electrode and wire employed.'

There's just one problem with this approach: how do you remove the 3D printed metal objects from the metal substrate they've been printed on? Generally, this would require very expensive cutting tools that drastically drive up the prices of a technology that is supposed to be affordable. Many cheaper alternatives tend to damage the objects in question, and would negate all the effort put into the printing technology.

Fortunately, the Michigan team have recently developed a removal tactic that will still be inexpensive and will leave the printed object intact. This post-processing method has so far proven successful with objects 3D printed in ER1100 aluminum. As they explained in their recent paper published in 3D Printing and Additive Manufacturing, this involves coating their substrate will specific substances that will ensure that the aluminium objects form a brittle compound with the substrate. While this still creates a weak attachment between the object and the printbed, a few taps with a hammer and a chisel easily releases the two. Not only will this leave the object in perfect shape, it also means you don't destroy your printbed upon every iteration. Finally, it's also inexpensive and very quick.

Key to this process are the 'intermetallic phases' that form between different metal structures. Welding two metal components (for instance, aluminium and iron) together results in a brittle interface between the two due to their different crystal structures, so industrial manufacturers of metal objects tend to avoid it like the plague. But purposely creating these brittle bonds between the printbed and the object proved to be perfect solution for budget metal printing: 'This brittle interface may have allowed the aluminum samples to be easily removed from the low - carbon steel substrate, not only via a lap shear test but also with a hammer and chisel, exploiting the low strength of this interface.'

As part of their experiments, the Michigan team first printed a control group that perfectly illustrates the problem. Printing 'commercially pure aluminum' on a printbed of 'commercially pure aluminum' resulted in, as can be expected, ' good joining between the printed and substrate materials. This result was expected because no compounds or coatings were applied to prevent adhesion.'

However, coatings of aluminum oxide and boron nitride proved to result in quite brittle formations. These were applied to two types of substrates: one of 1100 aluminum and another of A36 low - carbon steel. 'It was determined that boron nitride - coated low - carbon steel provided the lowest adhesion strength. Printing aluminum on uncoated low - carbon steel also allowed easy removal of the aluminum part with the benefit of no additional coating steps or costs.'

Furthermore, no deformation of the print substrates were observed during these experiments, meaning they can be reused again and again. 'This is both an economic and environmental benefit. Preliminary work indicated that the same substrate can be used several times. The aluminum oxide and boron nitride coatings can be scraped, sanded, or simply washed off with water to prepare the surface for reuse, an improvement over other 3D printing techniques such as laser melting and laser welding of metals, which require a sacrificial substrate.'

Images credit: SHAWN MALONE /

This could mean that commercial metal printing could be just around the corner, especially as a reusable substrate would keep the actual printing costs low. Joshua Pearce also seems very optimistic, going as far as stating that this could bring metal manufacturing to the developing world: 'Clearly, the ability to produce custom functional metal parts (e.g., bicycle components, water pump components, or small wind turbines) in a relatively isolated community would have far - reaching implications. Beyond the economic benefits, this technology may also have utility in education as assessed in work by UNESCO considering how 3D printing could be used for education in such communities.'

While its currently not clear what the next steps are (will they want to develop a commercial venture?), Pearce has said in the past that he intends to share his results on an open-source basis with the maker community. 'I anticipate rapid progress when the maker community gets their hands on it. Within a month, somebody will make one that's better than ours, I guarantee it.'

Perhaps we'll all have a metal 3D printer on our Christmas lists next year?


Posted in 3D Printing Technology


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