Copper-infused PLA for spur gears

Question

I am currently printing PLA infused with 80% copper powder. So far I mainly used it because it looks and feels really nice and post-processing is almost limitless, however recently I have thought that metal-like filaments might actually be a good idea for gears (in case I don't want to use polycarbonate or carbon fiber PLA).

I have been researching about the material properties of copper-infused PLA and found a few studies about the "strength", however, those seem to have exclusively focussed on how much weight can be suspended on a hook where it showed pretty good results. The only other info I found was an unsourced "it is more brittle", however the objects I printed so far do not feel more brittle.

Does anyone have any experience with spur gears printed from copper-infused PLA? Are there any advantages over regular PLA? Any downsides (I could imagine higher abrasiveness is not really helpful)?

Answer 1

With the right material, you could print the gear and then sinter it, resulting in actual metal gears. However, 80 % metal-filled PLA is at the lowest border to achieve this, and a lot of that technology is patented.

Filamet^TM

Filamet^TM is a Virtual Foundry product that contains around 80-92 % metal powder of 100-400 µm particle size, suspended in a carrier. The carrier material is supposedly PLA or at least functionally similar. The resulting filament is highly abrasive, requiring stainless steel¹ to print more than short sections. The high metal content also gives the material a memory of its spooled-up shape. This demands extra special treatment during printing to prevent snapping the filament in the shape of a pre-heater to get it spooled off properly. The same company also offers similar products for ceramics. After printing, the models are burned-out and sintered in an oven at very high temperatures. This sintering is done in a crucible filled with carbon and alumina, burning out the PLA carrier while retaining the shape. Their material-making process is patented (patent itself) and covers all their metal, ceramic, and glass materials.

_{1 - or something even more hardy, like an Olsson Ruby by 3DVerkstan}

MetalX^TM

The MetalX^TM system by Markforged uses a special printer and proprietary Bound Powder Metal Filament that contains an unknown plastic binder. A lot of this machine and surrounding peripheries are patented and information spare. Among others, their method of creating composite filaments and their binder material, support material & sintering process are only described in patents. From their advertisement I could deduce the following process: The MetalX printer prints the item with unknown print settings, resulting in a raw item containing metal and the binder. After wash-cleaning using a liquid known as Opteon^TM SF79 (Datasheet) to remove the specialty binder, the sintering happens in a free oven at 1300 °C, leaving behind a metal product. Free oven means here, that the printed part is not embedded in a filled crucible like with Filamet^TM.

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_{Disclaimer: I am not affiliated with either Virtual Foundry, Markforged, 3DVerkstan, any of their products or affiliates.}

Answer 2

At a guess, copper really isn't that strong so you're likely to see minimal improvements, if any.

The PLA carrier plastic is still PLA, with a low melting point.

The copper won't "fuse" with the PLA, it will still be flakes of metal embedded in a tiny pocket inside of a plastic structure.

However this is all speculation, and your best option for an answer is to print some gears and methodically test them against plain PLA, and perhaps a metal gear if you can. Try and use identical setups/bearings/pressures and times.

Perhaps a high torque and a high-speed test, in both lubricated and unlubed, for PLA, copper-PLA, and a straight metal gear? That would be 12 tests in all and clear out all questions.