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Hi all,

I am looking for a suitable material that can be drilled and machined after it’s printed. The application is in medial case planning. For surgeons to have a print of a patients bone that they can then use their normal instruments to ‘dry run’ the surgical case. The materials I have tested so far melt around the drill bit and are very difficult to machine. I have see clay like filaments that are hard at room temperature but can be carved and sculpted under certain conditions. What would this community suggest?

Thanks

Matt

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Hi @mttctr with FDM printing, melting is always going to be an issue because that’s the nature of the material used and how it’s printed (by melting) so I doubt there’s a solution. The various “exotic” filaments like clays, metals, etc. for FDM all still melt to one degree or another and some of them are quite poor at producing high detail, so may not be suitable even if they didn’t melt.

I think you’d need to look at another technology such as SLA or SLS that could produce a model not so prone to melting, but to be honest I’m not sure there are any guarantees their either, we’ll need an SLA/SLS expert to comment…

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Hey guys,

SLA resins, like Formlabs Tough, are somewhat machinable (you can drill it) before curing, but it is finicky. It won’t melt like FDM plastic will, but depending on the orientation of the print and the geometry, it does tend to crack/shatter if you’re not careful with it. Generally, I drill a pilot hole and gradually increase the hole size until it is what I need. Just going at it with the full size bit is a very quick way to break the print. For general machining, SLS is a better choice of the two, but even then, you are limited in what you can do.

One of 3D printing’s biggest drawbacks is lack of machine-ability post-printing, and this is why it’s mainly in the prototyping side of industry. Current machines are pretty accurate, but will not yield the tolerances you can get from classical machining applications (CNC, mill, etc.) and, as you’ve found out, it is difficult to machine prints at all. DMLS is a bit of an exception here, but that’s not something you see everyday and is mainly targeted at the high-end of the auto industry.

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There may also be some filaments that come out harder but i’m assuming they are doing it for more of a how is this hardware going to fit aspect. Is it possible to change their tooling or procedure for fitment rather than as a surgical op?

Sounds like a fun project to be on.

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Hi Matt,

We have been talking to someone about a similar plan, they find that the usual sawbones aren’t good enough.

We are planning to use polycarbonate as this has a higher melting temperature than usual FDM filaments, nylon is another possibility.

I have drilled polycarbonate post printing before to change some mounting holes and it was fine. Not done any extensive machining though.

Usually cutting 3d printed parts isn’t ideal as the lack of perimeters around a hole reduces the strength and leaves a bad finish, but I guess in this case it could mimic the structure of a bone quite well!

feel free to contact me at n.fry@create3d.uk, we can print these materials if needed.

Nick