Material Order of Preference for Machine Components?



  • PLA seems to be a convenient entry level option with good rigidity and processes easy but weakens earlier than other materials with increasing temps.

    ABS was favoured for components close to the hot end on the ormerod 2 and was a sugested upgrade path but is notoriously akward to process. Maybe a processing parameter issue but parts I have built have seemed brittle.

    My core xy build for work utilises a kit of PETG parts which seem more compliant and is higher temp than PLA. How does it sit relative to ABS in your opinions?

    Are there other materials that I should be considering now? PC-ABS sounds great from the low flamability point of view but equally seems as awkward as ABS to process?

    Think the nylons and purer PC blends are high temp processing?

    Aesthetic appearance isn't a concern of mine.


  • administrators

    @doctrucker I have been using Atomic Filament: Carbon Fiber Extreme for most of my gantry parts and am loving it. It is basically as easy to print as PLA, but slightly more compliant (less than straight PETG), with MUCH better structural integrity. The compliance can be an issue in parts that are too thin, or poorly designed. but in my C-Bot this only proved to be an issue in a new part that I designed poorly.

    The Tg of PLA can be an issue anyplace, not only near the hot-end. Even though I started with PLA for all my parts I never actually had a problem with parts near the hot end, somewhat ironically, it was actually my motor mounts that had issues first as prior to switch to a Duet the motors would run quite warm and eventually allowed the PLA to bend under the tension from the belts. Less surprisingly my bed mounts also suffered once I started heating my bed up to 100c+ to try and print replacement motor mounts in ABS. Eventually I was able to print replacement bed mounts in ABS and switched to the CF Extreme for pretty much everything else.

    I have used Nylon in the past for a few parts, it was awesome, but the challenging to get tuned well enough to print larger parts consistently.

    My current preference is:

    • Carbon Fiber PETG
    • ABS (anything exposed to ambient temp > 60c)
    • PLA (in a pinch / prototyping)

    -M



  • @msquared

    Yes, played that game too. Had exactly the same problems with my motor mounts when doing long 20hr plus prints. E3D Edge wasn't much help over PLA either. Unfortunately, I can't change nozzles with my Diamond hot end so the more abrasive filaments aren't an option. I ended up fitting heat sinks and fans to all my motors (apart from the 5 extruder motors - it doesn't matter too much if those mounts distort a bit).



  • Thanks for the suggestion. Any electrical or thermal conductivity increases with the CF PETG would be a welcome bonus too.



  • @msquared I starting using PLA my parts , but started using PETG because I was concerned about PLA bending with temperature, but in the end went back to trying PLA because I had so many problems with PETG being too flexible for parts like the carriage.
    I didn't have any problem with PLA until I started to increase the current to the motor and make them really hot.
    So what is CF PETG like for part you need to stress like the carriage ?.



  • another option for reinforced filaments is c/f nylon. I use the 3dxtech version. With a tg of 105 and an hdt of 102, which is inline with abs and far higher than cf/petg but with tensile and flexural modulus almost identical to cf/petg . Ive got pretty good stiffness out of this material by making it a little thicker than would be out of PLA



  • I printed most of my DBOT parts in PETG and some in PLA.
    But After some time the PLA cracked and I reprinted them in PETG.

    The DBOT has been running hard for over 1 year

    My VOTE is for PETG



  • I should have said that I've been running the D-Bot reasonably hard and have racked up over 100 builds (range from 0.5 - 7hrs) since last September not including many multiples of short test coupon builds and not yet suffered a component failure. Most parts are PETG. Two remaining PLA parts which are simply stepper mounted pulley covers.

    Beginning focus on machine optimisation and reducing issues like ghosting as far as possible. PETG is currently my default material for modified components and generally work with a minimum of 5mm sections with ribbing to reduce flex and unwanted oscillations as far as practical.

    Alas demands on the machine have meant that I've been running PLA, ABS, TPU64D, and PETG rather than really being able to focus on machine evaluation, material optimisation, or self education properly!



  • Also, keep in mind that not every PLA or PETG has the same properties. While, in general, PETG will be less brittle than PLA, I've had some PETG that creates prints that are noticeably more flexible than PETG from different manufacturers.

    Also, there are a number of modified PLAs out there that have increased flexibility (similar to PLA) as well as some modified PLA material that can withstand more heat than PETG after annealing in an oven.

    John



  • How's the dimensional/geometric stability of the PLA through heat treatment? I'm guessing this triggers come cross linking in the material?



  • Have you considered aluminum? It's cheap and easy to make very rigid, square motor mounts out of rectangular tubing. All you need is a saw and a drill and you can make a one in less time than it takes to draw it in CAD. Using aluminum helps cool the motor, too

    alt text

    The mount can be fixed to the printer's frame from either the sides or the bottom/top using t-nuts, carriage bolts, or whatever hardware makes sense for your printer's design. Smaller motors can be mounted inside the tube or outside, depending on how you are going to attach the mount to the printer's frame.



  • Another reason to use aluminium motor mounts is this extract from the wiki:

    "Note: it is highly recommended that the stepper motor casings be grounded, especially in belt-driven printers. Otherwise, motion of the belts causes static charge to build up, which eventually arcs over to the windings. If the motors are screwed to a metal frame, grounding the frame is sufficient."

    So really, with a plastic mount, we ought to run an earth wire from the motor body to the frame (assuming the frame itself is grounded). I've never got around to it myself, (neither has Mr Prusa et al) but according to the Wiki we should.



  • @deckingman I actually went ahead and did that on my build. Everything is properly earthed. Can't say it really made a noticeable difference, but I guess that's the point. You won't notice until sparks fly, then it's too late.



  • I have been using TitanX from Formfutura with excellent success, for both large and small prints. The parts are structurally sound and i have even used this product for components on my printer for both stepper mounts extruder mounts (direct drive) as well as linear rail mounts. There has been no compromise with the function or deformation of the parts. My printer is enclosed with chamber temperature sitting around 50C. There is near zero deformation when cooling the part.



  • @doctrucker said in Material Order of Preference for Machine Components?:

    How's the dimensional/geometric stability of the PLA through heat treatment? I'm guessing this triggers come cross linking in the material?

    With regular PLA, it is poor. The only modified PLA I've used is MakerGeeks Raptor PLA. At least in my experience, very good dimensional stability except on thin, flat pieces. When dimensional stability is important to me I'll print two pieces, anneal one, and compare it to the non-annealed pieces.

    https://www.makergeeks.com/collections/raptor-series-pla

    There are other modified PLAs out there, but I haven't tried them.


 

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