I’ve seen a lot of posts talking about Onyx and Markforged and why they’re so great but I’m curious to know why I don’t see many users reporting that they use PEEK or Ultem. There’s also PEEK with Carbon Fiber which honestly sounds like Onyx on steroids. Besides printers for PEEK being more expensive, is there a reason not to use PEEK? I mean they sound a lot stronger than Onyx especially the carbonx peek.
That’s before finding/tuning a printer to match the performance of a Markforged.
We used to use ULTEM for our high strength printed parts up until about 2019 when we got our own Markforged printers. In our case while ULTEM parts are very strong, the Onyx parts were generally strong enough, and when they aren’t we can add fiber reinforcement. The Onyx parts also print beautifully and with a .1 layer height you often can’t even see the layer lines whereas our ULTEM parts are pretty low resolution in comparison.
A big reason ULTEM isn’t as common is its high melting temperature. Until recently the only printers that could natively print ULTEM were high end Stratasys machines that cost over $200,000.
For us it is easier to iterate on the Markforged printers we have in our lab than have an outside group print parts for us in ULTEM on Stratasys printers.
We occasionally still print ULTEM Parts if we think we need the strength or if we need them printed quickly. There were a few on our 2019 robot, but there are none on the 2020 robot currently.
PEEK is most likely out of reach for hobby printers. However, PEKK is on the edge of hobby style printers. We recently installed a Slice Engineering Mosquito hot end with a 50 watt heater. It can handle the temps needed for PEKK. The big problem is getting a heated chamber on our printer that could give the ambient Temperature. Something to play with in the future. Stuff is expensive. Would rather design around it.
Onyx has a flexural strength of about 80 MPa. PEEK is about 100 MPa. Onyx is 1.18 g/cm^3, PEEK is 1.32 g/cm^3. So onyx is only a little worse than PEEK in terms of specific strength (strength-to-weight ratio). Ultem is a similar story.
In my experience, PEEK and Ultem are typically desired for their high melting point, not (just) their room-temp mechanical properties.