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The title of this post more or less says it all.

I am having a heck of a time getting PMMA (polymethyl methacrylate) to print on my Lulzbot Mini 2 (which uses all of the standard/default attachments). Lulzbot offers a demo-STL file (called the "Rocktopus" - found here: https://www.lulzbot.com/content/meet-rocktopus) that is used to evaluate whether or not the printer+filament are behaving as intended. Thus far, I have had no luck with its print.

Layer separation consistently appears to occur at various levels:

  1. sometimes at the interface between the first layer of deposited PMMA (i.e. the first layer of the raft)

  2. sometimes at intermediate layers above the raft (i.e. mid-layers of the Rocktopus)

I have scoured the internet trying to find parameter recommendations (e.g. https://onlinelibrary.wiley.com/doi/full/10.1002/mame.201900263) in order to arrive at successful prints. I have tried several different combinations of bed temperature, extruder/nozzle temperature, layer height, travel speed, etc based on the few articles I have come across: no luck.

I have seen a few recommendations buried on forums to get a heat enclosure cage, but these were not specific to the lulzbot 3d printing line. The heat enclosures are a $200+, so I was hoping I could I find someone on here that could confirm the necessity of this accessory product before I shell out the moneys.

My mini is paired with the most up to date version of Cura Lulzbot (edition 3.6.23).

Any assistance is greatly appreciated! Cheers~

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    $\begingroup$ From what I’ve read, PMMA/acrylic shrinks a lot as it cools, like ABS, which translates to warping and layer separation if you don’t have a heated enclosure. The key to printing high shrink materials is getting the ambient temperature up closer to the glass temperature of the plastic, in this case 100-120C. Poly Carbonate is known to have similar challenges. You can always outsource and order some parts made on an industrial printer, rather than diving into elaborate modifications. Here’s a video of this guy’s adventure in chamber building to print PC: youtu.be/79r5D9nCQfM $\endgroup$ Jun 4 at 19:12
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I was experiencing similar issues on my Raise3D Pro2Plus. I've printed near 20 small cylinders to try and fine-tune the settings to get densities that are close to the theoretical density and right now am sitting comfortably around 80 %. Here is what I've found

  • Temperature of the build plate and extruder have had a large effect on the quality of the print (obviously), to the point where 3-4 ° have a noticeable effect on print quality. I have settled on an extruder temperature of 252 °C and a bed temperature of 82 °C. I also print in an enclosure which I imagine is necessary due to the shrinkage seen in PMMA.
  • A lot of my problems were with bed adhesion. The Buildtak that came on the Raise3D worked for a while but the higher temperatures eventually caused the adhesive to fail and bubble up where I was trying to print. Blue tape and purple glue stick worked sometimes but would often detach halfway through the raft. What I've found that works reliably is Kapton tape covered in a purple glue stick. This has yet to fail me and the only downside is that I often have to reapply the Kapton after every 2 or so prints which is a small price to pay for me as my regular prints take 3-4 days.

Just for reference, I print at 30 mm/s, 1 mm nozzle, 0.29 mm layer height. I definitely get your frustration on trying to find a good resource for settings. Most I could find were generic ranges for temperatures and speeds.

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    $\begingroup$ Appreciate the input. What company do you purchase your PMMA from? Right now, I purchase from Push Plastic. Perhaps you use a different one. Cheers~ $\endgroup$
    – S.Cramer
    Jun 23 at 18:44
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    $\begingroup$ I use push plastics as well. I regularly print in larger formats so I need the 3 kg spools they provide. I believe I mis-spoke earlier, my print speed is 25 mm/s not 30. Just noticed it when I went to print something this morning. $\endgroup$
    – ZebraEagle
    Jun 24 at 21:38
  • $\begingroup$ I'm unfamiliar with the Raise3D Pro2Plus. Is it compatible with 2.85 mm filament or 1.75mm? (i.e. is your Push Plastics filament 2.85 mm or 1.75 mm) $\endgroup$
    – S.Cramer
    Jun 25 at 9:52

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