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I am working on refining my PMMA printing process and I am trying to print as close as possible to the theoretical 100 % density of the material. I am making good progress and am slowing increasing the extrusion multipliers to try and find a good set of print settings.

I recently have run into an issue where the bottom ≈1/3 of the test cylinder is coming out rather distorted (see picture). The problem seems to sort itself out as the finish around the top of the cylinder looks fine. Do any of you have any experience with PMMA or have seen this problem before?

My initial thought is that it is heat driven and as more material is added it becomes less of an issue as there is more mass to dissipate the heat. For reference I am printing on an Raise3D Pro2Plus, for my prints I am running the extruder at 250 °C and the heated bed at 100 °C. I am eventually going to need to print rather large cylinders and would like an even surface finish along the length of it.

Test Cylinders, right and left show distortion on the bottom and the center shows a bizarre print where half of the cylinder was fine and half came out very jagged.

Test Cylinders, right and left show distortion on the bottom and the center shows a bizarre print where half of the cylinder was fine and half came out very jagged

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  • $\begingroup$ would love to know if you arrived at parameters that allow for satisfactory printing. I wrote a post (here: 3dprinting.stackexchange.com/questions/16437/…) in hopes that someone had some wisdom to offer. Do you use any sort of heat-enclosure cage? $\endgroup$
    – S.Cramer
    Jun 4, 2021 at 18:15

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Commercial PMMA may soften already at 85 °C.

The higher you go away from the bed, the colder the air is, so the issues solves itself.

Try lowering the bed temperature, at least to exclude that as cause.

The second cylinder shows the very common issue related to uneven cooling. Probably your part cooling fan is blowing only from one side. Try using a better fan shroud or add a second part cooling fan.

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  • $\begingroup$ Thanks for the insight, I will give that a try this afternoon. I'm not sure if something just blocked the fan for that run because I've printed about 10 of theses and that's the first time I have seen that issue. $\endgroup$
    – ZebraEagle
    Jan 15, 2021 at 17:00
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    $\begingroup$ Just an update, I think the heating bed was causing the issue like you said. Even dropping the bed temperature a few degrees made a good bit of difference. $\endgroup$
    – ZebraEagle
    Jan 19, 2021 at 20:01

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