Any suggestions on how to avoid this?

[rjfrank]

Ok, I've printed 4-5 objects now and a couple of them have shown effects like this (see the distortion along the short vertical edge). Sorry kind of crappy images...

bad_1.jpg

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bad_2.jpg

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I am using Simplify 3D with the default settings for the M2 process. PLA with 215 deg extruder, 70 deg table. Prep the table by cleaning w/windex, drying and using aquanet to help the first layer stick. Could this be related to speed? Should I be dropping the table temp over the duration of the print? Any suggestions would be helpful.

Thanks.
rjf.

[jsc]

Really difficult to tell from that picture. Black is difficult to photograph. Try backing off from it to give it a chance to focus.

Can you provide the model? It looks like that surface is overhung, but it is difficult to tell by how much. Either it is overhang curling, in which case try turning the model so that that surface is towards the front, or it may be warping induced.

[benavery]

I'm guessing an overhang, printed in PLA, with the overhang pointed toward the back of the printer, so isn't getting sufficient cooling from the bed fan. Try rotating the model 180 when printing it.

More general question for everyone: Are there any better more general solutions to this problem ? It comes up often. Sometimes its not going to be possible for a model to be rotated, or to be printed in non-PLA. Do the guided fan vents work ? If so, should they be a standard feature of the M2 instead of everyone re-designing and retrofitting them. Its unfortunate there's no good way to fit a rear fan, or left/right fans on the M2 head

[jsc]

Ben, check out my fan shroud thread. I'm getting perfect overhung surfaces up to 60 degrees facing the rear, and very good surfaces up to 70 degrees facing forward.

[rjfrank]

Thanks for the information. I am attaching the model I was trying to print. I did not try rotating it. The bed fan was mentioned. I assume that is the fan angled downward (45 deg from the bed)? That fan has never come on for me (the one blowing directly on the extruder is always on). Should it? If so, how do I test/trigger it?

[jsc]

Okay, the overhang is not that extreme, so that should print fine without any issues. However, if you're not printing with any fan, that could definitely cause that. If you're using Simplify3D, go to the Cooling tab and adjust the setpoints so that layer 1 is 0% and layer 2 is 100%.

You're definitely going to want support for this model, though, if for nothing else those overhung pins that have nothing under them.

[rjfrank]

hmm, that is what my cooling is set to (layer 1 -> 0, layer 2-> 100) and that fan never comes on. Is there an easy way to debug that fan?

[rjfrank]

ok, M106 S250 and M106 S255 will enable the bed fan, but in the G-code it starts with:

M127
M140 S70 T0
M134 T0
M104 S215 T0
M133 T0
M108 S255 ; turn on M2 fans

and later:

; layer 2, Z = 0.38
M126 S255

which should probably be 'M106 S255'. Does that sound right?

[jimc]

the m108 command is the extruder fan. that should always be on. slice a file and find the beginning of the second layer. see if you can find an M106

[jsc]

M126 is "open valve". What??

Go to Tools/Firmware Configuration. Is the Select Profile drop down set to RepRap (Marlin/Repetier/Sprinter)? Under the FFF tab, Set Fan Power should say "M106 S$".