1 Topic by carl_m1968 (edited by carl_m1968 2018-08-09 11:58:40)

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Topic: Rough inside perimeters

Since this is probably a setting issue I have made the post here. My issue is that my outside perimeter look fine, but my inside perimeters are rough with small blobs and such sticking out.  I am printing some long cylinders for a project and I would prefer the inside to be smooth from printing as I can always sand the outside. They are more apparent to touch rather than sight and will interfere with an insert that need to go into the tube. So what would make the inside rough while the outside is smooth. I am doing .3 layers at 250C using PETG. My bed is at 65C and I am printing at 30mm/s. Tried .2 layers with same result. Went down to 240C with no real impact either. There are also a lot of very fine strings as well. Those can be cleaned out but could be a sign of part of the issue. I am using Simplify3D. This only seems to happen on curved surfaces. Flat surfaces have the same finish inside and outside.

Outside:
http://soliforum.com/i/?0pttLiQ.jpg

Inside Close:
http://soliforum.com/i/?6zNSSbx.jpg

Inside Overall:
http://soliforum.com/i/?EsPnVbm.jpg

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2 Reply by wardjr

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Re: Rough inside perimeters

Try “avoid crossing perimeters”.
Switch which perimeters are printed first. (Probably wrong term but you know)
This can be a tough one to solve, I’m just tossing ideas.

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3 Reply by yizhou.he

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Re: Rough inside perimeters

I would guess moisture in filament and nozzle temperature too high. Sometimes thermistor came loose make temperature reading not accurate can also cause this since actual temperature is higher than the reading.

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4 Reply by carl_m1968

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Re: Rough inside perimeters

yizhou.he wrote:

I would guess moisture in filament and nozzle temperature too high. Sometimes thermistor came loose make temperature reading not accurate can also cause this since actual temperature is higher than the reading.

I don't use thermistors, I use thermocouples and they are bolted to the sides of the heat block. The A to D converter for those thermocouples have been calibrated to account for the difference between the hotend and the heatblock which is 20c. The temp of the bed and hotends have been confirmed to be accurate by a thermo-camera that also displays the targets temp. I use an Axteeg X3 Pro that has configurations for multiple temperature sensor inputs. I am not limited to thermistors or their low temp capabilities. I went down to 240 which is the lowest recommended for PETG and all it did was make a bit more of a shine but the roughness was still there on the inside surfaces.

PETG does not absorb moisture as bad as others filaments and I live in a low humidity area.

Also as I said this only happens on curved surfaces. If it was temp or humidity then it would do the same on flat surfaces and corners and the outside surface would be affected as well.

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5 Reply by Kronikabuse

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Re: Rough inside perimeters

petg likes to be under extruded. Not agreeing with the nobody but It is sensetive to moisture. https://www.matterhackers.com/news/filament-and-water

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6 Reply by carl_m1968 (edited by carl_m1968 2018-08-09 17:04:03)

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Re: Rough inside perimeters

Kronikabuse wrote:

petg likes to be under extruded. Not agreeing with the nobody but It is sensetive to moisture. https://www.matterhackers.com/news/filament-and-water


Well that black was finished last night. I am going to install a new unopened spool of Natural PETG tonight so I will try the same settings with the new spool and see what happens. I just think it odd the only real issues are on the inside surface.

Nice promotional page for their Printdry though.

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7 Reply by yizhou.he

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Re: Rough inside perimeters

I think the outer surface is also affected. but it will be more obvious for the inside than outside when wet filament expands after heated.

PETG will typically flow nicely in the range of 230-265°C. But I think black usually requires higher temperature, again, moisture in filament will alter the optimal temperature.

Not that I have ever used PETG filament. Saw too many case on facebook group.

https://www.matterhackers.com/news/how- … g-filament

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8 Reply by carl_m1968 (edited by carl_m1968 2018-08-12 14:56:49)

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Re: Rough inside perimeters

Looks like it was moisture after all. Although the inside is still a bit more rough than the outside. So there is still something going on I have yet to pin down.

Update:

I got two new spools of PETG from Microcenter. I set my temp to 235 and I set optimize perimeter start points and it seem to have solved the issue. Now the insides are just as smooth as the outsides.

Printing since 2009 and still love it!
Anycubic 4MAX best $225 ever invested.
Voxelabs Proxima SLA. 6 inch 2k Mono LCD.
Anycubic Predator, massive Delta machine. 450 x 370 print envelope.