Thin Wall Calibration Too Thin...

Hey everybody. I just finished my custom machine and I have been doing a lot of calibrations recently. I am using Slic3r, Marlin, and Pronterface. My problem I have been having is that when I run the thin wall calibration test one of my walls is so thin that I can see right through it. I have been changing the extrusion multiplier around and I set my filament diameter correctly. I have also properly calibrated my E steps/mm. What I suspect is possibly something to do with retraction.

With this particular calibration it begins in one corner of the square, does all four sides, then it stops and it travels back over the two sides it just completed. Then it proceeds to cut between the two opposite corners so it ends up kind of forming like a Z pattern. It retracts just before traveling between opposite corners and it starts up again on the sides. If you are confused at all just ask. The thin wall is the side that it begins on after this Z travel. What are some things I could do to solve this problem.

Thanks in advance.

It sounds like you've got wipe turned on. When the head travels back over what it's just printed, any ooze gets wiped over that part of the print. When you start up again on a new side, your printer thinks it has more material than it actually does as some ooze was wiped off elsewhere, hence the thinner wall. You could try increasing your retraction distance and/or turning off wipe. It's probably a good idea to turn off wipe until you get your retraction settings correct anyway.

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[3DKarma.com] - suppliers of quality, affordable 3D printer kits and filament for the UK market.

Looks like I have wipe turned off and unchecked. It just looks like the hotend starts to move before it starts laying down plastic. Is there any way to make the movement pause for just a fraction of a second after a retraction so it has time to get the line of plastic out and started before it moves again?

Maybe play with the "Extra length on restart" setting in Printer Settings / Extruder 1.

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[3DKarma.com] - suppliers of quality, affordable 3D printer kits and filament for the UK market.

I saw that setting when I was messing around with other settings. At the time I just thought about it for a second and glanced over it. I will test that out. Thanks.

That worked perfectly! Thanks so much 3DKarma. I first tried it at 1 mm extra length extruded after the retract but that put out too much and the hotend ran into the blob and knocked the print out of place. So I then lowered it to 0.5 mm and it worked great. Hope this helps someone else.

Also, I wondered if the extrusion multiplier in Slic3r applied to this setting as well. So that, if in the future, I find my walls to be too thick I can change the multiplier and it will also affect this extra length. Is this correct?

Thanks again.

As I understand it, the rectraction length / length after retract are extruded length (what comes out of the hotend), so the multiplier should affect it, but I haven't played with it to be sure.

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[3DKarma.com] - suppliers of quality, affordable 3D printer kits and filament for the UK market.

Yeah it makes sense that it would. I asked because I am also experiencing holes being too small and plugs being too large. So I may end up playing around with the multiplier to get the extrusion to be the right size. Or should I change the extrusion width in the settings?

Holes being too small seems to be a result of the way the extruder pulls the filament around in a circle. The tension in the filament will decrease the diameter of the circle - it's especially bad on small holes. The fix is to design your holes with a number of facets no more than twice the diameter of the hole --so a 3mm hole with have 6 facets. You may also need to slightly increase the diameter.

Re the size of the plugs - you may need to calibrate your x and y steps per mm, as well as playing with the extrusion settings. Try printing the 20mm test cube and adjust your x and y steps per mm based on the actual size of the printed cube.

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[3DKarma.com] - suppliers of quality, affordable 3D printer kits and filament for the UK market.

Yeah, I did a little research and it seems like a big problem. I read on some blogs and stuff that increase the diameter by a some percentage can help. Also, I did see that designing the hole with fewer facets (faces on the inside of the hole?) can reduce the problem. My question is how do you design a hole in normal 3D CAD software to have fewer faces? I read that you can do it in OpenSCAD but I downloaded that and I'm not exactly fond of the code based drawing. If I could do it with my current software that would be great.

Edit: I guess I could just extrude a polygon with the less than or equal to 2x the diameter through my object.

What design software do you currently use?

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[3DKarma.com] - suppliers of quality, affordable 3D printer kits and filament for the UK market.

I mostly use Autodesk Inventor. I have SketchUp but haven't used it very much and I also have OpenSCAD as I mentioned in a previous post.

I don't know about Inventor, but in Sketchup you click on the circle tool, then enter the number of facets / sides you want (before clicking on the center point of the circle you're going to draw). The number will appear in the bottom-right of the Sketchup window.

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[3DKarma.com] - suppliers of quality, affordable 3D printer kits and filament for the UK market.

I will try to make a plug test in Inventor just using polygons instead of circles and I'll let you know how it turns out.