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Unprintable Part: What the &(/$§Q/&) is going on? :)

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Hey there, dear Ultimaker-Community!

After the first (sometimes painful) month with the UM2 with quite good results (as i think) it is now time, to ask some more experienced users...

Since a week or so i work with ABS (the Verbatim-Stuff) and after some tests figured out a perfect solution (for me) to avoid warping of any kind: i put about a tea spoon of Acetone on the build plate and spread it with a piece of flat ABS, which leaves a wonderful evenly very thin film of ABS, so that the printed piece sits absolutely flat on the build plate.

Nonetheless i have a part which brings me to the edge of a nervous breakdown. I tried it about ten times now: flat on the buildplate, sideways, with few ABS-Glue, with much ABS-Glue... i also tried (after the first squished layers) to adjust the buildplate WHILE printing... nothing helps!

The thing is that the error occurs ALWAYS exactly in the same spot, and in Curas Layerview it SEEMS to my novice eyes that the printer head makes indeed some unnecessary movements… but again, i am a rookie and it’s hard to navigate precisely through the layers with that unprecise slider-thingie the programmers inexplicably implemented.

This is a part of adafruits Ray Gun Blaster one can download on thingiverse, namely body-left.stl and body-right.stl. I thought it would be a good idea to start not with selfmade models but with models other people already successfully have printed.



Edited by Guest

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Wonderful, chrisw!

Thanks a lot, this is really useful! I searched a few days before for this, but found nothing...



it’s hard to navigate precisely through the layers with that unprecise slider-thingie the programmers inexplicably implemented.

A trick that helps with that:  When you're in Layer View of Cura, hold the + or to navigate 1 layer at a time.


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I just looked at that part in cura and it looks fine.

When you crop out the "good" parts of your part in the above image I would immediately think you have a z-stage issue where the stage drops too much for some layers and not enough for others and you get those underextruded gaps.

But it can't be that because the problem isn't on the entire layer, right? It's just in this one spot.

So then I thought - well it's pretty heavy overhang so maybe your fans aren't on? Make sure the 2 side fans are at 100% by the time they get to this level. This should be easy for you to eliminate.

My final thought is it looks like you used support... make sure the print speed for support is the same as your normal print speed - make ALL SPEEDS the same (well not travel speed). The problem is if you are printing the support slow and then print the outer edge fast you will initially get underextrusion until the pressure can build up in the print head. This last explanation is the only theory that fits what I see but I'm not certain this is the issue.

Another thought is that your axes are binding up as you move away from center. Do your 2 thin rods that go through the head look perpendicular to you? With the servos unpowered push the head around to see if friction increases in that corner of your printer.

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Hmm... to be honest: i thought when printing ABS it's the best thing to turn the fans completely OFF... !?

Until now i took the Cura Quickprint settings (Normal print) and modified it in the expert settings, but so far only the support angle and the Brim line amount.

The print speed is 50 mm/s, but i can't find a place to adjust the speed for the support... btw i am using Cura 15.04.2. What overall speed would YOU prefer?

I did the axis-check as you mentioned it and there seems to be no issue there. That would have been quite unlikely, as the error occurs also when i flip the part horizontally.

I also experimented with different support angles, from 60° to 5°, but that did'nt help anything.

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I didn't realize it was ABS.

I would have the fans come on to the minimum - 25% or 30% for those overhangs. I don't use cura support. I always design my own. This part doesn't absolutely need support although the inside may need some cleanup at the top of the arch. It will definitely need a small amount of fan.

ABS is tricky for me - if I use much fan then I don't get good layer bonding unless I raise the temperature. If I raise the temperature too much then I get ABS clogs. I have not printed enough ABS to be good at it. I try to do thicker layers with ABS to get good bonding - .2mm is about right. If a part has no overhangs I do zero fan. If it does have overhangs I do 30% fan.

I don't know but I suspect the "support speed" is identical to the "infill speed".

Set your speeds as shown in this photo and let me know if they are different.



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Hey, gr5!

Do you want to read something funny? I've only noted the download numbers of this model and unfortunately did not read the comments...


Everyone who has tried experienced the same problems like i did!

So, thank you for your help! I will go now and redesign this &%%//-Part...! ;)

Edited by Guest

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