WARPING - how to get this under control

Hi, after printing for roughly a month, I have still not mastered the corner problem. Even worse - I find it unpredictable for any printing exercise. Attached I have 2 examples, both for the RASPI extension I am currently trying to set up.
The piece that has been printed for the camera box is almost perfect. Almost no warping, extremly precise corners - super.
The RASPI holder came out pretty different last night. All 6 outer corners came out in a misfigured shape during the first 15-20 layers. After that, the holder could be finished in a very good way, meaning that the RASPI board fits into the holder very nicely.

But what could be the reason for these different warping results? Environment temperature (my printer is set up in my workshop where it's usually between 18 to 21 degrees)? Wrong calibration of the nozzle (I had to re-calibrate 2 days ago after moving the MENDEL from my office to my private workshop)? Uneven temperature of the heat bed (I have stuffed the volume with the cardboard as proposed in the buidling instructions). Anything else?
Do I slice it in the wrong way (I am using SKEINFORGE with the small changes as described in the building manual, I have not tried to change any of the additional parameters).
Thanks for any hint.

BR, Harald

Hi Harald,

interesting ... I had the same problem with the same parts ... look here.

Do you print on a clean glass sheet? I use a wood-glue-water solution for printing PLA.

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MfG / Regards

Stefan

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Blog / Gallery / Wiki / Mendel90 kit since Sep 2013 from Nophead / Original Prusa I3 MK3 since Feb 2018 /
OpenScad Workshop: Kursdateien
Octoprint Patron since April 2016

Hi Stefan,

Wow, thanks for pointing out the thread. Seems as if working with the Z_HOME_POS is doing the trick?

To answer your question: Yes, I am printing on the glass sheet - trying to keep it fat free using 'Waschbenzin', but also bought a can of 'Petroleum' recently where it says: Excellent for de-oiling.
So far I have been using the Faberdashery filament that was provided with Chris' kit. Today I have received a new spool of red filament from Reprapsource.com.

Tonight I'll be calibrating again, will check the Z_HOME_POS (so far I used 1 digit after the comma, but now I'll use a second digit) and also the extrusion speed.

What happened to your prints? You were satisfied I could read - but there was another post stating: "It is looking terrible" ;-). And after that, I did not find any new picture from you.

BR, Harald

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Mendel90 from Nophead; built X-mas 2014
Joined 'Thingiverse' as Harald007

Hi,

If you are printing directly onto glass without adhesive agents it is very important to have your E_STEPS_PER_MM and Z_HOME_POS accurately set.

I print with reprapsource.com PLA using the same settings that nophead recommends for Faberdashery filament. The only bed preparation I do is an occasional wipe with Isopropyl alcohol and a wipe with Pure White vinegar before each print.

If your bed adhesion is poor your prints will lift easily. There seems to be some material missing from the underside of your third photograph. Did that material tear away from the print during removal?

Regards,
Neil Darlow

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I try to write with consideration for all nationalities. Please let me know if something is unclear.
Printing with Mendel90 from fedora 25 using Cura, FreeCAD, MeshLab, OpenSCAD, Skeinforge and Slic3r tools.

I haven't tried white spirit or petrol. They may not be suitable. Pure acetone and ethyl acetate work. The cloth used matters as well. I use lint free cloth designed for solvents that comes with the acetone I buy or can be bought separately.

If all else fails you could try covering the bed with kapton tape for PLA.

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[www.hydraraptor.blogspot.com]

The best method I have found for consistent adhesion is to put a layer or 2 of glue onto the glass before you print with a glue stic. The brand I use is below but I am sure other brands would work the same.

[www.ebay.com]

What cloth do you use Chris? I've been buying my acetone from Rapid, where I thought you got yours from. Mine doesn't come with any lint-free cloth.

I use these: [www.easycomposites.co.uk]

I get my acetone here: [www.shinyhardware.co.uk]

It came with free cloths last time but they seem to be sold separate now: [www.shinyhardware.co.uk]

I didn't know Rapid sold acetone and can't find it on their site.

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[www.hydraraptor.blogspot.com]

Thanks Chris.

Acetone didn't previously appear in the search results, which I assumed was a pretty flimsy precaution against people setting up meth labs (or whatever nefarious uses there are for acetone). It could be found however by going via "Educational supplies", then "Chemicals", then "A" and look down the list. Last time I ordered a 1l bottle they sent me 2.5l by mistake so now I have way too much in a bottle that's very unwieldy for simply treating my print plate.

I searched for "Acetone" on Rapid just now and it shows up in the search results so maybe it wasn't intentional: [www.rapidonline.com]

Shinyhardware is cheaper in any case.