A detective story with high temperatures - advice needed  

A detective story with high temperatures - advice needed

We have a Prusa i3 Mk2S with MMU and we print on it from a long time a lot of PLA and PETG (from different brands). Last time when we printed PETG (in fact FormFutura's HDGlass) we used some hairspray in order to reduce the addesion but meanwhile we cleared the bed with Ethanol – we clear it regularly in order to print PLA in good conditions.

We use Slic3r PE (latest version) in order to generate our Gcode files.

Several weeks ago, we needed to print a handle which should be heat resistant and we used for this ColorFabb HT. The handle wrapped but it was still useable so we didn't repeat the print. The bed was at 80-90 degrees. The settings were PETG-based (IIRC) adjusted with the info from ColorFabb's site.

After this, we continue to print various PLA objects. After a while we needed to print another object with ColorFabb's HT. This time we tried Slic3r's settings for HT which has the bed at 105 degrees for the first layer and 110 for the next ones.

This attempt failed – the object didn't stick to bed but what's worse is that we found (after a lot of trial and error) that:

- the Live Z calibration wasn't good anymore.
- The PLA didn't stick to bed anymore, even in the areas not touched by the ColorFabb's HT.

After we did a very (and I mean VERY) good clean with ethanol, then the PLA started to stick again. We did this because we thought that there were residues of hairspray and/or other substances. What is odd is that the Live Z calibration value (of -680) wasn't good anymore – we recalibrated the
first layer using the printer's „Calibration” menu and we found a vaule around -570 (IIRC).

Ok – that was it, we thought. After some prints, we decided to print again the object using the HT filament. Failure again with the same simptoms: - the HT object, now with 110 degrees on 1st layer and large brim (15 mm) didn't stick to heatbed and, after this, PLA doesn't stick (again).

We cleaned again the bed even if it was cleaned just before using HT filament and the PLA started to stick again. Recalibrate the first layer and now the optimum value is different (again): -717.

Now we can print PLA in good conditions.

Before starting experimenting again with HT can someone explain what is happening?

Also, we think that now we will try with 90 degrees (only) for heatbed – any advice upon this?