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Rostock MAX v3 Bed Leveling Data Evaluation Request

Posted: Thu Mar 30, 2017 8:55 pm
by Christian79
I recently finished converting my RMAX v1 into a v3, everything that was not v3 has been scrapped. My hopes were that I would finally have access to my entire bed to print larger objects. I have used G29 and the auto calibration webpage to level the bed to within "0.04" but larger prints still have issues with curling. I know ABS is prone to curl but I have enclosed the printer and print slow (30mm/s, 50% on layer 1) at 100C (BED) and 235C (HOTEND), my issue seems to be my build surface has variations of .14mm across the center.

I tried to calibrate at room temperature, as instructed, but when doing so the height and overall calibration is way off when the bed is actually at 100C. As a result, I have found that the bed can be allowed to warm up to 100C and the hotend to 250C before shutting off the hotend and running the calibration script. The hotend stays at an average of 235 for the duration of the script while the bed stays at 100C. I must say the accelerometer board seems to be the weak link here, calibrating at 20C and then heating up to 100C and 230C expecting to hold the specs seems rather unrealistic. I know that the I2C connection is bad while the hotend is powered, but this powered off requirement seems a poor countermeasure for what is a design issue.

My hotend is E3D and I print on PEI. I still need to collect more data to see if this bed surface variation exists at room temp, if so it may be that my PEI is not truly flat. The bed clips are just tight enough to hold the glass, but are not bending it down. Please take a look at the attached image and let me know your thoughts. worse case I can live with 140 microns variation on layer 1, I just need to figure out the minimum first layer height to ensure that the ABS will adhere to all portions of the bed.

Thank you

100C-B 235C-HE Calibration Results (0.04 Overall).jpg

Re: Rostock MAX v3 Bed Leveling Data Evaluation Request

Posted: Fri Mar 31, 2017 4:57 pm
by Christian79
I am still having issues getting the bed to be consistent however, considering the degree of measurement the probe gives us, this could be normal. The process has gone from a piece of paper and a "feeling" to a readout with what seems to be 0.01mm repeatability. What I have found out is that MHackney was very wise to recommend letting the bed heat up AND sit for a bit. See my data below that shows the considerable changes in the bed from 10Mins of heating (time to get to 100C) and 35Mins. For my printer it seems that the MINIMUM warmup time should be 15Mins. All tests were done with the bed at 100C and the hotend at 250C before being shutoff due to I2C issues. Also I used my non contact temp gun facedown on the bed at the measurement points to show the variation in temperature I see in my bed. For these results the bed had been at 100C for 90Mins, as you can see there is quite a bit of variation. One thing to point out is that I let the bed heat with a towel on it however, I saw more temp variation from center at the edge than if I let the bed sit without the towel. In any event the data shown below represents the readings after letting the bed sit for 10Mins without the towel.

Remember + = Too Low and - = Too High

Time = 10Mins
Bed @ 10Mins.png
Time = 35Mins
Bed @ 35Min.png
Calibration Results T=10 to T=35
Calibration Results 10Mins to 35Mins.png
Finally I ran G29 again @ 40Mins
Bed @ 40Min After G29.png
Temperature Readings W/Bed @ 100C for 90Mins + 10 without the towel (Bed Surface is SeeMECNC BorGlass @ PEI 0.8mm)
Temperature Readings W-Bed at 100C.png