Hi all, I have an issue with one of my UMO+. I have 7 UMO+ machines and all of them are exactly identical. All of them have an E3D hotend setup with 0.6mm nozzle and dual 40mm cooling fans. Also the machines have an upgraded extruder that I've designed myself, which is way more powerful than the stock UMO/UMO+ one. Firmware and firmware settings are identical as well. The extruders use slightly different steps per E (less than 1% difference) after I calibrated them, I don't think this difference has something to do with it. The problem I run into is that one of the newest machines is acting weird. Somehow I can't run the same gcode file without having retraction issues. Normally I use 4-4.5mm retraction for Colorfabb PLA. But this machine somehow needs more than 6mm of retraction (which is pretty heavy for prints with a lot of retraction), or else a lot of blobs appear on the print's walls. I regularly season the filament with a drop of olive oil which works well against jamming issues, but this doesn't solve the retraction problem on this specific machine. Also I swapped extruders, which didn't solve the problem as well. Does anyone have any idea what could cause this problem? Would be great if you could help me solve it.
Is there a Bowden tube involved? if so, it could mean that on that machine the tube is less well seated in the collet, and the collet and tube are pulling out by 2mm when you retract. AFAIR you need to push the Bowden tube in while pulling the collet out to avoid this happening. See https://wiki.e3d-online.com/wiki/E3D-v6_Assembly#PTFE_Recommendations.
Temperature could also be an issue. PID tuning might eliminate some of your oozing as it stops you overheating your filament.
The Bowden tube sits all the way in and doesn't move. Shouldn't be the problem since this is identical as with the other printers. Also a checked for differences in Bowden length, but they are all the same length as well ± a few mm or so. I use the stock heaterblock from Ultimaker. I don't see any temperature fluctuations so I don't think this is the case. Also I can print the Colorfabb PLA/PHA within a range from 195-230 without any difference in stringing Things I tried by now: • Swapping the extruder from on of the printer from which I know it works fine. But this didn't work either. • Swapping the heatbreak in the hotend for a new one. Didn't work • I tried new and used 0.6 nozzles. Didn't work. • Install fresh firmware. Didn't work. • Calibrated steps per E. Didn't work. • Different materials, brands and colours. Didn't work. You can see the difference in the attached file. Black is how it should be (filament ran out), green is the same .stl file on the defect printer. Quite a difference.
So what's it like with black filament? I find a lot of difference between certain colours, e.g. white and black, due to filler composition and have to make adjustments to compensate.
Did you check and compare the temperature sensors of the hotends? There are production tolerances, so 210 on one hotend are not 210 on the other. Also the temperatur resistance between sensor an hot end block may be different. Both may have influence on the temperature of the filament itself
As mentioned, I tested multiple all kinds of materials/brands/colors (on multiple printers) to rule this out. This is not making any difference. I don't think it is temperature related. I haven't been testing with different themistors, but I do have tested in what range I can print a certain part without complications (on one of the printers that works well). When I print Colorfabb PLA/PHA above 230ºC, the product gets a bit more shiny because of the heat, but there is still no evidence of stringing or blobs. I don't think there is that many difference between all of the original Ultimaker heaterblock-sensor combinations. Maybe there is a few degrees tolerance, but not much more. It seems very hard to have multiple machines printing identical on each machine. The more machines I have, the more strange and unsolvable problems I run into.
