MakerGear Forum

I've had my M2 for almost 3 years now. Upgraded to 24V and then Dual extruder with stainless nozzles. Print several times a week on average mostly ABS and some PLA. I also use an Raspberry Pi with Octoprint. I print in a heated metal enclosure (average temps are 80-90F)

Recently my M2 has suffered a loss in print quality. It has been intermittent too and thus hard for me to track down what is causing it. Some prints come out amazing. Other prints the vertical walls end up with dips/indents. And other prints fail all together from a loss of extrusion. I have tried to be systematic about tracking down the issue reprinting files, trying different brands of filament, doing maintenance, reprinting with some success.. then it comes back.

Photos of poor print quality:

Failed print from loss of extrusion


Weird vertical surface (the gray knob should have straight sides like the red one in the lower part of the cylinder red one is printed in ABS on Prusa I3 Mk2)



Here are things I have checked/replaced:
-Switched to different filament color/brand - still had issues
-Measured filament diameters to be sure its in spec
-Re ran old Gcode to eliminate slicing issues and the printer finished the print but stopped extruding part way through
-Cleaned the nozzles with cold pulls with Nylon and found some gunk (I honestly thought this was the main problem I was having was partially clogged nozzles)
-Checked and cleaned the filament drive gears
-Checked both planetary gearboxes on the extruder drives and regreased and cleaned the older of the two.


Images from Cold pull using Nylon.. shows the progression from crap to clean


I thought I had the problem solved at this point.

Clean Prints:




Most recently the printer gave me an error and would not start a print. I have never seen this error before and I wasn't able to capture a screen shot fast enough but it said "Printer stopped due to errors. Fix the error and use M999 to restart. (Temperature is reset. Set it after restarting)"" From my research the most common issue this relates to is a thermistor failure. I tried restarting the print several times with the same error and could not get the printer to begin the print. I tried wiggling all the wires and connectors while watching the temperature graphs and the terminal while the hot end was at temp to see if I could cause the themistor to disconnect and did not see an issue. I disconnected the Octopi and connected via Simplify 3d and USB, uploaded the print file to the SD card and started the print from the SD. The print started without issue and ran the first few layers. I intended to continue printing from SD and when I went to disconnect my laptop I must have double clicked and hit reconnect which rebooted the Rambo and aborted the print. I reconnected the Octopi and tried starting from it and the print ran to completion. Photos of the prints are below. I know i needed more solid top filled layers but besides that the vertical walls have the strange dip and poor print quality of the threads (I have printed threads like this before that turned out great)

Poor print quality:


Weird dip in vertical wall and poor quality



For the most part I don't mess with any settings in S3d only infill and layer height.

Forward Plan:
- I am going to check thermistor wiring even more thoroughly and all wiring to the extruders.
- I may try running the same print with the Octopi disconnected completely.

- ??? any other suggestions as to what to look for

The M2 has been a great printer and most issues I have had have been easy to diagnose up to this point... This one has me scratching my head a little.

Thanks for the help.

ahaidet wrote:From my research the most common issue this relates to is a thermistor failure.

Replace the thermistor.

Just. Do. It.

Restore all your firmware & slicer settings to whatever you were using before you made all those changes and everything will be fine again.

A few folks discover a broken wire between the RAMBo board and the thermistor connector, but the vast majority of problems seem to come from an intermittent connection within the thermistor itself.

Ordered new thermistors now.

When E3 went from thermistor to thermocouple it was one of the happiest days of my life. I freaking hate thermistors, I cannot count the number I have destroyed before I even got them on the damn hotend.

Perhaps this is something Makergear could look at.

ANthony

I can't find any info on how you replace them?

Is it as simple as unscrewing a set screw and pulling out the old thermistor?

Yes, that is what you do to change the thermistor.

Changed the thermistor this past week. Reset Z offset and went back to profiles I have been using for awhile.
Printed some parts in ABS 3.5 hour print roughly.






Vertical surfaces still look poor and not vertical. From what I have found some call this "lower wall cave in"

I made some small changes to infill and reprinted one of the parts from the previous batch.



This looks even worse.

I decided to switch filaments and run some code I made a few months ago before the problems began.


Here is the part as printed yesterday. Which turned out not bad but the surface finish still looks poor just off the bed surface. The walls are not as vertical as they were on the previous print.




Here is the part as printed from a few months ago( with a nut inserted into the hole) Maybe a little better vertical surface finish but overall they look similar.



I then re-ran the code for the single part with the same code but the gray ABS. In general it looks just as bad as the orange ABS.






I tried checking the temps manually with both a thermocouple on my multimeter and non-contact infared. Both measurements agree with the thermistors within a few degrees of the set temp.

I am baffled on what to look at next. I have a friend with an M2 unfortunately he is running V3b hotend and single extruder so he can't run my exact code so he is going to print the same STL for me to compare.

Personally I would remove the nozzle and check it for a blockage.

Extrusion seems to be one issue, and cooling another. I never print abs, but in those pics where the outer perimeter is curved looks like excessive heat.

Personally I would just print something small and basic and just see how that looks, using very basic settings. Print a small cube, or cylinder.

Could this be the Rambo failing?

One thing I just remembered was a few months ago.. right before this all started to become a problem I found my electronics case fan stalled out/jammed with a small piece of filament. I replaced the fan immediately but I am not sure how long it was not working.

I do print in an enclosure like I said and the average temps are right around 90F degrees. If the fan was failed for awhile the board could have gotten pretty warm.