Could I have a bad thermistor in my MK4?
After having had problems printing with the default profiles for TPU and PETG, along with occasional issues with PLA not extruding consistently, and reading in the forums about others having issues with thermistors, I am wondering if that might be an issue with my MK4.
I'll just share my results with Amazon Basics TPU. The config file from Prusa didn't work - it had lots of stringing. I started with following Prusa's guide doc on printing TPU and flexible filaments, I was surprised to find they don't follow their own guidance in their own configuration files.
That didn't work well enough, then I started adjusting things based on other youtube and reddit suggestions. Still had problems and was burning through filament and spending too much time on printing using most of the shared files I found. I eventually created my own retraction tower file which prints in 5-8m and started documenting tests one by one until I had some decent results. I have the best success printing around 185-195 C, which is well below the Amazon recommended range (210-230 C). That alone has me questioning the printer reported temp values.
Anyone have a good method for testing the temp response and accuracy they could recommend?
Should I contact Prusa?
Supporting docs are attached, a pdf of my settings which I changed, and an image for each resulting test
RE: Could I have a bad thermistor in my MK4?
When I had doubt on the thermistor accuracy I used a non contact unit but the temperatures were not accurate due to metal emissivity.
So I got a few LCD Thermometer Temperature Reader Meter Sensor K Type Probe from ebay at about $10-15 each.
I glued the tip on the side of heat block and at the base of the extruder tip. I used high temp automotive epoxy ( just a small drop!). Wired them via the ombilical to the readers and it lasted over a month. I could compared the Prusa reading to my two readings and they were within 5-8deg C of each others.
Removing the epoxy was easy with a small chisel when done.
I now test new thermistors on a hot plate each time before installing as they vary more than the thermocouples I found.
Hope that helps.
REPAIR, RENEW, REUSE, RECYCLE, REBUILD, REDUCE, RECOVER, REPURPOSE, RESTORE
RE: Could I have a bad thermistor in my MK4?
This thread might answer your question. I'm waiting on delivery of a new thermistor now.
RE: Could I have a bad thermistor in my MK4?
Thanks for the link, that was a thread I was reading which gave me this idea. I still haven't found a method to test it directly.
I now can print PETG now at the spec'd temp ranges, with minimal stringing and blobbing. It took a few things, I'm not sure which actions were key or extraneous.
1. Printed PETG dehydrator parts at work printer, to use at home.
2. dried my petg at work drier for 5 hours
3. Dried PETG on home dehydrator for 12 hours.
4. Switched over to the generic PETG file
5. Switched to Original Prusa MK4 config, NOT the input shaper
6. turned on avoid crossing perimeters
7. Printed temp tower - dialed in at 230-235 as per mfg recommendations! 🙂
8. Adjusted retraction settings a bit
I'm also switching the idler arm to the one from @UkoTerpuh before I move over again to trying TPU again.
Make certain you are not printing in a draft before blaming the thermistor, slowing the print a little often helps too.
When changing from PETG/TPU to PLA load the PLA at the higher temperature and purge a little extra to make sure higher melting temperature residues don't hinder the flow.
Well done on the drying, it will save you a lot of misery in the long run.
Cheerio,
RE: Could I have a bad thermistor in my MK4?
@Diem - good points.
I have my printer in an insulated enclosure, I leave the door open to prevent temperatures rising too much. I found with it open about 3-4 inches the interior with PLA printing was around 22-24 C. Seems like a decent spot to be. I'd love to build some auto opening temperature controlled setup but I'm not sure where to start on that yet, and getting printing working is the first priority.
I have not experienced any clogging of the nozzle, or residues that I have been able to confirm. It's a good point about moving back to PLA. I'll keep an eye out for that.
I was concerned about this when my PETG comes out and curls on the nozzle. I've tried the cold pull method, and did not see any residue. However, I have continued to experience this issue. Mostly when printing slow it seems to be mitigated. But every so often I find burnt blobs of PETG in my prints. As my filament is white, they stand out a lot. I suspect these are from small bits of plastic sticking to the nozzle, and then later getting caught in the print.
Just yesterday, I started experiencing blobbing on my prints again. Figured that it was due to printing in the high humidity of my garage, and the filament was getting wet. So I dried it all day while I was at work, then printed again, and it was much improved. The air in my garage is about 13C this past week, and high humidity. It is probably colder now. It's over 70% humidity in my home, and while there is a heat pump running in my garage, there are a lot of air openings in my garage to outside, so I suspect the humidity in there is pretty high too.
I have been printing some parts for a dry box,
https://www.printables.com/model/72870-ikea-samla-filament-spool-roller/files
Unfortunately, when I assembled the first spool holder last night after my bearings arrived, the design did not work with my simple pull test. The bearings are stiff with heavy grease and the design leaves too much space between the bearing and the filament riding surface, as the spools moves sideways or tips from the high friction, it gets stuck between the bearing race and the step down in the shaft then it gets pulled off the stand. I'll try the original smaller diameter shaft design, but I suspect this design won't work due to the heavy grease in the bearings and they are shielded. I will likely redesign the shaft with an improvement before returning the parts I purchased for it.
RE: Could I have a bad thermistor in my MK4?
I’m also in high humid environment, being able to see the Atlantic Ocean. I print all my PLA and PETG in dry boxes, each with 50g of desiccant that I recharge about 1 a month.. A pain, but worth it in the long run. I use mostly air tight cereal containers and install a PTFE thingy and a shaft on 2 bearings.
RE: Could I have a bad thermistor in my MK4?
yes, just contact prusa you will get some two cubes to print, prepare some photos other stuff in advance for documentation, will be handy to have ready print for some tests, and very likely your printer is lso affected by that
RE: Could I have a bad thermistor in my MK4?
An update after some time. I've created a dry box with teflon feed tubes for 6 rolls of filament which sits on top of my printer enclosure. It has a LOT of dessicant in it which is color changing. I've had better printing success since implementing this setup, and it saves me a ton of time. It also helps to relieve me of the concern that wet filament is affecting my prints.