Feed motor stops during print of large items. UP300

This has been a long-going problem. Sometimes it requires head cleaning, but over a year of experimentation, I’ve found filaments that don’t clog the head when they cook-off in the print head tube.

Finally, I was able to observe a failure of the print feed mechanisms. I include my notes for Tiertime’s benefit, in case they can fix this issue.

It was after printing a large flat base, about 10cm x 20cm. The previous later completed correctly, however I noted that I didn’t see a filament on the border of the next layer. Fortunately, I was watching, since I have had multiple failures on this print, all at around the same time, though not exactly. As the large flat surface printed again, it was immediately apparent that the feed had stopped.

Lifting the top, I reached in and lifted the filament guide, and applied pressure to the filament. I saw some traces of filament on the workpart, but again, no feed, even though the drive should be gripping.

Next I paused ( something learnt from a previous failure, but too late to save the piece ) - and waited for a while, then resumed. It too failed, and would only leave filament traces when a lot of pressure was applied to the filament, though clearly the filament feed gear was impeding manually pushing filament through.

So I paused again, opened the application, and clicked on “extrude” which initially clung to the head, and seemed a bit cooked, but it was extruding. Then I knocked the ball from the head and it fed perfectly, without any pressure incoming to engage the filament to the drive gear.

Then I clicked resume, and the model resumed print, perfectly feeding this time.

During this entire time, the temperature was 98 to 100%.


  1. The print head may be cooling, but the temp does not reflect this, leading to a blockage, lack of flow, and then jamming, with the gear carving a notch in the filament.
  2. The drive gear is simply turning off for some reason. I don’t always see a notch carved in the jammed filament when I withdraw it, or it’s very slight.

As for the model? It resumed printing after this.

I know people have asked for a spool monitor before, and this would allow the machine to pause and request a clear of the head, which would be easy. It doesn’t address the issue however that the spool feed gear seems to be stopping in the middle of a print. I don’t know if it’s the stepper or maybe the drive overheats, but a simple pause and restart did not clear it. Instead I had to use Extrude to clear it.

I have the newer pane;, which, BTW, shows LCD NOT MASTE with the R missing - the touch panel has locked prior to clearing the issue, and I can’t turn the light on now… At least during the print. I assume it will resolve after I finish the print, but it’s annoying not being able to turn on the light. A remote light on the application would be a nice feature update.

I’m printing at 230 degrees in ABS, with board temp to 90C. Relatively low. And it’s a cool day here and it’s next to an air conditioner.

Hope this helps Tiertime track down the issue. :slight_smile: This was the first time I was able to experiment to get it feeding again and observe the issue as it happened. In prior prints, it just stopped laying down filament.


Additional note: Just rechecked the model with a torch, since I couldn’t turn on the light. It stopped printing on a flat surface again. No sign of lack of flow right until it stopped.It completed the prior path segment just fine, then just didn’t lay the next one down.

A third possibility is some slight lifting of the model, so that more pressure is needed to push the filament through, and perhaps the gear is warm enough that the plastic filament underneath is reaching the temperature range where is just rips rather than feeds. Though from the ends of the feed, where the flat ribbon becomes a point and connects to the border, I don’t think this is the case.

I think it’s caused by either the print head turning off while the temperature isn’t monitored, or the feed stepper simply stopping from turning.


I’ve been trying different things to address the issue. The latest is to run the head REALLY hot. About 15% higher than usual, which isn’t a good thing for ABS… So up around 250C for a 220C filament.

This seems to be working, and I’m not getting as many feed issues… So while I was originally leaning towards an explanation of feed failure, I’m now wondering if it’s just that the printer is taking too long to respond at a time when the head is cooling, and pushing out a high flow rate, leading to rapid cooling of the print head and subsequent failure of the feed mechanism mid-print.

If I run the print head hotter, the hypothesis is that if the heating is delayed, it will take longer for the head to cool below the liquid point of the filament.

It seems that once the feed gear starts to bite into the plastic, and the plastic tears, it loses it’s ability to grab again, especially when there’s back-pressure from the nozzle mid-print, and it won’t refeed until paused, and the filament is further extruded, even if the filament is pushed in by hand.

This leaves me wondering if there’s any way to build a system that regulates the print head temperature directly, rather than relying on the software inside the UP300 to do this?

Or can the thread that drives the print-head thermal regulation be made non-blockable by other threads?

I’ve noted that sometimes the print pauses, and I’ve also noted last print that sometimes the problem goes the other way - the temperature for the print head hit 105% on my last print, for a brief moment.


Some further information. Now I’ve had time to experiment a little more, running the filament VERY hot, eg, 260 for a 220 filament ( 20% higher than recommended ) will get through a heavy solid print run without failure. I’m not 100% certain, but the hypothesis is holding up to the test presently.

It seems that if the head is hot enough, the plastic within remains liquid long enough not to put stress on the feed gear mechanism causing the filament to tear. By the time the touch panel returns to normal operation and notes that the print head is cooling, it’s not too late to start heating again.

This is a workaround then ( always print very hot ) but it’s also a problem as it can result in color changes for some filaments, and it also causes visible marks in the external surface of some models due to both color change and a difference in the flow of plastic.

Question to tiertime - is there any way to increase the level of attention that the touch panel can provide to the print head temperature regulation?


May be the filament’s optimal print temp is hotter than you expected?
The Tiertime ABS’s recommend print temp is 260C.

Which extruder did you use? Please use HT extruder(ABS extruder) for ABS material.

Hi Jason,

Thanks - At the moment, I’m printing a filament with a temp of 220-240 at 260 just to make it print without jamming. It’s less than ideal because it tends to cook the filament in the nozzle when it does jam, and then I can’t just clear it and continue - I have to take the nozzle out and soak it in acetone for a few days to fix it.

Yes, I’m using the ABS head for ABS. It only ever has ABS and ABS+ in it. It seems to be that when there’s a high flow situation, that’s when it fails. So when printing a large surface area, or as it’s causing problems tonight, setting for 0.3 layers with Turbo speed.

It runs just fine, then just jams without notice, and stops printing. It’s a brand new spool of black ABS just for this print, and there’s a bearing in the filament box to reduce tension ( an early idea to fix the issue, but it works great, and avoids snarling, so I kept the bearing… Keeps the spool turning evenly without too much drag ).

The filament I get the best results from is eSun, which runs from 220 to 260, and if I run that at 260, I can usually print a solid large model at normal speed fairly reliably…

The jamming is the only real issue I have with the 300. if I print with a low density, most prints are OK, but when it has to feed large amounts of plastic with back-pressure from the model is when the issue occurs.

I’ve been slowly eliminating the causes for a while, and for a short period in the summer it got really bad, but that turned out to be the touch display ( which you helped me with previously ).

This seems to be the print head that is cooling that seems the most likely culprit at the moment, but that’s really hard to test for.

I’ll keep posting what I notice - I’m not 100% sure it’s the head cooling, but all things seem to point that way at the moment.

Thanks for the suggestions -