[Closed] How to unload filament correctly?  

Re: How to unload filament correctly?

Others, including me, have had the same problem. You'll find posts here on the forum about it. Yes, it's something that needs fixing! The way I get it to work is to instead first do a Filament Load immediately followed by an Unload. That seems to do the trick. (I've had to dismantle the extruder two or three times to get jammed filament out after trying to do an Unload. I'm afraid of it damaging the filament sensor if I pull too hard. )

The latest rev of the firmware added a slower move segment to the Unload, but unfortunately it has made little difference. It still doesn't work as the large 'blob' at the end of the filament stops it pulling out.

Re: How to unload filament correctly?

The new slower unload in RC4 made things worse for me. Previously I just needed to be quick on the draw, I but now there is no way to avoid it.

Re: How to unload filament correctly?

In fact this nuisance is not unique. I got the same problem before with other 3d printers.
I just expect Mk3 can handle this better.

In addition, this problem is not consistant. Sometimes it happens sometimes doesn't.

So I am not sure if it is caused by hardware problem, firmware problem, the material or just the technique to unload.

Perhaps we can share more experience and see what other people do to improve it.

Yes, load a short segment first then unload seems to be a feasible walkaround.

If this method works, I think a firmware update can include this load-unload mechanism into the unloading routine.

Re: How to unload filament correctly?

I have had the same issue one time when unloading PETG filament. If I remember correctly that was a while after the print had finished, i.e. starting with a cold hotend and preheating.
Obviousy the tip of the filament was not heated sufficiently, so the proposal to first feed a little bit of filament to make sue that the tip is melted and then immediately afterwards unload it sounds like a good solution which could/should be implemented in the firmware.

At that point I would also like to see that the print head is raised by some distance (maybe 30mm) after a print finishes, to have better access to the nozzle.
That would make it easier to check the nozzle for deposits, clean it, remove oozing filament etc.

Re: How to unload filament correctly?

I stayed on RC3 and dont have this problem, but had on previous FW versions.

What i did to avoid it was extrude some filament before unloading.... worked everytime (not a solution but at least i wasnt pulling hard on the filament to remove it)

Re: How to unload filament correctly?

This happens every time for me. I preheat the hot end as instructed and then select Unload Filament from the menu when it reaches temperature. The extruder retracts about 60 mm and then stops. If I try to pull the filament out further I can't. I can push the filament back in and pull it back up but I can't get it to come out all the way. I'm using the Prusa silver filament that came with the printer. Temperature is set to PLA.

Doing a load followed by a second unload doesn't help - in my case. I've been able to just force another filament in and push the old one through but this seems risky.

This strikes me as a major problem. How do we know if this is on PR's radar?

Re: How to unload filament correctly?

I am having the same issue here.

I would say it happens about 40-50% of the time when I switch filaments.

I end up having to lift the extruder idler to expose the extruder gears, then pull the filament out through the exposed extruder assembly.

It's quite inconvenient.

I can't quite make out whats causing it. It's like there is a little bulb or notch or something that is catching on the PTFE tubing... but I can't be sure.

Re: How to unload filament correctly?

Hi

I had the same problem 2 years ago when I first uses e3d hot end on my k8200 printer. I learn to first push 10 mm filament true the nozzle and then retract quick after this. I never had any issue anymore with my old printer. It works for 2 years now. So I think that's the solution. Prusa just need to make this cycle automatic and test the whole thing.

Greetings

Re: How to unload filament correctly?

Just adding my voice to the thread. Filament unload now a major PITA due to bulb on end not passing through top PTFE tube.

Re: How to unload filament correctly?

I have found with the new firware it does a quick feed and then a slow one, as other have stated, however if I keep pressure on it during the slow process it pops out at the end of the cycle. I think it may be quick, slow, quick, but have not confirmed in the firmware. The previous firmware I simply kept a firm pressure on it, and perhaps a bit of a tug, but it worked. I agree it is not as smooth as my MK2S, but I'm sure it is due to the Bondtech gears. I for one prefer the new method (RC4), but look forward to anything that Prusa may come up with going forward. The loading however has been spot on for me. One thought I have for others is that it may be due to differing levels of tension we may all have on the springs. It was pretty non specific as to the tension or number of turns in our out on the tensioner. Perhaps this is the delta between experiences.

Re: How to unload filament correctly?

I am having the same problem, but I am certain is has nothing to do with the bulb of plastic on the filament end.

The last three times I have unloaded I had the exact same problem. What is happening with mine (and I bet others) is the extruder motor is not backing out enough of the filament. Then the motor is still electrically engaged and will not allow the filament to be pulled out because the bondtech gears are still holding on the to the filament. In my short experience with a CTC Bizer (and the Prusa X carriage), the same would happen if I would try to manually move the x,y extruder head. The motors would be "engaged" and I would have to disable them or turn the machine off to disengage the motor and allow free movement. This, I think, is why the filament cannot be pulled out. The gears are still holding on, the motor is still engaged, so you cannot pull the filament out.

When the filament has not unloaded, I use the menu and hit unload again and it backs out just fine. I think it is a matter of not backing out enough distance.

I hope I have explained this well enough!

Re: How to unload filament correctly?

This happens every time for me. I preheat the hot end as instructed and then select Unload Filament from the menu when it reaches temperature. The extruder retracts about 60 mm and then stops. If I try to pull the filament out further I can't. I can push the filament back in and pull it back up but I can't get it to come out all the way. I'm using the Prusa silver filament that came with the printer. Temperature is set to PLA.

Doing a load followed by a second unload doesn't help - in my case. I've been able to just force another filament in and push the old one through but this seems risky.

This strikes me as a major problem. How do we know if this is on PR's radar?

What i meant was... Pre-heat - go to Settings, Move Axis, Extruder, and extrude a few mm.... Then Unload! It should unload and the filament comes out easy. 😀

Re: How to unload filament correctly?

So far we got two explanations

1. Bulb formation , filament can't pass through the PTFE tube ABOVE the gear
2. Filament caught AT the gears

For 1, people have tried to employ the LOAD-UNLOAD method with some success.
For 2, people need to open the extruder gear case to unjam.

I believe both conditions can be corrected by firmware updates by adjusting nozzle temperature, implementing automatic LOAD-UNLOAD sequence and optimising gear retraction length and speed.

Wish Prusa can put this high up on their update list.

Re: How to unload filament correctly?

So far we got two explanations

1. Bulb formation , filament can't pass through the PTFE tube ABOVE the gear
2. Filament caught AT the gears

For 1, people have tried to employ the LOAD-UNLOAD method with some success.
For 2, people need to open the extruder gear case to unjam.

I believe both conditions can be corrected by firmware updates by adjusting nozzle temperature, implementing automatic LOAD-UNLOAD sequence and optimising gear retraction length and speed.

Wish Prusa can put this high up on their update list.

I must be experiencing type 2 issues because I've tried removing the Filament Sensor Cover (including the PTFE tube) and I still can't free the filament.

Re: How to unload filament correctly?

This happens every time for me. I preheat the hot end as instructed and then select Unload Filament from the menu when it reaches temperature. The extruder retracts about 60 mm and then stops. If I try to pull the filament out further I can't. I can push the filament back in and pull it back up but I can't get it to come out all the way. I'm using the Prusa silver filament that came with the printer. Temperature is set to PLA.

Doing a load followed by a second unload doesn't help - in my case. I've been able to just force another filament in and push the old one through but this seems risky.

This strikes me as a major problem. How do we know if this is on PR's radar?

What i meant was... Pre-heat - go to Settings, Move Axis, Extruder, and extrude a few mm.... Then Unload! It should unload and the filament comes out easy. 😀

That worked for me, thanks!. I wonder if the timing between the "extrude a few mm" and the "Unload!" is critical?

Re: How to unload filament correctly?

This happens every time for me. I preheat the hot end as instructed and then select Unload Filament from the menu when it reaches temperature. The extruder retracts about 60 mm and then stops. If I try to pull the filament out further I can't. I can push the filament back in and pull it back up but I can't get it to come out all the way. I'm using the Prusa silver filament that came with the printer. Temperature is set to PLA.

Doing a load followed by a second unload doesn't help - in my case. I've been able to just force another filament in and push the old one through but this seems risky.

This strikes me as a major problem. How do we know if this is on PR's radar?

What i meant was... Pre-heat - go to Settings, Move Axis, Extruder, and extrude a few mm.... Then Unload! It should unload and the filament comes out easy. 😀

That worked for me, thanks!. I wonder if the timing between the "extrude a few mm" and the "Unload!" is critical?

Yes, it is... it needs to be "right away", or else the filament will have time to melt some more and create a bigger "blob" at the tip and as the printer is pulling it out it will cool down and get stuck again 😉

Re: How to unload filament correctly?

This happens every time for me. I preheat the hot end as instructed and then select Unload Filament from the menu when it reaches temperature. The extruder retracts about 60 mm and then stops. If I try to pull the filament out further I can't. I can push the filament back in and pull it back up but I can't get it to come out all the way. I'm using the Prusa silver filament that came with the printer. Temperature is set to PLA.

Doing a load followed by a second unload doesn't help - in my case. I've been able to just force another filament in and push the old one through but this seems risky.

This strikes me as a major problem. How do we know if this is on PR's radar?

What i meant was... Pre-heat - go to Settings, Move Axis, Extruder, and extrude a few mm.... Then Unload! It should unload and the filament comes out easy. 😀

So I put my kit together yesterday and found I had the - unload get stuck - when I printed the beer opener.

Would it be easier to just cut the filament and then extrude a enough to pass it all through the nozzle?

Re: How to unload filament correctly?

Since the latest firmware with it's fast, slow, fast unload I haven't had a problem,.

Re: How to unload filament correctly?

This happens every time for me. I preheat the hot end as instructed and then select Unload Filament from the menu when it reaches temperature. The extruder retracts about 60 mm and then stops. If I try to pull the filament out further I can't. I can push the filament back in and pull it back up but I can't get it to come out all the way. I'm using the Prusa silver filament that came with the printer. Temperature is set to PLA.

Doing a load followed by a second unload doesn't help - in my case. I've been able to just force another filament in and push the old one through but this seems risky.

This strikes me as a major problem. How do we know if this is on PR's radar?

What i meant was... Pre-heat - go to Settings, Move Axis, Extruder, and extrude a few mm.... Then Unload! It should unload and the filament comes out easy. 😀

So I put my kit together yesterday and found I had the - unload get stuck - when I printed the beer opener.

Would it be easier to just cut the filament and then extrude a enough to pass it all through the nozzle?

That wont be possible.... If you look inside the extruder, the gears can only push the filament until that point....

You always have to unload it. I dont have unload problems with the 3.1.1 B138 RC3 FW.