PLA Suddenly Jamming Mid-Print

I recently switched back to using PLA after I got tired of trying to use ABS (warping, de-lamination, et cetera) and I've started having issues with jamming.
My printer is the QIDI Tech (the version with the ATMEGA128 controlling chip) that has been re-flashed with Sailfish ver. 7.1.
The slicer is use is Slic3r.

So, this is what happens:

I load the filament in normally and without issue first. The filament during the loading extrudes out without any evident obstruction.
I then try to print a test piece ( http://www.thingiverse.com/thing:342198 this to be exact) and the HIPS/PLA start without problem. (the little test line at the start is smooth and clean)
I leave the print, and when I check on it halfway through I find that the PLA has stopped extruding.
http://i.imgur.com/SHg858s.jpg?2
Above is a picture of the failed print, see how the extrusion became wispy. By the point I had noticed, the printer wasn't extruding at all.
This was actually my third attempt with this print, the first one I stopped to modify some settings, and the second one jammed in a similar fashion (the build plate was also poorly leveled during the second print, which I fixed for the third).
http://i.imgur.com/Etm1Cji.jpg?1
Above is a picture of the first print (still on its HIPS raft). See how much better the print is.
The only difference between this print and the third one's settings is the fact that I turned on the filament cooling fan (as far as I can remember).
http://i.imgur.com/Yi7RnSn.jpg?1http://i.imgur.com/ugsm5Fl.jpg?2
Above are pictures of the filament I pulled out of the printer after the jam.

This link is to a ZIP file containing all the pictures of the prints and the removed filament: https://www.dropbox.com/s/95glrp2yg5...shoot.zip?dl=0
This link is to a .ini config bundle file for Slic3r which contains my current settings for PLA: https://www.dropbox.com/s/f2v88z6kbe...onfig.ini?dl=0
In the configuration bundle, untitled is for the PLA and untitled 2 is for the HIPS.

I found this article about jammed extruders mid print and how to save em.. :) Maybe it helps? https://3dprinterchat.com/2016/05/ex...ow-to-save-it/

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Originally Posted by Labbo1979

I found this article about jammed extruders mid print and how to save em.. :) Maybe it helps? https://3dprinterchat.com/2016/05/ex...ow-to-save-it/

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I'm afraid that that article didn't provide much help. I tested some of its theories, but I am still having clogging issues.

Also worth noting: I tried printing at 190c, 200c, 210c, and 220c. I still had clogging at various layers.

An update on what I've tried:

I took off the nozzle and cleaned it out using physical methods (I didn't do a chemical bath).

I also tried resetting the extrusion widths in the advanced print settings, but that didn't seem to help.

Quote:

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Originally Posted by Ryuluce

An update on what I've tried:

I took off the nozzle and cleaned it out using physical methods (I didn't do a chemical bath).

I also tried resetting the extrusion widths in the advanced print settings, but that didn't seem to help.

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I think it's the filament I'm afraid to say. PLA absorbs moisture rediculously fast, there is a slight fat section that won't go down the extruder pipe and gets blocked at the top, while the hobbed gear just keeps pulling away at it. See how you have that long stretched section? your PLA was a bit gooey and there was a bubble in it it got caught and the rest kept getting pulled down until it lost extrusion and stops spitting out plastic.

The fact it's pulling it tells me that the problem is on the top end, not the bottom end. If it was some old ABS stuck in there, you would just get a grind out and the filament would get blocked and you hear "click click click click" from the stepper motor. In this case, its not a problem of going into the pipe, it's a problem of a bulge in your PLA that won't go down the very first hole it needs to go into, the holy just above the hobbed gear.

Quote:

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Originally Posted by Geoff

I think it's the filament I'm afraid to say. PLA absorbs moisture rediculously fast, there is a slight fat section that won't go down the extruder pipe and gets blocked at the top, while the hobbed gear just keeps pulling away at it. See how you have that long stretched section? your PLA was a bit gooey and there was a bubble in it it got caught and the rest kept getting pulled down until it lost extrusion and stops spitting out plastic.

The fact it's pulling it tells me that the problem is on the top end, not the bottom end. If it was some old ABS stuck in there, you would just get a grind out and the filament would get blocked and you hear "click click click click" from the stepper motor. In this case, its not a problem of going into the pipe, it's a problem of a bulge in your PLA that won't go down the very first hole it needs to go into, the holy just above the hobbed gear.

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Hmm. That'd suck if that's the issue. Are there some good ways to test if that is definitely the problem? I don't have "popping" which I've heard is a common symptom of PLA hydration.

Though, I wouldn't be surprised if the moisture is the cause, because I do live in a fairly humid environment. But I was using the PLA before I started using ABS and it was working quite well for at least over a month without any special containment. Although, that was during the winter and subsequently a drier part of the year.

I just want to isolate if that is absolutely the cause, since that will allow me to more directly address the problem.

By the way, what do you mean by "pulling"? If you're referring to how stretched the filament is, I think that's because of how I pulled out the filament when I was removing the blockage. Most other times I removed the filament, it wasn't like that.

So, I've got some more footage and pictures to show about the printer.

First:

As I said, the filament would extrude without trouble when I load it.
https://www.youtube.com/watch?v=KvPL7LVysR0&
Above is a video of the printer extruding PLA when I ran the load filament script.
http://i.imgur.com/5BxG07B.jpg?2http://i.imgur.com/5BxG07B.jpg?2
The pictures above are of the extruded filament.

Second:

I decided to try a print so I could take photos of the jammed extruder from the inside.
Note: The first several layers printed without any trouble and very cleanly. Also, it seems that the printer jams when printing the infill, not the perimeters.
http://i.imgur.com/mJyMgti.jpg?3http://i.imgur.com/hGPULTm.jpg?3http://i.imgur.com/uPRGcsK.jpg?3
Above are photos of the inside of the extruder after jamming.
http://i.imgur.com/lsptt1B.jpg?2
Here is the end of the filament after I ran the unload script and removed it.
http://i.imgur.com/H9F94WL.jpg?2
Above is a photo of the incomplete print still on the bed.

Again, here's a link to a ZIP containing all the pictures in higher resolution: https://www.dropbox.com/s/aofvk4gja2...t%202.zip?dl=0

So, since I hadn't gotten any responses to this problem in a long time, I decided to try recording an entire print up until the point of jamming.
https://www.youtube.com/watch?v=9HsOrZOzD2g
(I'm sorry for the relatively poor quality)
The video above is timelapsed during the majority of the print for time's sake. If anyone wants, I can provide an unedited video of the print. Be warned, it's over an hour long.
I forgot to photograph the filament after removing it, but it looked fairly similar to the removed filament in my last post, except there was no small bend in the filament near where it was in the hot end.

Is the heatbreak/throat PTFE lined or an all-metal one?

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Originally Posted by Alibert

Is the heatbreak/throat PTFE lined or an all-metal one?

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PTFE lined. I actually fairly recently replaced the PTFE lining with a spare that came with the printer.

BUT, this is the more important part: I actually got a print to finish!
The print is soaking at the time of writing in limonene to remove the HIPS.

Here's what I did that made it (I think) work: I turned off the direct filament cooling.
So far, my theory is that the cooling apparatus was cooling the nozzle of the PLA extruder making the gear grind down the filament.
I plan to upload photos of the print when the support material is done. I haven't gotten a second print done yet to make sure it was not a fluke yet because I was having some trouble getting the PLA to stick to the raft of this other test print. I don't have the time to mess with it at the time of writing, but I'll likely give it another shot after some tweaking tomorrow.

Hi

If your fan is cooling off the hot end so it jams ... time for an upgrade.

Bob

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Originally Posted by uncle_bob

Hi

If your fan is cooling off the hot end so it jams ... time for an upgrade.

Bob

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An upgrade... on what part? If you're suggesting the entire printer, then no. This printer is only several months old, I know that it functions fine with ABS, and it worked fine with PLA before I switched to ABS.

The theory about the fan over-cooling the nozzle is still just a theory, I haven't the time yet to thoroughly test it.

Quote:

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Originally Posted by Ryuluce

An upgrade... on what part? If you're suggesting the entire printer, then no. This printer is only several months old, I know that it functions fine with ABS, and it worked fine with PLA before I switched to ABS.

The theory about the fan over-cooling the nozzle is still just a theory, I haven't the time yet to thoroughly test it.

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Hi

If the hot end is not doing what it is supposed to do *and* you believe it's properly assembled ..... time to replace the hot end.

I would try it with a couple of different PLA suppliers first.

Bob

We have had issues in the past with a layer fan. The fan is designed to cool the layer just printed which helps with things like bridging. However, we found that the fan was cooling the nozzle to the extent that filament cool and hardened on the nozzle causing a clog half way through the print as you describe. I hope this helps.

Okay, so I can't really give the full details, but through a lot of trial and error I feel that I am close to getting things working fully.

I have one last problem, and it is driving me insane, because I know what I want to do but I can't.

I want to disable the filament cooling fan when the printer prints the HIPS support material, and turn it on only for the PLA.
BUT, when I disable auto-cooling in the HIPS settings, the fan stays on anyways.
I found out that this is because Slic3r uses the M106 or M126 (depending on GCODE flavor) command to turn on the fan during the PLA, but it never triggers M107 or M127 to turn it off when the HIPS starts printing. I also see that most of the time the fan is enabled during the layer change rather than when the GCODE switches between the extruders.

Is there anyway to make the fan turn off for one filament and on for the other? I need to be able to do this.

Hi

A hot end cooling fan should be on pretty much all the time. That is a different fan (in most setups) than a filament post print cooling fan. They make it impossible to turn the first one off. The second one is indeed controllable. You get a problem when the software is a bit confused about which function a specific fan is performing.

Bob

Quote:

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Originally Posted by uncle_bob

Hi

A hot end cooling fan should be on pretty much all the time. That is a different fan (in most setups) than a filament post print cooling fan. They make it impossible to turn the first one off. The second one is indeed controllable. You get a problem when the software is a bit confused about which function a specific fan is performing.

Bob

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I am clearly talking about a post print fan, which I know should be controllable.
My issue is that I can't get the software to turn the dang thing off when I want it too.
Is there a way to fix this in slic3r? That's my question right now.

Hi

The fan setting may be confused in Slic3r or (more likely) it's confused in your Ramps (or equivalent) or your wiring.

Bob

Quote:

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Originally Posted by uncle_bob

Hi

The fan setting may be confused in Slic3r or (more likely) it's confused in your Ramps (or equivalent) or your wiring.

Bob

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Okay, I don't think you're exactly understanding what I mean.

Here's an example part of the GCODE I'm currently producing in Slic3r: https://www.dropbox.com/s/jitinycgas...gcode.txt?dl=0

You can see where the GCODE turns on the cooling fan using M106 at the top.

I've noted each location where I want the code to turn the fan on or off, which is at each tool change. (I also edited out all the repetitive GCODE for brevity's sake)

What you don't see is that several more times in the GCODE file (about 60 times), the GCODE runs the M106 command. This normally happens when the print shifts to a new layer.

With how the GCODE is currently generating, I cannot make the fan only turn on for the PLA and not the HIPS. This needs to change, but I can't figure out how to make it work correctly.

Hi

Ok, I promise I will no longer participate in this thread. Trying to work through a solution in an orderly fashion is obviously annoying you tremendously.

Bob

have you tried using cura ?

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Originally Posted by curious aardvark

have you tried using cura ?

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I had tried using Cura in the past, but I couldn't remember too much about it so I tried taking another look at it.
Unfortunately, it looks like Cura is lacking in settings compared to Slic3r. Honestly, I want to have as much control over the slicing as possible, and Cura isn't delivering.

Okay, so through the use of a lot of tweaks of the settings (the process of which was pretty much trial and error; thus I can't really give much depth where there is none), I have found that my current issue that prevents printing is one of two things:
A) I'm printing too cold and that grinds down the filament eventually. Easy enough to avoid.
B) The filament is buckling in the extruder.

Problem B is where I am stuck. I can't tell if I'm printing too much material too quickly and that's smashing the filament, if I'm printing too slow and the filament is heating up in the extruder, if I'm printing too hot in general, or if it's because of some other cause.

Below are two pictures of removed filament, you can clearly see where the filament has kinked and is preventing further extrusion.
http://i.imgur.com/hiJy5b2.jpg?1http://i.imgur.com/p0yQyiD.jpg?1

If you know what causes this, I'd greatly appreciate tips on how to prevent this.

Hi

Unless you have a really rotten hot end, there is no such thing as feeding to slowly. The extruder and hot end should be able to sit of hours with nothing moving through the system. If you have a really rotten hot end .... it's time to replace it. Simple check: The top of the hot end (where the filament feeds in) should be no more than warm to the touch when in operation. If you can't keep a finger on the top end of it for the count of five, it is to hot.

The simple check is still to tell the extruder to feed filament at the max speed setting. If that feeds fine for foot after foot of filament, the problem lies somewhere else. If it jams, swap out the filament and see if a different brand does the same thing. If two or three brands all do the same thing, your hot end thermistor may giving you bum data or your temperatures are simply set to low.

Bob

Quote:

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Originally Posted by uncle_bob

Hi

Unless you have a really rotten hot end, there is no such thing as feeding to slowly. The extruder and hot end should be able to sit of hours with nothing moving through the system. If you have a really rotten hot end .... it's time to replace it. Simple check: The top of the hot end (where the filament feeds in) should be no more than warm to the touch when in operation. If you can't keep a finger on the top end of it for the count of five, it is to hot.

The simple check is still to tell the extruder to feed filament at the max speed setting. If that feeds fine for foot after foot of filament, the problem lies somewhere else. If it jams, swap out the filament and see if a different brand does the same thing. If two or three brands all do the same thing, your hot end thermistor may giving you bum data or your temperatures are simply set to low.

Bob

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By "top of the hot end" are you referring to the top of the aluminum cooling block, or the top of the entire extruder block?
If it's the former, then there's a problem with my printer's insulation from the hot end to the cooling block. The cooling block gets real hot while printing, so much so that I can hardly touch it for more than a second or two. I kept lowering my print temperature until I reached a point where the prints were still jamming and the amount that did print was horribly de-laminated. I can't print any colder.
I'm worried that the heat is traveling up into the aluminum cooling block and softening the PLA thus allowing it to warp in the extruder.

In a makerbot-type printer (such as the Qidi Tech you have) the cooling block (the large alu bar which is used to fix the extruder with) will get hotter than, for example a E3D type cooling block. This is normal and a by-product of the design. However, you should be able to touch it without problems.

There are two things that determine the temperature of this block: 1) the amount of heat put into it (from the hotend) and 2) the amount of heat being taken out of it (via the cooling fins and fan).

As to 1): Do you still have the glass-fiber insulation around the heating block? If not, buy some from aliexpress and re-do it.

As to 2): Is the fan running? Is the cooling fin part with the flat side to the cooling block and the fins to the fan? You can improve the heat transfer by putting some thermal paste (as for CPU's in PC's) between the fins and the block (makes it a bit messy when dismantling though).

Finally, the makerbot design was intended to have ptfe lined throats (the part between the cooling block and the hotend) as the cooling block can not make a sharp temperature transition in the throat. If you want to print PLA, you will need this ptfe liner there.

As a beside: I have just installed a micro-swiss all-metal upgrade in one of my Qidi printers to be able to print in the 250-300 C range (polycarbonate and PEI). This one has a two-part throat, an alu outer part (good thermal conductance) and a steel inner/low part (poor thermal conductance) to the heating block. With extra thermal paste between the alu outer part and the cooling block it is claimed to be able to achieve the sharp temperature transition needed. Just tested it at 265 C (PC-MAX polycarbonate) and it worked just fine, no jamming. Will be doing PEI later this week when the sampel comes in (at 280 C).

One last final thought:
I have had a heck of a time in repairing the printer of the local primary school. It would also give all kinds of grief as to jamming, extruder grinding and patchy extrusion. It turned out that the thermistor leads would make contact and short at random times by vibration/head movement (the leads were jammend under a fixing screw keeping the fan in place). This would make the mainboard 'think' that the temperature was suddenly 300 C and it would stop heating. As the heating block cooled down through lack of heating the plastic would solidify and jam. I found that out by using a monitor function to monitor the temperature, heat the hot end to 150 C, and then wiggle the leads of the thermistor. When I did that I saw the monitored temperature jumping up and down. Took me a long time to find that one. :confused:

The point that the filament enters the hot end should be cold enough to touch when things are operating. This is the top of the cooler in most designs not the top of the heater block.

I wanted to give a pic, but I can't upload any ?

If you take the hot end off the extruder, the hot block is at the bottom. Between the hot block and the mount boss is a cooler. Ther top of the cooler should not be hot. Years ago hot ends were designed with poor coolers. Printed extruders melted and the designs improved. Modern hot ends are at room temp at the top of the cooler.

Okay, I know I haven't posted in a while. That's because I have been having intermittent jamming issues and I'm unsure why.


But, here's a new theory: The extrusion stepper motors are getting too hot.


I made a quick test where I left the nozzles heated for a while, and the aluminum cooling block stayed at a reasonable temperature.


Then, when I tried printing something the cooling block was very hot a while into the print and the stepper motors were even hotter on the backs.


I read here ( https://groups.google.com/forum/#!to...ot/gN_W4GieQwk ) that it's possible the stepper motors are running on too high a current. Is that possibly my issue? (As a reminder, the firmware I'm running is Sailfish ver 7.1)

Hi

The current into the stepper is an adjustable number. The motor manufacturer comes up with a number and you set that (or less than that) on the stepper driver IC. Typical numbers are in the 1 to 2A range on the motors. Typical settings are between 50% and 100% of the rating. Normally the stepper driver IC is the first thing to have trouble when current is set to high. People often crank up the drive to check things out and then later forget they did that back 20 weeks ago ....

One thing that *will* heat up the motors and cause jams is trying to extrude to fast. Another thing is a combination of layer height and extrusion settings that force to much plastic into the print. It has nowhere to go and ... you get
back pressure. Eventually the extruder gives up. To much or to little tension on the extruder drive (the part that engages with the filament) can also create the same sort of issues.

Modern hot ends run with cooling blocks that are "cold" at the top end of the unit. If not, you have a fan problem There are other possible design issues in the hot end assembly that could cause the over heat problem. Given how close everything in a normal extruder is to each other, indeed, when one part over heats, it's hard to figure out what is what.

Bob

Quote:

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Originally Posted by uncle_bob

Hi

The current into the stepper is an adjustable number. The motor manufacturer comes up with a number and you set that (or less than that) on the stepper driver IC. Typical numbers are in the 1 to 2A range on the motors. Typical settings are between 50% and 100% of the rating. Normally the stepper driver IC is the first thing to have trouble when current is set to high. People often crank up the drive to check things out and then later forget they did that back 20 weeks ago ....

One thing that *will* heat up the motors and cause jams is trying to extrude to fast. Another thing is a combination of layer height and extrusion settings that force to much plastic into the print. It has nowhere to go and ... you get
back pressure. Eventually the extruder gives up. To much or to little tension on the extruder drive (the part that engages with the filament) can also create the same sort of issues.

Modern hot ends run with cooling blocks that are "cold" at the top end of the unit. If not, you have a fan problem There are other possible design issues in the hot end assembly that could cause the over heat problem. Given how close everything in a normal extruder is to each other, indeed, when one part over heats, it's hard to figure out what is what.

Bob

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I'm going to assume your first point is that I shouldn't need to adjust the current into the stepper motors (which is something I still am suspicious as to whether or not it may be part of my problem).

So, I have tried both reducing the extrusion multipliers and the speed of extrusion, and I only end up with more problems than what I started with. The printer doesn't even start with a good first layer and the whole print is a mess before the third layer.

Also, the Qidi Tech doesn't have the ability to adjust the tension on the extruder drive.

Hi

Given the lack of adjustment on your printer, you appear to be stuck without much you *can* do to fix the problem. We seem to keep running into "can't do that on this machine". It appears that about the only thing you can do is to buy various brands of filament, fully scrub out the extruder and hot end each time and try them all ....

Bob

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I read here ( https://groups.google.com/forum/#!to...ot/gN_W4GieQwk ) that it's possible the stepper motors are running on too high a current. Is that possibly my issue? (As a reminder, the firmware I'm running is Sailfish ver 7.1)

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What are you current settings on the digpots? You can read them out via the Rep-G sailfish program.

I have several Qidi's and a Flashforge (all running sailfish 7.x), and none of those get hot steppers during printing.

Can you find any serial number/product number on the steppers and look up the advised currents?

Quote:

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Originally Posted by Alibert

What are you current settings on the digpots? You can read them out via the Rep-G sailfish program.

I have several Qidi's and a Flashforge (all running sailfish 7.x), and none of those get hot steppers during printing.

Can you find any serial number/product number on the steppers and look up the advised currents?

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So, I found that the VREF pot. settings for my printer were as follwing:
X: 118
Y: 118
Z: 40
A: 118
B: 118

The stepper motors on my printer are all the following model number: 42HB34F08AB 06. (I found a specifications sheet here: http://voltom.ru/info/42HB34F08AB-06.pdf )

The advised current says 0.8 A/Phase, but I don't know what the VREF settings mean in practice (and I'd prefer not to have to grab a voltmeter and measure manually).

According to the link below, to have an output of 0.8 A, I should change the VREF to 85.
https://github.com/jetty840/Sailfish...x3/DigiPots.cc

Hi

While you are poking around, I'd check the other settings as well. The Z axis looks a bit low. If the X and Y have the same motors as the extruder, they would need fixing as well.

Keep in mind that as you drop the current, the drive torque out of the motor will decrease. This will make the extruder more likely to jam.

Bob

Not sure any of this helps, but...

a) Stepper motors are designed to run hot. I've never seen the temperature on spec sheets, but multiple sites mention stepper motors capable of operating at temperatures of 85 to 100 degrees C. That's hot. They are intended for heat to pulled out of the mounting surface of the motor, something 3D printers rarely do a good job of.

b) Based on the data sheet, those 42HB34F08AB 06 are lower current/higher coil resistance than what at least the reprap wiki recommends for 3d printer use. This could explain why these motors run hotter than others for a given current setting on the stepper driver.

c) As Bob mentioned, you'd typically have issues with the stepper driver before you'd have problems with the motor itself. The stepper driver chips are designed to simply stop driving the motor if the chip gets too hot. Motors don't have any kind of protection built into them.

d) Be aware that once enabled, stepper motors ALWAYS have current flowing through them, and thus are ALWAYS consuming power and generating heat. The only time this isn't true is when the printer firmware has the stepper motors disabled. Once the stepper drivers are enabled, coils are energized to act as a brake and provide the motor with holding torque. This could explain why motors are cool when the printer idles with the hot end hot but then heat up in use.

Hi

I just noticed the torque spec on your motors. The sheet lists it as 2.4 kg cm. That is the same as 33 inch ounces. Either way it is about half the torque that most of the recommended motors put out. It also is a fairly high inductance motor. That will limit your ability to step it fast, unless you are running high voltage drivers.

Heat wise, a stepper is "good" to about 150 C (the insulation temperature spec ...). That is an internal number. The temperature on the surface will be way below that. It still will be up in the "ouch" 70C range before there is a problem.

Bob

I have much the same problem, would putting thermal paste between the hot end and the aluminium cooling block help? I have a MP select mini.

Quote:

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Originally Posted by Evonix

I have much the same problem, would putting thermal paste between the hot end and the aluminium cooling block help? I have a MP select mini.

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Hi

The MP Select Mini has it's own set of issues. The "simple answer" there is to slow things down and not go nuts on retraction or slowing down the fan. Since it's a Bowden setup, you will have to live with a bit of stringing.

Bob