Is this heat creep?

[Brad Warren]

About 50 hours of printing, my Rep 2X has started giving me air prints constantly. Today it was 6 hours into a flawless print (see: ANGER). When I pull out my filament  it has a groove in it where the the plunger ground it out, and the end of it is all bulbous. Does that indicate heat creep, or is the bulging head normal? ...Perhaps a poor choice of words...

[Damian Gto]

Its not that big problem with ABS.

If you get a grow then it can be that you print to fast for the temperature you are using.

It can also be that you have to little pressure on the filament. 

The blob is normal when you unload the filament.

[Joseph Chiu]

Hi Brad,

That mushroomed head is normal for filament that's been backed out of the extruder.  The filament getting jammed can be caused by a number of reasons -- looking at your filament, it looks like that bulb runs about 35 mm from the drive gear to the tip - I don't know about the 2X (I've only had a chance to glance quickly inside one so far), but with the Mk 7/Mk 8 extruder design, that would be about the distance from the drive gear to the middle of the heater block.

The most common reasons for filament jamming are (in no particular order):

  1 - Backpressure at the nozzle when you overextrude.  Solution: increase filament diameter when slicing to extrude less plastic

  2 - Wild swings in temperature because of PID control problems when alternating between high-duty-cycle and low-duty-cycle areas in the print.  My solution: turn on a box fan and blow it at the printhead -- the resulting thermal flow into the air will dominate the heat transfer, so that changes in plastic flow rate will have less effect on the hotend temperature.  Proper solution: better PID tuning or feed-forward correction of the hotend

  3 - Excessive retractions in the same spot -- If you have a lot of retractions in between small features, the same spot on the filament can get chewed up enough to the point where the extruder can't effectively push the filament anymore, and then it just keeps grinding away at the same spot after the filament is no longer moving.

  4 - Filament infeed problems - tangled or knotted filament.  Solution: make sure that your spool is not knotted. I still have to take a video on how to do this.  I have to get someone to work with me on that.  I feel silly taking videos of myself with my own camera.

  5 - Filament quality problems - filament feeding blocked by a bulge in the filament (or worse, a knot where two filament are tied together, or even taped together).  If this was the cause, you should be able to spot the actual obstruction.  Solution: remove obstruction if it's an isolated incident.  Or switch to higher quality filament.  

  6 - Filament feedpath problem - the feed tube friction may be too high from wear (not likely with you since your 2X is, I'm guessing, new and has low hours on it).  Solution: replace feed tube, or go to a tube-less arrangement.     You mounted filament incorrectly.  Solution: Mount filament to avoid sharp turns or other sources of resistance.

  7 - Clogged nozzle - accumulated dust/dirt or actual debris in filament.  Solution: clear nozzle, ensure filament is clean.

I actually have a hypothesis which I think may be reason #6:  the room is getting too warm.   Given that it was printing well for 6 hours, most everything else in your machine should have reached their steady-state temperature.  But if you are printing in an enclosed area, the printer can act as a space heater and, eventually, the air temperature is much higher than when you started. I think the room temperature could affect the printer either by directly affecting the extruder or possibly by affecting the accuracy of temperature measurement.  This is an educated guess, however, and not a well tested hypothesis.  If Makerbot or anyone else would like to let me borrow their 2X for a while, I can run some tests! ;)

Best,

Joseph

On Sat, May 18, 2013 at 10:12 PM, Brad Warren <ryl...@gmail.com> wrote:

About 50 hours of printing, my Rep 2X has started giving me air prints constantly. Today it was 6 hours into a flawless print (see: ANGER). When I pull out my filament  it has a groove in it where the the plunger ground it out, and the end of it is all bulbous. Does that indicate heat creep, or is the bulging head normal? ...Perhaps a poor choice of words...

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[Joseph Chiu]

Ooops, that hypothesis would be reason #8.  After I said reason #6, I realized two more and added them to the list!

[Brad Warren]

Well Joseph, I hope it's not from poor quality filament, since I'm using Toy Builder Labs ;)

But #8 is interesting. I purposely let my room get hot because my 2X shipped without a lid. So I figured that to avoid curling I'd just let the room get hot. So I'll open the window and turn on the fan and see what happens.

[Joseph Chiu]

Well, in that case, #5 is definitely not your problem.  :)   But filament is filament, so any of the other 7 reasons could affect ours as well.

On Sun, May 19, 2013 at 8:42 AM, Brad Warren <ryl...@gmail.com> wrote:

Well Joseph, I hope it's not from poor quality filament, since I'm using Toy Builder Labs ;)

But #8 is interesting. I purposely let my room get hot because my 2X shipped without a lid. So I figured that to avoid curling I'd just let the room get hot. So I'll open the window and turn on the fan and see what happens.

On Sunday, May 19, 2013 7:38:43 AM UTC-7, Joseph Chiu wrote:

Hi Brad,

That mushroomed head is normal for filament that's been backed out of the extruder.  The filament getting jammed can be caused by a number of reasons -- looking at your filament, it looks like that bulb runs about 35 mm from the drive gear to the tip - I don't know about the 2X (I've only had a chance to glance quickly inside one so far), but with the Mk 7/Mk 8 extruder design, that would be about the distance from the drive gear to the middle of the heater block.

The most common reasons for filament jamming are (in no particular order):

  1 - Backpressure at the nozzle when you overextrude.  Solution: increase filament diameter when slicing to extrude less plastic

  2 - Wild swings in temperature because of PID control problems when alternating between high-duty-cycle and low-duty-cycle areas in the print.  My solution: turn on a box fan and blow it at the printhead -- the resulting thermal flow into the air will dominate the heat transfer, so that changes in plastic flow rate will have less effect on the hotend temperature.  Proper solution: better PID tuning or feed-forward correction of the hotend

  3 - Excessive retractions in the same spot -- If you have a lot of retractions in between small features, the same spot on the filament can get chewed up enough to the point where the extruder can't effectively push the filament anymore, and then it just keeps grinding away at the same spot after the filament is no longer moving.

  4 - Filament infeed problems - tangled or knotted filament.  Solution: make sure that your spool is not knotted. I still have to take a video on how to do this.  I have to get someone to work with me on that.  I feel silly taking videos of myself with my own camera.

  5 - Filament quality problems - filament feeding blocked by a bulge in the filament (or worse, a knot where two filament are tied together, or even taped together).  If this was the cause, you should be able to spot the actual obstruction.  Solution: remove obstruction if it's an isolated incident.  Or switch to higher quality filament.  

  6 - Filament feedpath problem - the feed tube friction may be too high from wear (not likely with you since your 2X is, I'm guessing, new and has low hours on it).  Solution: replace feed tube, or go to a tube-less arrangement.     You mounted filament incorrectly.  Solution: Mount filament to avoid sharp turns or other sources of resistance..

  7 - Clogged nozzle - accumulated dust/dirt or actual debris in filament.  Solution: clear nozzle, ensure filament is clean.

I actually have a hypothesis which I think may be reason #6:  the room is getting too warm.   Given that it was printing well for 6 hours, most everything else in your machine should have reached their steady-state temperature.  But if you are printing in an enclosed area, the printer can act as a space heater and, eventually, the air temperature is much higher than when you started. I think the room temperature could affect the printer either by directly affecting the extruder or possibly by affecting the accuracy of temperature measurement.  This is an educated guess, however, and not a well tested hypothesis.  If Makerbot or anyone else would like to let me borrow their 2X for a while, I can run some tests! ;)

Best,

Joseph

[David Celento]

Nice summary, Joseph! My guess is heatsoak caused stripping of overly soft filament which was caused primarily by poor heat dissipation of the extruder.

Since this can't be easily changed, I like Joseph's suggestions of cooling the room (fan, etc) and reducing packing value to minimize resistance. Might also try a couple drops of high temp vegetable oil on filament end before feeding through tube.

[Damian Gto]

Remember he is talking about ABS, its very different than PLA.

Also I made a solution for the heat problem that some that use PLA has: http://www.thingiverse.com/thing:74333

Also you should not cool much when you are using ABS. There is a reason why we use a closed 3dprinter when we are using ABS.

If I remember correct the glass temperature is 110c for ABS and I can not see that temperature will ever be in the filament tubes.

If that is the case you should cool the filament tube and the filament inside, not cool inside of the 3d printer.

[Joseph Chiu]

Brad, did you sort out your problem?  GIve us an update!

--

[Kalen Rixon]

I'd also like to add that I've been experiencing a similar problem on my Rep2 and only just fixed it. I was noticing that my printer was air-printing any model that took more than an hour to print. At first, I had no idea what could possibly have changed, then i realized the seemingly obvious:

I had been recently enclosing my printer with clear acrylic panels, and a hood, to keep the airflow constant and reduce warping. And while the newly enclosed space did reduce warping, it also overheated the extruder, which led to it jamming. Here's how I fixed it: I cut a 100mm hole in the hood and put in a fan to expel the air inside the printer, which would slowly draw cooler air through any openings in the casing. I then reduced the printing temp from 230C to 210. 

The result is the best of both worlds. I'm printing long jobs with almost no warping. The next thing I'd like to try is installing an intake fan and a second heat sink on the extruder motor (as per wingcommander's recommendation)

[Dan Newman]

A heatsink such as

http://www.lightobject.com/35mm-x-35mm-heatsink-P163.aspx

can be affixed to the backside of the stepper motor with heatsink adhesive.
Note that the motor backs are not as flat as you might prefer for such
an application thus greatly reducing the effectiveness of the heatsink.
And you do need to check the clearance past the build platform arms
when the extruder carriage has travelled all the way to the back and the
Z platform is raised to the top. If there is a clearance issue, you can
move the Y stop a bit forward with the endstop block which is one of the
STLs from

http://www.thingiverse.com/thing:84729

Since I have some of those heatsinks around I checked the clearance on
my Rep 2 and it works. I do not know if the clearance is the same on the Rep 2X.
Also, I have those aluminum arms from Bottleworks installed on my Rep 2. (And Rep 1
as well.) Installation of those Al arms necessitate use of that new endstop
block.

Dan