Worn extruder hobbed pulley  

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JohnnyricoMC
(@johnnyricomc)
Estimable Member

After a few failed prints where no more filament would come out of the extruder unless I unloaded and loaded filament again, I decided to check if debris had built up between the "teeth" of the hobbed pulley. What I found was several teeth had "bent" upwards (in the direction opposite to the rotation direction). Clearing the little amount of debris that had built up didn't solve extrusion stopping or pausing midway through the print.

Has anybody else encountered a similar issue before? Did you replace the pulley with another brass one, or did you find one of the same dimensions from a stronger material?

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Posted : 22/10/2016 11:02 pm
david.t2
(@david-t2)
Noble Member

I'm using this one on self-built MK2 extruder and it works quite well.

Posted : 22/10/2016 11:23 pm
Omikron
(@omikron)
Estimable Member

I'm using this one on self-built MK2 extruder and it works quite well.

Are they the same specifications as the original one? No changes in diameter? Did you have to change your e-steps?

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Posted : 23/10/2016 4:25 am
Nigel
(@nigel)
Honorable Member

My self built extruder works well. Is your hobbed pulley aligned correctly? Loading and unloading filament works perfectly for me. And my prints are great. Also check the tension on the idler bolts on the extruder. Too tight or too loose?

I have printed many 100's of hours with this MK2 kit build upgrade from a MK1. The hobbed nut shows no wear. It was transferred from my MK1 printer. So has more hours of printing.

Nigel
Life is keeping interested and excited by knowledge and new things....
Posted : 23/10/2016 7:28 am
david.t2
(@david-t2)
Noble Member

Are they the same specifications as the original one? No changes in diameter? Did you have to change your e-steps?
They are almost same. By "almost" I mean that it works well without need of changes in filament path geometry, but some e-steps tuning was necessary. My current value for E-steps/mm is 151.5.

Posted : 23/10/2016 11:53 am
JohnnyricoMC
(@johnnyricomc)
Estimable Member

My self built extruder works well. Is your hobbed pulley aligned correctly? Loading and unloading filament works perfectly for me. And my prints are great. Also check the tension on the idler bolts on the extruder. Too tight or too loose?

I have printed many 100's of hours with this MK2 kit build upgrade from a MK1. The hobbed nut shows no wear. It was transferred from my MK1 printer. So has more hours of printing.

Well, my printer was preassembled by PR so I trust the hobbed pulley was aligned properly (and I did get several weekends of printing out of it). I figure I'll try a slightly looser idler once I've ordered and received some replacement hobbed pulleys.

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Posted : 23/10/2016 5:56 pm
JohnnyricoMC
(@johnnyricomc)
Estimable Member

Installed the replacement today and after some adjusting of the idler prints seem to go well. As an added bonus, I now only need to use a live adjust Z value of -0.550mm instead of -1.150, which means the PINDA probe doesn't have to sit so uncomfortable close to the bed. I'd guess the extruder assembly was attached to the X carriage at a less favorable angle.

I'll probably do a larger testprint before trying the tower of Pi again.

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Posted : 31/10/2016 8:48 pm
ayourk
(@ayourk)
Reputable Member

Installed the replacement today and after some adjusting of the idler prints seem to go well. As an added bonus, I now only need to use a live adjust Z value of -0.550mm instead of -1.150, which means the PINDA probe doesn't have to sit so uncomfortable close to the bed. I'd guess the extruder assembly was attached to the X carriage at a less favorable angle.

I'll probably do a larger testprint before trying the tower of Pi again.

I think -0.550 is still too high of a value, but I guess it might depend on what material you print. You could always come over to the Prusa MK2 Google Hangout and we could assist you further. I know of at least 1 person where his Live Z adjustment is -0.100.

Dimensions PNG and an 8 inch (200mm) or greater caliper is recommended....
Posted : 31/10/2016 9:59 pm
richard.l
(@richard-l)
Member Moderator

I think -0.550 is still too high of a value, but I guess it might depend on what material you print. You could always come over to the Prusa MK2 Google Hangout and we could assist you further. I know of at least 1 person where his Live Z adjustment is -0.100.

-0.550 is definitely acceptable. Anything over -1.000 I would look into adjusting the PINDA. On my other printers with bed leveling my z-offset, which is basically the same as the live z adjust, range from -0.450 to -0.850.

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Posted : 01/11/2016 4:13 am
Nigel
(@nigel)
Honorable Member

My Z adjustment is -0.65 I am getting great prints. I watched a video today from Makers Muse about first layer settings. Helpful. As I use Simplyfy3D as my slicer of choice whilst experimenting with others that do not seem equal to its great prints. Angus mentions rafts, which I use with prints that need supports, it is a good outcome mostly. The supports do not fall over.

Nigel
Life is keeping interested and excited by knowledge and new things....
Posted : 01/11/2016 5:14 am
Nigel
(@nigel)
Honorable Member

The beauty of Simplyfy3D supports is that they are easy to remove after the print. And you can edit them during the slicing process before a print. < saved many prints of mine.

Nigel
Life is keeping interested and excited by knowledge and new things....
Posted : 01/11/2016 5:20 am
JohnnyricoMC
(@johnnyricomc)
Estimable Member

After the hobbed pulley replacement, my printer has been running pretty darn solid, I might even say better.

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Posted : 04/11/2016 6:48 pm
Omikron
(@omikron)
Estimable Member

After the hobbed pulley replacement, my printer has been running pretty darn solid, I might even say better.

What did you end up replacing/adjusting?

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Posted : 11/11/2016 9:45 pm
JohnnyricoMC
(@johnnyricomc)
Estimable Member

The little toothed gear on the extruder motor, the one that bites into the filament and pushes it into the extruder's PTFE tube. The assembly instructions refer to it as "extruder hobbed pulley".

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Posted : 11/11/2016 9:55 pm
simon.p
(@simon-p)
Trusted Member

The little toothed gear on the extruder motor, the one that bites into the filament and pushes it into the extruder's PTFE tube. The assembly instructions refer to it as "extruder hobbed pulley".

What did you replace it with?

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Posted : 13/11/2016 12:39 pm
JohnnyricoMC
(@johnnyricomc)
Estimable Member

The same part, I got in touch with PR's support to purchase a replacement and a spare.

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Posted : 13/11/2016 12:45 pm
jay.b
(@jay-b)
Trusted Member

I purchased a couple of brass ones from a seller on Ebay. Mine kept coming loose, and would move out of alignment. I thought I had stripped the allen set screw head and could not get it tight. When I put it on the machine I found out the problem was not in the allen set screw head but the allen wrench shipped with the machine was just a bit too small. Once I was able to get the set screw tight there have been no more problems.

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Posted : 14/11/2016 7:25 pm
JohnnyricoMC
(@johnnyricomc)
Estimable Member

I've had good experiences using torx screwdriver bits in lieu of hex bits.

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Posted : 14/11/2016 9:07 pm
Omikron
(@omikron)
Estimable Member

I've had good experiences using torx screwdriver bits in lieu of hex bits.

Yikes! That may be almost functional in an actual emergency but that is a recipe for stripping both your screwdriver and the screw! No one should do this unless they have absolutely no other choice and they understand and accept the risk of stripping something out and making it 10x harder to remove.

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Posted : 15/11/2016 3:25 am
JohnnyricoMC
(@johnnyricomc)
Estimable Member

Can't disagree on that. Which is why I use only my cheapest Torx bits for that sort of workaround, only when my hex bits "skip" despite being the right size. 😕

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Posted : 15/11/2016 4:10 pm
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