Wade's hobbed bolt creating chips off the filament?
January 15, 2012 10:32AM
Dear all,

I'm having some trouble with extruding 3mm filament thru the accessible wade's extruder. I've tried speeds as low as 10mm and varied the strength of the Idler, but nothing seems to be working.

I was thinking that it could be the sharpness of the hob? Or is there something that I'm missing?

Thanks, Ollie.
Re: Wade's hobbed bolt creating chips off the filament?
January 15, 2012 11:07AM
Can you push the filament by hand easily through the hotend? Besides grip problems, your hotend might be [partially] blocked or not reaching the right temperature.

misan
Re: Wade's hobbed bolt creating chips off the filament?
January 15, 2012 11:21AM
I haven't tried it without the extruder yet, but applying extra force with the extruder it goes through fine. I've tried it at 200 degrees, but I only made it yesterday, :/ wow this one got blocked quickly, ill open it up and share my findings, thanks Misan
Re: Wade's hobbed bolt creating chips off the filament?
January 16, 2012 09:10PM
I posted this previously for others, but here it is again.

It might be useful to know which hot end design you are using.

You need to determine what the real culprit is.

1. Using too high a temperature, and/or thermal barrier hole too narrow.

PLA in particular expands quite a bit when heated near the melting point. It also becomes very soft long before it melts. If the thermal barrier tube diameter is too narrow, the filament can seize against the walls as it warms up.

To test for this condition, remove the hobbed bolt, and try pushing filament through by hand. If the temperature is OK, you should be able to push through with ease. If you cannot easily push the filament through, try pulling it back out. If it is stuck, then your filament has seized in the termal barrier. If you are brave enough, try drilling the barrier out in diameter increments of 0.5mm. You should not need to exceed 4.0mm diameter.

DO NOT proceed to adjust roller bearing pressure against the hobbed bolt until you can push filament through by hand. You will never solve the problem.

2. Using too low a temparature.

I don't think this is the case. Easy enough to check, right?

3. Bearing against the hobbed bolt too loose.

If you were able to push filament through by hand with ease, and if the hobbing is full of plastic dust, then your roller bearing is not tight enough against the filament. Tighten it beyond the point where the big gear can move, and slowly back off the pressure until the filament begins extruding.

4. Bearing against the hobbed bolt too tight.

If the bearing is too tight, the stepper motor should stall, and lash the big extruder gear backwards at regular intervals when you try to extrude. Slowly back off the pressure until the filament begins extruding.
Re: Wade's hobbed bolt creating chips off the filament?
January 16, 2012 10:51PM
Thanks jcabrer! You have NO IDEA how helpful this was to me!


[johnbiehler.com]
Re: Wade's hobbed bolt creating chips off the filament?
January 17, 2012 02:12PM
Oh but I do, my friend smiling smiley

johnbiehler Wrote:
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> Thanks jcabrer! You have NO IDEA how helpful this
> was to me!
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