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Opinions on my hobbed bolt please

Posted by Emin8 
Opinions on my hobbed bolt please
March 21, 2012 12:19PM


I am having problems with my Longboat Prusa.

My filament is getting stuck. It is getting squashed flat or is being nibbled at by the hobbed bolt. It does work for a bit but then stops by getting jammed and I have to dismantle it and start again.

I am sure the hot end is a good temperature as I can feed the filament through by hand pretty easily. I have tried different pressures on the idler wheel.

I am wondering if my hobbed bolt is up to the job?

I have looked at the Wades Extruder Wiki and the quality of hobbed bolt there seem to be much better.

What do you you reckon?

Edited 1 time(s). Last edit at 03/21/2012 12:19PM by Emin8.
Re: Opinions on my hobbed bolt please
March 21, 2012 12:34PM
That looks pretty shallow/dull, and could certainly be your problem.


www.Fablicator.com
Re: Opinions on my hobbed bolt please
March 21, 2012 01:45PM
A hobbed bolt should look more like the following:



Bob Morrison
W├Ârth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse
Re: Opinions on my hobbed bolt please
March 21, 2012 04:18PM
You may just have too much tension on your idler if the filament is being squashed. Try loosening it up a bunch, then gradually tighten it till it catches but no more.
Re: Opinions on my hobbed bolt please
March 21, 2012 07:31PM
I bought this hobbed bolt from ebay and it works well:

ebay_hobbed_bolt

The hobbing on the bolt that originally came with my wades looks a lot like yours and it gave me the same problems.

Karl
Re: Opinions on my hobbed bolt please
March 21, 2012 08:49PM
I too bought a longboat kit. My bolt looks like yours.
Assuming you've tried different tensions to rule out insufficient or too much tension on the extruder idler springs, I would guess that your hobbed bolt is not the cause of the problem.
If there is something causing a block in your hot end insulator then this will cause the hobbed bolt to chew up the filament when it gets stuck.
This happened to me loads until I changed the hot end insulator to stop it jamming up with bits of PTFE or hot plastic cooling up the insulator tube. I also pointed a small PC fan at the top of the insulator to cool the filament at the top. Now it never jams.

If you haven't already, check out the posts in the forum about the hot end insulator problem.
Re: Opinions on my hobbed bolt please
March 22, 2012 12:15PM
Looking at the other hobbed bolts mine does look a bit pathetic.

It doesn't have the concave radius which I reckon helps a lot. Mine is prone to squashing I think as a result. Mine just looks a feels like someone has tickled it with something sad smiley

Replacement ordered!

Cheers
Re: Opinions on my hobbed bolt please
March 22, 2012 02:15PM
I don't know how you hob your bolts but if you just put the tap into your drill press and spend a bit more time pressing the bolt into the spinning tap you will happily get that concave radius. It just requires a bit of patience and some oil to facilitate the cutting. Especially when you have teeth on the bolt already you should have no trouble getting the tap to catch and start the bolt rotating to cut deeper. It's really hard to screw it up especially since even if you do strip the hobbing you can just file it down and cut anew, thereby also accomplishing the objective of making a more concave indentation.
Re: Opinions on my hobbed bolt please
March 22, 2012 04:18PM
I too have the longboat kit and my hobbed bolt is a lot like yours. But I did notice when I was assembling mine that the hobbed section did not line up well with the holes that the filament feeds through, so during initial assembly I messed about with washers to get it to line up properly, this may be the problem with yours.

George
Re: Opinions on my hobbed bolt please
April 04, 2012 03:21PM
There was no problem with alignment.

I have a new hobbed bolt now and I have no problems!

Conclusion - The hobbed bolt shipped with the longboat prusa was not up to the job, or at best would of had to be set up perfectly with lower feed speed probably.

thanks all.
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