Bondtech Dual set-screw

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jetdillo
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Bondtech Dual set-screw

Postby jetdillo » Fri May 18, 2018 9:00 pm

Does anybody know what size the set-screw for inner hobbed gear on the Bondtech Dual is ?
I have been having a hell of a time trying to get it to seat correctly. Looks like I've got one of the ones that didn't come with LocTite on it and now I can't get it to stay tightened down. It looks like most of my issues w/ jams and clogs over the past month or two finally come down to this being loose and letting that gear slide around.

I'd like to try replacing the set-screw before removing the extruder, taking it apart, etc.

I've messaged the Bondtech guys here and at their support address a couple weeks ago and haven't heard anything back.
I realize this is not strictly Raise3D-related, but there's enough of a user community here that I thought I'd get a quicker response.

Jetguy
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Re: Bondtech Dual set-screw

Postby Jetguy » Fri May 18, 2018 9:32 pm

It's a standard M3 sized setscrew, however, it's extremely short, like 1mm or less. Early versions were sent with too long of a screw and you used a Dremel abrasive cutting wheel to carefully grind it away to not stick out as the gear rotates. I fully admit, the extra short version of the screw is easy to strip out. You cannot use a ball end driver and must use good hardened hex keys of the exact size (not worn out and rounded). There just is not much surface area to grip and so the failure of a round or non-hardened key leads to easy stripping.

Jetguy
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Re: Bondtech Dual set-screw

Postby Jetguy » Fri May 18, 2018 9:38 pm

The shortest ones I found on Amazon are 2.5mm long https://www.amazon.com/Team-Losi-Set-sc ... B004KPJ84K

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jetdillo
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Re: Bondtech Dual set-screw

Postby jetdillo » Tue May 29, 2018 10:19 pm

Jetguy wrote:The shortest ones I found on Amazon are 2.5mm long https://www.amazon.com/Team-Losi-Set-sc ... B004KPJ84K


I ordered these and they showed up in the mail over the weekend. They are, indeed, just a bit longer than the one I removed from my left-side extruder. Time to get out the Dremel and grinding discs I guess. I'm really hoping this fixes the problem. I really seemed to be on the verge of getting dual-nozzle printing working last month.

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jetdillo
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Re: Bondtech Dual set-screw

Postby jetdillo » Tue Jun 05, 2018 8:36 am

"I don't want to cause any fear or alarm..." :)
But I think I've got it :)

Thanks Jetguy for the Amazon link.
I ordered a pack of these :
https://www.amazon.com/gp/product/B004K ... UTF8&psc=1

to replace the set-screw that had some how worked its way loose and refused to seat anymore. This more than anything else turns out to have been the source of so much of my problems over the past couple months with dual extrusion, printing with Polysupport, etc. Without that screw seated correctly, the hobbed gear inside would slap back and forth and occasionally pinch the filament and bind it up tight.

I got out my Dremel and got grinding. I managed to grind out a few that were at or very close to 2mm in size, then picked a likely candidate, dabbed liberally with LocTite, screwed it in with a flat-ended hex-key and let it sit the rest of the day.

That appears to have done it for now. I was able to print out a couple different two-tone cubes and checkerboard-like objects tonight, the Bondtech clicking away(the good sort of clicking) happily. I'm now back to futzing with retraction and stringing between the object and wipe-tower leaving little blobs and nits on the side of the print.

Next up is to get back to trying to print dual with PolySupport. That might have to wait until next weekend though.
Thanks again to everybody here who helped me get this far !

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jetdillo
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Re: Bondtech Dual set-screw

Postby jetdillo » Mon Jun 11, 2018 7:50 pm

One week later and I wanted to just bump this thread a bit to point out that replacing the set-screw on my left extruder has indeed solved the problem. I took a 2.5mm M3 set-screw, like I mentioned in the link above, ground it down to 2mm, dunked it in Loctite Blue, wiping off the drips and screwed it into the inner gear. I let it sit overnight (man, not printing anything over a weekend, that took some self-restraint :) ) , then did some test loads/unloads, made a few calibration cubes, etc. and it all worked.

It's been working solidly ever since and makes me wonder if it wasn't loose from when I first got my unit last fall. The performance difference is really just night-and-day.

Just wanted to post one more update here so this will show up the next time somebody does a search on Bondtech, set-screws, grub-screws, etc.

tja
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Re: Bondtech Dual set-screw

Postby tja » Sun Jun 17, 2018 9:12 pm

I haven't fitted my Bondtech dual yet. Is there a way to tell if it has already been Loctite'd?

Jetguy
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Re: Bondtech Dual set-screw

Postby Jetguy » Sun Jun 17, 2018 11:50 pm

No, the best way is still to inspect it and just do it (apply threadlock) yourself. It doesn't take that long to do it right and you know it's done right- because you did it.


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