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Hobbed bolt variation

Posted by Fl0yd 
Hobbed bolt variation
April 03, 2013 09:24PM
Here's an interesting read on a hobbed bolt variation(not my own). I'm still assembling my kit, but this looks like a reasonable alternative.

Can anyone offer their criticisms?
Re: Hobbed bolt variation
April 04, 2013 01:49AM
As long there is no force measure, how many kg it can lift, it is hard to say
Re: Hobbed bolt variation
April 04, 2013 08:31AM
That brings up an interesting point. I have yet to see rankings, in universal terms, for the various methods of pulling or pushing filament. For example, I also see a lot of "just keep cranking", or "how much tension is enough" posts on the idler tension springs in a Wade's setup. It would be very appealing to me if we could find a way to universally guide a person to the correct amount based on their setup.

I've tried searches on the wiki but haven't found what I'm looking for. Is there a chart or similar representation, that lists the extruder type, hobbed bolt variant, stepper motor, type of plastic, (possibly manufacturer since the quality varies so much, and how many Newton's of force (or how many grams can be lifted before filament failure) the combined unit can push/pull through itself.

Has anyone seen a comparison like this? With this kind of data, I think we could begin to hone in on the ideal settings for hobbed bolts and discuss the variants with something more than conjecture.

Re: Hobbed bolt variation
April 04, 2013 10:10AM
i found one

i should do the same for the emr [forums.reprap.org]
Re: Hobbed bolt variation
April 04, 2013 11:52AM
I thought I'd read most of nophead's blog, but didn't remember seeing that. That's definitely on par with what I'm looking for with an updated look at the more recent hobbed gears and bolts.
Re: Hobbed bolt variation
April 20, 2013 02:13PM
In my bolts, I use hobbing that looks more like Camiel's hobbed shaft in the linked article. I don't cut a valley into the bolt, just hobb on the surface of the shaft, abuout 6mm wide.
Re: Hobbed bolt variation
May 14, 2013 08:06AM
Actually I have mixed feelings about the measure... Still, I agree I need to check my bolt traction, but as nophead indicates, it depends on the filament nature. Eg. nylon is often springy and will stretch a lot compared to PLA, while ABS is softer and will deform easily but the let the bolt dig deeper in it for less idler tension (what's the "best" idler tension in this regard?)... There is no single measure nor setup imho.

Also, "the maximum traction the better" may not be a good way of life imho!... Better have a setup where you minimise friction, especially with bowden tubes. To illustrate this, think about replacing the idler with a knurled non-rotating surface and for sure you will get a higher traction... but no better print! winking smiley

And finally, some may like a bolt that is able to let the filament slip a bit instead of carving it stupidly to the point it will never re-engage (as I had before). This happens all the time with overextrusion, so a bolt that is able to slip a bit without incurring such irreparable damage to the filament is also a desirable property.

my two cents (oh, and something to copy/paste to my blog... with some force measures anyway -- better than nothing indeed)!
Re: Hobbed bolt variation
May 25, 2013 07:10AM
Short update: I still did no measure of the force, but I recently stripped the bowden tube on the push-fit connector metallic fins because the filament would not slip on the bolt! Actually that's bad because I clogged my nozzle with bits of PTFE... grinning smiley
You may check the pics here [www.tridimake.com]
Re: Hobbed bolt variation
July 18, 2013 04:37AM
I have yet to see it elsewhere than on my feeder winking smiley
Idem so far, you cannot buy it, you have to make your own!
Re: Hobbed bolt variation
November 01, 2013 11:47AM
Here is original design by me smiling smiley

At now I use milled gear (similar to mk7) with same extruder's body

How many kilos? Please check this video smiling smiley 5.6kg torque tested
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