Hobbed bolt variation

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?

As long there is no force measure, how many kg it can lift, it is hard to say

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.

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Fl0yd

i found one
[hydraraptor.blogspot.de]

i should do the same for the emr [forums.reprap.org]

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.

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.

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!

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)!

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...
You may check the pics here [www.tridimake.com]

I have yet to see it elsewhere than on my feeder
[www.tridimake.com]
Idem so far, you cannot buy it, you have to make your own!

Here is original design by me
[www.thingiverse.com]

At now I use milled gear (similar to mk7) with same extruder's body
[www.thingiverse.com]

How many kilos? Please check this video 5.6kg torque tested
[www.youtube.com]