I like the outer geometry of Arcol's new versions Mini-Hyena drive gears,

I like the outer geometry of Arcol’s new versions Mini-Hyena drive gears, but it looks like the teeth are too spindly for the soft brass. You can see in the larger pictures that they are pretty mangled already. The tooth profile looks like an improvement, but still not ideal. I’m also sad to see that there’s no smaller gear suitable for a NEMA14 extruder…

Also, the most recent version of his hot end looks like sushi :stuck_out_tongue:

Too bad it still seems that I can’t order a mini-hyena anywhere. :frowning:

But a new version means that it soon will be available.

Yeah - Kinda sad I hadn’t got in on that kickstarter at the time. The 8x5 mini hyena is what I was eyeing. Can’t wait for these to be available - I don’t want to send makerbot any of my money.

I’m having to organise production benches and a “Mad Scientist’s Apprentice” (for want of a better phrase) to keep up with demand for extruders. They’re starting to sell fairly quickly.

@Whosa_whatsis Mangled? I see asymmetric teeth, but none damaged. http://www.flickr.com/photos/48806889@N05/8268842357/

edit: oh nevermind, the first pic does look bad at full size

It got smacked in the gob by an aggressive batch of filament at a party?

Why is it brass i wonder?

Brass meets the absolute minimum hardness requirements (unlike aluminum), but is still relatively easy to machine (unlike the stainless steel we make our drive gears from).

Also, it does not corrode.

@Whosa_whatsis Do you know how those are machined? A single-point cutter, perhaps?

I wonder if a gear hob could be used. It might make a harder material easier to work with. Unfortunately, I think they are expensive - and use without the hobbing machine could be tricky.

Also, what about machining and then hardening?

Our Tatsu drive gear teeth are made with a thread mill on a big 5-axis CNC machine and then hardened. I’m not sure about the Hyenas, though I know that you can’t thermally harden brass like you can with steel.

Yep with the direct drive stuff we tested, brass worked, but wore out over a shorter period. With this design, if the load is distributed well enough, it would be just strong enough to use brass.

Don’t read too much in the apparent “mangledness” of the mini hyena’s teeth. I’ve been using hyena bolts (which have the same geometry and are made from the same material) for a while now and even when they look very mangled in the photos (less so in person, but still visible), they still bite down rather well. The teeth do get bent easily (although it’s not from the filament, but usually happens during cleaning), but that doesn’t reflect on the bolt’s ability to grip the filament at all.

Too bad that they won’t be making the 8x5 mini anymore.