New Hyena-mini advice or review wanted.

After some independent advice.
I just bought a hyena mini extruder drive gear. The website shows a nice photo with apparently even teeth and in particular states the design eliminates orphan teeth (ie irregularities in the pattern which may cause slight errors in extrusion likely to occur at the last tooth cut around the circumference).
At a quick glance, it looks the same as the photo. The teeth have probably been ground as they are very thin, and feel quite sharp when rubbed with a finger.
However my concerns are:
1. On the face of it, all the gear teeth are distorted by the manufacturing process , so they the gear is essentially 'handed' (ie will bite differently rotated one way than the other). I would have thought this would mean that extrusion and retraction aren't quite even, and potentially introduce inaccuracies in the print.
2. Because of the distortion, there are two orphan teeth which are much closer together than any of the other teeth. If the web site hadn't mentioned it, I probably wouldn't have even considered it, but I would have thought if one was a problem, then two would have been even more so. The gear is 12.5mm in diameter, and the teeth are cut into a 1mm groove (making this point 10.5mm diameter. There are 26 sets of 3 teeth around the circumference, which means the "orphan" set will only be encountered every 33mm.
3. There is some pitting on a couple of teeth (bearing in mind it's brand new), and I'm not sure if this is likely to contribute to failure or poor prints down the line.

I know I could probably complain and get it replaced or refunded and then just make my own or get a mainstream gear (which would be cheaper too), but I quite like the design with a couple of small sharp teeth supported by a heavier duty tooth. I also have a project next weekend for which I wanted it, and as it took 14 days to arrive I don't have time to return it.

I'm therefore after some independent advice as to whether I'm likely to regret sticking with it in the long term. If it's likely to cause more frustration and failed prints, I'd rather bin it now, as I bought it to aleviate the frustration of my previous one which intermittently ruined prints. I can't find any reviews of comparisons of the current design, but if anyone knows of one, a link would be helpful.
I've attached some pics, but please note the teeth on this gear are very fine, so the photos exaggerate the distortion (Sorry, not sure how to resize them to properly fit the screen, so I've uploaded a small version too).




Thanks
David

Edited 1 time(s). Last edit at 08/16/2013 02:55AM by dgm3333.

i personally think it should be okay.. i guess you should test it out and see how it runs,

Its quite funny you posted about this as I have just received my hyena bolt and the cuts look identical. Yes I had a few similar concerns and contacted the supplier.

TBH I was more than happy with the response. Basically I was told that that is normal to look like that and it will work fully, as intended, so I wouldn't be too worried.

I now can't wait to get it installed as see how I get on.

Wow.. these things look really sharp. I mean.. literally sharp. LOL. I wonder if they are going to stay that sharp. Maybe they didn't have to be that sharp to begin with, so it may not matter even if they get dulled.

However, if some of those tips get bent, and break off... Well, I shouldn't mention the "J" word...

With so many "J" issues I have been having lately, I was also thinking about this bobbed bolt thing. And, my idea was actually somewhat to the opposite direction - instead of using metal teeth which can dig into the filament, what about using some tacky and soft material like rubber? You know, like tires.

I think there will be plenty of friction to push the filament with force. Also, when something got stuck, it would slip off rather than digging into the filament and chewing out, or with enough friction it may just stop the gear and motor without slipping. Either case, I will like it so much more than chewed out filament - we have no other choice to pull it out and cut it off and feed it again. Oh yeah, and there's always some clean up to do as well.

Well, that was just some day dreaming I had anyway - since 3D prints take long time to complete, it leaves us a lot of time to "think" LOL


Please keep us posted on how well this Hyena hobbed bold performed. If they are worth the money, I sure would like to try myself.

By the way, was this bolt compatible with what you already had? Was it a simple replacement?

Zach (?from Makerbot) tried a variety of rubber wheels a few years ago. I thought they worked, but not sure why they aren't used now. Possibly wear on the wheel or metal teeth had superior grip.

There is a drop-in replacement for the 8mm hobbed bolt with hyena-cuts (the 'hyena hobbed bar') also on the web site.

I'm using the "mini" (which is actually larger diameter) because I wanted to increase the contact face. This blog: Simon Kühling Comparison implies that diameter is at least as important as tooth dimensions in increasing grip, and I'd thought it was likely for some time, so I finally thought I'd try it.
The mini is not exactly a drop in replacement, but simple to modify a Wades extruder to fit, and lots of 'direct-drive' designs around if your motor is internally geared (this is the Makerbot style extruder). The question is will the existing gearing be sufficient? (I don't know).

What does it mean by "internally geared"? The motor has some gears just like we have in Wade style extruders? Would there be certain indication or term in the motor's technical specification if the motor is internally geared?

I've been always wondering how those direct drive extruders have enough force to push the filament without any gears.

Also, with gears we have more precision, so I was also wondering about that on direct drive extruders... Do these internally geared motors have smaller step size than conventional 1.8 degree?

So, how has this Hyena bolt been working out for you guys? Is it a disappointment? Is it really better than conventional hobbed bolts? Is it just like a well made regular hobbed bolt, but nothing really spectacular?

I am in process of printing replacement parts for my extruder (in case one of them in my current extruder breaks). However, since I got an extra motor and hot end, I am thinking about just making another fully functioning extruder, instead of a pile of spare parts.

I got spares for the other hardware, like screws and stuff, and the only thing missing are a couple of bearings and hobbed bolt (btw, I have Greg's Wade extruder). The bearings are pretty much standard, but I am wondering if I should try this Hyena bolt.

But before spending money on it, I would like to if it is at least worth trying.

Another option I am considering is... making a hobbed bolt myself. It will only require a small investment, like an M3 tab, as I have other basic tools, such as a drill, vice, and etc. I've seen some video instructions, and they all seemed pretty easy (well, I'm pretty sure it will be a lot more difficult when I try myself).

But then again, since ready made hobbed bolt is not that expensive, and one should last pretty long time, if I can make one myself, which actually works, it will be for my satisfaction and ego more than anything else... In other words, if there's a hobbed bolt with innovative design (like Hyena) which outperforms other home made or commercially made ones, then I would be more than happy to just purchase that.

I started out making my own hobbed bolts. They were successful, but crude. Then I decided to spring for a hyena bar. Totally worth it.

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- akhlut

Just remember - Iterate, Iterate, Iterate!

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