by schlem, published

Skulltruder by schlem Feb 11, 2013


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Behold and fear my Skulltruder! This is a set of spur gears for the Printrbot or any printer using Wade's accessible extruder. 13:43.
Reworked from Brook Drumm's Printrbot's involute herringbone gears, (which were ultimately derived from works by Wade and Frost) http://www.thingiverse.com/thing:16990 and Cleaned Skull by ssd (http://www.thingiverse.com/thing:4126 .
Watch one come to life:

New 4mm drive gear!

This work is licensed under the Creative Commons - Attribution - Non-Commercial license. This license applies only to the files and documents available for download from the Thing Files section of this Thing.
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UPDATE: There are now THREE versions of the Skulltruder - a 5/16 inch and and an 8mm to fit your favorite hobbed bolt, in addition to a straight spur designed (tooth profile poached from thing #41808 by jameswood).
I ditched the small skull on the small gear. It never printed well with the hole through the forehead and the reduction in size. The NEW! small gear has some nice features, including cleaned up teeth, and a strengthened area for the set screw. The small gear designed by jameswood is as his original.
Thanks to Emmett, I have a better understanding of involute gear geometry, and I should mention that these two gears are designed to work together. If you use a different drive gear (on the stepper) you may have issues with smooth meshing because of different variables in the tooth profile. They were both ultimately derived from Greg Frost's 9/43t herringbone extruder gear drive.
If you change gears on your extruder, you will need to change your mm/rotation calibration in firmware / slicing software.

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Printed M8 version but my 8mm hobbed bolt does not fit? The head is too large for the hex slot.

Do you trust the dimensional accuracy of your printer? Have you printed calibration objects and adjusted your steps/mm? What material? Have you tried different hardware? Is this a homemade bobbed bolt?

The 8mm hex in the Skulltruder is 12.98mm across the flats. A non-structural 8mm bolt head is 12.8 mm, I have found this to be a good tolerance for both desktop FDM machines and SLS processes like Shapeways uses. It is possible that your hobbed bolt is a structural fastener, which will measure 14.4mm across the flats and will not fit the recess. I have never seen a hobbed bolt in this dimension, but it could certainly happen, particularly if it were homemade.

I hope that helps.

I do trust it, the dimensions on the hex slot of my printed gear across the flats, using calipers, is 12.98 mm. But it looks like my bolt must be industrial grade? It is 13.9 mm from flat to flat. I bought it from Leap3D on eBay http://www.ebay.com/itm/3D-Printer-Hobbed-bolt-for-Greg-Wade-Extruder-Prusa-i3-Mendel-Reprap-M8-/122015966733?hash=item1c68b7e60d:g:0CIAAOSwOVpXYK7h

Not to worry though! I figured out how to import the mesh into Fusion 360, make it a solid, and modify it. I can reprint my custom gear :) Awesome design, thank you.

Excellent! May it serve you well!

Love these! Printed clean, looks cool, and works great. Killer work! Thanks!

can someone tell me what estep they used on nema 17 5mm shaft with these gears please?

For best results, you should calibrate your extruder yourself: http://reprap.org/wiki/Triffid_Hunter's_Calibration_Guide

Hope that helps!

How do you get the gears too closely . You are still processed after ?

I'm sorry, I don't know what you are asking. The featured white gears were printed by Shapeways in "strong flexible nylon" with a selective laser sintering machine. Does that help?

Can you design the small gear to work with a 4mm shaft?

Done. If you have a 3Dprinter, it behooves you to learn how to pwn the designs that are available to you.
It is your destiny.
Pretty soon you'll be making the next awesome 3D printed thingamajig.
Start with Tinkercad - they have lessons. Pretty capable freebie.
Then run wild:
http://reprap.org/wiki/Useful_Software_Packageshttp://reprap.org/wiki/Useful_... -most of these are FOSS

Awesome. Thanks. I typically use 123D Design. I just wanted to make sure the hole remained centered.

What printer / motor are you using that has a 4mm shaft? A fairly trivial modification - I bet you could do that as easily as I.

I wasn't paying attention and ordered some low profile steppers that had a 4mm shaft. What program would u recommend?

For that kind of easy alteration, I use Tinkercad. It's a great STL Swiss Army Knife.

any chance someone could remix this with straight teeth? im not a fan of herringbone gears...

Done, designed for a 5/16 hobbed bolt. Lemme know if you need an 8M version.

Thanks, I really appreciate it. I guess i didn't know that it was in an empirical measurement. I only use metric for all my stuff, as things like unit conversions and gear ratios are easier to figure out. Idk why everybody doesn't use it.

Im not sure wether the bolt in my extruder is metric or empirical, but i guess I can print it out and give it a shot. I would have done it sooner, but I've had some projects that I've been working on.

The actual difference at the head is trivial. A little trimming and it can be made to fit easily. If it really is just too tight, I can make the M8 version later this week.

I think that could be done. Busy week. stay tuned.

Tomvdb - This should work fine on any extruder design based on (or probably similar to) Wade's. You may need to shim the large cog out from the extruder body for best results, or, worst case scenario, make your own 5/16 hobbed bolt. If your extruder uses a different bolt (?) you could rework the hex inset in the middle. Cheers!

So will this work on the regular Wade extruder?

Did this work for you?

Haven't tried it yet, but will try it out this coming weekend.


I use it on a Printrbot laser-cut extruder and on a printed Wade's extruder, and it works wonderfully. I have used FFF printed gears and (my preference) laser-sintered nylon by Shapeways.

Thanks, I'm asksing tom because we have the same printed printrbots, using 8mm bolts (13mm head). So I think it will not fit properly. If you make the openscad file available I can try and adjust it. Thanks. This looks very cool while it is printing, and you used the perfect sound track for the video :)

I (ahem) created this in Tinkercad before I learned OpenScad, but I have been meaning to adapt this to M8 bolt head. I >could< make an alternate part, but I think I want to put another hex in the center rotated 60 degrees so that either M8 or 5/16" bolts can fit... Thoughts?

I think for better grip it will be better to use separate parts (but I'm no expert).

DONE. STLs are named accordingly.

awesome you are the best! thanks.

Further, I have Netfabbed them, so they should be manifold.

thanks, I finally made it and it is working pretty nice.

love it, did you try a herring bone gear in addition to spur design?

You asked about trying the herringbone vs the spur gear... Not sure what you mean. This is just a rehash of the Printrbot herringbone gear, which is a rehash of Wade's, I believe. I have a laser-sintered version on order with Shapeways, but I wanna try printing it just to see how it comes out.

Yeah, I started asking silly questions before looking at the STL render. thanks for trying to answer my jackassery though.