Extruder Big Gear M8 Head sizes wrong?

iv been seeing this on a few extruder designs now and not sure why anyone would do this.

http://reprap.org/wiki/File:Engrenage.jpg

an M8 Hoobed bolt of M8 clearly does not fit and would move around before turning the gear.

are these just mistakes or is there a reason??

It might be that the person that assembled it, has heated up the bolt when putting it in, thus melting the plastic a little bit and embedding it a bit into the gear center.

On the other hand.. If they didn't do that, maybe they glued it, and if thats not the case... Welll, then it's just plain stupid

It is not supposed to be like that!

I agree, and just look at those teeth -they look like they've been filed by hand!

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Waitaki 3D Printer

not a printing issue. this is from the I3 Rework files. looking at the STL and print iv done its over sized. iv seen the same on some i3 compact extruders.

any one know were the i3 rework source files are? or at least just the extruder files so i can rework the big gear to fit a normal hobbed m8 bolt?

im amazed everyone building i3 reworks have not seen that the bolt clearly does not fit??

and yeah would use other gears but they then crash into x-carriage

If you have the STL, the bolt hole can be redrawn to suit 8mm

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Waitaki 3D Printer

can you suggest a program to edit the STL im only aware of arty type programs for importing STL files. nothing that you can edit sizes with etc like autodesk, scad, solidworks etc

It looks like a mock up, you can also see smooth rod coming out of the idler, which has not been cut to length.

Anyway, M8 bolts come in different flavours, some with 13mm hex and some with 12mm hex. In Europe you are most likely to find 13mm.

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Enlightx
can you suggest a program to edit the STL im only aware of arty type programs for importing STL files. nothing that you can edit sizes with etc like autodesk, scad, solidworks etc

I use Sketchup for things like that.
Can you post the STL if you have it, I would be interested in seeing what they've done.

Edited 1 time(s). Last edit at 04/09/2014 05:23AM by waitaki.

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Waitaki 3D Printer

STLs for i3 Rework are here
[www.thingiverse.com]

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Ralf
It looks like a mock up, you can also see smooth rod coming out of the idler, which has not been cut to length.

It's not the Idler, it's the smooth rod of the X-axis. It's not a mock up, someone trimmed out distracting parts of the picture The teeth on the big gear look gruesomely cut haha.

Doh..

And the cut seem to be made in a image manipulation program, so it is probably fully functional.

Well, actually, that's the same STL as the bog standard gear that's been around for ages. I'm wondering if they did use a bolt with a smaller head as Ralf mentioned?

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Waitaki 3D Printer

Wow...looks like it was printed with a potato!! Or some newfangled mega extruder with a 4" nozzle!
:-)

The bolt face in the gear is slightly larger than a nominal 13 mm bolt head. My latest batch of Hive 76 hobbs and other 8 mm bolts are nominal 13 mm head, around 12.78 or so on each. The gear measures as printed about 14 mm nominal or 13.8 mm or so. I measureed about the same in the file. I may resize it but I'm looking to use herringbone gears (the lash in the stock gears can be noticable) but haven't gotten around to it just yet. It does work even with the mismatch in the head size. The issue isn't so much the head szie but the play in the gears though I haven't yet done any critical printing comparisons.