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High Resolution Herringbone gears for Greg's Wade Reloaded extruder.

by ronanwarrior Jun 2, 2013
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M3 nut for the set screw doesn't fit, hole is too small.

While trying to adapt MCAD's gear() module to use an easier to understand "helix_angle" parameter in place of the "twist" parameter, I thought I'd look at your gear as reference, but I think your gears's helix angles are slightly off.

From WadeL_double_helix(), I see that your rim_thickness = 11/2 = 5.5, and your twist = 200/teeth.
From WadeS_double_helix(), I see that your rim_thickness = 25/4 = 6.25, and your twist = 200/teeth.

Since the gear twist here is the twist being passed into linear_extrude, you need to factor in both your rim_thickness and pitch circumference (number of teeth, assuming your circular pitch is right) in order to get a matching helix angle.

See https://en.wikipedia.org/wiki/Helix_angle for the detailed calculation on this. I've also integrated this MCAD's involute_gears.scad library, as you can see at https://github.com/hyperair/MCAD/blob/master/gears/involute_gears.scad, so you can now just specify a helix_angle instead of calculating how much to twist.

The small gear isn't properly scaled it seems. The center hole is too narrow for the shaft of my extruder motor, and the opening for the nut is so tight I can't get it in. I printed it 0.2mm with PLA.

Small circular holes are problematic. See http://hydraraptor.blogspot.it/2011/02/polyholes.html for a proposed compensation. This is included as part of MCAD: https://github.com/hyperair/MCAD/blob/master/shapes/polyhole.scad, and I'm planning to adapt the gear's bore to use that module.

I really like the level of detail, how sharp the gear teeth are, how clean the design is... but when I printed it, the lower solid portion of the gear contracted more than the upper "ring" of gear teeth resulting in the plane of gear teeth not being parallel to the gear axis. Any suggestions on how keep this from happening? I used a heated bed (110C) and no cooling fan. Extruding ABS at 230C.

M8 trap is still not okay. Its too wide.

The highres large gear is incorrectly sized. M8 hobbed bolt trap is way too big.

It seems it is now corrected, it is now about 14 mm wide.

I just printed one and it's still wrong, it should be 12.8mm but it's 14mm, which is way to big. Shame really cause they are nice! Hoping the author can resolve the issue

I don't know exactly what is going on, my M8 bolt heads are also the standard 12.8 mm. They fit perfectly in the hi res big gear. Slic3r must be doing something odd. In any case try the shape above, I've tweaked it and it should fit better. Tell me how it goes!

High Res Herringbone Big Gear With 12.8 and 13 mm Hex Head for Greg's Wade Reloaded Extruder
by Yvan

Dude, you are a legend. I failed dismally to print a previous version of the small herringbone gear. But this one came out b-e-a-utifly when using a cooling fan as the printer prints the teeth :)