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Some gears

precisionmetal

Stainless
Joined
May 16, 2005
Location
CA
Hope it's not out of line to post photos of parts or jobs here.

These are some .3 Module 20° gears I cut for a robotics company today. (that's just under 85DP) They are .077" wide.

The customer supplied existing gears that they wanted to "match" geometrically (difficult for a number of reasons -- reverse engineering is often more difficult than designing from scratch... and the original gears in the little tiny planetary system were poorly made so measurement was a bit difficult).

Regardless... cut on a 1994 Agie 170 HSS using .004 wire.

point3modulegears.jpg
 
My own software. (it pays to have a Dad that's been in the gear cutting and design business for close to 50 years).


I basically generate the involute profile from the base circle to the major diameter for one flank. After that, it's all fairly simple CAD work to mirror that flank, create the geometry under the base circle, and radially copy for the number of teeth.
 
Really! Is the involute a true curve or is it points? If it's points, how many are there? Or rather, how long are the straight lines?
 
Points -- then I either fit a spline to them, or connect them all with straight lines (depends on my approach for a given gear).

My program allows me to choose a "deviation from theoretical" for the connecting lines, and the point spacing is determined by that. Down close to the base circle, there are of course many, many ponts... and fewer and fewer the further up the flank.

Maybe there's a better way... I just haven't found it yet. Definitely still learning.
 








 
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