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Manufacturing Errors


3djim

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Does anyone have, or know where published, data defining manufacturing tolerances for gripper production? The parameters I have in mind are: 1) wire diameter, 2) spring loop outer diameter (the "wind looseness"), 3) angle between handles when gripper is at rest.

I've seen some casual reference in the grip board to wire diameter error of .001" and .002", which I interpret as a max of +.002 or -.002 from design value.

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  • 3 weeks later...

Some references I've found on manufacturer and gripper product Web sites:

wire diam: +- .002"

handle angular spread: +- 2 degrees

handle depth on spring leg: +- 1/16"

coil outside diam: +- 5%

I've also seen from certain spring manufacturer pages: actual torque is about +- 10% of design.

So, a gripper designed for 200 lbs force x 2.625" moment arm = 525 IP closing torque could be off +- 52.5 IP or +- 20 lbs force! That number is consistent with the errors calculated from "gripper equation" when above geometric tol's are put into the equation.

This info is illuminating especially when trying to compare grippers. No wonder gripper manufacturers shy away from producing a line of relatively closely spaced "betweener" grippers. See some of my other posts for "theoretical gripper equation".

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