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# Perfectly parallel double linkage grippers - how?

## Perfectly parallel double linkage grippers - how?

(OP)
Hi! Trying to figure out how they get the double-linkage gripper to be completely parallel throughout the stroke. This is a good example of what I mean

Couldn't find resources how to get it done. What's the formula or design methodology to get it to be perfectly parallel?

Playing around with the distances/lengths and locations of holes, I was able in my designs to get it to be "nearly" perfectly parallel, but there is always a tiny angle shift in the start and end of the motion, but never perfectly parallel. I must be missing something obvious, some core principle. Would appreciate help.

-Alice
Replies continue below

### RE: Perfectly parallel double linkage grippers - how?

This is basic 4-bar-linkage stuff. The arms need to be the same length and the distance between the pivot points needs to be the same on both ends. That should, ideally (neglecting backlash) result in parallel motion. If this is not the case with how you are modelling it, then how you are modelling it is wrong.

### RE: Perfectly parallel double linkage grippers - how?

(OP)
Thanks @BrianPetersen, it's working. Indeed, it felt like it was something basic. :) If you know any links/resources on grippers design, whether free or paid, feel free to drop 'em

### RE: Perfectly parallel double linkage grippers - how?

Get a mechanical engineer's handbook. There will be a section on linkages.

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P.E. Metallurgy, consulting work welcomed

### RE: Perfectly parallel double linkage grippers - how?

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