Perfectly parallel double linkage grippers - how? 1

[Alice24]

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

https://www.youtube.com/watch?v=6UfB5HnEkek&ab_channel=MechMotions

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

 

[BrianPetersen]

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.

 

[Alice24]

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

 

[EdStainless]

Get a mechanical engineer's handbook. There will be a section on linkages.
There are actually some old books that solely address these linkages.

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P.E. Metallurgy, consulting work welcomed

 

[robyengIT]

Google (free download) : "ingenious mechanisms for designers and inventors"

Google : "parallel linkage mechanisms"