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How do the 3D printed fingers work?

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Posted · How do the 3D printed fingers work?

So at work I am baffled by a problem to bend a flat plate (3mm thick max) using string where the string is encased in the plate. So naturally I 3d printed some plates and attached a string but found as suspected that the plate would only bend when the string had some angle > than a few degrees getting progressively easier to bend approaching normal. This led me to researching how other similar designs accomplish this and ultimately my question. I have seen many pictures but not a very good write up on how the fingers bend in the 3D printed prosthetic, when the string bending them is parallel with the surface. It appears that most of the designs do it this way so the strings aren't all over the place which makes sense. The only way that I can think of is that the fingers are already bent and the string pulls them erect but it appears to work the opposite. So if anyone could shed some light on this I would be grateful.

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Posted · How do the 3D printed fingers work?

Hmmmmmm - plate sounds a bit inflexible - what are you hinge arrangements, or is it flexible in some way?

Anyway - with the e-nable fingers the pulling string is almost always offset from centre - so when pulled applies an asymmetric force around the fulcrum and hence the bend in that direction.

I have played around with this - the further away from the fulcrum you place the string, the stronger the pull force, but the lower the potential overall movement.

I have also played with non-linear 'holes' for the string - placed closer to the fulcrum, so when the finger is flat it takes a degree of force to pull, but as the finger bends the string can rise in the elongated 'tunnel' improving its force characteristic. The point of this was to vary the hole shape in each finger and thus control which bend started first.

Pop a piccy of what you are trying to do if you want and it may be clearer.

James

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