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Heart Shaped Box Cam 3

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vbottle28

Mechanical
Apr 30, 2012
9
Hi all, I'm trying to use a box design heart shaped cam to obtain a uniform velocity profile in traversing motion (see attachment) the problem is the cam jams in the dip, i've tried making other versions of the cam without the dip but then it just gets stuck in the new section.

The material is laser cutter acrylic (ok maybe not brilliant for friction but its convenient!)

HSC.jpg
 
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What is the follower, how is its motion constrained, what is the radius of the follower "tip" relative to the slot width? Can you live without the follower dropping into the notch? Try making the inside of the notch have a radius larger than the follower tip.
 
I think you have a pressure angle problem in 'the dip'.
To resolve it, you need to make the base circle bigger, i.e. move the dip farther away from the center. That may in turn force you to use a larger blank or a smaller stroke.


Mike Halloran
Pembroke Pines, FL, USA
 
btrueblood:
the slot is 3mm wide and the inside of it varies from 5mm from the centre of the cam to 45mm. The follower is just a bar with a pin in the slot (clearance fit). The bar is also constrained to move in one place as it passes through a slot.

MikeHalloran:
this looks like good advice, moving the slot outwards by 5mm makes a lot of difference! Thanks

camandfol.png
 
a suggestion to improve the design would be to have a roller at the pin, rather than a fixed pin, especially with plastic as the base material for the cam. (It almost looks like an obround at the end of the bar..)
 
Ah yes, the one we actually manufactured is round :)
 
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