[olympic1]

The pictures show the part and the fixture, the problem i am having is the part moving around. I can not put in pins or any kind of mechanical holding because i have to touch all four sides. My question is is there anything i can do better to get some more vacuum pressure basically.

I am using a venturi that is pulling 27.5 in/hg and the part is decently hard to lift up but it is still sliding. i know this is the nature of the beast but im open to idea if anyone has any!


Thank you
-Vic

[jeffrey001]

You could try to add more chambers in the vacuum section, more friction.

Jeff

[bhurts]

How are you actually cutting the part. It might help to leave material all the way around .01-.03 and the take light passes working in to finish size.

Ben

[olympic1]

How are you actually cutting the part. It might help to leave material all the way around .01-.03 and the take light passes working in to finish size.

Ben

The part gets an angle on the small and larger side of the trapezoid. it also gets small flats (.025 deep) on the equilateral sides. So the cuts are already very small

[rowbare]

You are limited by the small surface area of your part. It might be worth your while to investigate other options such as Mitee-Grip from Mitee-Bite or freeze chucking.

bob

[olympic1]

edit: looked into everything you suggested. The problem is speed (of course) the mitee grip im sure would work but would require a lot of time. The freeze chucking is awesome! but once again 90 seconds to install and 90 to remove just wont cut it.

thanks for the suggestions guys

[keebler303]

If your o-ring is too stout, your part may not sit very solid on your fixture, basically allowing it to roll around on the o-ring. Also, the only thing holding your part in place is friction. It looks like the contact area is very small so you might not get a lot of friction. It might work better to have a small waffle pattern inside your oring so you have some grooves to make sure the vacuum gets to the whole surface but also some more support for it to help hold it still.

It is not possible to get any more holding force. atmospheric pressure is ~14.7psi so that times the area of your part inside the o-ring is the max force. Looks like maybe 10lbs in your case.

[rowbare]

I am not sure if it is possible with what you are doing but using mitee-grip, you could put down a sheet of material and cut out a large number of items at once.

bob

[victorofga]

part is so small that the vacuum can not be sufficient..

I fyou were finishing up parts comes from press, then make 2 side with simple clamping

and 2 angled side in softjaw..

if you were work of sheets, then best to cut ""strips"" as wide as the part tall.. and as long as your vise wide..

then in softjaw cut the angled sides..

in my opinion this vac experiment took atleast time as you could make 50 of this part..


================================================== ================

one more thing you can try, if you want to go anyway with vacuum, cut a thin rubber as not only work as a seal, but between the two surface, so part can not slide so easy..

imagine this rubber seal same shape than your trapezoid part, but in the middle a hole like 30 percent of the area...
cut it off something like a rubber glove?

==========================================
just like kebler saying, the vacuum can not be raised no matter how strong is your vacuum.. its only the atmospheric pressure..

the force is less than if you were press with your finger..

[dbtoutfit]

I have had to deal with this exact same issue.

One day Baxter the robot (same guy on Solidworks splash screen 2014) came to visit they were trying to sale me (I was a automotive manufacturing engineering manager at the time) and we were using venturi pumps.
Baxter has different end effectors, and one is a suction cup powered by a med size venturi pump and it held small half dollar and larger items very well.

I purchased some suction cups made for vacuum and kept our failed fixture with rope gasket like yours and placed the suction cups in the center. The suction cups set a little higher than the gasket and when you open the vacuum it pulled the part down tight on the rope gasket.

If you looking for something for 20 or less pieces then this may not be practical.

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