Vacuum Chuck design

[JDona]

Wanted to experiment of making a vacuum chuck to hold a small part I need to make.

I got a dedicated single-stage Vacuum Pump (4.5CFM) which in theory should be enough.

The pocket for the 1/8 Soft Neoprene is 0.1" deep and 1/8 width

When I test it, I can't lift up the workpiece at all so I know there is a good vacuum there, but sliding it sideways is easy.

Does this mean the 0.1" o-ring pocket needs to be a little deeper?

Appreciate any input from anyone who did these before.

Cheers

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[kstrauss]

How big is your "small" part? Realize that the holding force is a maximum of only 14.7 pounds per square inch.

[popspipes]

I machine wood puzzle blocks on a home made vacuum fixture and I use locating pins, as holes in the backside of the parts are OK.

[Steve Seebold]

I use a sylicone that I get from McMaster part number 9627T12

I machine the parts ckets 1/8 inch wide by .100 deep and I have never had a part move on me.

[popspipes]

I use silicone tubing, it is hollow and flattens out under vacuum and gives more surface holding area, Mc Master sells it.

[JDona]

Thanks guys,

How big is your "small" part? Realize that the holding force is a maximum of only 14.7 pounds per square inch.

The chuck is 4.3" x 2.3".

I use a sylicone that I get from McMaster part number 9627T12

I machine the parts ckets 1/8 inch wide by .100 deep and I have never had a part move on me.

That's Durometer 60A. I am using 1430K55 which is Durometer 50A, which is softer. So could it be that? My pocket is the same as yours. Are you able to rotate the stock around the chuck? I can, with a slight force, but I can't lift the stock up with hand-force at all.

I don't believe the bolts to secure the chuck to the T-Slot table are leaking, but I wanted to do another chuck with a flange to hold the bolts or clamps outside the vacuum area, so thought I come here for inspiration and ideas before milling the second chuck.

Will keep 0.1" & 1/8 width pockets. I am assuming I don't need more contact points between the chuck and the stock as the idea to have more contact points between the bottom surface of the stock and the vacuum area.

[skrubol]

Can it slide freely, or just a mm or 2? How 'sticky' is the gasket you're using? The 100 lb of holding force you've got does nothing to hold the part from sliding if there aren't alignment pins or a high-friction surface. If it only slides a little bit, your o-ring grooves are probably a hair too wide and the gasket is rolling.

[CadRhino]

The mistake I made was using a 1/8” Ball em instead of a straight sq em.


QUOTE=JDona;2212360]Wanted to experiment of making a vacuum chuck to hold a small part I need to make.

I got a dedicated single-stage Vacuum Pump (4.5CFM) which in theory should be enough.

The pocket for the 1/8 Soft Neoprene is 0.1" deep and 1/8 width

When I test it, I can't lift up the workpiece at all so I know there is a good vacuum there, but sliding it sideways is easy.

Does this mean the 0.1" o-ring pocket needs to be a little deeper?

Appreciate any input from anyone who did these before.

Cheers[/QUOTE]

[JDona]

No, it does not slide freely, a constant force on the corner of the stock will make it rotate or slide. I see about the alignment pins. The idea is to be able to mill fully around the part in one op without having to flip the part or trace & tabs. Going to try to get a softer gasket to make sure it gets fully compressed.

Can it slide freely, or just a mm or 2? How 'sticky' is the gasket you're using? The 100 lb of holding force you've got does nothing to hold the part from sliding if there aren't alignment pins or a high-friction surface. If it only slides a little bit, your o-ring grooves are probably a hair too wide and the gasket is rolling.

The mistake I made was using a 1/8” Ball em instead of a straight sq em.

I am using straight sq em. Thanks for the input.