Vacuum Chuck

JimDawson

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My son is working on a project and decided that the easiest way to hold the part is with a vacuum chuck, due to the part final size there is no other really practical way to hold it. Because of some other considerations, glue or double sided tape was not practical to use in this case.

But of course not to be content with just any old device, this one has to have a universal base with interchangeable and sacrificial top plates, and can be held in the vice or clamped to the table. So.......

The base was made from 2'' thick 6061 about 9'' x 5.5'', left over from a job. The top plate is 1/2'' 6061, also leftovers, machined to fit in the base pocket. There is an O-ring to seal the vacuum between the two pieces.

Once installed, the top plate is faced off, then the vacuum channel pattern is milled in as needed for the part. Since the vacuum channels are very shallow and the back of the plate is supported 100% by the base, these top plates can be faced off and used for the next project if needed. Or if you have a recurring job, then all you have to do is select the correct premade plate and you're off and running.
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The chuck in the mill with the plastic blank in place.
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Another top plate blank.
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And the fixture for making the top plates. The fixture screws down to the tooling plate that is pretty much permanently bolted to the machine table. This allows very quick setups because all of the fixturing is designed to fit the tooling plate bolt patterns and locating pins. Once set up, it only takes a few minutes to crank out the top plate. I think he made a half dozen or so.
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A full 3D view in the A360 online browser based viewer https://a360.co/2GkeXuA

The top plate
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The assembly
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Then powering up the system: The Harbor Freight 3 CFM vacuum pump. (Shown with its optional auxiliary cooling system) :grin:
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You'll note the professional vacuum line routing :) We didn't want to cut the tubing. 1/4 inch nylon tubing.
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and another shot of the vacuum line routing
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Over all the system works well, and seems to do a fine job of holding the plastic parts in place. Haven't had one slip yet. If needed, stop pins or a pocket could be added to the top plate. Total out of pocket was the cost of the HF pump with a 20% off coupon, had everything else on the shelf, leftovers from other projects. We do have a 3 phase, 3 HP vacuum pump on the shelf, but it would have been more trouble than it's worth to set up for this project, not to mention way overkill.
 
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Latinrascalrg1

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Very interesting! Is there a need for any intermediary Membrane of some type to keep the vacuum intact during use or is it necessary to have perfectly flat surface holding dimensions? What vacuum pressure will it reach and what is the minimum pressures required for your purposes?
Thanks in advance for sharing.
 

JimDawson

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Very interesting! Is there a need for any intermediary Membrane of some type to keep the vacuum intact during use or is it necessary to have perfectly flat surface holding dimensions?
Just a flat surface seems to be working OK. The parts blanks are pretty flat to start with and then are lightly faced both sides before any real machining is done.

What vacuum pressure will it reach and what is the minimum pressures required for your purposes?
Thanks in advance for sharing.
The minimum pressure required is unknown. We checked the vacuum with an automotive tuneup vacuum/pressure gauge and it pegged it out. I don't have an A/C gauge set here to have a good read on the pressure, but it is better than 30 inches, the pump is rated at around 22 microns.
 

Eddyde

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Nice job!
I used to make vacuum hold-down jigs when I had the custom woodworking shop, they were usually made of MDF with a couple coats of lacquer to seal them up. As a gasket, Polyurethane foam weatherstripping was used in a shallow channel around the perimeter or I would coat the top of the jig with contact cement and let dry thoroughly. Often these were used to send thin parts through a wide-belt sander, never had one slip.
 
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