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Old 06-07-2018, 10:25 AM
Jim_in_PA Jim_in_PA is online now
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Default Vacuum Fixture for Small Sign Production

This week I started to move forward on setting up for a small sign thing for equestrians after making some prototypes that I like. Because these will be personalized, I needed a work holding setup that was accurate, quick and secure. Vacuum is excellent for this and that's the route I chose. I happen to have a nice Gast vacuum pump that I've owned for many years for lathe work. It's not appropriate for larger CNC tasks, but perfect for fixtures that hold smaller workpieces. So I relocated it from the lathe stand to under the CNC machine and then proceeded to create my fixture for these small signs.

I chose to use some Corian scraps for the fixture...no leakage, easy to cut and very durable. I created the design in VCarvePro, starting with the existing prototype sign profile to provide a recess that increases lateral hold and then milled an air chamber and gasket groove. The end result...



Since I need provide for an air path from a connection to the vacuum pump, I setup for a double sided job using indexing pins so I could flip the workpiece and route a groove in the underside of the top layer to provide for that path. Note I stopped this groove shy of the edge so its essentially asymmetric nature wouldn't interfere with drilling a 1/2" hole in from the edge for the air connection.



I then used Gorilla glue to laminate the machined piece to a second piece of Corian, using cauls to insure things stayed absolutely flat. Once that cured overnight, I cleaned up the edges and then drilled my 1/2" hole for the threaded air connection. Theoretically, I should have used a slightly smaller drill bit and then tapped the hole, but I'm not setup with tooling for that, so I decided that I'd get just enough bite from the threads cutting their own and then the epoxy would insure everything stayed tight and sealed. And that turned out to be accurate, especially since the nature of vacuum pulls the connector tighter, rather than the opposite as it would with compressed air.



Interestingly, when I tested the holding power, even without a gasket installed (material arrives tomorrow), I could not pry the sign blank off the fixture even with a flat screwdriver.



So this is setup job one ready to go. I have a few more things to work on before I start offering actual product, but I'm happy to be making progress. I'm setup with the local Corian distributor, too. I seem to be getting pretty comfortable with the toolpathing aspect of these simpler projects and get get through a design and set of cutting files pretty quickly at this point. Still "walking" before "running", but going in the right direction.
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SR-44 (2018), 1.7kw spindle, Performance Premium, USB, Keypad, T-Slot table (y-axis configuration), WinCNC, VCarve Pro

Non CNC stuff...

SCM/Minimax - slider/JP/BS
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Retired from full time work in the telecom industry 9/2017
Commission work for equestrian tack storage and other custom furniture and cabinetry
Located Bucks County PA
http://bvww.us
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  #2  
Old 06-07-2018, 06:21 PM
de5 de5 is offline
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Good job Jim, That ought to work well. Is there any reason you made it so much bigger than the sign? I'm cheap and try to cut the corian closer than that.
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  #3  
Old 06-07-2018, 07:38 PM
The real JP The real JP is online now
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This pic is a bit extreme but a few of these could help you work with many different sized pieces. You could make some flat ones out of mdf and paint them to seal them as well.

Painted mdf is what the vacuum tables are on the non phenolic camaster machines.

You don't need a block the same size as the project unless stiffness is an issue.

Just an idea anyway.
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  #4  
Old 06-07-2018, 08:13 PM
Jim_in_PA Jim_in_PA is online now
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Quote:
Originally Posted by de5 View Post
Is there any reason you made it so much bigger than the sign? I'm cheap and try to cut the corian closer than that.
I guess in an ideal world I could have made the fixture smaller, but I used the two pieces of scrap in the size they were already cut to by their former owner...Mr. Outten. :) In one sense, there's an advantage to this size in that it allows me to use the tee track clamps to hold it down in the center portion of my table and provides plenty of room to work by both the human and the machine. The mass isn't a horrible thing, either.

I still can't get over how secure this setup holds the workpiece and I anticipate I'll use this method for other things I decide to produce that require customization/personalization. In this case, the job is stall plates for equestrians...horse and owner name. There will be a standard graphic, but for "a little more money", a custom graphic can be part of the deal, too.

----

JP, that's a pretty crazy looking setup! But yes, the "puck" method can provide a lot of utility for all kinds of work.
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Jim Becker

SR-44 (2018), 1.7kw spindle, Performance Premium, USB, Keypad, T-Slot table (y-axis configuration), WinCNC, VCarve Pro

Non CNC stuff...

SCM/Minimax - slider/JP/BS
Festool "a good collection"
Stubby - lathe
Oneida Cyclone
more...

Retired from full time work in the telecom industry 9/2017
Commission work for equestrian tack storage and other custom furniture and cabinetry
Located Bucks County PA
http://bvww.us
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  #5  
Old 06-08-2018, 08:27 AM
tbrookins tbrookins is offline
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I love that design. I will be using your idea for sure!
thanks for sharing
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  #6  
Old 06-28-2018, 05:27 PM
Jim_in_PA Jim_in_PA is online now
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I had the opportunity to test this fixture today while fleshing out the personalization tool path setup for the signs that will come off of it. It held really well while doing the v-carving, even considering that the material I was working with was "more porous" than the Corian will be. Setup is simple with a couple of steel rods to register square with the bed and then a quick x-y zero via the laser to set the center point. The test cut was "very crispy" using an Amana insert 60 V-bit and didn't move an iota. The tiny lip in the fixture combined with the vacuum works great to hold the blank in place.

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Jim Becker

SR-44 (2018), 1.7kw spindle, Performance Premium, USB, Keypad, T-Slot table (y-axis configuration), WinCNC, VCarve Pro

Non CNC stuff...

SCM/Minimax - slider/JP/BS
Festool "a good collection"
Stubby - lathe
Oneida Cyclone
more...

Retired from full time work in the telecom industry 9/2017
Commission work for equestrian tack storage and other custom furniture and cabinetry
Located Bucks County PA
http://bvww.us

Last edited by Jim_in_PA; 06-28-2018 at 08:45 PM.
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  #7  
Old 06-28-2018, 11:16 PM
Charlie_L Charlie_L is offline
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Jim,
Looks like you are having fun.
If you want to eliminate the xy laser zero I think having a home position saved would accomplish that for this operation.

When I save my home positions I find it best to NOT save the z setting, leave that blank.

For what it is worth,
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  #8  
Old 06-29-2018, 08:40 AM
SCHEPEBC SCHEPEBC is offline
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Not sure if this helps but if you create a program with two holes to be drilled and then in your separate program file for your sign, so your x y zero is the center of the one dowel/pin hole, then put those two points in you other program and hold the zero with the same pin, you shouldn't have to use the xy laser. Basically you would pull up the "pin location" program and run it wherever on your table, then slip the pins in and put your vacuum top on and secure it down. Open the "sign program" and everything (in x and y) is zero'd out already since you kept the same zero point (dowel hole). Now the vacuum fixture is zero'd relative to the dowel pin centers in x and y and all you have to worry about it Z. I hope this makes sense haha. I found my laser isn't super accurate and if you do it this way and use a tight slip fit dowel/pin, you are holding off the machine tolerances and not your eye with a laser. You probably have some movement you can allow, but times that you can't, it helps out greatly. Hope that it helps. Fixture looks good though!
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  #9  
Old 06-29-2018, 09:45 AM
Jim_in_PA Jim_in_PA is online now
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Charlie, thanks for the reminder on saving the position...very doable and it will be done...today. :)

SCHEPEBC, I already have the steel locator pins there specifically to place the fixture in exactly the same position every time. They are only into the spoilboard until the fixture is clamped down. Those holes were drilled at the same time as the fixture was created. I've not had any issues with the laser being variable accuracy...if anything, it's my eyes. :) But Charlie's mention of saving the position means I won't have to worry about it going forward. A minor variability for this particular production step wouldn't matter much anyway given it's just v-carving two lines of text on a pre-cut blank in "approximately" the same position each time. (the specific text is variable)
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Jim Becker

SR-44 (2018), 1.7kw spindle, Performance Premium, USB, Keypad, T-Slot table (y-axis configuration), WinCNC, VCarve Pro

Non CNC stuff...

SCM/Minimax - slider/JP/BS
Festool "a good collection"
Stubby - lathe
Oneida Cyclone
more...

Retired from full time work in the telecom industry 9/2017
Commission work for equestrian tack storage and other custom furniture and cabinetry
Located Bucks County PA
http://bvww.us
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  #10  
Old 06-29-2018, 10:38 AM
BradyWatson BradyWatson is offline
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As time goes on you'll most likely narrow your selection of jigs down. Along those lines, so you don't have a gajillion dedicated vac fixtures, you can use what I call a 'Vacuum Mask'. It is mentioned in part here, along with my own invention, the BradyVac (and BradyVac II). I also invented what is called 'Vacuum Film' which is great for holding small parts. Keep in mind some of these ideas are obsolete, but it's still a good reference for those who are learning about vacuum hold down.

By using a vacuum mask, you can direct vacuum under the specific shape you want to hold using any non-porous material. Just offset the profile of the finished part to the inside so when you cut through, you don't break the vacuum seal. It's much easier to store vacuum masks (and cheaper) than it is to store entire vacuum jigs.

For the base/plenum - you can use any non-porous material - OR seal MDF on the back and edges. Then machine a grid into it. It doesn't HAVE to be deep in order for vacuum to flow across it, but the depth should be considered for times when you want to use D-shaped gasketing that crushes down and creates a seal when vacuum is applied. This essentially means that you can snake the vacuum gasket material around the grid to confine the vacuum when the grid is larger than the part to be held. McMaster has D-shaped gasketing. Durometer matters...you want it to crush down to seal, but not so much that the part being held is sitting on jello.

For Spoilboard Cover mentioned in one of the articles, you can get that from AllStar Adhesives. Truth be told though, I haven't used gasketing on anything other than some shop-built vacuum pucks I 3D printed. Most of the time you can seal off a gasketless jig by rubbing in some sawdust from the surrounding area after you swap out the material blank.

Have fun playing with vacuum...which by the way, works in ALL directions. I have some pucks I made for assembly that hold a perfect 90 deg angle and other configurations.

-B
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