Vacuum Hold down for wood.

[HomeCNC]

Does anyone know anything about building a vacuum hold down setup? I would like to have one for my CNC router I am building. I know I will need a vacuum source. I just got a vacuum pump on Ebay.

Should I add a tank to this so I have a resovoir of, I guess (no air)? How do I build the vacuum plate that will hold the wood?

[CNCadmin]

One way is to make a air tight box that has many 1/16"-1/8" holes in it. Than a very strong vacuum source. You can place tape or alike around the object to provide max suck. A industrial vacuum clearner I belive would work.

[balsaman]

I have heard you don't need the little holes. Just use a MDF box. The mdf is porus and will hold the part. Use 3/8" or 1/2" MDF on the top. Add supports inside the box to keep the top flat under the suction.

Eric

[CNCadmin]

Originally posted by balsaman
I have heard you don't need the little holes. Just use a MDF box. The mdf is porus and will hold the part. Use 3/8" or 1/2" MDF on the top. Add supports inside the box to keep the top flat under the suction.

Eric

Yes,but that will take alot of vacuum.

[Laff Riot]

Call a local sign shop. Ask for a piece of Coroplast that is scratched and unsellable. If they try and charge you more than 15 bucks look for another one.

Coroplast is basically plastic cardboard. If you have ever seen a Real estate or Polical sign up close you know what I mean. Coroplast has a series of hollow tube flutes 1/8" that run the length of the material. Block off one end of the coroplast with Duct tape. Grab a shop-vac with the wide pickup nozzle and using a copious amount of duct tape and cardboard seal the other end onto the shop-vac nozzle.

Use your CNC machine to pop a couple hundred holes into the Coroplast tubes for the vac.

You now have independently suctioned tubes. You can block off sections with tape when not in use. Make sure you allow enough air into the shop-vac to not stress out the motor - you can always block off holes again. Block only as many holes as needed to give you hold down. On the plus side you also get dust collection

If the coroplast does not have a smooth enough surface for the type of work you want to do ask the signshop for AlumaCore. It is the same thing as coroplast except that it is skinned with .020 aluminum on the face and back and the tubes are about 1/4" thick. Absolutely smooth. About double / triple the cost of corpolast though.

The coroplast is cheaper but IMO go for AlumaCore if you can get it. If you cannot find either locally I can give you a list of suppliers.
Let me know the type of materials you mill - I have several specialty bases that I built to switch out in seconds on my work system. If you need a sketch, gimme a shout.

[balsaman]

Yes,but that will take alot of vacuume.

He said he bought a vacuum pump, which is perfect for this setup. A vacuum pump is usually low volume, so the holy board doesnt usually suit it. The holy board is better for a shopvac, as you pointed out.

Eric

[hardmill]

Give me a day and illl sketch something for you.
What size are you looking at.
Not much vacuum is req. Ill let you know what you
need, pretty simple actually.

[ger21]

I work in a commercial cabinet shop with a large cnc router with a vacuum pod system. We have a VERY large pump and it will draw through MDF a little, but not enough to hold parts still. Most large commercial routers that draw through MDF spoilboards use even larger pumps. I'm not sure exactly how they are rated, but these pumps are larger than the cnc's we're talking about here and VERY expensive. I think I have a better solution. Last year I built a vaccum veneer press with a compressed air powered vacuum generator for under $100. This will draw much more vacuum than a shop vac. Go to http://www.joewoodworker.com for the article on how to build it. Then get a copy of ShopNotes issue 40, which has plans for various hold down jigs and a vacuum table, which should be a good starting point for a cnc vacuum hold down table.
http://www.shopnotes.com/
This is what I plan to use on the router I'm getting ready to start building.

Gerry

[HomeCNC]

Thanks to everyone for the advice on vacuum clamping. I have also been searching the Internet and have found some information.

Gerry, I have been a subscriber of Shopnotes for about 3 years now. I have that issue and forgot about it!!!

This site has some vacuum plates that they sell. I like the way they use the vacuum tape on plastic plate. Just make one ¼” hole and with creative use of the vacuum tape you can open gates or close them to fit your work size.
http://www.qualityvak.com/kaccess.html

[HomeCNC]

This is my idea for my Vacuum hold down plate. I will start with two plates that are 12" X 24" X 3/8" Alum. (I was going to have a 24" X 24" until I saw the price!!) I cut an o-ring grove in the lower plate (you can get o-ring stock in a roll from McMaster Carr). I drill a cross hole and place a hose barb in it. I make a 1/8" pocket in the upper plate so I have a vacuum chamber inside the two plates. I drill and thread 1/4-20 holes in a 2.25" hole pattern in the top plate. I plug the holes with rubber sealed cap screws. Now I built about 10 or so, small clamping plates that are about 2" square and 1/2" thick Alum. I cut an o-ring grove in both sides and drill a 1/4" hole through the middle of the plate.

To use this thing I just remove a screw and place a clamp plate over the screw hole to receive vacuum. This gives me the ability to create vacuum hold down shapes where I need them.

[CNCadmin]

Very nice that should work very well!

[paulried]

Here is one I saw while visiting ShopBot in Raleigh, NC. Pretty simple and hooked up to a vacuum cleaner. The plate at the front is what regulate the amount of vacuum. The grooves where sealed with clear varnish bottom and side. The parts are caulked together to avoid vacuum leaks.