[garagefela]

Hello all,
At the moment my router is still in the planning stage and will of the moving gantry style, I would appreciate some feedback on my plan to use a vacuum table and any cheap alternatives for a vacuum pump.

Most of the work to be done on the router will be various shapes to be completely cut out of mdf sheet ranging from 3mm to 12 mm using as small as possible dia cutters.

The only way I can think to do it is to have a vacuum table with sacrificial top boards made of mdf these would be dedicated top boards to cut out particular shapes.

Eg, I need to cut out 50 small cats out of a sheet I would place the sacrificial sheet which has the 50 cats already outlined on it.

What do you think about that?

Where can I obtain a vacuum pump for this duty? I believe a normal vacuum cleaner will only pull about -10 kpa vacuum or approx -1.3 psi, possibly not enough as some of the parts will not have a big surface area.

Has anyone "made" a vacuum pump out of any sort of pump or compressor?

Thanks very much. Michael

[buscht]

http://www.joewoodworker.com/veneering/makingbags.htm

This technology could easily be transferred over to your application. He goes through step by step on how to make a vacuum press and where to get components.

Good luck

[turmite]

garagefela there might be a better way than vaccum if these parts are real small. In addition if they are actually cut from mdf you will have to seal them or your vacuum will pull right through the sheet. Use material that is a few thousands thickerand do not cut all the way through the sheet. Run the sheet through a wide belt sander to remove the excess material and bingo!

Mike

[Cantabrianz22]

Hi there,
I made a low cost vacuum pump out of a car airconditoner pump, an old 1/3 hp
electric motor and a gas bottle. The pump has a magnetic clutch that I powered
with a 30 year old battery charger. The clutch is dissengaged so the motor
can start easily powering the pump via the rubber V belt. The pump can extract
air to 90%+ vacuum. I also swapped the hoses over to see how much it
would compress air...the pressure got dangerously high (6bar) so I turned it
off quick! I used a small gas cylinder for the vacuum pressure vessel, it
really is too small, I recommend a 9kg gas bottle or bigger. I realised a pure
vacuum is only one atmosphere (naturally) lower then that we live in so you
can't fit much of nothing (a vacuum) in it. Whereas an air compressor
compresses many atmospheres into it's tank. The next thing I need to do
is make the pump switch on and off automatically and automatic pump oiling.
Steve

[CNC Pro]

When I was ordering my first CNC Router, I opted not to get the 5hp rotary vane pump offered, and sought something more economical than the $8,000.00 option.
What I found has been serving me well for nearly 5 years of production time.
My shop is located in a rural part of the state surrounded by dairy farms. I contacted the local milk pump dealer to see what might be available, to my surprise he informed me that he has been hauling used vacuum pumps (by the truck loads) to the salvage yard. Apparently, as farms have increased in size, and demand for larger pumps (20hp +) has made the smaller units obsolete.
I purchased (1)-reconditioned pump with 20-gallon reserve tank, oil reclaimer, on the stand for $500.00. It’s powered by a 3-hp 220v motor and even came with a 1-year warranty. I also purchased 3 used pumps for $75.00 one of which I’ve fitted with a 1hp 120v motor that I’ve fitted to a sheet vacuum lift I designed for loading full sheets of material on the CNC’s.
The 3-hp unit performs so well that I’ve connected it to the second CNC with no drop in performance. Parts are readily available and very economical.

[CNCRob]

Here is a thread I stated a while back about my vacuum table http://www.cnczone.com/forums/showthread.php?t=17535 , But I think you would need a lot stronger vacuum than the one I used to pull through the sacrificial to boards unless you sealed them off some how.

[belli]

Hi garagefela,

I made my 'vac-clamps' from off cut pieces of PVC, look at this thread to see the pictures:
http://www.cnczone.com/forums/showth...t=33585&page=2
They cost about $4 each and the vacumm generator (venturi) about a further $20.

Cheers,
Greg

[darde]

cnc pro
I have a couple of milk pumps also. I have not got them installed yet.
Do you have them with a spoil board that you draw through or with vacumn pucks.

[CNC Pro]

Hey darde,
Both of my routers have grid type tables. But, I’m designing an auxiliary table and pods that I can simply drop on the grid top. I’ve been able to secure thin materials by simply using MDF spoilboards, for more complex or thicker materials, I dedicate a spoilboard with either adhesive backed vacuum seal or the corded type.
I hope your milk pumps have the oil reclaimers, my first system didn’t, and I was going through gallons of oil a month (not to mention the mess). My latest pump has the reclaimer, and I’ve only used about 2-1/2 gallons in more than 2 years running 12+ hours a day.

[darde]

I would like to see some pictures of your grid top or some info if you don't mind on your pod system. I have looked at doing somthing like that also.

[mattgill]

Our vacuum pump is 1.5hp, and under optimum conditions (valve closed), will pull 29" of vacuum. We've been able to suck a 3/4" mdf spoilboard (16"x 24") tight to the gridded table (of a Haas SR 100), with about 12" - plenty to hold it tight.

When we put a spoilboard 4x larger than that on the grid, the vacuum is only about 5" - too low for my taste, both for solidity and safety. (in large part due to more porosity in the greater surface area of mdf...)

So my question is this: If I add another 1.5 or 2.0 hp vacuum pump to the same vacuum line (basically having two vacuum pumps running simultaneously on the same vacuum pipeline), will they *fight* each other, or will they move twice the volume of air, and hence create a higher vacuum (double?) amount?

-Matt

[ger21]

Depends on if the line is large enough for the CFM that you're trying to pull.

[mattgill]

I'm thinking it is, but haven't done the calcs:
20 CFM per vac pump x 2 = 40 CFM through 3" pipe. Assuming the pipe dia. is big enough (I can make it bigger), it seems to me that the cfm's and inches would add together. Reasonable line of thought?

Thanks!
-Matt

[ger21]

One thing you can do is cover areas of the spoilboard that are not being used. You need to use something that's not porous, like maybe a sheet of acrylic, or melamine coated board.

[RomanLini]

I'm curious why people need a bazillion horsepower vacuum pump? Even a low performance $50 home vacuum cleaner pulls a couple PSI under atmospheric, so that is a couple of pounds pressing down on every square inch of the material. With larger sheets especially there would be thousands of pounds holding the stock down.

Is it an issue with cutting many small parts completely out of the sheet, so the vacuum is compromised by all the cut area before the job is done?

[rowbare]

Is it an issue with cutting many small parts completely out of the sheet, so the vacuum is compromised by all the cut area before the job is done?

That is pretty much it, with the really big pumps, you don't have to worry as much about breaking the vacuum seal where as with a vacuum cleaner, as soon as the cutter goes through the material you have problems. The big pumps suck so much air that they can maintain vacuum in spite of leaks (within reason).

bob

[ger21]

I'm curious why people need a bazillion horsepower vacuum pump?

Mainly to keep the CFM up.

It's possible to use a smaller pump, but you'll need dedicated fixtures with minimal leakage. Keep in mind that if you cut MDF or particle board, you'll lose vacuum right through the parts, whether you cut through or not.

You also need to overcome cutting forces, which will push your parts around, rather than cut them.

High powered pumps are mandatory for production cutting of sheet goods, like building cabinets.
We have 2 25HP pumps on a 5x12 table. We used to use a 5x10 spoilboard, but I switched to a 5x12 because changing it to cut 12ft parts took too long. But the 5x12 gives about a 20% reduction in vacuum.
Our table has digital vacuum gauges, and I can see the vacuum drop with every few inches of cutting.
Even with the 2 big pumps, anything under 250sq inches is onion skinned. .008" is left and cut with a second pass. This is undesirable, because you're cutting everything twice. But it's better than having to re-cut damaged parts.

[RomanLini]

Thanks for the info.

[chicken1]

hi im new on here and thinking of getting a cnc for my home "hobby" projects. i work for a cabinet factory and we have 2 komo cnc's 5x10. we have a compressor foreach i think there 50 horse but any way we used mdf spoilboard for 4 years then we tried LDF wich is less dense of coarse and it gave us at least 10-15 pounds more psi to hold parts. we have cut mat 2" thick 4x4 square with multi pases of corse but ldf works well if u can try that it might help get more vac.and yes we block off the rest of unused table with scrap ply hope this helps

[Rmurph]

There's been mention of sealing sacrificial boards on here, and I wanted to offer my technique: 1 - use the same dimensions for your spoilboard, and your product material (for me it is invariably 4x8 sheets of mdf which are usually actually 49" x 96.875"). 2 - roll 2 coats of white glue (like Elmer's) along the edges of the spoilboard, followed by 2 coats of primer. This gives an air tight seal and you can reuse your spoilboard for many cuts. Note - it is ideal to use a wide resurfacing bit to mill away the top 1/16" or so of the spoilboard. This a) improves suction since the original surface of the mdf is treated in some way that impedes the suction more than a naked layer of mdf. And b) ensures that your working surface is level in every way in relation to the router itself. So if your Z Axis is a hair higher at 48" on the X Axis than it is at 0" on the X Axis, this makes the surface identical and the imprecision won't effect the product.

Hope that helps anyone on here! = D