Vacuum table Setup Advice

[Lee Roberts]

My friend Ralf use's one of these pumps http://m.ebay.co.uk/itm/271844104827 for his diy vacuum system quite successfully, below is the build video from his youtube channel:

https://youtu.be/viVbB5mzSaw

There are some other videos there too, detailing his machine and the vacuum setup.

.Me

[JAZZCNC]

What your cutting also plays a big part here.!
That setup Lee linked to is great for wood etc with larger area and he's made a cracking job of it. But with small parts and high cutting forces on material like Ali or steel then it would struggle I reckon.
It's horses for courses really. If your cutting hard materials then you'll need good well sealed high vacuum and/or select your cutting parameters carefully.

[andy_con]

am I right in saying all I do is connect the vacuum table to where the compressor sucks air into to fill up, open the oil drain value (which releases air from the compressor) turn the compressor on and it have suction?

I just need to find a good balance between the amount of air coming out of the compressor and the amount being sucked in?

so would something like this do

http://www.ebay.co.uk/itm/SILENT-TYP...item33a7ebc3c1

Couldn't do what.? Was you referring to my suggestion because Big is good when it comes to a vacuum generator.
The cyclinder doesn't need to be massive just strong to handle the vacuum. Your only creating a reservoir of vacuum to help with the intial suck down and to save the compressor or vacuum pump from running all the time.

Like a Compressor has Preassure switch you can get a Vacuum switch that does the reverse and switches on when vacuum drops below set amount.

For small parts like this you don't need high volume but do need High vacuum pressure so a small tank pulled down to high vacuum will work. With small part like this you will be better with sealed around the part setup rather than pulling a whole area of a plate which will waste some vacuum.
That Vacuum fixture plates is ok for wood and larger pieces that fill most of the area but for best hold down you'll be better with grid system and seal just the area your using.

[andy_con]

yeah I'm machining ally and all the way through

What your cutting also plays a big part here.!
That setup Lee linked to is great for wood etc with larger area and he's made a cracking job of it. But with small parts and high cutting forces on material like Ali or steel then it would struggle I reckon.
It's horses for courses really. If your cutting hard materials then you'll need good well sealed high vacuum and/or select your cutting parameters carefully.

[JAZZCNC]

yeah I'm machining ally and all the way through

Well there's your problem doubled then.!! Soon as you cut thru you release vacuum. So even more vacuum is required. IF the remaining area is small you'll need high vacuum to hold onto it.

Really with small parts then vacuum is only any good if you have dedicated jig that will hold full high vacuum in areas of the parts that don't cut thru.

End of the day it's logical if you think about it. Surface area is the key, so if the part is small there's much less area to hold onto so higher vacuum pressure is required to hold it but less volume needed. Large parts have more surface area so a lower vacuum pressure can hold it because there's more to hold onto. Start cutting thru and large area then volume of vacuum required is more but cut too much and at some point the pressure will drop and you'll loose grip.

[andy_con]

this is my goal, datron make it look so easy...



datron make it look dead easy



I was just testing with a small bit of scrap ally I had, but what I actually want to machine is 250mm by 160mm by 5mm thick.

Well there's your problem doubled then.!! Soon as you cut thru you release vacuum. So even more vacuum is required. IF the remaining area is small you'll need high vacuum to hold onto it.

Really with small parts then vacuum is only any good if you have dedicated jig that will hold full high vacuum in areas of the parts that don't cut thru.

End of the day it's logical if you think about it. Surface area is the key, so if the part is small there's much less area to hold onto so higher vacuum pressure is required to hold it but less volume needed. Large parts have more surface area so a lower vacuum pressure can hold it because there's more to hold onto. Start cutting thru and large area then volume of vacuum required is more but cut too much and at some point the pressure will drop and you'll loose grip.

[JAZZCNC]

this is my goal, datron make it look so easy...

datron make it look dead easy

Argh.!! . . It's Dangerous watching expensive Pro-level machines because you have a lot of specialised and expensive things there all working together to make it look that easy. Which are not always obvious.!!

First there is a high power Vac pump or system designed to cope with the vacuum loss doing the sucking. The Vac table is a high Density hole pattern table type optimised for holding small parts. Then you have fact they are using special permeable Matt systems like VillMill which has a adhesize layer to help hold it down and distribute suction evenly.
Then quality 60,000rpm spinlde taking relatively small DOC at high feeds rates with quality Carbide tooling connected to a sophisticated cooling system greatly helping ease things along.!

Now I'm not saying milling small parts can't be done but it is a different ball game to larger pieces with more surface area so requires certain methods to be employed. Or Buy expensive Vacuum systems like Datron offer designed to cope with it.!

Can't just throw it on standard table with relatively low pressure sucking directly from the pump then cut thru it or take heavy cuts and not expect it move.
If it was that easy we'd all just use Henry's and Vacuum table for holding every thing.!!

[andy_con]

Im well aware datron stuff is in a different league, I have their price list and know how expensive the kit is



am I right in saying all I do is connect the vacuum table to where the compressor sucks air into to fill up, open the oil drain value (which releases air from the compressor) turn the compressor on and i have suction?


I just need to find a good balance between the amount of air coming out of the compressor and the amount being sucked in? Or buy that digital gage


so would something like this do

http://www.ebay.co.uk/itm/SILENT-TYP...item33a7ebc3c1


How do I work out if a compressor will give me the required suction?


Vacuum tables UK sells mats without holes in, so could this be another possible improvement?


http://vacuumtables.co.uk/product-ca...-and-mats/mat/

[Boyan Silyavski]

As Dean says- be reasonable.

Now you know, the most important thing is to find the most sticky mat possible. I would go further and say that best result is a combination of screws and vacuum, hence, custom fixture for each part done in quantity. I also have thought to make the sticky thing from casting silicone gasket in shape if necessary

Not trying to sell, but if you have a total of 30 euros to spare, i can send you a slightly used brand pressure switch with digital pressure readout and analogue 5v output, which new goes for around 80-90euro at least. PSA4-102VP. I have 2 of them if sb needs. so you could use it to read negative pressure, switch on off compressor by relay / if additional deposit for vacuum, and so on...

as i said any 1hp-2hp air compressor, take out inlet filter and fit there vacuum hose. Usually 3/8" adapter. Rarely 1/4". At the output fit some connector so the compressor blows out at all time, without switching off. Furthermore a vacuum deposit made from propane bottle could be fitted between vacuum hose and air inlet, plus the switch could stop compressor when desired negative pressure achieved. So electricity is saved.

[andy_con]

ok so mat important, I may have to buy a few and test them. not a problem

screws are a no, if it cant be done 100% by the vacuum table then I wont be doing it. like I say part size is 250mm by 160mm by 5mm thick

id rather have the vacuum table completely separate from mach3. but thanks for the offer.
ok will see what compressor I can find for a cheap price. does the size of the tank on the compressor matter? or is it just the power that's important?

sorry but I don't get the purpose of the propane bottle? do I really need that?

As Dean says- be reasonable.

Now you know, the most important thing is to find the most sticky mat possible. I would go further and say that best result is a combination of screws and vacuum, hence, custom fixture for each part done in quantity. I also have thought to make the sticky thing from casting silicone gasket in shape if necessary

Not trying to sell, but if you have a total of 30 euros to spare, i can send you a slightly used brand pressure switch with digital pressure readout and analogue 5v output, which new goes for around 80-90euro at least. PSA4-102VP. I have 2 of them if sb needs. so you could use it to read negative pressure, switch on off compressor by relay / if additional deposit for vacuum, and so on...

as i said any 1hp-2hp air compressor, take out inlet filter and fit there vacuum hose. Usually 3/8" adapter. Rarely 1/4". At the output fit some connector so the compressor blows out at all time, without switching off. Furthermore a vacuum deposit made from propane bottle could be fitted between vacuum hose and air inlet, plus the switch could stop compressor when desired negative pressure achieved. So electricity is saved.