Vacuum table Setup Advice

[andy_con]

My compressor in very big so probably couldn't do that

Work peice was 100 by 120 mm

[JAZZCNC]

My compressor in very big so probably couldn't do that

Work peice was 100 by 120 mm

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.

[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]

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]

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.