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Vacuum table Setup Advice
im after some advice on vacuum pumps for a vacuum table setup.
i want to do exactly this -
http://youtu.be/jDrRICZq4KQ
no idea if its the right sort of table, but been looking at this table as its the perfect size for my mill
http://vacuumtables.co.uk/product/va...ble-vt3020-gr/
would this pump do and im assuming im going to need a liquid seperator as my mill has flood coolant?
http://www.ebay.co.uk/itm/Robinair-R...c=1&rmvSB=true
thanks
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Re: Vacuum table Setup Advice
I think it should work. A friend has similar size pump and the plate you aim to use is fairly small.
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Re: Vacuum table Setup Advice
ok thanks
im assuming as im machining all the way through a vac-mat will be better as it wont suck as much coolant in and a proper holed matt?
https://www.hoffmann-group.com/GB/en...ats-1/p/385040
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Re: Vacuum table Setup Advice
It will not suck dust and metal, that's for sure, due to the micro holes. It will hold steadier also, due to friction.
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Re: Vacuum table Setup Advice
Quote:
Originally Posted by
Boyan Silyavski
It will not suck dust and metal, that's for sure, due to the micro holes. It will hold steadier also, due to friction.
how does it work with a normal holed mat? does the table suck metal into the pump?
(sorry ive never used a vacuum table before)
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Re: Vacuum table Setup Advice
Depends how fine is the sucking hole. Not the vacuum hole you see on pictures 3-6mm, but the real sucking hole in the vacuum hole center, it could be 0.5-1mm . Its a good idea the vacuum table to be made from 2-3 pieces and that could be dismantled for cleaning or repair.
http://www.mycncuk.com/attachment.ph...id=15901&stc=1
The vacuum table from the first link was ok and they have mats. any mat from superstore 2-5eur per meter will do the job, some experimenting is needed. cause they sell ridiculously expensive the mats.
Or just DIY around the vac-mat
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Re: Vacuum table Setup Advice
anyone know anything about these pumps?
http://www.mastercool.com/product/90...-single-stage/
seems fairly decent, says its designed for continuous use, there are many brand new ones on ebay so am rather tempted
I'm assuming 6cfm will be enough power?
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Re: Vacuum table Setup Advice
been trying to do a vacuum table setup but an failing badly.
I purchased this -
http://www.ebay.co.uk/itm/CNC-Vacuum...item487aa50799
and today I got the uni-jet 75
http://www.cattaniesam.co.uk/suction...ry/uni-jet-75/
the guy from ebay recommends 3cfm, if I worked it out correctly the uni-jet does 1250L/min which is 44cfm. so in theory plenty of suck.
got a 32mm pipe coming out of the vacuum pump, then just before the table reduced down to 10mm as that's what you need to plug into the vacuum table. length of pipe maybe 2 metres
when on and you try to move the work piece with your hand, you can but its bloody hard, its stuck down pretty dam well. you have to really really force it to get it to move with your hand. but when trying to machine it, it seems to move so easily.
I'm using a 6mm cutter, with a z depth of -0.5mm with a feed rate of 300mm/min
anyone got any advice?
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Re: Vacuum table Setup Advice
UNI-JET 75
Max. vacuum level: 140mbar (continuous service)
Are you sure you have got the right pump?
you need ~25 Inches Hg which is around 850mbar vacuum
My air compressor at home pulls on the inlet 0.94 bar =~ 940 mbar =705.05993009406 mmHg
Your pump is way off, it seems.
Who told you to look for CFM? you dont have 4x8 machine where you need 20HP pump with CFM rating.
Unscrew your air compressor/ what ever size, 1-2hp is ok/ inlet filter and connect the vacuum table and check what i am talking about. Dont worry about the continuous use, nothing will burn. In fact it runs cooler. Temperature rises from compression, not suction. If your compressor is newish it will make damned good vacuum.
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Re: Vacuum table Setup Advice
Ok, so I have the wrong pump?
Not sure what you mean by
you need ~25 Inches Hg which is around 850mbar vacuum
What's an air compressor got to do with a vacuum table
Sorry I don't fully get your reply
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Re: Vacuum table Setup Advice
i am saying that the job could be done by any 1-2hp air compressor with or without additional expansion chamber. which cost for 2hp ~70 euro at any home depot.
so you can hook the compressor and check if you have all right, cause with the compressor should work Ok without any problem.
what i am saying is that a typical air compressor pulls 6x more the vacuum compared to the pump you have bought
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Re: Vacuum table Setup Advice
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Re: Vacuum table Setup Advice
I don't understand how you can use a compressor, but will take a look at that other thread at lunch.
A compressor blows air, not sucks air
I only have a small compressor
BB24D:
http://www.bambi-air.co.uk/uploads/f...dget-Range.pdf
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Re: Vacuum table Setup Advice
For a compressor to compress air it must first suck the air in through the inlet filter. If the inlet is blocked or choked it will pull a vacuum. Boyan has suggested trying to use that vacuum to operate your vac hold down. that would be a very simple and cheap (free) way to check if the system works. Good luck. G.
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Re: Vacuum table Setup Advice
Ah now that makes perfect sense thanks.
When you say the system works, I know the table and bits work as work peice does get held down just not strong enough.
I'm assuming you wpuld only use a compressor to test not as a final solution as the compressor would need to be running for an hour straight to draw a vacuum whilst you do the machining?
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Re: Vacuum table Setup Advice
Quote:
Originally Posted by
andy_con
Ah now that makes perfect sense thanks.
When you say the system works, I know the table and bits work as work peice does get held down just not strong enough.
I'm assuming you wpuld only use a compressor to test not as a final solution as the compressor would need to be running for an hour straight to draw a vacuum whilst you do the machining?
depends on your priorities. yes, i suggested to test it using the compressor which makes perfect hold down.
having in mind a compressor on a boot sale is 20-30euro or brand new is 70-80euro, who cares if it will last an year or 2. electricity price and noise are the only real life concerns. people have reported compressors running like that more than an year without any problem. as i said before this is much more easy for the compressor than to compress.
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Re: Vacuum table Setup Advice
ok ill give it ago, thanks
ive never in my life seen a compressor that cheap. mine is a silent one and new its about £400-500
just about to read that other thread you linked to.
with the current uni-jet vacuum pump i purchased, how important is size of pipe? should i be aiming for big or small piping to the vacuum table?
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Re: Vacuum table Setup Advice
The other option if you have a good compressor is to use a Vacuum generator and pull a vacuum into a cyclinder.
This way your not stressing the compressor motor or if usiing the Compressor tank has the vacuum reservoir risking the chance of Compressor tank imploding because it's not designed for vacuum.
Also you don't say how small the part is your trying to hold.? Small parts are difficult to hold due to less surface area so you may need a dedicated Jig with better Vacuum seal to maximise the pull down.
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Re: Vacuum table Setup Advice
My compressor in very big so probably couldn't do that
Work peice was 100 by 120 mm
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Re: Vacuum table Setup Advice
Quote:
Originally Posted by
andy_con
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.
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Re: Vacuum table Setup Advice
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
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Re: Vacuum table Setup Advice
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.
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Re: Vacuum table Setup Advice
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
Quote:
Originally Posted by
JAZZCNC
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.
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Re: Vacuum table Setup Advice
yeah I'm machining ally and all the way through
Quote:
Originally Posted by
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.
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Re: Vacuum table Setup Advice
Quote:
Originally Posted by
andy_con
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.
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Re: Vacuum table Setup Advice
this is my goal, datron make it look so easy...
https://www.youtube.com/watch?v=jDrRICZq4KQ
datron make it look dead easy
https://www.youtube.com/watch?v=GNsA70whfoQ
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.
Quote:
Originally Posted by
JAZZCNC
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.
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Re: Vacuum table Setup Advice
Quote:
Originally Posted by
andy_con
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.!!
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Re: Vacuum table Setup Advice
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/
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Re: Vacuum table Setup Advice
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.
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Re: Vacuum table Setup Advice
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?
Quote:
Originally Posted by
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.
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Re: Vacuum table Setup Advice
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Re: Vacuum table Setup Advice
You'll notice I'm not commenting on the Compressor setup and thats because I don't agree with it. Not saying it doesn't work it's just not correct way IMO and just a lottery to when it dies.!.
The better way is to have a dedicated Vaccum pump(or Generator) pull a Vacuum into reservoir tank that is strong enough to hold high vacuum pressure. Fit a Vacuum switch so pump is turned on / off has required. If used with good sealing practises then you'll hold small parts no problem.
The secret really is simply lowering the vacuum loss so often dedicated Jigs or Pods with unbroken Vacuum seal work best or the only way without getting silly on the Vacuum system.!! . . . Mats etc work but only to a point and the cutoff point will depend on part size and size/amount of cut-thru.
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Re: Vacuum table Setup Advice
So I'm assuming you would need an in and out for the reservoir tank?
So table in, compressor out (so to speak)
Still not sure I get the reservoir tank, so you just remove all the air from it, so it then wants to pull the air from the vacuum table and acts as suction for the table?
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Re: Vacuum table Setup Advice
Just think of the reservoir as a storage system for the vacuum so that there is vacuum available sometimes when the demand would be greater than the instantaneous capacity of the pump. G.
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Re: Vacuum table Setup Advice
Ok cool
Are these any good
http://www.clampusystems.com/Venturi.html
Some claim 90% odd vacuum
Not saying they are a perfect solution but are they worth considering if you have a big enough compressor?
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Re: Vacuum table Setup Advice
Quote:
Originally Posted by
andy_con
Yes they work good but again you need a Reservoir tank because they struggle to provide enough volume direct from the generator.
Having reserve of vacuum is what you need for when vac loss happens. Otherwise you need a powerful vac pump.
Just think of it has the reverse of a compressor, you wouldn't try using air tools with no air in your tank because the pump would struggle to keep up with the demand. It's just the same but with negative pressure.! . . . Holes in your work piece are like having a high CFM air tool.!
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Re: Vacuum table Setup Advice
fair enough, was just a thought.
I'm tempted to just put a good quality vac pump on my credit card, do it properly first time.
any recommendations on single phase vac pumps?
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Re: Vacuum table Setup Advice
Quote:
Originally Posted by
andy_con
fair enough, was just a thought.
I'm tempted to just put a good quality vac pump on my credit card, do it properly first time.
any recommendations on single phase vac pumps?
My advise is speak to someone who deals with Vacuum tables/pumps and tell them what your trying to do because your not wanting simple Vac holding when it comes to small parts with thru holes.
Or better still stand back and look for alternatives to do what your wanting. There will be other less expensive ways.!!
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Re: Vacuum table Setup Advice
will do
I know there are less expensive ways but home brew also means faff. sometimes its nice to buy something off the shelf
is 250mm by 160mm small?
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Re: Vacuum table Setup Advice
just been doing some ebay searching, I'm guessing this bad boy would solve all my problems?
http://www.ebay.co.uk/itm/Becker-Vac...item3ab170353d