[Gippy]

Hi guys,

I'm looking for a local source or importer of sacrificial Vacuum card / matting.
or any other alternatives?

I can get it from Europe, but wow this stuff is expensive.

cheers
Simon

[Routerfiend]

Hi You could use MDF. Works a treat.

[Gippy]

Hi mate, Yeah if I can't get hold of the vac pass through matting - MDF for sure,nice and cheap

[RCaffin]

But seal (paint) the MDF around the edges. Also consider covering the unused top area with rubber or plastic: that will economise on pump power.

I can't help feeling that 'vacuum matting' is a bit of a sucker bait in many ways.

Cheers
Roger

[Gippy]

But seal (paint) the MDF around the edges. Also consider covering the unused top area with rubber or plastic: that will economise on pump power.

I can't help feeling that 'vacuum matting' is a bit of a sucker bait in many ways.

Cheers
Roger

Yeah starting to think so too, especially when its around $80 a sheet, I may even look into cheap acrylic sheet and spray on super glue to start with. Gluing aluminium to mdf could be a pain.

[RCaffin]

Funny thing about vacuum tables. You see all these fancy ones with a grid of holes everywhere - totally wasted. Seriously.

My vacuum table (used mainly for milling PCBs) is a block of black PE. It has a SINGLE vacuum hole in the middle, and an air connector out the side. Long drilled hole from edge to middle.



The secret is that I machined the top of the vacuum table flat while it was bolted down, but I did it a shade 'roughly'. That is, there are fine machining marks all over the top, and they are sufficient to distribute the 'vacuum' everywhere. You do not need big air holes! I put wide paper painters tape down on the PE around the edge of the PCB to get a bit of a seal at the edges. You could also use thin (floppy) sheets of silicone rubber. Once the vacuum pump has got going, I get most of 1000 mbar (1 atmosphere) pressing down on the PCB to be milled. It does not move. Very little air leak too.

Cheers
Roger

[jatt]

Also consider covering the unused top area with rubber or plastic: that will economise on pump power.

Found just about any flexible plastic (wrapping) works. PVC fabric offcuts work well, if you have access to that kind of thing. Easy to push around the table if its large.

[RCaffin]

PVC fabric offcuts work well
Bingo! Thanks for that idea! Scraps of waterproof fabric coming...

Cheers
Roger

[Spurry]

In the UK, the matting that can be used is actually the inner sole lining of shoes. It might be worth having a word with any supplier to a footwear manufacturer.
Pete

[Gippy]

Thanks guys, looks like I'm off to Spotlight to check out their fabric section. The misses reckons they have something similar to inner sole lining.

[Spurry]

Simon
If it helps, one of the brand names is Texon, where it is described as "premium quality cellulose insoling material".
The same stuff from the CNC vendors is sacrificial diffuser sheet. Guess which is cheapest??
Pete

[CaptainVee]

Funny thing about vacuum tables. You see all these fancy ones with a grid of holes everywhere - totally wasted. Seriously.

My vacuum table (used mainly for milling PCBs) is a block of black PE. It has a SINGLE vacuum hole in the middle, and an air connector out the side. Long drilled hole from edge to middle.



The secret is that I machined the top of the vacuum table flat while it was bolted down, but I did it a shade 'roughly'. That is, there are fine machining marks all over the top, and they are sufficient to distribute the 'vacuum' everywhere. You do not need big air holes! I put wide paper painters tape down on the PE around the edge of the PCB to get a bit of a seal at the edges. You could also use thin (floppy) sheets of silicone rubber. Once the vacuum pump has got going, I get most of 1000 mbar (1 atmosphere) pressing down on the PCB to be milled. It does not move. Very little air leak too.

Cheers
Roger

If you mill pcb's you do not put any force on the work piece.
If you want to do serious work with a vacuum table PE is useless, as is a single hole for bigger work pieces.

The hole point (pun intended) is that you spread the area the vacuum acts on.

With your one hole at 1 bar you get 1 kilo of force if it's surface is 1 cm2.
If you use 10x10 of the same size holes you get 100 kilo's of clamping force.

[RCaffin]

Hi Captain Vee

I regret that I am going to have to say that your physics is not quite right. You have seriously misunderstood how my vacuum table works. Your calculations are just plain wrong (fortunately).

The surface of my vacuum table is slightly rough. The single small vacuum hole in the middle can suck air from the entire covered surface, out to the edges of the object being held down. There is no real air seal until you get to the taped edges. So you take the atmospheric pressure and multiply by the surface area of the object being clamped and you have the holding force. Been there, done that.

The case you are describing would only apply IF the surface of the vacuum table sealed right at the edge of the holes. You can do this with some of the commercial rubber mats - at vast expense. But they are a sort of confidence trick: they cost so much they MUST be better - right? Chuckle.

If you mill pcb's you do not put any force on the work piece.
Absolutely no force at all? You can not have milled and drilled any PCBs. Carving into FR4 can create enough force to move a PCb far more than a line width.

Cheers
Roger