Why not using hard foam and mill a grid on its upper surface. A round groove around with a string of soft foam or rubber very slightly exceeding the top and it is finished. It works here extremely well, also when milling wood and thin aluminium.
Jean-Claude, Switzerland
----- Original Message -----
From: designer_craig
To: Homebrew_PCBs@yahoogroups.com
Sent: Tuesday, February 15, 2011 6:24 PM
Subject: [Homebrew_PCBs] Re: PCB drilling vacuum table ??
I wondered about the air flow thorugh MDF but the idea came from a post I saw a couple years back that I now can't find. The guy was using 1/2" material to build the vacuum chamber and had to paint the non table areas to hold his vacuum. Now he may have been using particle board and calling it MDF, particle board is much less dense.
I don't want to use 1/2" or 3/4" that I can get at the home center, just too thick and heavy. My brother sent me a link showing the stuff is available from 1/8" to 1-1/8" thick. As for the air flow, it only needs to transport a very small volume of air over a relative long time since the PCB stock material is sealing the top surface of the MDF.
I have some 3/4" MDF, guess I should go slab off a 1/4" thick piece on the band saw and see if it works.
Criag
--- In Homebrew_PCBs@yahoogroups.com, "Ben L" <bhleavi@...> wrote:
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>
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> > On 13.Feb.11 20:11, designer_craig wrote:
> > > I am about to build a vacuum table to hole down the blank stock when I cnc drill my boards. I am looking some low cost sacrificial material to use between the board and the vacuum table.
> > >
> > > The material needs to be thick enough so as not to drill into the vacuum table and be some what porous to allow air diffusion for a good vacuum grip.
> > >
> > > The ideal material would be something like 1/16" thick MDF. I have heard MDF is fairly porous. I have only seen MDF in 1/2 and 3/4" thickness. Possilble some sort of construciton paper or cardboard. Guess I need to do some experiments.
> > >
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> > You should be able to find 1/4" MDF, just mask the unused MDF.
> >
>
> If I understand him correctly he was wanting a backer board to protect the table top but also wanted it to have air flow for the vacuum to hold down the board. I don't think that your going to get much air flow thru what I call MDF of any thickness. Maybe the Masonite Hardboard Peg Board material would do what he wants.
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> Ben
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