Re: Using Vacuum to hold down sheet metal.

Hello,

MDF is used without any holes in larger cnc routers with a
regenerative "blower" providing the "suck". (Means MDF by itself is
somewhat porous; a factor to keep inmind when you want the most
holding power.

Shop vacs as vacuum sources DO work, BUT...

They usually depend upon the airFLOW through them for motor cooling.
Hooking one up to a closed system will likely burn th emotor out.
Folks using them extensively have learnt to add a t-fitting with
valve so that some airflow is asured to prevent this.

IBAG makes a commercial rubber mat designed for vacuum holding use
in machining metal. Might want to have a look for ideas and
inspiration...

Hope this helps,

Ballendo

P.S. FWIW, I'd use double sided tape, or some other means... (And I
LOVE vac clamping...)

--- In CAD_CAM_EDM_DRO@yahoogroups.com, John Dammeyer <johnd@...>
wrote:

>
> I have some 0.050" thick sheet metal in which I want to drill/mill

a

> number of holes along with a rectangular cut-out. The G-Code is

done.

> Things look like they will end up in the right place.
>
> I was thinking of building a vacuum assembly to hold the metal down
> while milling. I've put in mechanical stops to prevent shifting

but I

> was thinking if I built a box and connected the shop vac that I'd

be

> able to use lots of little 1/8" holes through the MDF frame to

suck down

> the metal.
>
> A bit of math tells me that the 7 square inches of a 3" diameter

vacuum

> hose translates into about 575 holes 0.125" in diameter.
>
> But do I really need that many. I plan on only putting holes

under the

> metal where the mill does not do any cutting so no leaks.
>
> Would this work? Is it better to use a vane type vacuum pump

instead?

> The milling cycle for all the holes is about 00:05:45 so that

would mean

> the shop vac would be straining for a fairly long time perhaps
> overheating.
>
> Suggestions?
>
> Thanks,
>
> John
>