How to cut Ali sheet metal on router with vacuum bed?

[nickk]

Hi, I have had a bit of a search around your site and its the most informative forum i've come across!

Wondering if anyone can advise on a problem I am having;

We've just got a haas cnc router at work and a vac bed, Its a good bed, reaches around 29 Hg, with 2 massive vacuum pumps. But we are having problems with it sealing.

The cutter is slightly lifting the sheet and throwing dust and swarf under the sheet. After a few parts it looses more and more vacuum.

I tried adding tags today which helps a bit but still far from ideal.

Using 6mm Belin single flute cutter (33060).

Most of the stuff we cut is around .020"

We have ordered some different cutters that are apparently 'down cutters', which i presume is a reverse helix.

According to the Belin catalogue we should be running the 6mm at 72ipm at our max rpm (15000). But can only get to about 30 max before the parts start lifting.

Do you guys think these will help and does anyone have any ideas?

Cheers
Nick

[carlcnc]

Nick
whats your Hg with no material on table?
thin stock is a real pain ,
if parts are several of the same , you could try
a dnshear.but you should cut a shallow say 1/4x1/16 deep slot in spoilbd ,also .020 material will cut fine with a 1/8 or even 1/16 cutter.
Carl

[carlcnc]

"We have ordered some different cutters that are apparently 'down cutters'"

My bad, didn't read the whole post!

[nickk]

Thanks for the fast reply.

I forgot to mention we are currently using 9mm MDF board under the sheet metal, with vacuum sucking through it.

Is the idea of cutting grooves in it to allow somewhere for the dust/swarf to accumulate and not hold the sheet up?

Not sure what our Hg is with no material, but after i cut out some square test pieces 5in x 5in it dropped to about 22 Hg, mostly i think from the sheet being held off the MDF by swarf and dust.

There is a alarm system hooked into the router which shuts the machine down if vac drops below 27 Hg.

Nick