Holding down Styrene sheets

Plastic experts help needed.

I have a DIY FLA CNC machine and works well. I made a vacuum box from MDF and sealed all sides but the top. Using a shop vac to suck vacuum. It seems to hold down my Styrene sheets (0.040') but when cutting the parts I loose vacuum. My question is what would you recommend to hold down the sheets as the vacuum system does not seem to work. I am using a upcut bit. Afraid that when using a downcut I get chips under the sheet and then also lift the sheet.

Would love to hear from all of you!
Thank you!

I doubt your shop vac is strong enough to provide vacuum pressure sufficient to hold down your parts; it's good for cleaning up chips, though. Look for a real high-volume low-pressure vacuum pump. Usually these are single-stage rotary vane type pumps. Size it to be in scale with the size of your vacuum pod.

Thank you very much for your reply.

What would you consider a good size pump. My box is 20"x24"

Subdivide your box into multiple compartments. As you cut thru and lose vac shut off that compartment so the others still have vac and hold the sheet
Dave

That is an other great idea. Thanks beone

If your wanting to do this cheaply..... what 1 shopvac wont hold down 2 or 4 might hold down. I think there is even someone out there that sells a setup with 4 vacuum/shopvac motors for this purpose.