[marko63]

I was wondering if anyone had any secrets or input into being able to hold PETG or Lexan sheets to a CNC router table. I am running a KOMO MACH II router with a very good vacuum pump and have no issues at all holding MDF and other woods but I am having a real hard time holding plastics to the table. They lift off of the table with hardly any effort and move around when being machined. Any input would be appreciated.

Thx

[ConeGuy]

Which vacuum pods are you using? Have you checked their sealings?

[routalot]

Are you using a pod and rail machine or a spoilboard?If its a spoilboard,I would suggest a facing cut and then lay a piece of plastic film on the areas which are exposed after locating your workpiece.You can't do much more than that.

[marko63]

I'm using a MDF spoil board and have fly cut both sides of it. Also blocked off all other portions of the table that are open beyond my 4'x8' sheet of PETG. This is only related to the plastic materials like PETG, Lexan and Plexi Glass. There is a huge difference when trying to hold these materials compared to MDF or other substrates...….

[he1957]

You could try some single sheets of newspaper (or similar) between the spoil board and work piece (similar to the plastic film mentioned).

[marko63]

were are you suggesting to put the newspaper?

[he1957]

were are you suggesting to put the newspaper?

Top down according to your post:

Top layer = Workpiece
Paper (and plastic film on exposed areas as suggested if needed)
Spoilboard of MDF machined/surfaced (through which vacuum is passing (presumed by previous post). I didn't ask if the edges are sealed because you implied you have been using this successfully.

Vacuum Source sucking the above towards pump :-)

Does that make sense?

[marko63]

OK I got it. Let me give this a shot. thank you for your help.

[routalot]

I couldn't find a value for the coefficient of friction of MDF on MDF,but I would bet it is a lot higher that the values for just about any plastic.That still wouldn't explain why you are able to peel the plastic off the table.I would be tempted to have a close look at the vacuum system to see if it is operating at peak efficiency.For example-have you ever machined a groove in the spoilboard?If so some dust might have got into the system and there may be a filter that is a bit obstructed.Have you got any joints in the plumbing to the pump that have worked loose?The situation is puzzling as plastic normally seals really well.