Holding plastic sheets

[obsadene]

Hi, could someone recommend a method of attaching plastic sheets 3/16" thick to the engraver/router table. Vacuum is out of the question IMO as I need to cut through the material. (Actually I need to make grooved 20"x 1.5" parts out of the 20"x30" sheet). Without holding the material down the groove depth varies as the spiral flute router bit tends to lift the sheet. I'm fairly new to this so any thoughts would be appreciated. Thanks,
Mark.

[LeeWay]

I cut a lot of 3/16" lexan on my router. What I do is cut out finished part outlines by hand. The I have templates which have been pocketed to accept these part blanks.
I use small toggle clamps then to hold the parts down.

I also use a 2 flute straight carbide cutter made by Onsrud. It is designed to cut polycarbonate. Not have a spiral, it's far less prone to any lifting of the material.

I do have a video of this machine cutting up on You Tube.

"http://www.youtube.com/watch?v=iSeBz-YqLb4"]YouTube - Home Made CNC Router

[aminear]

have you tried double sided tape

[cglj08]

This may be new to some.What i do is:
(Table has low volume-high vacuum .. but this may be better than just
pegboard on fan vacuum systems.)
First I glue a 4 x 8 sheet of 1/8" PVC plastic on top of the MDF spoilboard.
(rubber glue w/roller)(can use cheaper non or near non porous sheets)
(presurface mdf and or resurface glued sheet for Z accuracy)
The purpose of this sheet is to stop the airflow.To block it off.
(masking tape around the sides helps)
Then I apply a 4 x 8 piece of rubber foam to the top of the sheet.
(Allstar Adhesives ---www.allstaradhesives.com--- has 4' wide rolls of
1/16" self sticking foam rubber. AND MUCH MORE!!)(I'm just a happy customer.)(pop bubbles ,if any)
The purpose of this rubber is to create a seal to stop horizontal air leakage
between top of cutting surface and bottom of material to be cut.
Then using the part drawings I offset the outsides 0.187" to the center
of the part,and offset inside cuts to the outside ...to create areas that
will be under the finished part ... in these areas only do I want to have
my vacuum hold the part. Toolpaths are made of these areas and set to a
cut depth that will cut through the rubber and the plastic sheet to expose
the MDF thus allowing airflow in these areas only.(areas for scraps as well)
(stay away from the edges of the parts by 0.5" when possible)
(ensure enough support for your parts)(usually just cut squares in these
areas ...faster)(some times just make 1/4" holes spaced 1/2" for reusability)
This will leave rubber under the edges of the parts ...like gaskets.
Then when I cut out the parts I use a cut depth that DOES NOT cut
through the plastic sheet so that I don't lose air in the cutting process.
The vacuum guage says the full 29 bars start to finish.
Every one I've shown the results to has tried to pull off the parts and
all have quicky grabbed a screwdriver.
Too bad this is so expensive. So I'm trying to come up with a disposable
version.Also the used spoilboards are hard to store for reuse.But this method
lets you cut very fast.... very fast !!!(Komo VR805Q 999.9999 in/min)
Let me know if this helps anyone ..REALLY...I'd just like to know.
CGLJ08@AOL.COM

[OldEngraver]

We have been using this method for about 15 years. Assuming the bed of your machine is slotted aluminium or similar, we just use a sacrificial sheet of 1/16th ABS plastic sheet double side taped to the bed, then use more strips of D/S tape to attach the material on top of that for engraving and profiling. We use a paint scraper to detach the labels or badge blanks afterwards.