Cutting 3mm Komatex/Sintra?

[billp]

Has anyone had luck in cutting out parts in 3mm PVC foam board (Komatex/Sintra by trade name)? I have a couple of full sheets to cut parts out of, and in my first test cut I used both a spiral upcut .125" bit, ( lifted the piece continuously, and cut through a few "tabs/bridges"when it did), and a .125"two flute straight bit which left a LOT of swarf ( yes it's a real word...) in the groove. I am going to try and order a spiral downcut, but of course that won't be here until tomorrow. In the interim I'm wondering if there are any other tricks people know of...Thanks

[Ken Brisk (Unregistered Guest)]

Bill,

I have used good old carpet tape. Worked well.
Good luck.

[billp]

Ken,
Thanks. I may have to go that route, problem being there are 80 pieces to each sheet being cut out,and there are 6 sheets to cut.....
I've thought of "scribing" all the parts with a thin pass to determine where everything should be, and then going with the tape and hoping for the best. Of course I'm trying to automate as much of this as possible so I don't have to remove/add 80 pieces of tape with each run. But that might still be easier than screwing into the spoilboard, and then watching the pieces flip flop anyway.
I've got the client coming to the shop tomorrow to see what he thinks about the edge quality so far, and that could be the deciding factor ( it always amazes me how we tend to agonize over little ripples, and then the client says, "thats EXACTLY what I was looking for"....).

[stevem]

Bill,

Get a pressure foot/dust collector to solve both the lifting and the swarf problems. A pressure foot will keep the sheet against the table even with the use of an upcut spiral bit. In addition, it keeps small parts for being thrown to the side at the end of the cut.

[billp]

Steve,
Does the size of the part come into play when using a foot like this? OR do I have to "size" the opening to the smallest part I expect to cut?

[stevem]

Bill,

You should be alright as long as some portion of the foot is pressing down on the part throughout the cut. I’m cutting parts as small as 2.5” X 4”, using only the pressure foot to anchor the part to the table. I’ll try to post a pic of my setup tomorrow.

[joe]

Bill,

Great post as allways.

Of all the materials I've cut, PVC seems to have the roughest edges. We've used Up draft, Down and strait flutes but haven't solved the problem yet. Sanding Komatex, Trovacel, Centra, Etc are slow and tedious. Hope someone has the answer.

One of my Gerber routing friends seems to get good cuts but his router is a servo unit.

Good routing to you.

J

[artisan]

In my experience with Komatex and other PVC products, I have found using an upcut spiral at a slower feed speed to work best. We cut many, many sheets here for letters and for various fabrication parts. Generally we use the 3 mil for lettering and use no vacuum or tape.....just screws or hold-downs. If you slow down the router feed rate to around 1 ips, the PVC will cut like butter (nice edges) and not lift from the table....D

[billp]

Thanks to all who sent me info/tips on cutting this stuff. Here's what I learned (so far);
First off I needed to "fly cut" my table so it was perfectly flat. With the Alpha this only took 20 minutes as I was able to run at 5IPS as I took off a skin of .05". Having the flat table made everything which followed MUCH easier.
Secondly instead of using my standard drywall screws to hold the piece in place I went to pan head machine screws. This took the "pucker" factor out of the Komatex, and prevented the dimples and flopping I got on my first try.
Then I slowed things down considerably -from 3 IPS to 1.25 IPS. BIG difference in cut quality, and the material stayed exactly where it started with NO lifting. I ran the file at 11,000 RPM...
And with all of the above factors in play a straight bit has worked perfectly because even though I get a lot of swarf in the kerf area, it adds to the holding power of the part, and then just drops off with a wipe of the hand.