Machining plastic

[WATERJET71]

Hello,

What's the best way to hold a thin sheet of ABS lets say .125 thick the parts meassure arround 8.00 x 6.00 need to machine a big window on the center about 7.00 x 5.00 (kind of a picture frame) then I need to make a groove all the way arroun about .080 deep .094 wide in between the 1/2 inch arround the frame Can I use double back tape? if I can what kind?

Tx

[Peter Gibbs]

Hi double sided carpet tape works for me in a milling application cheers Peter

[WATERJET71]

Hi double sided carpet tape works for me in a milling application cheers Peter

tx peter, who carries that kind of tape? I dont have much experience on machining thin stuff I have never use the tape technique.

[txcncman]

Do not use foam tape, it is too thick. Sources: Wal-mart, hobby, craft stores. Online: Buy Double-Sided Tapes at FindTape.com

[stevespo]

I like this paper tape #505-2521 from Enco. I use a lot of it for small parts and hard to hold items.

With thin plastics I'd recommend a decent amount of tape and use a straight bit (no upcut) to help prevent lifting. It's less of an issue with light passes, but an upcut will tend to pull the slippery plastic (thin sheets) up off the tape.

Steve

[osphoto]

Carpet tape from Harbor Freight.

[PriddyShiddy]

I have used the cloth carpet tape, but never used a strait flute which would have been much better. The paper tape seemed to keep plastic down a little better and I could take a finishing pass leaving a .005" floor and it worked great. same cut on carpet tape would break through in some places gumming up the cuter. I think the cloth was just too soft/mushy. Again, the right cutter may have made that a non-issue.

The .005" floor would usually break away as the tape was peeled off the sub plate, but required deburring... sharp blade makes that fast.

I did a job for 60 license plate frames out of .062" engraving plastic and didn't want to spend hours playing with tape so I made an aluminum fixture with tapped holes around the inside of the window (3parts wide) and around the outside. I made 3x .25" plate with matching through holes about the size of the inside window with "fingers" sticking out where no machining would be done (hold down plate). Then 3 larger windows of .25" aluminum that matched the holes around the outside of the part.

I stacked the plastic and match drilled them all on the drill press using the hold down plate as a template. put down the plastic, put on the smaller hold down plate, tighten 4 screws and machine the outside and face while I drill/load more plastic. When the program was done doing the outside and face I had already added the larger window, tightened down, and removed the inside hold down plate. Then the program would finish by cutting the inside window out (threw 2 screws in finger tight ti keep the window from flying away).

every part was good since the plastic never moved. the outside was held down before the inside was released.

these frames had lots of contours around both inside and outside. I could barely keep up drilling and loading with three parts fixtured. 4 parts might have kept my coffee from getting cold