Sintra / Komatex cutting help

[kivimagi]

Hey Folks,

I've done a fair amount of reading here about cutting sintra/komatex, and thanks to a few of these posts have selected the bit, and feeds/speeds.

I've even read about carpet tape, and using screws as a hold down, and tried it. It works ok, but I'm looking for something better, or something with a little less setup time like vacuum.

Is it realistic for me to think about using vacuum? I'll be cutting all the way through, and so then I become concerned about loosing the all important "vacuum"

Any thoughts you have would be appreciated.

Enjoy your long weekend coming up, always a nice weekend for banging out a few new projects.

Regards,

Ryan

[Brady Watson]

Ryan,
I've cut a ton of 3/4 & 1" Komatex using the BradyVac II fixture & a single Fein Turbo III shopvac. It will hold most parts as fast as you can cut them. You can see how you can make your own BradyVac fixtures by reading the article here (http://www.shopbottools.com/Brady%27s_tricks.htm)

-B

[elcruisr]

I cut a lot of sintra on a 5 x 12. While we do have a 15 hp regen for vacuum hold down this stuff holds down really well with vacuum because it's not porous. We just throw scrap laminate over the empty areas.

[kivimagi]

Brady/Eric,

Thank you for the responses, I'm encouraged.

Do you still find the need for tabs with these hold down methods, or is the holding power superior enough to get by without it?

[elcruisr]

All depends on the size of the parts. The system I have will hold parts down to around 6 square inches depending on part thickness and cutting speeds and the lateral forces they create.

[Brady Watson]

Ryan,
As Eric points out, it depends on the footprint of the part. The larger it is, the easier it is to hold down. Eric is using a universal type vacuum configuration where vacuum bleeds thru a bleeder board. If you have a lot of the same parts to cut, then make a purpose built vacuum fixture as I have alluded to before.

In terms of tabs and holding it down, in most cases you will not need them. If you are short on vacuum holding power, many times you can just do the cuts in more passes to reduce the cutting force placed on the part. It is also important to set your start points (where the tool enters and exits) to minimize part rotation at the last second. If you find that vacuum works until you get about 1/2 way thru the sheet, then just lay a plastic trash bag over the already cut areas and let vacuum seal it off - restoring your original holding power.

It's ain't rocket science...you'll do fine if you pay attention to what is happening and observe changes you might want to make while the 1st sheet is cutting. If you have several sheets to cut, use the BradyVac II. If you have to cut only one or different layouts on your sheets, then use the BradyVac I, and just be a bit more conservative with your speeds and stepdown rates. As long as you don't use a down-cut spiral bit, you should be fine...Oh, use dust collection unless you want the Y motor driving over PVC chips that have statically attracted themselves to the Y rack.

-B

[elcruisr]

On top of Brady's good points I might also say that there are times when tabs can be a good thing. If I'm doing a production run with say, 40 parts per sheet and 40 sheets, then I tab everything together is what's known as a "single sheet" cutting strategy. The idea is that I can pull the entire group of parts off the table to an outfeed table as a single sheet, clean and load another sheet and start cutting fast. While that sheet is cutting I can cut the tabs and separate the parts from the removed sheet during a cutting cycle. This reduces cycle time and ups my income! When cutting large numbers of parts that are bid per piece, cutting cycle time can become a big deal....

[kivimagi]

Eric,

Are you using a laminate trimmer to clean up the parts?

Regards,

[elcruisr]

On wood products yes, on Sintra a razor knife and my 48" horizontal belt sander for cleanup.

[wcsg]

Recently I've been cutting about 600 small parts from a 3/16" thick single cast acrylic sheet. I'll use 4 small pieces of carpet tape to hold the sheet down. I run two files, one to drill 9 small 3/16" holes for drilling the sheet to the spoilboard with drywall screws then the second for the cut file. I use 1/8" Belin Single flute down spiral bits for cutting the parts in a single shot.

All the cut material shavings stay between the sheet and part keeping it wedged from moving also keeping it a nice edge. I've also done this with 1/2" PVC. So far I'm liking this method since I have no vac table and using less carpet tape