Drilling heavy Acrylic

[bleeth]

I have to drill multiple holes in several panels of 1" Acrylic and they must be clean top and bottom. Holes are to be 1/2" D. Any of you plastic fabricators out there have the correct tool, speed, and strategy fort this. These panels are expensive and on a long lead time and we can't afford a slip.

Dave

[scottcox]

Dave,

I just cut a bunch of 1" diameter holes in 1.5" thick acrylic. I used a 1/4" diameter Onsrud 63-727 bit at 18K moving at 2 ips and plunging at 0.1 ips. That 0.1 ips plunge rate may sound sloooow, but anything faster just lifted my gantry up and the hole didn't cut deep enough. Some ramping moves may help if you can squeeze them in there.

I used an inside profiling path at .25" stepdown. Both top and bottom, still masked, were very clean with only micro-sized chipouts on the bottom where it plunged through.

I was pleased with the results and my customer was thrilled.

I've made it a habit to talk to the Onsrud tech-support folks before trying something new. Their suggestions have so-far been a great starting place for feed and speeds.

Good luck.

Scott

[scottcox]

And somewhere on the forum ( I couldn't find it this morning) is a topic discussing a product that you spray on the steel parts of your bot so the acrylic chips don't stick to it.

The chips were a problem as they would land on my rails and get run over. Though I never saw any defect in the product because of that, I cringed ever time a heard it.

[Brady Watson]

Dave,
I would use a 3/8" diameter cutter and do stepdowns of about .125 per pass @ .4 IPS. (remember...that 3/8" bit is going to be moving very quickly @ 1 IPS in a .5" hole...so reduce speed to less than you think)

Leave .005 to .01 allowance on the holes on the multi stepdown toolpath and make a 2nd toolpath @ full depth to clean it up. You should be fine using an XL .375" end mill/upcut spiral, but I recommend an Onsrud 52-xxx series with 3/8" diameter. It is a 2-flute spiral-O and does a superb job on acrylics.

Use carpet tape to hold it down.

-B

[bleeth]

Sounds like good advise guys. (The sheets are 4' x 8'. I reckon they aren't going anywhere with the vacuum.)

Thanks

Dave

[btk]

Scott,

I am not sure if it works for Acrylic, however
for foam, I have used "Static Guard" to help keep chips from sticking to steel parts (and plastic windows).

Brian

[robtown]

Cast Acrylic is preferable if you have a choice in what type of acrylic you can order. and definately don't overdo it on your z plunge speed, it can cause lost steps in Z and X or Y. Recovering from a few lost steps in Z is no biggie, but if you lose your place in X or Y, that's an expensive mistake.