[alex989]

I recently bought my first cnc machine. It is one of those really small table top models from China cutting area is 130mmx90mmx40mm the spindle that comes with it is rated at 30 watts. I really would like to replace this with an rc brushless motor so I have the ability to cut acrylic that is the whole reason I got it to cut acrylic pieces. I read that to cut acrylic you normally want a motor that can spin up to 18k and to use O-Flute end mill. Since I plan to use just 3.175mm size end mill. What type of power figures should I be looking for in the motor watt wise? Also max diameter for the motor I can use on it is 36mm for inrunner and 35mm for outrunner.

[awerby]

I doubt that RC motor will do a very good job of cutting acrylic; usually they spin fast, but have very little torque. If that's what you mostly want to do, you should probably trade in the router on a laser cutter.

[alex989]

I doubt that RC motor will do a very good job of cutting acrylic; usually they spin fast, but have very little torque. If that's what you mostly want to do, you should probably trade in the router on a laser cutter.

My main hobby is rc and you'll be surprised by how much torque modern rc motor have. Any laser cutter that can actually cut not engrave will cost at the very least 3 to 4 times as much as this little cnc.

[ger21]

I read that to cut acrylic you normally want a motor that can spin up to 18k

At 18K, you're chances of melting the acrylic are very high. 10,000 rpm is usually more than enough.

[alex989]

Ah I see I was going off this Link
It recommended a O-Flute end mill and to run it at 18k rpm

[skrubol]

RC motors don't have the bearings for milling (your current 30W spindle probably doesn't either,) nor a convenient way to hold an end mill.
Have you tried using the existing spindle? 30W isn't going to cut fast, but it may do ok on acrylic.
18k RPM is probably ok for milling acrylic, (but you need to keep the feed rate fast or it will melt.) Slower RPM's should be fine as well, just slow the feedrate proportionately. You may also have to take very shallow depths of cut to not overload the little 30W motor.

If you do decide to replace the motor, your best bet is probably an 800W water cooled spindle and appropriate VFD. Those are usually 24k RPM units, but can be run as slow as 6-8k RPM (though with only 1-200 W of cutting power at those speeds. Still a lot more than 30.)