Reverse engraving help

[EL34]

I have some of the Rowmark Ultramatte reverse engraving acrylic plastic.
http://www.rowmark.com/rotary/ultra-...es_reverse.asp

Basically it's a 1/6" product that is clear on the front and black (or many other colors) on the back. You reverse engrave the colored side and then use acrylic paints to paint the engraving.

Pretty slick looking stuff once it cut and painted.

I called Rowmark to ask about typical cutting speeds and motor speeds but they didn't know or have any technical data.

Usually this sort of material is cut on an engraving machine and I guess there must not be motor speed and feed rate settings? Just a guess.

I am using my small cnc machine to reverse engrave with a single flute 60degree carbide engraving bit.
Did one short test engraving yesterday and it came out ok, not awesome, but ok.

I have my cnc machine tool running through a Variac, so I can slow the motor down from it's 30,000 max rpm. Not ideal, but it works ok on plastics.

Long winded post I know:
Just wondering if anyone out there has used this material and has some suggestions on feedrates and motor speed settings?

Thanks

[EL34]

Hmm,
no one has an idea just roughly what a typical feed rate or spindle speed would be used on plastic engraving material?

[CNCRim]

Feedrate between 18 to 25 and S4500min faster the better. HSS tool.

[EL34]

Thanks tex,
That spindle speed was 4500rpm correct?

I tested 15 on the feedrate in mach3, that seemed pretty good. I'll bump it up and see how that goes.

[EL34]

I used a Variac to slow my motor speed way down.

Need to get a motor speed control unit instead of using the variac, which reduces the ac voltage to the motor.

Anywho,
Feedrate of 20 in Mach3 worked out real good with the Rowmark material.

Cutting depth of .10 to .15 looked good

Made several faceplates for guitar amplifiers and theay all came out great.