So, I have a CNC router, and I'm somewhat constrained on the variables at my control presently. Namely, I am limited to a spindle RPM between 10k and 23k, and a maximum feed rate of 80IPM.
We'll get to that in a moment -- but, as a newbie, I have a (very important to me) equation to figure out before I really get started routing acrylic. I'd like to get feedback on it _before_ I start to avoid the same mistakes I made in wood ($40 in bits broken in 5 minutes == a stop to any work until the next payday).
So, my question is pretty straight-forward: I need to cut a number of small holes (think 0.196" and smaller in diameter) for screw pass-throughs, I have a 1/8th single-flute up-cut spiral bit, and a whole slew of drill-bits. For holes like the the .196", would it be wise to use just a standard drill bit (knowing I bottom out at 10k RPM), or to use the 1/8" carbide router bit?
So, in that light: should drilling in acrylic be done by drill-bits, or by router bits? In whichever situation, does anyone have any advice on plunge rates?
To the constraints I mentioned earlier, everyone out here seems to like very low spindle speeds and moderate feed rates, or very high spindle speeds and exceptionally (to my limited budget at least =) high feed rates. I'm a bit confused, as when I calculate out for the "optimum" rates, using the formula on plasticrouting.com, I always end up with something in the range of my machine... That is, given I'm forced to choose one of the factors, I choose RPM at 10k, and if Cl = Feed/(RPM * CuttingEdges), and I'm using a single-flute helix, and an optimal range (according to the above website) for Cl is 0.004 to 0.012, I get Feed == 0.008 * (10000) == 80IPM. Of course, as 80IPM is my "maximum" speed, I consider that I could tune for "worse" finish (theoretically) and choose 0.006 which gets me closer to 60IPM, and staying well away from my upper limit and relaxing the possibility of positioning errors.
But why do I get such drastically different ranges using that formula than what people talk about on here, and shouldn't bit size play a role in the formula? I.e., shouldn't my 1/4" bit be able to be pushed faster than the 1/8" bit?
Thanks for any advice!
!c