designer_craig wrote:
>
> I am looking for the surface feet per minute and feed per turn numbers
> for small carbide drills in FR-4. My 5400 RPM maximum going to be
> well below the 30,000 to 60,000 RPM used by a real PCB drilling
> spindle but it should still work fine if I use the correct feed rate.
> Anyone got a reference for these parameters.
I would point pages 24.16 and 25.8 from printed circuits handbook 6th
edition. But nothing real there, you need cutting speed (sfm) and chip
load values from your laminate datasheet, but i never found any of those
values for any laminate i have used. I use 'guessed' values after
stressing with this plenty of times too. But never got results as good
as i wish.
http://books.google.pt/books?id=g9Q8RekeKaAC&pg=PA5http://books.google.pt/books?id=g9Q8RekeKaAC&pg=SA25-PA8The same book also points 500 as sfm and 1mil for chip load as normal
values for fr4. I use this as example from one laminate:
Suggested Drilling Parameters For Isola DE104i
SPINDLE Surface Speed
DRILL SIZE SPEED per Minute INFEED CHIPLOAD
inch mm RPM SFPM SMPM inch meter mil mm
min. min. rev. rev.
0.010 0.2540 89,763 235 71.63 65 1.651 0.70 0.018
0.015 0.3810 80,214 315 96.01 80 2.032 1.00 0.025
0.020 0.5080 60,161 315 96.01 90 2.286 1.50 0.038
0.025 0.6350 53,476 350 106.68 80 2.032 1.50 0.038
0.030 0.7620 47,747 375 114.30 85 2.159 1.80 0.046
0.035 0.8890 43,654 400 121.92 88 2.235 2.00 0.051
0.040 1.0160 42,972 450 137.16 107 2.718 2.50 0.064
0.050 1.2700 34,377 450 137.16 85 2.159 2.50 0.064
0.060 1.5240 28,648 450 137.16 72 1.829 2.50 0.064
0.080 2.0320 21,486 450 137.16 55 1.397 2.50 0.064
Similar to what i did for me i put this on a spreadsheet and trunk the
rpm to 5400 and reduced the feed rate proportionally to the rpm
reduction. But i give no warranties.
drill speed feed
inch rpm in/min
0.01 5400 3.9
0.015 5400 5.4
0.02 5400 8.1
0.025 5400 8.1
0.03 5400 9.6
0.035 5400 10.9
0.04 5400 13.4
0.05 5400 13.4
0.06 5400 13.6
0.08 5400 13.8
You put so many effort, dedication and cost on the bridgeport that you
may like to build a smaller, lighter and faster machine just for pcbs.
Simao