Re: [CAD_CAM_EDM_DRO] Calculating mechanical forces

cnc002@... wrote:

>In a message dated 8/1/2005 11:05:01 PM Eastern Daylight Time,
>elson@... writes:
>
>Think your round ways and linear bearings can keep the
>machine within it's tolerances with 332 Lbs of force? Well, maybe you
>have a
>smaller motor.
>
>Jon
>
>Jon:
>
>For years we ran round Thompson type bearings and ways on our CNC routers
>with 12 to 15 Horsepower motors, turning 20,000 rpm and cutting thru wood,
>particle board, fiberboard etc. at speeds up to 400 inches per minute. We held
>+/- 0.001" tolerance with no problems on materials where you could measure
>that close. I think round bearings and ways would work just fine with a very
>small motor like most mills run. Plus, the cutting speeds are also slow.
>
>

I'm no expert here, but I suspect the difference lies with the spindle
speed and cutter diameter.

Your spindle at 20k RPM is 100x faster than the spindle in Jon's
example. The torque (and cutting force) is therefore 1/100 as much.
Your motor is 10x the power, so in the end you have roughly 1/10 the
force on the screw. Also, the cutters you used were probably much
smaller than a 2" diameter - that would also linearly reduce the force
on the drive screws.

Am I way off here, or is that close to the answer? :)

- Steve