Re: [CAD_CAM_EDM_DRO] Spindle power VS Motor power

fortino wrote:

>Jon,
>
>Ok. I see your points. But it still doesn't answer the question. The reason
>I ask this question is
>that there is a friend of mine who has a big CNC milling with a dead
>controller. The spindle is 20 kW.
>So, If I put like 200 watts motor for each axis. Would the spindle be
>considered too much?
>
>I suspect there are general rules that would give me estimate that the
>spindle should be A times of motor
>axis.
>
>

No, this is what I was trying to tell you, there is no simple spindle
power x constant = axis power.

The weight of the machine table and the acceleration and max velocity
are very major
components of the calculation. The size of cutting tools and the speed
range are also
very important. For instance, if this is a high-speed machining center,
that could be
20 KW at 25,000 RPM, in which case the tool forces on the work will be
small, but the
need for very rapid feedrates of the table will be needed. Here, a very
high peak
acceleration is needed, but the average force will be small. If this is
a huge, geared-down
machine, designed to use 8" cutters at 100 RPM, 20 KW translates into
huge cutting forces
that need to be counteracted by the axes. Here, the feedrates will be
low, but the
average torque from the motor may be quite high.

Anyway, just to throw out random numbers, with a 20 KW spindle, I would
thing a large
CNC mill would use servo motors with at least a 1-2 KW continuous
rating, and probably
a 5-10 KW peak rating. Most modern machines use rapid feedrates of at
least 400 IPM,
and many exceed 1000 IPM. This takes some pretty strong motors, just
for acceleration,
regardless of spindle power.

Jon