Do spindles have power band?

Maybe an obvious answer to my question, but maybe some background will give context as to why I ask the question.

I have a pro4848 but use a dewalt router. I recently got a new machine that uses the 4 HP Hiteco spindle. to reach my preferred chipload at 350 IPM with my 2 flute bit, I need an RPM of 14k. With my router, it would definitely have trouble keeping constant power without getting bogged down if I tried that speed. With the 4 HP (or even the spare 3hp one I have), is 12k-14k an issue here? I was assuming that spindles with VFD are specifically designed for this reason. Or rather, can they deliver the rated power throughout more of the rpm range than a regular router can?

Can the 4hp or older 3 hp spindle handle full 3/4" DOC with a 1/4" endmill or 3/8"?

Spindles have a pretty flat power band. At most RPMs they can deliver nearly full power.

Unlike a router when they get bogged down they can apply more power when needed (to a point)

This is the huge advantage of a spindle over a router. You can sometimes find power band charts for spindles if you look them up.

Thank you! That’s exactly what I was thinking. I’m thinking I may be approaching the limits of a 1/4" tool’s strength/deflection at 350 IPM and it’s probably ideal to move to a 3/8", and I can do two passes instead of 3 now.

Sounds like you’re heading in the right direction!

@Arcrunner you can see the powerband for yourself on the last PDF link on the store page

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Thank you, I think I saw this a few days ago, but the combination of it being part Italian and I think, showing stats for either two different spindles or the spindle operating in 220 and 380v configurations, confused me. But looking at the solid lines in the graph, am I correct in deducing that the torque is basically flat across most of the rpm range, and then dropping slightly as it reaches max rpm? So the range where I want to operate (12k-14k) has plenty of torque there?

I think your reading is correct, whereas the solid line is full load (S1?) and the higher broken line is 40% load (S6?). I could be reading that wrong. My interpretation of the voltage side is that it’s 220V into the VFD and 380V output to the spindle motor via 3 phases.

Not constant power, but closer to contant torque. The 3hp spindle had an almost flat torque curve, so the power was inversely proportional to the rpm right from 24k rpm. So at 24,000 rpm it was 3hp, at 8k rpm you only have 1hp, and at 1k rpm, only 1/8hp. You also have much less inertial so hitting a little knot at low speed will stop the spindle quick with that low hp and angular momentum.

The 4ph Hiteco is better. This is the curve:

You can see the torqe actually drops at the higher rpm and then peaks at 18k and down. I’d guess it was designed this way on purpose because you’d usually like to have more torque at lower speed and so they can compramise at the higher speeds. This way it can hold max power output down to a lower rpm instead of degrading immediately below 24k rpm.

As far as what you can cut with the 4hp spindle, I can’t imaging ever stalling that spindle with a 1/4" or 3/8" endmil (but I haven’t tried either) at 14k rpm. I think you’d start a fire, snap the bit, or start missing steps on the steppers before stalling the spindle.

I can take a 0.125" DOC on Mesquite (very hard, and knarly knots) at 100ipm, 60% stepover with the 4hp spindle at 16k rpm with a 2-3/4" planing bit (Amana RC-2263).

Thank you. As I plan to put the 3hp on my original 4848, I should still be more than fine then at 12k-16k RPM? It should definitely be at least better than my old router, I think.

Yes, and way quieter as well.

Worth noting that better VFDs/Vector drives can alter that. A sensorless vector drive with voltage injection can boost the power at lower RPM more effectively. (e.g. a Hitachi WJ200)