How much load can this spindle take?

[Akhil]

Spindle link :

https://robokits.co.in/automation-control-cnc/spindle-motor-for-cnc/cnc-square-spindle-3.5kw-er25-air-cooled-82mm-220v-18000rpm


Can this spindle turn a twist drill of 25mm dia through mild steel 40mm thick plate??
Please Explain.

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[joeavaerage]

Hi,
that spindle is rated at 3.5kW at 18000rpm.

power =torque x speed

power in Watts W
torque in Newton.meters Nm
speed in radians per second s^-1

torque =power /speed
=3500 / (2 x PI x18000/60)
=1.86 Nm

So about 2Nm, and that will not drive a 25mm drill through steel, you'll need 30-40Nm for that. 2Nm is enough
for maybe a 5/15 or 3/8 drill, maybe 1/2 if you babied it.

The problem with high speed spindles is that while they sound very powerful (because they're so fast) they have very little
torque.

Craig

[NIC 77]

Hi,
that spindle is rated at 3.5kW at 18000rpm.

power =torque x speed

power in Watts W
torque in Newton.meters Nm
speed in radians per second s^-1

torque =power /speed
=3500 / (2 x PI x18000/60)
=1.86 Nm

So about 2Nm, and that will not drive a 25mm drill through steel, you'll need 30-40Nm for that. 2Nm is enough
for maybe a 5/15 or 3/8 drill, maybe 1/2 if you babied it.

The problem with high speed spindles is that while they sound very powerful (because they're so fast) they have very little
torque.

Craig

The higher end spindles don't work the same as the budget spindles do. The torque vs speed graph graphs are different. And they give you the parameters to program your V/f curve into your VFD, which can be significantly different from spindle to spindle.

Look at this example from an HSD spindle:

https://www.hsdusa.com/bo/allegati/Files/2710_es508.pdf

It has it's highest torque below 8000 RPM. So the math you used would not work for this spindle from HSD.

For the spindle the OP mentioned, you just assumed that max power was only developed at max RPM, and that the max torque was constant throughout the RPM range, or was there a chart in the link somewhere that I missed? Anyway, your assumption (unless I missed a spec in the link, it's possible) is probably correct in this instance. For inexpensive spindles, this is usually the case, and they may or may not even bother to give you a graph.

A 25mm diameter drill into steel....well that would need to be spun very slowly, lol. Off the top of my head, I'm guessing like, 60 RPM, or around there would be not too far off. So yeah, it's ridiculous to think that this spindle could do it. Unless you had a separate tool holder attached to a gearbox with a high gear ratio, and you just used the spindle as a motor to drive the gearbox. Lol, then yes, it might be able to.

[dazp1976]

"How much load can this spindle take?"
Not much.
You need a mill for that.

[mactec54]

Spindle link :

https://robokits.co.in/automation-co...-220v-18000rpm


Can this spindle turn a twist drill of 25mm dia through mild steel 40mm thick plate??
Please Explain.

25mm drill in steel with this spindle or any type of high speed spindle like it, will not drill a 25mm hole in steel 12mm drill would be a struggle

[Akhil]

Oh that's really sad. All of you seem to be correct. Did talk to the supplier today after a lot of waiting.
Thanks.
Could you direct me towards a workable solution?

[joeavaerage]

Hi,
one solution is to use a big radial arm drill press, really this is exactly what they are for.

If you wish the use your CNC mill then you might consider a circular tool path and mill a circular pocket with a normal size,
say 10mm endmill. In order for that to work your machine can have no backlash otherwise the hole will be out of round.

Craig