machining aluminium with 1.5kW spindle

[JAZZCNC]

Generally speaking the best speed for aluminum is 8000 rpm. Thats what my tests show. 25 ipm feedrate is good feedrate to start with. No coolant or soap water or sprayed alcohol via airbrush.

That's far too general and you can't say "Best Speed" because there is no "one" best speed for cutting aluminium there are far to many factors come into play which determine the speed.!! . . . . Material grade, cutter size, No flutes, DOC, Cut type ie: slot or side cutting, step over, coolant type . . . .And thats before you get into Spindle power and machine strength.

Can tell thou 100% There is no ONE speed does all and you'll fluctuate between 7-15K when cutting ALi with 4-10mm tooling with varying no of flutes and DOC & S/F etc.

Experiment is the best way to learn speeds & feeds and dont be affraid to cut deep, just be prepared and accept that you will break tools while finding the best cutting conditions for your machine and material.

[Boyan Silyavski]

Thats what i meant, in general. I remember doing a lot of experiments and always there was some smallish problem. And a lot of broken bits and melted aluminum :-). Then i read somewhere, /i don't know where exactly, but it was a person doing alu jobs everyday/ that speed 8000RPM is the key. And so it was, at least for me.
Again as you say- quite generally speaking.

[EddyCurrent]

1. Reading the VFD manual for torque boost (need to check it has this and suspect it will heat the spindle)

This is not applicable to your issue, Torque Boost is to produce initial torque from standstill, for example to get a heavy load moving, it usually cuts out at low frequency or when the speed you selected has been reached.

[routercnc]

Thanks Eddy. I misunderstood what that was for and this afternoon (before reading your reply) I experimented with boosting the voltage by 10% in the region of 4500rpm [default was 5% at 720rpm] and also had the DOC set to about 1.5mm. It happily cut a slot 50mm long (6mm 2F Carbide bit) without problems.

Now I'm confused. If the boost is momentary until the speed is reached it wouldn't have affected the torque delivered during the cut since I allowed the tool to reach the required speed before starting the cut. Perhaps everything was cold (tool and workpiece) and I would need to machine for longer to see if this was actually better.

Anyway before I could experiment further I had to take the machine out of action to send one of the ballscrews away for straightening so I'll have another play when it returns.

Thanks for the advice - I don't think things are so drastic as I first thought.