Milling Aluminium - too fast?

Hi All,

I have a 6040 CNC that I want to use to mill a 2mm thick aluminium plate, 150mm x 150mm overall. I need to mill the profile, several holes and slots, the narrowest one being 2mm wide. I am using a 1mm end mill. I have used several feed & speed calculators but when I do a dry run, ie, above the workpiece, the feed speed seems very fast. The calculators give me a spindle speed of 15,000 rpm and a feed speed of 42 mm/sec. For such a job, what do you experienced guys think are good settings for feed rate and spindle speed? Yes, I have read several tutorials on milling aluminium but 42 mm/sec?

Cheers

Gary

Gary,
How many flutes does your endmill have, what is the flute lenghth, tool stick out and depth of cut are you calculating for?
What calculators are you using and are you sure that the calculators are giving you mm/sec? mm/min is more common, I've assumed a single flute cutter and plugged the numbers into HSM Advisor and I'm not getting numbers anything like yours,
Regards,
Nick

Hi Nick,

It is a single flute, carbide, length 10mm and depth of cut 0.5mm each pass

Cheers

Gary

Quote:

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Originally Posted by magicniner

What calculators are you using and are you sure that the calculators are giving you mm/sec?

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There is some very simple maths you can apply to sense check the cutting data you have quoted.

42mm/sec = 2520mm/minute
Your cutter has one flute and rotates at 15000rpm,
Divide mm/minute by (rpm X flute count) to get chip load, the amount each flute will have to cut through.
So
2520mm/15000 = .17mm chip load on that tooth = Ping! Next cutter please ;-)
Ballpark for your job will probably have 2 zeros after the decimal point.

Attachment 23576

- Nick

Thanks Nick. I understand that calculation. So the starting point for any calculation is the maximum chip load for the chosen end mill, according to its' manufacturer. From your screenshot, tool stick out (to minimise flex?) of 15mm, a spindle speed of 15000 rpm and feed speed of 57.15 mm/min will enable my 1 mm endmill to do its' job without breaking.

Cheers

Gary

Gary,
With a perfect machine, yes. Calculators will assume industrial machine quality, power, rigidity and spindle TIR plus near perfect lube & chip clearance, an air nozzle on the cutter and the occasional dab of WD is usually a big help on small cutters in aluminium jobs.

I'd suggest you CAM your job with those settings and then run a test, start off with the feed reduced somewhat on your controller, 60% or so, and see how it goes, if it's running smoothly you can move towards 100% feed in steps, some jobs will run faster, some slower, keep a work book with a section logging the ideal settings for the cutters and materials you use.

- Nick

Hi Nick,

Yes, all that makes sense. I have a tin of WD40 by the cnc. I'll start at 25mm/min as you suggest and see how I go from there. I have a pack of 10x1mm end mills so I should be able to get to the end of the job :)

Thanks

Gary