Need help with cutting Aluminium

[suspension]

I have been cutting aluminum for the past couple of days using my 6040 Chinese CNC. Although I manage to mill the parts I want, not that pleased with the whole process and the finish. The biggest issue being welding of aluminum to the cutter. I've tried 2 flute 4mm uncoated carbide cutter, 2 flute 4mm coated carbide cutter and 3 mm 3 flute HSS cutter with no much of a difference. I am running the spindle at 24000 RPM, feed rate at around 480mm/min and depth of cut is 1mm. I am using a metal cutting coolant together with a high pressure air stream. The issue arises when I cut deep slots of around 10mm. First few phases goes smoothly and when the depth of the slot is around 5-6mm, welding starts to happen. Here are the things I tried:

1. Reduce RPM, but this increases vibration/noise considerably so not an option.
2. Increase federate. Although this seem to solve the problem, my machine misses steps at higher speeds, so not an option either.
3. These slots are cut as the final milling operation to remove the part from the remaining stock. Rather than cutting a slot with the width = cutter's diameter, I increased the width of the slot and ordered cuts based on depth. This also reduced the problem considerably, but not fully.

None of the above mills are specifically designed for Aluminum although they have either 2 or 3 flutes.

Since I have run out of options, I am thinking of buying some aluminum specific mills from here:
https://www.shop-apt.co.uk/

They list several roughing end mills for aluminum. Will they do a better job in cutting these slots?

Cheers
S

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[awerby]

You don't say what kind of aluminum (or aluminium) you're using, but it makes a big difference. Some are soft and gummy and will machine poorly no matter what you do, and stick fiercely to your cutters. Go with a known machinable alloy that's hardened - harder alloys are actually easier to cut. 6061 T6 is popular in the US, but you'll probably have to check around wherever you are for an equivalent.

To make slots, it's best to rough them with a cutter that's smaller than the full width of the intended slot, taking repetitive shallow cuts down the middle, and then finish with a climb pass to clean up the edges and achieve the full width.

I've never used specific roughing cutters for aluminum, only for steel. Usually a 2-flute cutter is good, but since your spindle is so fast and doesn't seem to like slowing down, you might try a single-flute endmill: Precision Cut Single Flute CNC End Mill, Premium Carbide,Cutters

[coherent]

Coated bits don't work well with aluminum. Aluminum is sticky and you need to use a uncoated carbide (prefered) or HSS. Use a upcut single flute bit with a high helix. The high helix clears the gummy chips better. The more flutes/cutting edges the more heat generated, hence the single flute. Make sure its new/sharp.
Other than that, slow down the rpm to around 18k then you be able to cut cut within the cut speed capabilities of your machine without loosing steps. Also the larger bit you can use the better within reason. A 1/4in is a good all around diameter for aluminum. Smaller diameter bits will generate more heat and require faster cut speeds.
Good luck!.

[suspension]

I am using the spec 6082T6. According to mu vendor these are suitable for machining. I will look in to the cutters you mentioned. Thank you.

[suspension]

@coherent
Thanks for the info. I have never tried single flute cutters so far. Maybe its time to test them out. Cheers.

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I've never used single flute cutters before. Maybe its time to try one. cheers.