Deep Slot Milling in Aluminium - Optimum Cutter Diameter

[guy_]

In my experience, chip welding (recutting) is the risk with deep slots in loominum. Pretty much all of the cutters I've broken over the last 2 years have been due to this. The best solution in my situation seems to be to ensure a constant supply of flood coolant, which both cools the chips down and clears the from the danger zone. I don't know if that would work for you, depends how much coolant you get get in there. Must admit, I do get a bit carried away with the feeds and speeds which probably doesn't help.

Using a smaller cutter and an adaptive path might at least reduce the chip size a bit and leave more room for chips and coolant to evacuate. If you are doing a 25mm deep slot with a 4-5mm cutter, you will be doing it in several (4-5?) stepdowns.

Dunno what others think?

To be honest, I haven't had any chip welding while using flood coolant. Even if the cutter is running through a pile of chips it sounds grainy and generally to be avoided but it hasn't actually damaged the bit so far. The flood coolant is not as good at removing the chips in a deep slot though, when compared to an air pressure feed. Unless the coolant is pumped into the slot at high pressure, which makes a massive mess of the enclosure, the chips kind of sink in a pool at the bottom of the pocket / slot.
As for the step downs, I'm pretty new to this and am being very conservative on cutting depth. I won't go more than 1mm cut depth for a slot. As I'm not cutting for cash, I don't mind high cycle times and although my machine is capable of cutting deep pockets in Al, I don't want to risk any more carbide cutters.

[JAZZCNC]

I won't go more than 1mm cut depth for a slot. As I'm not cutting for cash, I don't mind high cycle times and although my machine is capable of cutting deep pockets in Al, I don't want to risk any more carbide cutters.

There's part of your problem straight away, Carbide likes to be pushed hard and 1mm Doc isn't enough with a 6mm tool. Could easily double this and more without breaking the tool.
Next is the intermittent cut caused by the holes you drilled, Carbide doesn't like shocks and intermittent cutting, I would stop doing this.

I find Mist cooling with plenty of air is better than flood for slots.

[guy_]

To be honest, I'm not sure what you mean when you say that carbide likes to be pushed hard. I know that it can be pushed hard and my DOC could be bigger but I'm just getting to grips with what my machine is comfortable with. The intermittent cutting is really the same as any stepover. I know carbide is brittle but I haven't seen any damage to my bits from doing this.