First cut in aluminium. Disaster.

[Zeeflyboy]

Depends what spindle you are using - when you have the 2.2kw 24krpm spindles Like I'm using there they really don't perform well at low rpm, so for good alu cutting on them you need to either have unrealistically high feed rates for a hobby machine where you start running into rigidity issues, or you need to move to something like a 2 flute or single flute cutter.

I wish there were some 12,000rpm options in the water cooled spindle variety at around 2.2kw but it seems you either drop down to 8krpm max (and those are massive!) or stick with the 24k rpm and try to make do with single flutes etc for the best results.

[JAZZCNC]

It's all about how you approach the job with high speed spindles. If you use 3 flute roughing cutter you can hog away big lumps at good feeds then finish with full depth pass. Works out quicker and cheaper because less wear on tooling.

Now to the OP your always going to struggle with 4 flute cutters with such low feed rate. Know this is going to sound crazy but needed to be more aggressive not less.! . . You really should have been double the feed.

[Ukmiller]

I would cut alloy at 6000rpm and take smaller cuts and go faster on the feedrate with coolant on.
If the chips get big then it will jam up.
My machines have flood coolant.
The ideal would be air jets to blast out the chips.

[Boyan Silyavski]

On a small mini mill i dont see how a good result will be obtained when deeper cuts than 1mm??? Normal 2 flute carbide cutter 30 degree upcut will give best results all over. 5 euro from China. There are better made for aluminum bits but they are not made for small machines anyway. They are made for serious machines and can give much higher material removal rate, which in this case is not viable.

What aluminum you are cutting? No name piece of aluminum could be absolute shit to cut. Buy only aluminum alloys made for certain purpose.

From my experience i can cut using any bit up to 3 flutes. Even straight ones or carbide tipped made for wood only. And result is always perfect. The key i say again is the machine rigidity. Any vibration heats the process excessively and things happen. Use the HSMAdviser calculator and you will see that perfect cut is never so deep as many people think.

As a general rule of a thumb that perfect cut happens at 12k rpm 1500mm/min 1 mm depth with any bit 6-12mm.


the tool stick-out is the another detail you should pay attention to. As even if machine is sturdy, the unnecessary stick-out changes the game quite much.

[Ukmiller]

I have some end mills that are the following spec.
12 diameter 4 flute.
30mm flute length.
42 degree helix.
Solid carbide with a high hardness rating.
They are what i use for every material.
I can use them on plastic and alloy and stainless no wories.
If i am cutting an external profile in alloy i can go full depth cut and cut with the side of the cutter and cut 1mm off the profile at 3000mm/ min with coolant on.
Internal holes and pockets i just run 0.5mm cuts at high feedrate so it doesnt take long anyway.
But we dont do high volume work so thats ok to us.
Maybe if we had a high volume we would have to use specific alloy cutters to speed up internal machining

[Edward]

Well, since I originally posted, I've been learning a bit about my mill and no more endmills have been broken.

I now use the Alu-power carbide 2 flute and 3 flutes from Cutwel. They are a little more expensive but they work well. I know it's overkill but I like good quality sharp and shiny tools :)

My mill can only do 2000revs. which I always use.

Using Fusion360 with Adaptive to cut a pocket or remove material I use an 8mm 3 flute cutter, Helix plunge down fairly slowly (20degree angle) to about 6mm depth with a plunge feed of 300 and WOC of 0.5mm. Once it reaches the 6mm depth, I go faster at 350 feed and 0.5mm to enlarge the pocket. Then repeat the same with the next 6mm depth and so on.

I use no coolant or air, just a vacuum to suck the swarf. No problems at all at these settings.

It's fairly conservative, I am sure I could go deeper at these settings.

I have tried more WOC, up to 1mm, but that's when the problems start. The TTS type tools can start pulling out of the collet with the consequent accident to follow.

I am sure that if I just used a normal R8 collet only, I would be fine with 1mm width cuts, but with an 8mm cutter it seems to be too much force for the collet to grip the TTS tooling properly. It's fine with smaller diameter endmills though.

Edward

[Ukmiller]

2000 is quite slow for alloy but if you have no coolant or air then i would say you couldnt go any faster anyway.
Aluminium melts so easily and can break cutters