First cut in aluminium. Disaster.

**Edward** · 27-01-2017

With my Sieg2.7 mill all cnc converted, I have been testing it with a few scrap pieces of Delrin, cutting pockets holes, etc, to fit various ballbearings.

This helped me get acquainted with Fusion360, using Adaptive clearing first, then finishing off with 2 passes of Contour, etc.

So far so good, perfect and smooth results and I was feeling quite smug:)

So this morning I tried aluminium for the first time, just a typical hole of 30.05mm on a 15mm thick scrap, like you would do to fit a ballbearing, so I could check accuracy and so on.

My feeds were 200mm/min and the adaptive cut was set to 2mm both for radial and plunge. 8mm endmill, at top 2000revs.

It all started very well......but then, as the endmill got close to the periphery of the 30mm circle, disaster struck. The whole thing jammed. Luckily I was there to press the e-stop and no major damage happened. I lifted the Z. The endmill had some aluminium welded to it, I tried to snap it off, but it is too welded, so goodbye endmill, it was nice while you lasted:) F&^%*

So next time I will be more conservative, maybe I will reduce the feed to around 150mm/min and the depth (both radial and axial) to around 0.4mm. I know this will be fine because I regularly use this when milling manually on another smaller mill. If successful, I will increase this depth as I gain experience, just to find the limits of the machine, which I reckon may be at around 1mm deep at 150mm/min or thereabouts. Trial and error.

Any advice?

Edward

**Dangle_kt** · 27-01-2017

I had the same problem, chip weld isnt really about speeds and feeds from what I can tell (well it might be if they are way out I suppose).

Anyway - chip clearance is critical, as is the right endmill - to begin with try 3 flute HSS endmill of a decent size, and use compressed air directed at the endmill at all times.

I used a 3 flute endmill, but it was TiLAN coated, and thats no good for alu! OOPS! Lesson learned, either plane carbide or HSS for Alu.

**Edward** · 27-01-2017

Thank you. It was a nice 8mm carbide endmill that I normally use with manual milling and it cuts nicely, though I normally go a lot more conservatively. I have the helicoidal ones made for aluminium too, but in any case, I think the depth I set was quite brutal for this machine, even though the manufacturer recommends 3.2mm cuts, but of course this is for big professional machines.

Edward

**Dangle_kt** · 27-01-2017

Am I right in thinking it was cutting ok at first? If so its not the aggressive cut that was the problem.

The more extreme cut will make many more chips, which need evacuated - When I get chip weld its from a build up, once it starts it then snow balls. What were you using to evacuate the chips?

**Edward** · 27-01-2017

I think it soon started to clog up, as you say, progressively, I was vacuuming the swarf as it happened. I am now going to try the same, but reducing the feed and depth, so how it goes.

**bikepete** · 27-01-2017

Also try squirting on some WD40 as a cutting lube - may help prevent sticking...

**njhussey** · 27-01-2017

Blowing air is much better for clearing chips than vacuuming.

Ideal scenario is an £8 mist system from ebay coupled to a pot of WD40 and a compressed air supply.

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**komatias** · 27-01-2017

Reducing the feed will not do much. You need to evacuate the chips and keep the cutter cool.

With a carbide tool on, I have in the past, when out of soluble oil, just used compressed air with fine results.

That said, how many flutes endmill did you use? Not good to use 4 unless you know what you are doing. Preference is 2 with a rapid helix to assist evacuation.

**Edward** · 27-01-2017

It was a four flute normal carbide end mill, and not the ones designed for aluminium.

I have now tried the same but with a reduced depth of cut and reduced feed and it has done it well, albeit taking quite long.

Guys, I have a lot to learn regarding the optimum feeds and depth of cut, and lots of tests to do, I don't want to run before I can walk. But I thought I would post my first experience as I am sure many of you have been there too:)

Thank you for all the suggestions.

**njhussey** · 27-01-2017

Best way is to do what you've done, try...ask...listen then try again, ultimately only you'll know what works for your machine best which you'll find by trial and error. You'll snap bits, ruin work pieces and all that before you find what works!

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