Question Aluminium milling disaster

Hi,

Had my first go at milling aluminium today - and the first failure. Broke my favourite 3mm 2 flute carbide cutter!!

Parameters I used were:-
Spindle - 18000rpm
Pass depth - 1mm
Cutting speed - 10mm/sec
Ramps set to 5mm

Tool appears to have broken near the bottom of a 12.5mm profile cut and had build up of swarf on the cutting tip. The vacuum system appeared to be removing swarf but clearly was inadequate judging by the state of the tool tip.

Any suggestions for modifying the cutting parameters would be gratefully received. Do I need to have cutting fluid present as well?

I really don't want to have to revert to my mini mill - a 10 minute job on the Stepcraft would be a 1 or 2 hour marathon on the mill - once I have a viable machining plan sorted.

Disaster picture!!

Looks great!

There are many different types of Aluminium, so some are good for milling, some not. However, I think your spindle speed is much too high. I did some experiments with 6000 rpm and pass deeph of 0,25mm using a 2mm 4 blade (?) endmill. Also I always use some drops of a mixture of water, dish-liquid and grain-alcohol for cooling.


Good luck!

Hi Hartmut,

Thanks for the suggestions. Aluminium grade is (mis)quoted as 6083T6 - I'm sure it's meant to be 6063T6, that is supposed to machine OK from what I can discover.

I'll do as you suggest and reduce pass depth and spindle rpm - sounds as though gin might make a good coolant - for me I mean

I was wondering if machining the hole as a pocket rather than a profile might make chip clearance easier - I don't need another broken endmill?

Thanks again,

Peter

Hi Peter.

I presume that you've read the CNC Cookbook article on milling alumnium?

blog.cnccookbook.com/2012/03/27/10-tips-for-cnc-router-aluminum-cutting-success/

I plan to have a go at this in due course for cutting a foldable net out of 1.2 mm aluminium plate and for milling a piece of bar.

I bought a 2 mm two flute carbide end mill for this.

I can run your parameters through GWizard if you want. Do you have this software already?

Regards.

Doug

Doug,
Thanks for the CNC Cookbook link - I hadn't come across that before to be honest and the section on aluminium was well worth reading. Your offer on GWizard is much appreciated too - there is a limited time trial available as well.

I've examined my disaster in more detail today, and it would appear that the cutter broke before reaching the bottom of the circular profile. Almost certain that it was build up of chips that caused the problem - this means the standard Stepcraft vacuum system is nowhere near strong enough to clear chips at the bottom of the groove. Since my router is inside the house, an air mist to cool and clear chips isn't a viable option either.

Having though about the design, the 17mm circular hole can be drilled and then turned on my lathe using a 4 jaw to centralise the work. Also if I make the top square instead of a fancy curve then everything else can be done on my mini-mill. I tried milling the same material using a new 5/8" end mill and around 3000rpm, and it all looks fine if I vacuum the chips away continuously on a 1/2 mm cut.

The end result will be a ballnut mounting adapter.

Peter

Pass depth.

drop that to 0.1 or 0.2mm and keep the feed high and you will see very different results.

Ok when I machined ally on my 420, I knew plunging was an issue so 0.1mm is probably a good idea.
I was machining a profile so i came in from outside the job , fooling the machine i had a larger cutter and just edited this in mach 3 over several passes. Edit tool 1 diameter make it say 4mm when its a 3 mm and run the program with an edit of 0.2 smaller each pass.
As for lubrication, anything wet applied before your first cut will be good.
I use an uncoated end mill and with T6 is ok, but for a better finnish on the final cut use something light in lubrixation.
I know wd40 is not deemed to be the correct lube, but i dont have probs, so you could use Spit, sewing machine oil, anything wet will work.

I just started reading the CNC Cookbook aluminum article. Does anyone have g-wizard settings for a 600 with a Kress? Thanks!

davidbitton wrote: I just started reading the CNC Cookbook aluminum article. Does anyone have g-wizard settings for a 600 with a Kress? Thanks!

David,

Forget G-Wizard. I have. It's not that specific and not particularly helpful.

https://www.stepcraft-systems.com/en/forum/operation/3910-problem-with-dimensions-using-fusion-360-uccnc#45078

On this thread, I had a go at milling 1050A aluminium cut using a 2 mm 2 flute TiAlN coated solid carbide end mill at 0.1 mm depth per pass, 900 mm/min feed rate, 30 mm/min plunge rate and 12,500 rpm spindle speed. It was a mess but the piece was recoverable with a lot of manual filing. I subsequently realised when trying to use the same cutter a few weeks later on acrylic sheet that it should have been run in the REVERSE direction. D'oh! I'm afraid that I haven't tried another cut to see how big a difference that would have made, but I suspect it would cut o.k. running with the flutes in the correct direction.

Nevertheless, harder grades of aluminium should mill better and the application of a supply of compressed air to the cutter for cooling and to aid chip removal is highly recommended. I don't currently have a compressor.

Doug