[Villageauto]

Hi Guys

I have a small cnc 290 x 290 x 90 bed with 2kw motor . I want to be able to cut out some parts in aluminium from 6mm plate, I think the better product could be 6061 or what do you suggest i heard of 2011-T3 and 7075 in T6? I wanted some help in choosing the correct tool for the job and the correct settings like feed rate and speed of tool, also lubricating the work while cutting ..I have tried some cheap cutters but they seem to clog up with sticky aluminium then either break or get blunt quickly .. I guess I need to buy brand name bits .. but would like some advise on what bit is best to do the job.etc I could post the dxf of the part i need to work on.

I have a similar issue with 2mm carbon fiber plate

Best regards R

[aarggh]

I use the cheap Chinese 3 flute cutters for aluminium, and go for a small DOC but keep the speeds up high. The trick is to use a lube, while the fumes are nasty WD-40 actually works the best here, or alternately I use a lanolin based lube on bigger jobs so I don't have to put up with the smell of WD-40. Start off with as small a DOC as you can and keep the speeds high, and just increase the DOC to a point your happy with.

Without the occasional small squirt of lube, the aluminium will immediately gum up as you've found. You don't need to soak it, just a fine mist every so often is more than adequate to stop the aluminium from sticking to the cutter..

When I get time, I'll be setting a misting system on my machine for this purpose.

cheers, Ian

[RCaffin]

Hi VillageAuto

Well, I assume you are in Australia. That explains a lot. Since we don't have any manufacturing industry in Australia, our main Al supplier Capral has decided we don't need machining alloy here in Oz. So all they make and sell is designed for bending. That means all the available Al is like chewing gum, and machines accordingly. Built Up Edge (BUE) is a constant fact of life here, and BUE ==>> broken cutters.

Since a few manufacturers do exist, a couple of small importers do bring in good machining alloy from USA. However, since Capral offers no competiton, these importers happily double and triple the USA retail price. I find that a bit too steep to accept.

China tried to export some better machining alloys to Oz at a good price, but Capral screamed 'dumping' and got some of them blocked. But Capral could not block the 6082 alloy, which is a fair machining alloy, because they don't sell it themselves. China then shot themselves in the foot by not doing adequate QC on their exports, and some bad 6082 arrived - with either inclusions or holes, I forget which. So the importers pulled back.

5083 sheet alloy is definitely like chewing gum. I machine it, but with some tricks. The 6060 alloy is slightly better but is still 'poor' for machining. The 6061 alloy is better. 2011 alloy is good stuff but only comes from Capral in round bar - no flats. 7000-series alloys are definitely good, but you will pay an arm and a leg for them as they are all imported at great profit.

I have imported Fortal, which is like 7075 alloy, and it is so very nice to machine. It is used in USA for mold-making. What is called 'tooling plate' is also good for machining, but it can be a bit pricy. Just finding it can be difficult.

Now, machining aluminium. You should really buy cutters designed for aluminium. They are different from 'standard' cutters designed for steel: sharper and with different flutes. Chinese ones are cheap enough on eBay, but they are a bit brittle. Go for cutters designed for an HRC number as high as possible. Do NOT use the same cutter on steel then aluminium. Very BAD idea. Do not use the TiAlN coating: it does not like aluminium. A Zirconium coating is best, but not always available. Plain carbide is usually adequate.

The real secret to milling aluminium, even the grotty grades, is to use an air blast to clear the chips away continuously, and to use pulsed mist lubrication. A 1 second pulse every 30 seconds is often about right. This is NOT to cool the cutter but to keep the cutter surface ever so slightly 'wet'. You do not get BUE on a wet cutter. The air blast prevents recutting the chips, which kills the finish. It helps.

I use my secret recipe for the mist: 3 parts kero to 1 part (very cheap) olive oil. The parts come out 'dry', and olive oil is unlike so many commercial cutting oils which turn out to be allergy-inducing, bacteria-growing, expensive to buy and really expensive to dispose of (legally). Look up Minimum Quantity Lubrication on the web, and believe it.

Cheers
Roger

[InMesh]

That is some good advice and information thank you .