How much deflection to expect...

[Wal]

Right, the build is nearing completion with homing and limits nearly all sorted, just need to machine me some new switch mounts - the ones on at the mo are rough fabricated jobs and I thought it would be cool for the machine to make nice ones for itself. Here's a vid of the mill cutting the switch mount profile shape into a block of semi-scrap 6082 I have lying about:



In the vid I’m using a 4mm square end-mill (2 flute) which is spinning at 12000rpm with the work feeding at 400mm/min. My initial depth of cut was 0.5mm with a 12.5% step-over. it’s a climb milling operation. Ignore the holes - they’re not part of the job, I used the plate to cut spacers from a while back… By and large, I'm pretty chuffed with how this test cut came out.



I've also had a go at perspex, which machines very well at the same settings as above (but with a faster feed-rate of 1200mm/min).

The other day I tried milling these switch mounts out of the ali that Apple use for their Mac Pro towers, which just shredded up like this:



I tried a few different feeds/spindle speeds, but to no avail. Earlier this evening I tried machining 'em using some old 3mm ali sheet that had been lying under my dads bench for probably the last 20-odd years, still no joy. Any recommendations on the grade of 3mm aluminium sheet I should be looking at for this kind of profile cut?

Cheers!

Wal.

[Clive S]

Wal Looking like a very nice and cable machine, don't scratch it lol , I remember Dean saying more than once that some of the best machines are achieved by people with daytime jobs with no mechanical back ground because they will listen and learn. Well done. ..Clive

[Wal]

Clive, listening and learning is half the story - not only is this site a great resource, but I've said it before and I'll say it again - to have been able to come over to yours and have a look at your build and learn from you was an invaluable privilege - I've no doubt that this project would have taken me considerably longer and been weaker for it had you not spent the time and effort patiently talking me through the stuff I didn't have a clue about. Thanks again!

Wal.

[Jonathan]

The other day I tried milling these switch mounts out of the ali that Apple use for their Mac Pro towers, which just shredded up like this:

Any recommendations on the grade of 3mm aluminium sheet I should be looking at for this kind of profile cut?

Were you using any coolant? A little spay of anything wet can make all the difference. 6082 is a readily available grade that's easy to cut. Avoid 5xxx series grades.

[Wal]

Heh, yeah - I guess it is a bit bag-pipey - should've had it sprayed tartan..!

I didn't use coolant on the profile cuts into the sheet, Jonathan. I may give it a go sometime, but to be honest the tearing was brutal from the moment the mill touched the surface, whereas the 6082 billet cut very nicely! I'm trying to get hold of some 6082 sheet (ali warehouse don't carry it) so if there's anywhere you can recommend then do let me know!

Cheers!

Wal.

[Jonathan]

Bear in mind coolant doesn't just cool - it lowers the coefficient of friction (i.e. it lubricates) between the tool and the metal. That means less heat is generated to start with...