Milling: low depth passes or all the width?

[PEU]

Im doing my 1st steps in aluminium milling and I have one doubt:

Which method is the best, milling the piece in low depth multi passes at normal feed or mill the whole height of the piece at very slow feed?

Im using a 7000-27000 grinder and an 1/8" 2 flute endmill, the piece height Im cutting is 15mm (0.6in)

The first piece I made I used multiple passes, but since I finished it, this question is puzzling me.

I see advantages in both methods, I need some advice.

Thanks


Pablo

[ShayArnett]

the proper way to do it would be to calculate the chip load for your tool, and feed at whatever depth you can at that speed without chatter or missing steps.... milling slower at full depth might get that cut done quicker but it will also wear your tool out quickly

[PEU]

And how I calculate that?

Thanks


Pablo

[PEU]

I need advice on this one. Thanks


Pablo

[yukonho]

As a rule of thumb, you generally cut at a depth no greater than the radius of the bit you are using. If you try to cut .6" material in one pass with a 1/8" bit, you will go about 1/2 mm before you break your bit.
Milling aluminum on a router is a bit of a hit and miss procedure. Chipload is the amount of material each flute of the bit cuts on each revolution. With a router, the bit is spinning super fast, so the feed rate needs to be high. You can look up chiploads and do the calculations, unfortunately I dont have a source for this info at hand.
I would recommend having your router at about 60-70% RPM, take 1/16" depth per pass, and feed about as fast as you can. This is a starting point, have plenty of bits ready and be prepared for some trial and error on this one.
A milling machine, bigger bits, more torque and properly calculated speed and feedrates are the proper way to cut aluminum, but if your router is rigid enough, you can get reasonable results.
colin

[PEU]

Ok thats a starting point, Thanks Yukonho, so 1/3 of cutting diameter for the depth as a rule of thumb and slowly increasing feed rate till I feel comfortable with the chipload.

I also have a 1/4" 2 flute end mill, will try that one today.


Thanks


Pablo

[cut more]

Pablo,
Try this site for feed rate and spindle speed calculations.
http://www.robbjack.com/html/tech.html
I do not know what you have for a router but I was routing 6061 aluminum this weekend with mine, 1/4" 2 flute endmill .025" depth @ 20inches / min. between 10,000 and 16,000rpm.
Hope that helps

[PEU]

Yesterday I cut this piece with the 1/8" 2 flute endmill:



I used: 500mm/min (about 20ipm) and 0.2mm passes (.008") but this was my 1st time, I will be braver today


Pablo

[jkeyser14]

What sort of power does that dremel output? .008" is not very deep per pass. I'm using a 1/4 hp motor and taking passes at .050" and could easily go deeper except for fear of breaking the bit.

Just