How Do You Mill-Engrave Aluminum?

[tim_whitcher]

Hi, I've been wanting to engrave (or mill, not sure of the term) .25" aluminum sheet. My idea is to use a single stroke font and cut along the path, in a single pass. I'd like to cut 3/32 to 1/8 in depth, using a 1/8, 1/4 and/or 1/2 bit. I would then fill the stroke of the letters with paint. Anyone doing this? What type of bit is needed? What feed rate and spindle speed? Any other tips? Thank you.

[paco]

Hi Tim!

I'd say routing (assuming your using a router or 8000-20000 RPM spindle). Depending on your bit diameter (CED) you might have to go with shallow pass (0.01-0.04")... gotta test; depends on other variables... many types of bits "can" be used. Are you using a Bot for this?! I'd suggest to keep the RPM low and to lub. So far, I have prefered standard wood router bit (carbide tipped) for this purposes but I do use some 2 flutes end mill too.

Sorry, I can help you with the painting... but I believe AL require "special" primer/paint...

[tim_whitcher]

Yes, Shopbot with a Porter-Cable. So, shallow passes, low rpm. What about feed rate? Thanks!

[paco]

With a router (such as PC 7518) you will observe intense chattering (beware of bit breakage) from around 0.5"/sec. at 10 000 RPM with a 1/4" CED 2 flutes end mill. This is with a 0.02" stepdown. You may feed faster if higher a RPM but you may sacrifice tool longevity from heat build up... keep lub handy; mostly in "soft" AL... spraying every few seconds until a channel develop from the toolpath which will retain the lub... then you may spray less.

I've founded that the PC 7518 is'nt the right tool (though it can do the job) for AL routing since it does'nt keep a steady speed when loaded hard... I had to keep the feed lower or it'll bog.

With a 1/8" CED standard wood router bit, I feed quite the same but with a stepdown of about 0.015" not much... this is with a Milwaukee 5625 router motor.

One more word of caution with small CED bit; beware of hold down since it sometime make the sheet AL bend upward resulting in a deeper stepdown into the material in the first pass... and keep the hold down VERY solid in any AL routing...
4923

[Brady Watson]

Use an engraving bit...It is made for well...engraving! I recommned the Micro 100 brand engravers. You can get one with .25" shank, double ended with .005 tip for about $24.

-Brady

[tim_whitcher]

I'm really interested in a wider stroke to the letter than an engraving bit can provide. I also want the routed path "flat" with a 90 degree "wall".

[olecrafty]

Use a 2 flute flat bottom coated endmill. the trick is cooling I use a constant flow of air through a small nozzle with a needle valve for control. 10k to 12k rpm should be enough spindle speed. your travel speed will be trial and error

[dingwall]

A milling cutter designed for aluminum helps a lot too.

Paco, does your Milwaukee maintain constant speed under load better than the PC?

[paco]

#!?$* sure is!!!
4924

One thing shocked me recently; while visiting an industrial show, I walked up to a CNC vendor which has this spindle installed on is CNC router and it was as noisy as my MK motor at 22 000 RPM...!?
4925

On AL, when I use a 1/4" CED, I use a 2 flutes end mill; it's pretty much like a spiral up "wood bit" but when looking at it closer, I can see that the flutes are smaller thus a more rigid tool... and this tool bit was a few dollar less than an Onsrud...!?

[Call-Tech]

I just cut a mold out of t-6 last week on my shopbot and it worked great. I used a carbide router bit 1/4". I worked dry and took .030 per pass and a speed of 13,000 at .5 ips.