In the same boat...trouble roughing aluminum

[rc-cellar]

I just finished mounting up a new Porter-cable 690vs router to home-built cnc. Cuts thru wood and plastic just like butter. Will carve Elvis-on-lexan at a later date. Right now I'm feeling the urge to build a big-ass r/c monster-truck (giant T-maxx)...I'm sure you all can relate.

I want to cut shapes into 6061 plate 1/8 to 1/2 thick. I was having some limited success with my poorly-mounted, beat-up, Bosch laminate trimmer.... it was a struggle, but I managed to cut out a few parts (like those router mounts). Now I have added a bigger router, stronger mounts, a cold-water cooling system (ice-maker kit from home depot),and a good work-hold system.

Drilling goes OK (10Krpm still seems fast to me). Finish passes not bad (shaving a few thou with 1/4" carbide 4-flute endmill).
Roughing-out is a different story. I thought the new setup would chew right through, but Evil vibrations are causing the tool to stray. I am forced to take light cuts at slow feedrate...not good. It is obvious there is some flex in the router-shaft or slop in the bearings.

I have read all the great suggestions here about different tooling, upgraded bearings, spindles, motors, etc.... I get the feeling that a router will never work well on aluminum, just because it spins too darn fast. Does anybody agree with this?

If I were to go to a spindle arrangement (strictly for aluminum), what tool rpm and HP should I be shooting for ??
What speeds do Bridgeports or VMC's run??

[JavaDog]

Are you sure you are going fast enough?

From what I have been reading, it seems like 18k is the bottom end for Aluminum with a CNC router...someone please correct me if I am wrong.

[ger21]

I wouldn't call 18K the bottom end. With a 1/4" tool, you want a chip load of .002-.004. Depending on your feed speed, you may need to go much slower than 18K. Also, a 1/2" cutter might cut a lot better, due to the bit being a lot stronger. I cut wood all the time on a commercial router, and 1/4" bits always make a LOT of noise when cutting, while 1/2" bits are virtually silent (when sharp) cutting a lot faster.

[NHughes]

I have much experience cutting with aluminum. Very successful, couple of things to remember, have a look at my machines on the classified section one under machines (nhuges is lister) and one under instructional (nhughes is lister)
the key thing to cutting aluminum is the tooling and the type of machine and the cutting fluid.
16k rpm is best, 1/4" diameter tool is best, feed rate of 50+ ipm is best, however, the machine needs to have screws, not belts,or racks for driving the axis.
The spindle if bosch or porter cable has .008" runout in the spindle so you will need to use a much higher quality spindle and the rigidity of the linear bearings is also critical,
drop me a line if you need more help
multicutnc@yahool.ca