Tried to mill Al with router dont like cut surface

[eerikkarts]

First I am newb in CNC but I am learning so dont beat me too hard

OK I tried to mill some aluminium with my gantry router and at all I am pretty satisfied with hole result but its not perfect

When i cut the detail bit leave not smooth surface, You can see on pics

Bit is 1/8 inch and spindle head is Kress 1050 max RPM's are 32000
Bits are 1/8" Carbide 4 flute endmills from Kyocera Tycom and
1/8" 2 flute carbide endmills made by Kemmer Precision

I tried to mill by chip load calculation.
Usualy carbide tools have chip load for Al .0010/ SFM 600-1200
My gantry top speed is 37ipm
So I'm calculated a litle bit and got recommended RPM's from 18336 (RPM = (3.82 x SFM) / D)
By this spindle speed i need to archive feedrate IPM = RPM. x CHIP LOAD x F
it will be ~73IPM with 4flute and 2flute = ~36IPM

I am tried follow by calculations but results are similar with 2 flute endmill surface even worse by 36IPM, 4 flute leaving this surface what on picture on ~18000-20000rpm's even tried 10IPM on max RPM's ~32000

I tried climb cut, always used coolant and results are still similar with minor difference.

What I am doind wrong? Maybe recommend what settings to try?
Or no chance to archive better surface

Sorry for my bad english

[VWSatOz]

you might be getting "chatter" meaning vibration from having too many teeth in contact with the workpiece during a heavy cut. Due to the thickness of the work and the spiral of the cutter then with multiple teeth cutters you will have maybe 3 teeth rubbing on the side surface at once. This increases the vibration problems 3 times compared to having only one tooth making contact. When one tooth is in the cut and asecond tooth starts to make contact you then get twice the side deflection, the cutter lifts off more or vibrates more. One way to get over the problem is to buy a SINGLE flute cutter with a high spiral angle and take a light enough finishing cut so you have the smallest contact patch possible and the smallest side force between the cutter and the workpiece, this will also reduce the contact area and so minimize the vibrations the cause the poor surface finish.
Alternately you can grind away 1flute fron a 2 flute cutter to create your own single flute type. Climb mill all the time to get best results of accuracy without deflection undercuts and to avoid drawing swarfs into the tangency zone.
The spindle may also not be rigid enough design to not get vibrations. Vibration and chatter might also be reduced if you slow the rpm speed and/or increase the feedrate per tooth. The heavier chipload seems to dampen the vibrations within the chip itself.
The cutting edge must be very sharp and flutes highly polished and not coated. Special bits are available specially made to cut aluminium.
Never let a cutter dwell into a corner of a pocket with linear moves. For example a 2mm radius must not be made with a 4mm diameter cutter, you could use a 3mm cutter with a circular toolpath to get less contact and less chance of chatter in the corner.
Very shiny surfaces can result and highest accuracy without taper of the sides.
Carbide cutter is much more rigid than HSS. Keep the cutter length protruding from the chuck as short as possible, even reduce the flute length by grinding off the end if you must. Grinding slightly on the neck diameter of the cutter to create a shorter flute length just near the bottom also works if you must have a long reach down into a deep pocket, and don't cut the bottom and the side at the same time as one vibration/deflection affects the other.
I hope all this helps! Keep experimenting! These all tricks I learned by trial and error!

[LeeWay]

One other thing you might try is to leave just a tad bit of material on for a finish pass. Depending on the depth, do a finish pass in one or two passes. If you get the cutter bending away on a finish, you could use a little larger cutter or take off less.
No matter though, I think a finish pass would give you a better finish.
Perhaps not a lot better, but possibly. The spindle you have is known for being pretty good. I get a pretty fair finish with my PC on the router table. It has the problem of the spindle actually floating upward on hard cuts, so I have to keep them shallow and fast.
I have a little Ridgid trim router on my mill and use it specifically to cut profiles in aluminum sheet. It works great for that and has nice finished edge. It too has the floating spindle issue, so not real good for surface finishing, although it was likely as good as I had on the manual X2.