Noobie trying to mill aluminium with a 6040

[GaryWilliams]

Hi All,

I have a 6040 CNC machine with an 800W watercooled brushless motor. Using Artcam Express 2013, Mach3 and a UC100 motion controller. With this setup, I can quite happily design and mill 2D shapes, usually in MDF. I have the 6040 housed inside a perspex & MDF enclosure with a dust extractor nozzle close to the workpiece, connected to my vacuum cleaner.

I need now to be able to mill 2D and 3D shapes in aluminium. I have the G-Code and have milled two test pieces out of MDF and an old offcut of kitchen worksurface. The 2D shapes will be milled out of 6mm aluminium plate and the 3D shapes, out of 40mm aluminium block. I purchased two good quality end mills, one is a 6mm 2 flute, the other a 3mm 2 flute. I have used the various calculators to determine the correct spindle speed and feed rate. They all give fairly comparable results so I guess they must be correct. However, when I set the 6040 going, she seems to be rushing too fast and the surface finish is poor.

I have watch many YouTube videos of people happily milling 3D shapes where the 6040 seems quite happy. My first attempt is shown in the attached photo. I did use a cutting oil sprayed onto the end mill from an aerosol can. To what should I set the spindle speed, feed rate, step down, etc, to correctly mill this 3D block? Is slot milling a sensible idea?

Any help gratefully received.

Regards

Gary