T6,Brass Feed/Speeds NOOB here

[franzschluter]

Hi,

Recently I've begun my journey into milling with a regular CNC gantry (Alu frame). So far I haven't had any problems cutting on wood and plastic. But now I have projects that require on working with Aluminum T6. I use Rhinocam for providing toolpaths and feeds. So far everything has no problems but figure everything seems to be too "slow". I know there are multiple threads regarding feeds and speeds but I am having this big headache sitting for hours just reading through them all and converting them to metric system and not to mention understanding what people are refering to. Again I would like to apologize, for this topic has probably been covered already a thousand times. But I just can't get the picture straight... And hope somebody would give me a number on what I should enter in my cam software.

For example:
I use the following parameters:
4mm flat end mill (2 flutes HSS)
No coolant but with vacuum to rid the chips. Sometimes I use the regular cutting oil or alcohol to cool the bits. But found it not necessary since the bit barely even heats up? I go on feed hold, switch off the spindle.. Touch the bit.. And figured it to be luke warm. So I guess I'm running too much on the safe side...

RPM 9000-10,000
In my mach3 software it says 650units/min under the feed dialogue. My units being in mm, would then mean 650mm/min. I use a depth cut of 0.15mm and step over D/4 or 25%.

During cuts everything seems to run fine except that my chips come out as powder? I have no idea if this is normal. The entire process on pocketing a 310x310mm to 2mm depth takes me 8 hours. I think this is just to slow or is this about right?

I have 3 spindles at home and have no idea which I should choose.
-Suhner Spindle 3500-24,000 rpm 1kw
-Proxxon Spindle 900-6000 rpm 250W
-Maho Gildemeister Spindle 45,000 rpm 5kW

With cutters, I do also have a set of collection and broke a few also. I figured for example that my carbide cutter tends to build a layer of aluminum on the bit whereas the HSS would do perfectly fine.

In terms of rigidity I guess I am using a hobby CNC gantry router from BZT. It's a PF600 model. And as much as possible would like to run everything within safe parameters.

What I would want to know is an approximation of what parameter would be not too slow and not too fast for a 4mm HSS end mill 2 flute. 0.15mm seems too friendly compared to the videos I see on youtube. To be more exact..

I'd like to know the following parameters:
StepOver Size:?
Depth per pass:?
Feed Speeds: Cut feed I have set to 650mm/min? Can I go faster?
Plung Speeds: 25mm/min? Slow But maybe a little more or?
Ramping: 10 degress 0.5mm height?

I figure when I get this value I could then approximate for smaller cutter diameters since 4~6mm would be the largest cutter to be mounted on my router.

Best Regards
Franz