Originally shared by Marcus Wolschon
I have the earlier model of this one:
http://www.carving-cnc.com/cnc6040-series/cnc-6040z-s80-new-router-engraver-drilling-and-milling-machine.html
The very limited 60mm Z travel is the downside of this machine.
Do you think I can mill longer replacements for the 2 sides from AlMgSPb ?
I want the “bridge” of this portal mill to be higher, so I can use the 4th axis to mill parts with a 60mm radius instead of just a 60mm diameter.
What do you think?
Is that possible?
Is this aluminum easy to mill but too weak for the job?
Any better way to do this?
Definitly make new sides. Use aliminium easy to machine and strong enough for sure. The only thing I would think is the gantry 60mm higher might have more sway left to right. But you could stiffen this with a piece of the same aluminium running the up the sides facing out wards to make it less flexible. If you need tips machining aluminium let me know 
Is AlMgSPb strong enough?
Pretty sure that’s a 6000 grade aluminium I was going to sugest some thing like that or 6061. If possible make it a few mm thicker than the original
I have no idea what that means. 
yea i would use almgsipb but if you can make it a few millimeters thicker plate than the one currently on the machine so as to make it more ridgid.
What rpm and feed rate would you start with using… Say… A 6mm 2 flute cutter?
what rpm can you reach and how much power has the machine ? is the cutter hss or carbide?
HSS
24K RPM max (1.5KW water cooled)
I have a working mist cooling.
I would have started cutting - 0.5mm at 20K RPM going a slow 100mm/min, then increased the speed judging by the sound I hear and then increased the layer depth based on me not seeing any deflection of the tool or unhealthy sounds. Then slowly lowered the RPM looking at the sounds the machine makes, the surface quality and the shavings.
im used to using carbide on a very ridgid machine that went to 12k rpm and at that i would take 10mm depth of cut with a 10mm carbide 3 flute high helix endmill moving at about 1 meter a minute. but for you i would suggest 12K rpm 1mm depth of cut endmill as short as needed in the collet and start feeding at 500mm and you could go up to 1200 or 1500mm per minute. but again i need to hear the machine and see its capabilities