An air blast is a great addition to your machine if you often mill aluminium. It blows air towards your cutter for clearing chips and is normally also configured to supply small amounts of lubricant. This greatly decreases your chance of chip welding and will also improve the surface finish.
When providing lubrication it's also called a minimum quantity lubrication (MQL).
Firstly you'll have to decide which MQL kit to get. They can sometimes be a bit pricey but one can also easily go the DIY route, there are plenty of videos on YouTube on this.
The available kits can be separated into three different groups of delivering coolant:
You can choose one fitting your budget and needs, here are some examples:
Fogbuster (pressurized coolant tank)
Dynacut (venturi effect / pressurized coolant tank) (German website)
Coldend (peristaltic pump)
Of course an air compressor is needed and you should follow the specifications of the manufacturer of your MQL kit. Compressors can be really loud, buying one which has acceptable noise levels is advised.
For reference I'm using a Weldinger FK95 compact which provides 90l/min@4 bar and measures about 68dBA at 1 meter distance (unfortunately the noise specifications of most manufacturers don't hold up very well). When milling it runs about 50% of the time.
Plenty of lubricants exist but when milling aluminium the cheapest one is probably 20% isopropyl alcohol mixed with 80% distilled water, which yields great results. Datron also uses this coolant for their machines.
Isopropyl alcohol is highly flammable and while the 20% mixture will not directly burn, the alcohol might evaporate and form an explosive mixture with air. Only use this coolant in a well ventilated area, try not to inhale it and never use it on ferrous metals because of potential sparks! Also make sure it's compatible with your coolant kit.
Solenoid valves (optional)
If not already included in your kit you can wire your controller to automatically control your MQL system by installing solenoid valves on your coolant and air tubes. You can either buy valves fitting the output voltage of your controller if it can supply enough power or you can use relays in between if it doesn't.
With the M7 macro you can turn your air blast on, M9 turns it off again. Your CAM software likely also supports this and each tool/operation can be configured to use the coolant or not.
If puddles form during milling then reduce your coolant flow.
I have been successfully running air-blast on my PNC with LinuxCNC using the configuration settings seen below with a MESA 7i96 Controller.
Configuration was fine tuned with the following;
With this setup, an M7 (Mist) code will use a solenoid tied to an output of the MESA and open for one second, and close for 1 sec until M9 has been called. By changing the “setp siggen.0.frequency 1” value (shown as “1hz”) you can adjust the cycle at which it turns on and off.
In this same setup, an M8 (Flood) will open that same solenoid and leave it open until an M9 has been called by the code.
# external output signals loadrt siggen addf siggen.0.update servo-thread setp siggen.0.frequency 1 loadrt mux_generic config="bb4" addf mux-gen.00 servo-thread # ---coolant signals--- setp mux-gen.00.in-bit-00 0 setp mux-gen.00.in-bit-01 1 net pulse siggen.0.clock => mux-gen.00.in-bit-02 setp mux-gen.00.in-bit-03 1 net flood iocontrol.0.coolant-flood mux-gen.00.sel-bit-00 net mist iocontrol.0.coolant-mist mux-gen.00.sel-bit-01 net coolant <= mux-gen.00.out-bit net coolant => hm2_7i96.0.ssr.00.out-01