Aluminium - CNC Milling Guide

IMPORTANT DISCLAIMER : 
There is a wide range of different aluminium alloy types. Each of them have very different properties that can modify a lot their milling outcome.

Here we will be talking about the most commonly milled aluminiums (6061, 7075, 7005...) and generalize the way to mill them, but for more advanced milling parameters, please refer to metal and/or end mill suppliers for recommended feeds and speeds, and adapt them to your machine's capabilities.

EVO being an entry level CNC, it can handle some aluminium milling but it should remain occasional as it will be a bit intense for the machine.
If you take very shallow passes (but therefore extend a lot the milling time) you can still obtain perfectly nice results. 

Remember that you'll most likely need to help the tool to cool down (unless the job is very short) and/or blow air to evacuate the chips : both of those actions in order to prevent the metal to melt and clog the tool, which will lead to tool breakage, the most common mistake happening when learning to mill metals.

Keep an eye on your tool, if you see any buildup of materials in it you can pause or stop the job to save your tool before it breaks. And correct your parameters to build less heat. (can be reducing the spindle rotation if it is not to low, or moving a bit faster if possible, or reducing the depth of cut, or adding coolant...).

Cutting parameters suggestion for EVO:

• Machine : Mekanika EVO
• End mill : Ø 6mm / 1 Flutes Carbide / Upcut spiral
• Feed rate : 500 mm/min
• Spindle speed : 16 000 rpm
• Depth of cut : 0.75 mm

The FAB and PRO increased rigidity and spindle power will make milling aluminium a lot easier. They'll allow faster feed rates and bigger depth of cut compared to EVO, but tool cooling will remain the main bottleneck to the parameters.

For occasional aluminium cuts, you can use simple tips like WD40 spraying to lubricate the cut and/or air blowing on the tool to evacuate chips and help cooling down the tool. But if you plan on milling longer series of aluminium jobs, then installing a fixed lubrication or air blowing system on the machine could be mandatory to free you from spraying manually the tool all along.

Always test your parameters first, keep an eye on the tool for any clogging. If materials starts to build up in the flutes and creates long strings of aluminium, it means it is to hot and aluminium chips melt and weld themselves together, which will lead to tool breaking as soon as it will be full of material.
If this happens, stop the job and change your parameters to build less heat.
(can be reducing the spindle rotation if it is not to low, or moving a bit faster if possible, or reducing the depth of cut, or adding coolant...).

Parameters used in the video :

• Machine : Mekanika PRO S / Standard-Z / Spindle VFD 2200W
• End mill : Ø 6mm / 1 Flute Carbide / Upcut spiral
• Feed rate : 800 mm/min 
• Spindle speed : 18 000 rpm
• Depth of cut : 1.5 mm

• For heat dissipation and better chip evacuation, 1 flutes bits are often the best choice for aluminium roughing. 
• Cheap ways to help with cooling the tool are Spraying WD40 or any coolant liquid regularly during the milling, or simply spraying compressed air on the tool constantly (this also helps to evacuate the chips).
• Use ramps or helixes instead of plunges for the entry in the material.
• Chips should be sharp and not melted. Melted chips means there is to much heat buildup, so you should change parameters to reduce friction (can be reducing the spindle rotation if it is not to low, or moving a bit faster if possible, or reducing the depth of cut, or adding coolant...).
• If you break your tools in aluminium it could be either because you go to fast (chips are to big and the tool can't handle it) OR because you are going to slow (chips are to thin and melting, clogging the tool that becomes unable to cut).
•  If the surface finish is not good, it can be related to various things: 
• check that your stock is fixed strong enough and not vibrating
• check your tool's edges to see if it is damaged
• use the shortest tool possible for the job to avoid tool deflection.
• Test different feed/speed (most likely : reduce feed rate or increase spindle speed, within the machine's capabilities).

You can find here a link to a feed and speed calculator for the most classic materials, and safe values adapted to each of our machines.

MEKANIKA CNC FEED & SPEED CALCULATOR 

IMPORTANT NOTE: this is made to help you find parameters for your milling, but you should always think by yourself and enter cutting parameters that are matching your own setup.
Calculating the theorical values in this table is easy, but many parameters in your setup may make them unfit for your case. Always start with low engagement and speed, and test deeper/quicker parameters progressively.