CNC Machining of Aluminium and Stainless Steel: Is there a Difference?
Blog | January 30th, 2019Used on a predetermined material, CNC equipment produces super-precise dimensional profiles. For automobiles, the aerospace sector, even in woodworking, the computer numerical control language processes raw parts and transforms them into beautifully realized end-use components. Focusing more on aluminium and stainless steel, not wood, we’ll see today whether there’s a difference in those materials, well, as far as their CNC machining requirements are concerned. Starting with aluminium, this softer alloy is generally easier to machine.
CNC Machining: Aluminium Alloys
Slotted into a 5-axis gimballing CNC machine, the turning and milling tools begin their work. Being a softer metal, there’s no need for cutouts or weight-reducing subtractive cutting on a workpiece. Indeed, if the raw materials are sourced from a generally weaker alloy family, such subtractive operations will structurally undermine any load-bearing capability, as imposed by a client’s parts specs. Before moving on to stainless steel milling, do remember that aluminium melts at lower temperatures. CNC tools, many of which generate abrasive heat, can cause micro-welds. Tool RPM control is important here, as is the cleaning of cutting edges, which accumulate gummy aluminium shavings.
Processing Hardened Stainless Steel
Moderate to high quantities of carbon diffuse their way into the ferrous structure. Heat treatment processes further manipulate the alloy and harden it or add a measure of fatigue resistance to its base material features. Materially tough, the CNC tools used to mill and otherwise carry out subtractive forming operations on stainless steel receive new instructions from the software. On inputting the metal’s density and alloy hardness, the numerical codes put the brakes on the spinning tools. Their high RPMs drop lower so that the forming work doesn’t cause tool damage. Feed rates drop, chip loads lower, and material removal speeds rise, all in response to the presence of a hardened stainless steel workpiece. A fine processing balance takes over now. Finer layers of carbon strengthened, nickel loaded iron are stripped away, and the job completion time increases, but that’s the price of working with hardened steels.
There are ways around the differences listed above. Some of them improve the process while others significantly reduce the time it takes to form an end-process product. Coolants and tungsten carbide tools handle friction and tool dulling forces, as encountered on stainless steel parts. For aluminium CNC cutting, weld prevention guidelines and coarse cuts are eliminated when tri-fluted milling tools take over from general-purpose turning tools. So, yes, there are indeed differences between aluminium and stainless steel CNC machining, but those differences are offset by specialized tooling configurations, plus changes to the feed rates and tool RPMs.
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