What considerations would you have when switching the material of a machined component from aluminum to steel?
Pocket depth and overall manufacturing time. A very generous rule of thumb is max 5x diameter of end mill for steel, 10x for alum, and 15x for plastics
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Thinking about aluminum vs. steel at a high-level, we can reference this table here:
| Aluminum | Steel | |
|---|---|---|
| Material Properties | Less dense than steel | 2.5 time denser than aluminum, Higher Modulus of Elasticity |
| Strength-to-Weight Ratio | Typically not as strong as steel, but 1/3 the weight | Steel is strong and is less likely to warp, deform, or bend under weight, force, or heat. 3x heavier |
| Cost | Cheaper | More expensive |
| Manufacturability | Much more malleable than steel. Aluminum becomes stronger in cold weather | -High resistance to wear and abrasion, more difficult to handle, high hardness, harder to form than aluminum |
| Thermal Properties | Becomes soft above 400 degrees, Melting Point: 660 °C | Steel has much higher temperature capacities , Melting point: ~1500 °C |
Steel is much harder to machine than aluminum given that it’s three times stiffer than aluminum (3x Young’s Modulus), and often will have to use special alloys of steel to actual drill/mill the desired features. These alloys can range from carbon-steel or cobalt-steel for example.
Switching to steel, you can expect machining times to increase by 3-10 fold and the design considerations listed by @tonezone.
With steel as well, given the higher melting point (1500 C), machining operations with the tool moving at high speeds can actually induce work hardening in the material itself. This is where the material will become harder as lots of heat is generated.
A general design guide is shown here:
