CNC Telephone Case Manufacturing

• 1
  Key takeaways
• 2
  How CNC telephone case manufacturing actually runs
• 3
  Tolerances that matter on a phone housing
• 4
  Material selection and wall thickness limits
• 5
  Finishes and where they fail
• 6
  CNC milling versus injection molding for phone cases

A milled case starts as a solid block, not a molded shell. We face the block, rough the pocket with a 6–10 mm carbide end mill, then semi-finish with a 3–4 mm tool. A 1–2 mm ball nose runs the final pass at 0.05–0.1 mm stepover. That stepover is what decides whether you see tool marks after anodizing.

The outer profile and the inner cavity both need datums that match the phone. On a 3-axis machine the case has to be flipped two or three times, and every flip adds stack-up error. On a simultaneous 5-axis center with a Ø400 mm rotary table, the shell, the camera opening, the speaker slots, and the side button reliefs come off in one setup.

Aluminum 6061-T6 and 7075 are the usual picks for a rigid, thin housing. 6061 machines cleanly and anodizes evenly. 7075 gives higher yield strength for a 0.8 mm wall but costs more and anodizes to a slightly darker tone. Titanium TC4 (Ti-6Al-4V) shows up on premium or ruggedized units; it cuts at roughly one third the speed of aluminum and needs sharp tooling and flood coolant.

Plastics behave differently. PC and ABS cut fast and take a bead blast well, but they scratch and they flex at thin walls. POM and PEEK hold threads better and stay dimensionally stable, which matters if the case carries inserts, screws, or a sealed battery door.

The headline tolerance for CNC telephone case manufacturing here is ±0.005 mm, but not every feature needs it. Chasing that number across the whole part adds cost with no benefit. Spend it where the phone actually touches the case.

Camera lens bore is the first critical feature. If the bore is 0.05 mm undersized, the lens module will not seat flat, and one corner of the image goes soft. We hold the bore and its counterbore to ±0.02 mm and check it with a pin gauge and a vision system rather than trusting the machine readout.

The second is the side button relief. Buttons need 0.1–0.15 mm of travel clearance. Too tight and the button sticks in cold weather; too loose and it rattles. We cut these slots with a 2 mm end mill and verify with a gauge pin at final inspection.

Third is flatness on the back plate. A 75 × 150 mm back face that bows 0.1 mm will rock on a table and will not sit flush against a wireless charging pad. Roughing, stress relief, and a light finishing pass keep flatness under 0.05 mm on aluminum.

Wall thickness sets the whole design. For aluminum, 0.8 mm is workable for a housing that stays in a pocket. Go to 0.6 mm and the part deforms under thumb pressure and during anodizing. Stainless 304 or 316 can go thinner at 0.5–0.6 mm because the modulus is higher, but it weighs more than twice as much per unit volume.

Magnesium AZ31B and AZ91D sit between the two. They are light, machine well at high spindle speed, and take a hardcoat anodize for wear resistance. The catch is corrosion control and the fire risk during dry cutting; chips must be kept wet and cleared continuously.

For plastics, PC at 1.2 mm holds shape through a normal drop. Below 1.0 mm the tabs that snap into the phone body start to crack after repeated assembly. PEEK at 0.8 mm is stiff enough for a sealed enclosure but costs several times more than PC.

What is available from stock: aluminum 6061, 6061-T6, 2024, 5052, 5083, 6063, 6082, 7075, ADC12; stainless 303, 304, 316, 316L, 420, 430, 431, 440C, 17-4PH; titanium TA1, TA2, TC4; copper and brass C101, C110, C36000; plastics ABS, PC, PMMA, POM, PA, PEEK, PP, HDPE, and carbon fibre sheet.

Anodizing is the default for aluminum phone cases. Clear anodize keeps the metal look; color anodize gives you the housing tint; hardcoat adds wear resistance on the corners and around the charging port. Type II color anodize on 6061 is the most predictable combination.

Bead blasting before anodizing controls gloss. Fine glass bead at low pressure gives a soft matte that hides fingerprints. Skip blasting and the part shows every machining line after anodizing, because anodize does not fill or hide tool marks.

Electroless nickel and zinc plating are for steel or for parts that need conductivity. Laser marking works on anodized and coated surfaces with a minimum character height of 1.5 mm; below that the mark fills in and is not readable. Powder coating adds 40–80 μm and can bridge a 0.1 mm gap, so mask any mating surfaces before coating.

Plating and coating change dimensions. A hardcoat anodize adds roughly half the oxide thickness to each surface. If a bore is already at the upper limit, it will close up after coating. We list which surfaces to mask on the drawing before the finish operation starts.