1. Is CNC machining cheaper than injection molding?

CNC machining is cheaper than injection molding at low volumes, typically under 500 parts, because it requires no tooling investment. Injection molding has a higher upfront cost, usually $10,000 to $75,000 for tooling, but produces parts at significantly lower per-unit cost at volume. At 100,000 units, a part that costs $47 to machine can cost $0.80 to mold. The cheaper process depends entirely on volume, not the process itself.

2. At what volume does injection molding become cheaper than CNC machining?

Injection molding typically becomes more cost-effective than CNC machining somewhere between 500 and 5,000 parts, depending on part complexity, tooling cost, and per-unit machining cost. For simple geometries, the crossover can sit closer to 1,000 to 2,000 units. For complex parts with high CNC setup costs, the economics can shift earlier. There is no universal breakeven number – it must be calculated for the specific part, geometry, and tooling quote.

3. Can injection molded parts hold tight tolerances?

Injection molded parts can hold tolerances of +/-0.005″ to +/-0.010″ on most features with proper tool design and process validation. Tight-tolerance bores, however, frequently require post-machining to hold dimensions reliably across a production run because material shrink during cooling introduces variation the mold alone cannot fully control. Tolerances that CNC machining holds natively often require additional steps in injection molding, and that secondary cost belongs in any honest process comparison.

4. When should I switch from CNC machining to injection molding?

The right time to switch from CNC machining to injection molding is when three conditions are true simultaneously: confirmed production volume justifies the tooling investment, the design is stable enough that post-tooling changes are unlikely, and the geometry has been reviewed for moldability before the tool order is placed. Switching at the right volume with the wrong design is as costly as switching at the wrong volume entirely. The geometry review should happen while the part is still being machined, not after the purchase order goes out.

5. What is the break-even point between CNC machining and injection molding?

The break-even point between CNC machining and injection molding is calculated by dividing the tooling cost by the per-unit savings injection molding delivers over CNC. For example, a $30,000 mold on a part where CNC costs $45 and molding costs $3 per unit breaks even at approximately 715 units. Every program has a different break-even because tooling cost, part complexity, and machining cost vary. The break-even should be calculated on confirmed volume, not projected volume, because tooling cost that never amortizes is sunk cost, not savings.