Engineers and product teams often face the same question: CNC or injection moulding? The answer depends almost entirely on how many parts you need and where you are in your development stage.
What Is CNC Machining?
CNC machining is a subtractive process. A block of material (metal or plastic) is cut by computer-controlled tools to create your part. It requires no tooling investment. Each part is machined individually from the same programme.
This makes CNC ideal for prototyping and low-volume production. You can order 1 part or 100 parts without any upfront tooling cost. Design changes are as simple as updating your CAD file.
What Is Injection Moulding?
Injection moulding involves creating a mould (usually steel or aluminium), then injecting molten plastic into it under pressure. Each cycle produces one part in seconds. The mould itself can cost anywhere from Rs 50,000 to Rs 5,00,000 or more depending on complexity.
Once the mould cost is paid, each additional part becomes very cheap to produce. This makes injection moulding highly cost-effective at high volumes but expensive and inflexible at low volumes.
The Break-Even Point
The break-even point is the quantity at which the total cost of injection moulding becomes equal to or less than the total cost of CNC machining. Here is a rough estimate for a simple plastic part:
| Quantity | CNC Total Cost (est.) | Injection Moulding Total (est.) | Better Option |
|---|---|---|---|
| 1 to 10 parts | Rs 500 to Rs 5,000 | Rs 55,000+ | CNC |
| 10 to 50 parts | Rs 5,000 to Rs 20,000 | Rs 56,000+ | CNC |
| 50 to 200 parts | Rs 20,000 to Rs 60,000 | Rs 60,000 to Rs 70,000 | Break-even zone |
| 200 to 1,000 parts | Rs 60,000 to Rs 2,00,000 | Rs 65,000 to Rs 80,000 | Injection Moulding |
| 1,000+ parts | Rs 2,00,000+ | Rs 70,000 to Rs 1,50,000 | Injection Moulding |
Note: Costs vary significantly by part geometry, material, and vendor. These are indicative estimates only.
Other Factors That Affect the Decision
Design Changes
If you are still iterating on your design, CNC is better. Changing a CNC part means updating your CAD file. Changing a moulded part means modifying or remaking the mould, which is expensive and slow.
Material Options
CNC works with metals and plastics. Injection moulding is limited to plastics. If your part needs to be aluminium or steel, CNC is your only option regardless of volume.
Lead Time
CNC parts can be ready in 2 to 5 days. Setting up a new injection mould takes 3 to 6 weeks. If you need parts quickly, CNC wins at any volume until the mould is ready.
Surface Finish and Tolerances
CNC offers tight tolerances and excellent surface finishes. Injection moulded parts are consistent across large runs but limited by mould quality and material shrinkage characteristics.
How ProtoMandi Helps You Decide
ProtoMandi supports CNC machining and 3D printing for prototyping and low-volume production. Our engineering team can review your part and help you understand when the volume justifies a move to injection moulding.
For startups and product teams in early development, starting with CNC prototypes on ProtoMandi means you can validate your design before committing to a mould. That one decision can save you lakhs.
Upload your part file on ProtoMandi and get a quote that helps you understand your options at every volume level.