Cost comparison: Additive manufacturing vs. CNC
Break-even analysis and TCO calculation for series production.
1. Introduction: When does the layer structure pay off?
The question “Is 3D printing cheaper than milling?” can never be answered with a general yes or no. Additive manufacturing (AM) and CNC machining (subtractive manufacturing) are subject to completely different cost curves.
While CNC is unbeatably affordable for simple geometries and large batch sizes, additive manufacturing shows its economic strengths for complex, functionally integrated components and small batch sizes. This guide will walk you through calculating the total cost of ownership (TCO) and determining the break-even point.
The rule of thumb of complexity
Complexity is expensive in CNC manufacturing (more setups, expensive special tools, long milling times). In 3D printing, complexity ("complexity for free") is largely free, as the printer often requires less time and material for a hollow, complex grid than for a solid block.
2. The cost blocks of CNC machining
Traditional machining from solid material (billet) is an established process. The cost structure consists of:
- Material costs (semi-finished products): Usually very low (per kg), but during machining often 50% to 90% of the material is produced as chips (scrap) ("buy-to-fly ratio").
- Setup costs: Programming the CAM software, setting up the clamping devices and measuring the tools takes time. These initial costs (NRE) make small batch sizes uneconomical.
- Tool costs: Milling cutters and drills wear out, especially with hard materials such as titanium or Inconel.
- Machine hourly rate: CNC machines usually work extremely quickly, which reduces the price per piece for large series.
3. The cost blocks of additive manufacturing
Metal 3D printing has a completely different cost structure:
- Material costs (powder/wire): Specific metal powder is very expensive. However, the material is (almost) 100% integrated into the component; there is hardly any waste.
- Setup costs: Almost zero. A 3D model can be prepared digitally (slicing) and printed directly without special clamping devices.
- Printing time (machine costs): Setup is slow. A PBF print can take days. This means that the machine hourly rates are the dominant cost factor.
- Post-Processing: Support structures must be removed and functional surfaces (threads, fits) almost always have to be CNC milled.
4. The break-even point (BEP)
To visualize when which procedure is worthwhile, place the cost curves of both procedures on top of each other. The X-axis shows the number of pieces (batch size), the Y-axis shows the unit costs.
Scenario A: The simple milled part (e.g. a solid flange plate)
Result: CNC almost always wins. The set-up costs of the CNC machine are spread out from a quantity of 10, and the actual processing time is extremely short. 3D printing would be a complete waste of material and time.
Scenario B: The complex component (e.g. distribution block with internal cooling channels)
Result: AM wins with small to medium batch sizes (1 to 1000 pieces). In order to manufacture this part conventionally, several individual parts would have to be milled, drilled and then laboriously soldered/welded. 3D printing prints the part “in one go” (assembly consolidation). The break-even point is shifting massively in favor of additive manufacturing.
5. Take a holistic look at total cost of ownership (TCO)
The biggest mistake in purchasing is to only compare pure “part costs”. An honest TCO calculation must take into account the following indirect factors:
| Indirect cost factor | Advantage of 3D printing |
|---|---|
| Warehousing (inventory) | Instead of keeping thousands of spare parts in stock (capital tie-up), we print “on-demand” (digital warehouse). |
| Time to Market | Prototypes and first series components are available in weeks instead of months. No waiting times for molds. |
| Operating costs of the component | An additively manufactured aviation component that is 30% lighter saves kerosene worth thousands of euros over its service life. This immediately overcompensates for higher manufacturing costs. |
6. Recommendation for action for companies
Do not look for existing milled parts to print 1:1 - this is usually uneconomical. Instead, look for assemblies that you can combine or for components whose delivery times from external suppliers (e.g. castings) are unacceptably long.
As soon as you minimize the use of materials and maximize the performance of the component through Design for Additive Manufacturing (DfAM), industrial metal 3D printing becomes more and more profitable in modern manufacturing every day.