CNC Milling vs Metal Stamping: Which Manufacturing Process is Right for You?

Preface

In modern manufacturing, CNC milling and metal stamping stand as two core processing technologies, each possessing unique technical characteristics and application advantages. As manufacturing evolves toward higher precision, efficiency, and lower costs, selecting the appropriate processing technology has become a critical factor for enterprises to enhance competitiveness. This report provides a systematic comparative analysis of these two processes from multiple dimensions including processing principles, technological capabilities, economics, material properties, production cycles, and precision quality, offering scientific decision-making basis for manufacturing practitioners.

1. Processing Principles and Fundamental Differences

1.1 CNC Milling: Digital Subtractive Manufacturing

CNC milling (Computer Numerical Control Milling) is a precision machining process controlled by computer programs, essentially a material removal subtractive manufacturing process. This technology uses rotating multi-edge cutting tools (mills) to cut materials such as metals, plastics, and wood to produce complex-shaped parts.

Core Working Principles:

Tool Rotation: The spindle drives the milling cutter at high speeds (up to tens of thousands of RPM)

Workpiece Fixation: Materials are clamped on the worktable, movable along X, Y, Z axes

Cutting Motion: Tools cut materials according to programmed paths, removing excess portions

Digital Control: Precisely controls tool path, speed, and feed rate through G-code

The fundamental characteristic of CNC milling lies in its discrete processing nature, removing material point by point through tool paths, much like a precision “digital carving” process. This processing method gives it a natural advantage in handling complex 3D geometries.

1.2 Metal Stamping: Die Forming Manufacturing

Metal stamping is a processing method based on metal plastic deformation, essentially a material forming manufacturing process. This technology uses dies and stamping equipment to apply pressure to sheet materials, causing plastic deformation or separation to obtain parts with specific shapes, dimensions, and properties.

Core Working Principles:

Die Action: Uses pre-manufactured die cavities

Pressure Forming: Applies enormous pressure to force plastic deformation of metal sheets

Batch Replication: One-time die manufacturing enables rapid production of numerous identical parts

Multi-process Combination: Typically includes punching, blanking, bending, drawing and other processes

The fundamental characteristic of metal stamping lies in its die dependency, with the processing process resembling a “stamping” procedure but with immense force. This processing method gives it significant efficiency advantages in mass production of thin-walled sheet metal parts.

1.3 Comparison of Fundamental Differences

Comparison Dimension	CNC Milling	Metal Stamping
Processing Principle	Material removal (subtractive manufacturing)	Material forming (plastic deformation)
Processing Method	Discrete processing, point-by-point cutting	Integral forming, die press forming
Tool Dependence	Universal tools, quick changeable	Special dies, long manufacturing cycle
Processing Process	Tool movement, workpiece fixed or moving	Workpiece fixed, die movement and pressure application
Material State	Material is cut and removed	Material undergoes plastic deformation

2. Technological Capabilities and Design Freedom

2.1 Technological Capabilities of CNC Milling

CNC milling demonstrates extremely high flexibility and complex processing capabilities:

Main Advantages:

Complex 3D Machining: Can process very complex 3D geometries, free surfaces, internal cavities, deep grooves, and fine features

Integrated Machining: Can integrally mill structures that would otherwise require multiple assembled parts from a single blank

Rapid Prototyping: New parts can be processed by modifying CAD models without physical dies

Multi-material Adaptability: Suitable for metals, plastics, composites and other materials

Technical Limitations:

Thin-wall Processing Difficulties: Very thin walls are prone to vibration or damage due to cutting forces

Internal Sharp Corner Limitations: Limited by tool geometry, cannot process true internal sharp corners (tools have rounded corners)

Deep Cavity Processing Challenges: Deep cavity processing requires special tools and processes, with lower efficiency

Processing Precision Range:

Standard precision: ±0.01mm

High-precision processing: ±0.001mm

Surface roughness: Ra0.8-Ra3.2μm

2.2 Technological Capabilities of Metal Stamping

Metal stamping has unique advantages in thin-wall part processing and mass production:

Main Advantages:

Thin-wall Part Manufacturing: Specialized for producing sheet metal parts, can efficiently manufacture various sheet metal components

Fine Feature Forming: Features like SIM card tray slots on phone frames can be achieved through precision stamping

Surface Texture Replication: Die cavities can be etched with patterns to directly press surface effects like leather grain or hairline finishes

High Production Efficiency: Multiple processes can be completed with a single stamping, with fast production speeds

Technical Limitations:

Design Geometry Limitations: Difficult to manufacture closed internal cavities, complex 3D geometries, and self-intersecting surfaces

Draft Angle Requirements: Drawing parts usually require draft angles for mold release

Material Plasticity Requirements: Materials must have good plastic deformation capabilities

Die Complexity: Complex shapes require multiple processes and complex die structures

Processing Precision Range:

Ordinary stamping: ±0.1mm

Precision stamping: ±0.01mm

Surface roughness: Ra1.6-Ra6.3μm

2.3 Comparative Analysis of Design Freedom

Design Element	CNC Milling	Metal Stamping
3D Complexity	★★★★★	★★☆☆☆
Thin-wall Structure	★☆☆☆☆	★★★★★
Internal Cavity Structure	★★★★☆	★☆☆☆☆
Surface Texture	★★★☆☆	★★★★★
Fine Features	★★★★☆	★★★★★
Material Thickness	Unlimited	0.1-10mm (special up to 25mm)
Design Changes	Fast and flexible	Costly, long cycle

3. Economics and Cost Structure

3.1 Cost Structure of CNC Milling

The cost structure of CNC milling mainly includes the following aspects:

Main Cost Components:

Equipment Depreciation: CNC machine tools have high investment costs, with depreciation accounting for a large proportion

Labor Costs: Requires professional operators and programmers

Tool Consumption: Cutting tools are consumables that need regular replacement

Material Costs: Significant material waste (chips), material utilization rate 60%-80%

Cost Characteristics:

High Unit Cost: Significant material waste, long processing time

Relatively Low Initial Investment: No need for expensive dies

Economical for Small Batches: Suitable for prototypes and small-batch production

Cost Stability: Unit cost does not decrease significantly with increasing quantity

Typical Cost Range:

Ordinary CNC machine tools: Processing cost 30-80 yuan per hour

High-precision machining centers: Processing cost 80-200 yuan per hour

Single part processing time: From several minutes to several hours

3.2 Cost Structure of Metal Stamping

The cost structure of metal stamping exhibits typical economies of scale:

Main Cost Components:

Die Costs: Die design, manufacturing, and debugging costs are very high, accounting for the largest proportion of total costs

Equipment Depreciation: Stamping equipment has high investment costs

Material Costs: High material utilization rate (70%-90%), but requires specific 规格 sheet materials

Labor Costs: High automation level, relatively low labor costs

Cost Characteristics:

Extremely Low Unit Cost: Once dies are completed, each part’s production cycle is measured in seconds

Extremely High Initial Investment: Die costs can reach hundreds of thousands or even millions of yuan

Economical for Large Batches: Requires huge production volumes to amortize high die costs

Significant Cost Reduction: Unit cost decreases significantly with increasing production volume

Typical Cost Range:

Simple dies: Tens of thousands of yuan

Complex dies: Hundreds of thousands to millions of yuan

Stamping processing: Several cents to several yuan per piece (for large batches)

3.3 Economic Comparison and Break-even Point Analysis

Break-even Point Analysis:

Let:

Cm: CNC milling unit cost

Cs: Stamping unit cost (excluding dies)

Tc: Total die cost

Q: Production quantity

Break-even point when Cm × Q = Cs × Q + Tc:

Q = Tc / (Cm – Cs)

Practical Case Analysis:

Assuming a certain part:

CNC milling unit cost: 100 yuan

Stamping unit cost: 10 yuan

Die cost: 100,000 yuan

Break-even point Q = 100,000 / (100 – 10) ≈ 1,111 pieces

This means that when production quantity exceeds 1,111 pieces, stamping process becomes economically superior to CNC milling.

Economic Selection Recommendations:

Small-batch production (<1,000 pieces): CNC milling is more economical

Medium-batch production (1,000-10,000 pieces): Requires specific analysis considering product lifecycle

Large-batch production (>10,000 pieces): Stamping process has obvious advantages

4. Material Properties and Effects

4.1 Effects of CNC Milling on Materials

CNC milling has relatively minor effects on material properties during processing:

Material Property Changes:

Basically Maintains Original Properties: Using rolled or forged blanks, basically maintains the original properties of the base material after processing

Surface Stress State: Cutting process produces certain processing stress on the surface, but the affected depth is shallow

Microstructure: Minor effect on material microstructure, mainly concentrated in the surface layer

Material Utilization:

Relatively Low Utilization Rate: Usually between 60%-80%

Chip Generation: Produces large amounts of chips that need recycling

Material Waste: High waste costs for precious materials

Applicable Material Range:

Metal Materials: Aluminum alloys, stainless steel, carbon steel, titanium alloys, copper alloys, etc.

Non-metal Materials: Plastics, composites, wood, stone, etc.

Hardness Range: From soft materials to high-hardness materials (below HRC60)

4.2 Effects of Metal Stamping on Materials

Metal stamping causes significant plastic deformation during processing, with notable effects on material properties:

Material Property Changes:

Work Hardening: Stamping process causes work hardening, increasing material strength but reducing plasticity

Stress State Changes: Residual stresses generated inside the material may affect subsequent processing and use

Microstructure Changes: Grain deformation, increased dislocation density, material property anisotropy

Material Utilization:

Relatively High Utilization Rate: Usually between 70%-90%

Scrap Types: Mainly produces scrap and skeleton materials, easy to recycle

Nesting Optimization: Material utilization rate can be further improved through nesting optimization

Applicable Material Requirements:

Plasticity Requirements: Must have good plastic deformation capabilities

Common Materials: Low-carbon steel, aluminum alloys, copper alloys, stainless steel, etc.

Thickness Range: Usually 0.1-10mm, up to 25mm in special cases

Unsuitable Materials: High-carbon steel, cast iron and other brittle materials

4.3 Comparative Analysis of Material Effects

Effect Factor	CNC Milling	Metal Stamping
Material Property Changes	Basically maintains original properties	Work hardening, property changes
Material Utilization Rate	60%-80%	70%-90%
Material Waste	Large amount of chips	Scrap and skeleton materials
Material Adaptability	Almost all machinable materials	Mainly plastic metal materials
Surface Integrity	May have machining marks	Surface quality depends on dies
Subsequent Processing	Rarely needed	May need annealing to eliminate stress

5. Production Cycle and Supply Chain

5.1 Production Cycle Characteristics of CNC Milling

CNC milling has rapid response advantages in terms of production cycles:

Lead Time Characteristics:

Rapid Startup: From CAD model to first part may take only a few hours or days

Short Preparation Time: Mainly includes programming, tool preparation, fixture installation, etc.

Short Debugging Cycle: Program debugging and first piece confirmation are relatively simple

Production Flexibility:

Easy Design Changes: Only need to modify CNC programs, no need to remanufacture tools

Multi-variety Small-batch: Suitable for rapid switching between different product productions

Emergency Production Capacity: Can quickly respond to urgent order requirements

Supply Chain Requirements:

Raw Material Requirements: Needs block or bar raw materials

Tool Supply: Requires stable tool supply chain

Technical Support: Needs professional programming and operation technical personnel

5.2 Production Cycle Characteristics of Metal Stamping

The production cycle of metal stamping is mainly limited by die manufacturing:

Lead Time Characteristics:

Long Die Manufacturing Cycle: Die design, manufacturing, and debugging may take several weeks or even months

Large Preparation Investment: Requires significant preliminary preparation work and investment

Complex Process Verification: Requires multiple trial runs and adjustments

Production Stability:

Large-batch Advantages: Once dies are debugged, production stability is high

Continuous Production Capacity: Can achieve 24-hour continuous production

Good Quality Consistency: High consistency of mass-produced parts

Supply Chain Requirements:

Raw Material Requirements: Needs coil or sheet raw materials

Die Manufacturing: Requires professional die manufacturing suppliers

Equipment Maintenance: Needs professional stamping equipment maintenance services

5.3 Production Cycle Comparative Analysis

Cycle Element	CNC Milling	Metal Stamping
Design to Production	Few hours to days	Few weeks to months
First Piece Time	Short (hour level)	Long (week level)
Mass Production Speed	Slow (minutes per piece)	Fast (seconds per piece)
Design Change Response	Fast (program modification)	Slow (die modification)
Equipment Utilization Rate	Medium	High (continuous production)
Product Switching	Fast	Slow (requires die change)

6. Precision and Surface Quality

6.1 Precision and Surface Quality of CNC Milling

CNC milling has significant advantages in precision control:

Precision Capabilities:

Dimensional Precision: Standard precision ±0.01mm, high precision up to ±0.001mm

Geometric Precision: Can ensure accurate forming of complex geometric shapes

Positional Precision: High relative positional precision between features

Surface Quality:

Surface Roughness: Ra0.8-Ra3.2μm, higher finish can be achieved through polishing

Surface Texture: Regular tool marks, can be reduced through process optimization

Surface Integrity: Machined surfaces are relatively intact with no obvious deformation

Influencing Factors:

Tool Precision: Geometric precision and wear status of tools

Machine Precision: Positioning precision and repeatability of machine tools

Cutting Parameters: Cutting speed, feed rate, cutting depth, etc.

Material Properties: Hardness, toughness and other properties of materials

6.2 Precision and Surface Quality of Metal Stamping

The precision and surface quality of metal stamping mainly depend on dies:

Precision Capabilities:

Dimensional Precision: Ordinary stamping ±0.1mm, precision stamping ±0.01mm

Shape Precision: Shape precision control is difficult due to material springback

Repeatability Precision: High repeatability precision in mass production

Surface Quality:

Surface Roughness: Ra1.6-Ra6.3μm, depending on die surface quality

Surface Texture: Can replicate any texture on die surfaces

Surface Integrity: May have stretching marks, scratches and other defects

Influencing Factors:

Die Precision: Manufacturing precision and surface quality of dies

Material Springback: Elastic recovery characteristics of materials

Stamping Parameters: Pressure, speed, temperature and other parameters

Lubrication Conditions: Lubrication has significant impact on surface quality

6.3 Precision and Surface Quality Comparison

Quality Indicator	CNC Milling	Metal Stamping
Dimensional Precision	±0.001-0.01mm	±0.01-0.1mm
Geometric Precision	High	Medium
Surface Roughness	Ra0.8-Ra3.2μm	Ra1.6-Ra6.3μm
Surface Texture	Tool marks	Die-replicated texture
Shape Consistency	High	High batch consistency
Dimensional Stability	High	More affected by temperature

7. Application Fields and Typical Cases

7.1 Main Application Fields of CNC Milling

CNC milling is widely used in fields requiring high precision and complex shapes:

Aerospace Field:

Engine components

Complex aircraft structural parts

Precision instruments and equipment

Medical Device Field:

Artificial joints and implants

Precision medical equipment parts

Surgical instruments

Automotive Manufacturing Field:

Prototyping and small-batch production

Engine blocks and cylinder heads

Complex transmission system parts

Electronic Equipment Field:

Precision mold manufacturing

Connector and interface parts

Heat dissipation structural parts

7.2 Main Application Fields of Metal Stamping

Metal stamping is mainly used for mass production of thin-wall parts:

Automotive Manufacturing Field:

Body panels

Chassis structural parts

Radiator and air conditioning components

Electronic Equipment Field:

Mobile phone frames and housings

Computer cases and radiators

Connectors and plugs

Home Appliance Manufacturing Field:

Washing machine and refrigerator housings

Air conditioning fins

Small home appliance parts

Building Hardware Field:

Door and window hardware

Pipes and connectors

Decorative hardware

7.3 Typical Application Case Analysis

Case 1: Mobile Phone Frame Manufacturing

CNC Solution: Milling from aluminum profiles, suitable for small batches and customization needs

Stamping Solution: Using precision stamping and drawing processes, suitable for mass production

Selection Basis: When production exceeds 100,000 pieces, stamping solution is more economical

Case 2: Aerospace Engine Parts

CNC Solution: Must use CNC milling, requiring complex 3D machining and high precision

Stamping Solution: Not applicable, cannot achieve complex internal cavities and curved surfaces

Selection Basis: Part complexity and precision requirements dictate the use of CNC milling

Case 3: Automotive Body Panels

CNC Solution: Only suitable for prototyping and small-batch production

Stamping Solution: Only choice for mass production, high efficiency and low cost

Selection Basis: Production volume and cost factors determine the use of stamping process

8. Decision Guidance and Best Practices

8.1 Process Selection Decision Flow

Based on the above analysis, establish a systematic process selection decision flow:

Step 1: Production Volume Assessment

Small-batch production (<1,000 pieces): Priority consideration of CNC milling

Medium-batch production (1,000-10,000 pieces): Need comprehensive analysis of cost and time factors

Large-batch production (>10,000 pieces): Priority consideration of metal stamping

Step 2: Design Complexity Analysis

Complex 3D structures: CNC milling is the best choice

Thin-wall flat structures: Metal stamping has advantages

Hybrid structures: Consider combined process solutions

Step 3: Precision and Quality Requirements

Ultra-high precision requirements (±0.001mm): Must choose CNC milling

Ordinary precision requirements (±0.01-0.1mm): Both processes can be considered

Special surface quality requirements: Choose according to specific needs

Step 4: Cost-benefit Analysis

Calculate break-even point

Consider product lifecycle

Evaluate design change possibilities

8.2 Process Combination Strategies

In practical applications, process combination strategies are often adopted to leverage respective advantages:

Stamping + CNC Combination:

First obtain basic shape using stamping

Then use CNC to machine precision features and complex surfaces

Suitable for parts with both thin-wall features and precision requirements

CNC + Stamping Combination:

First use CNC to make prototypes to verify design

After design finalization, make dies for stamping production

Suitable for new product development and transition to mass production

Multi-process Integration:

Combine 3D printing, casting, CNC, stamping and other processes

Achieve efficient and low-cost manufacturing of complex parts

Represents the development trend of modern manufacturing

8.3 Best Practice Recommendations

For CNC Milling:

Optimize Tool Path: Reduce idle travel and improve processing efficiency

Choose Tools Appropriately: Select suitable tools according to materials and processing requirements

Control Cutting Parameters: Balance efficiency and quality, extend tool life

Strengthen Process Verification: Use simulation software to verify programs and reduce trial cutting time

For Metal Stamping:

Optimize Die Design: Consider material springback and optimize die structure

Select Appropriate Materials: Choose materials with good plasticity according to product requirements

Control Stamping Parameters: Reasonably set pressure, speed and other parameters

Strengthen Die Maintenance: Regularly maintain dies to ensure production stability

9. Development Trends and Future Outlook

9.1 Development Trends of CNC Milling Technology

High-speed and High-precision Development:

Spindle speeds continue to increase, reaching 40,000-60,000 RPM

Positioning accuracy developing toward nanometer level

Multi-axis linkage technology becoming increasingly mature

Intelligent Development:

Adaptive control technology widely applied

Machine learning optimizing processing parameters

Predictive maintenance reducing downtime

Green Manufacturing Development:

Advances in tool materials and coating technology extending tool life

Optimization of cooling and lubrication technology reducing environmental pollution

Improvement of chip recycling technology

9.2 Development Trends of Metal Stamping Technology

Precision Development:

Continuous improvement in precision stamping technology accuracy

Increasing maturity of micro-stamping technology

Wide application of composite stamping processes

Automation Development:

Popularization of fully automatic production lines

Robot integration applications

Development of intelligent inspection technology

New Material Applications:

Stamping technology for high-strength steel plates

Stamping processes for aluminum and magnesium alloys

Stamping technology for composite materials

9.3 Integrated Development of Both Processes

Process Complementarity Trend:

Blurring boundaries between CNC milling and metal stamping

Increasing maturity of hybrid manufacturing technology

Flexible manufacturing systems integrating multiple processes

Digital Manufacturing Trend:

CAD/CAM/CAE integration

Virtual manufacturing and simulation technology

Digital twin technology applications

Sustainable Development Trend:

Promotion of green manufacturing technology

Establishment of circular economy models

Achievement of carbon-neutral manufacturing goals

Conclusion

As two core processes of modern manufacturing, CNC milling and metal stamping each possess unique technical advantages and application fields. Through the in-depth analysis in this report, we can draw the following key conclusions:

Fundamental Process Differences: CNC milling is subtractive manufacturing while metal stamping is forming manufacturing, which determines their fundamental differences in processing principles, technological capabilities, and application scenarios.

Economic Comparison: CNC milling is suitable for small-batch production, metal stamping is suitable for large-batch production, with the break-even point usually between 1,000-10,000 pieces.

Technical Capability Complementarity: CNC milling excels in complex 3D machining, metal stamping excels in mass production of thin-wall parts, and they can complement each other in many applications.

Integrated Development Trend: With the development of manufacturing technology, the two processes show an integration trend, forming more flexible and efficient manufacturing solutions.

For manufacturing practitioners, selecting the correct processing technology requires comprehensive consideration of multiple factors including production volume, precision, cost, and time. In practical applications, single processes or combined processes should be flexibly used according to specific needs to achieve optimal economic benefits and technical effects.

With the continuous development of intelligent manufacturing technology, CNC milling and metal stamping technologies will continue to innovate, providing stronger technical support for the high-quality development of manufacturing.

1. Processing Principles and Fundamental Differences

1.1 CNC Milling: Digital Subtractive Manufacturing