Principles of Forming Technology for Metal Stamping Parts
Metal stamping (five-metal stamping) is a manufacturing process that uses dies and presses to apply external force on sheet metal, causing it to undergo plastic deformation or separation, thereby obtaining parts with specific shapes and sizes. It is widely used in automotive, electronics, electrical appliances, construction hardware, and precision components.
The core principle of stamping forming is controlled plastic deformation of sheet metal under external force, combined with precise tooling guidance to achieve repeatable, high-efficiency mass production.
1. Basic Principle of Plastic Deformation
When sheet metal is subjected to external force exceeding its yield strength, it enters the plastic deformation stage.
Key behaviors include:
Elastic deformation (reversible)
Plastic deformation (permanent shape change)
Work hardening (strength increases during forming)
The stamping process relies mainly on plastic deformation to shape materials permanently.
2. Force Transmission Mechanism in Stamping
The press machine provides vertical force, which is transmitted through the die system:
Press → Punch → Sheet Metal → Die
During this process:
Punch applies compressive and tensile stress
Die provides shaping constraint
Sheet metal flows under controlled resistance
This coordinated interaction determines final part geometry.
3. Material Flow Control Principle
One of the most critical principles in deep drawing and stamping is controlled material flow.
During forming:
Excess flow → wrinkling
Restricted flow → cracking
Therefore, material must flow in a balanced and stable manner.
Key control elements:
Blank holder force
Draw beads
Die clearance
Lubrication conditions
4. Stress State Transformation Principle
During stamping, sheet metal undergoes complex stress states:
Tensile stress (stretching)
Compressive stress (buckling risk)
Biaxial stress (deep drawing zone)
Shear stress (cutting/blanking zone)
The balance of these stresses determines whether the part is formed successfully or fails.
5. Volume Constancy Principle
In plastic deformation, metal volume is assumed to remain constant:
Material thickness decreases when area increases
This principle is fundamental in:
Deep drawing
Stretch forming
Flanging
It explains thickness reduction and material redistribution during forming.
6. Tooling Constraint Principle
The die system defines the final shape of the part.
Functions include:
Guiding material flow direction
Controlling deformation zone
Preventing instability (wrinkling or tearing)
Ensuring dimensional accuracy
The accuracy of the die directly determines product quality.
7. Friction and Lubrication Principle
Friction plays a dual role in stamping:
Too high friction → cracking, surface damage
Too low friction → wrinkling, loss of control
Proper lubrication ensures:
Stable material flow
Reduced surface defects
Lower forming force
Extended tool life
8. Energy Transfer Principle
The stamping process converts mechanical energy into deformation work:
Press energy → Plastic deformation energy + heat + friction loss
Efficient forming requires minimizing unnecessary energy loss while maintaining stability.
9. Springback Behavior Principle
After unloading, elastic recovery occurs due to stored internal stress.
Factors affecting springback:
Material strength
Thickness
Forming radius
Stress distribution
This is especially important in precision forming and automotive components.
10. Process Integration Principle
Modern stamping often uses multi-stage forming:
Blanking
Drawing
Trimming
Flanging
Calibration
Each stage builds upon the previous one to achieve final shape and accuracy.
11. Key Technical Control Factors
To ensure stable forming, the following must be controlled:
Material properties (ductility, thickness, strength)
Tool design (radius, clearance, surface finish)
Press parameters (force, speed, stroke)
Lubrication system
Process sequence
Conclusion
The forming process of metal stamping parts is based on the principle of controlled plastic deformation of sheet metal under external mechanical force. Through coordinated control of stress distribution, material flow, tooling constraints, and friction conditions, complex shapes can be produced efficiently and accurately. Understanding these fundamental principles is essential for improving product quality, reducing defects, and optimizing mass production processes.
References
Altan, T., & Tekkaya, A. E. Sheet Metal Forming: Fundamentals. ASM International.
Hosford, W. F., & Caddell, R. M. Metal Forming: Mechanics and Metallurgy. Cambridge University Press.
Kalpakjian, S., & Schmid, S. R. Manufacturing Engineering and Technology. Pearson Education.
Lange, K. Handbook of Metal Forming. McGraw-Hill.
ASM International. ASM Handbook, Volume 14: Forming and Forging.
