Detailed explanation of several stripping structures of stamping dies In the stamping process, the stripping structure is a key design to ensure that stamping parts and waste materials can be smoothly separated from the die. Different stripping methods directly affect production efficiency, die life and product quality. The following are common stripping structures and their technical characteristics in stamping dies: 1. Fixed stripper plate (Fixed Stripper Plate) Structural principle: The rigid stripper plate is fixed on the die or template, and maintains a fixed gap with the punch (usually 1.5-2 times the material thickness). The material is pressed during stamping, and the stripper plate forces the material to be stripped during the return stroke. Applicable scenarios: Thick plate blanking (plate thickness ≥1.5mm) High-precision punching (such as motor silicon steel sheet) Roughing station of progressive die Advantages: simple structure, strong rigidity, no elastic component loss. Stable stripping force, suitable for high-speed stamping (≥500 times/minute). Disadvantages: Unable to flatten the material, prone to warping. Sensitive to material thickness fluctuations, precise control of the gap is required. Design points: Unilateral clearance between the stripper plate and the punch: C=(1.5∼2)×t
(t is the material thickness). The guide length of the guide pin must be ≥1.5 times the punch diameter to prevent eccentric loading. 2. Elastic stripper Structural principle: The elastic force is provided by springs, polyurethane rubber or nitrogen springs to press the material during the stamping process, and the material is released elastically after the stroke is completed. Typical structure: spring stripper plate, rubber pad unloading, nitrogen spring ejection. Applicable scenarios: Thin plate stamping (plate thickness ≤1mm, such as mobile phone metal shell) Precision blanking of bending and stretching processes that require pressing to prevent wrinkles (such as connector terminals) Advantages: Dual functions of pressing and unloading to prevent material movement and deformation. Adapt to material thickness fluctuations and have strong fault tolerance. Disadvantages: Elastic components are prone to fatigue (spring life is about 500,000 times, polyurethane is about 300,000 times). High-speed stamping may cause incomplete unloading due to hysteresis effect. Design points
Polyurethane rubber compression is ≤30% to avoid premature aging.
3. Ejector System Structural principle: Use ejector, ejector plate or pneumatic push rod to eject the stamped parts from the die. Common types: mechanical ejector (rod linkage), pneumatic ejector, hydraulic ejector. Applicable scenarios: demolding of deep-drawn parts (such as stainless steel cups), parts with complex shapes (easy to get stuck in the die), automated production lines (cooperating with manipulators) Advantages: large and controllable ejection force (pneumatic/hydraulic systems can reach several tons of thrust). The ejection timing can be accurately controlled to avoid deformation of parts. Disadvantages: complex structure and large mold space occupation. Pneumatic/hydraulic systems increase maintenance costs. Design points: The ejector distribution needs to avoid product functional areas (such as sealing surfaces).
4. Pneumatic assisted demolding (Air Blow-off) Structural principle: A compressed air nozzle is set in the mold, and air is blown to assist the parts or waste to be detached at the moment of mold opening. Often used in conjunction with the ejector. Applicable scenarios: lightweight thin-walled parts (such as aluminum foil parts) products with high surface requirements (avoiding contact marks of ejector pins) stations where small waste is difficult to discharge (such as micro-hole punching) Advantages: non-contact stripping to avoid scratches on parts. Directional removal of dead corner waste. Disadvantages: dependent on stable air source, high energy consumption. Noise is high, and a muffler needs to be installed. Design points: nozzle aperture: 0.5-2mm, air pressure 0.4-0.6MPa. Injection angle 30°-45° to avoid airflow directly hitting the mold cavity. 5. Scrap Cutter Structural principle: a cutter is set at the end of the progressive die to divide the continuous waste into small segments for easy collection. It is divided into upper cutting, lower cutting and side cutting. Applicable scenarios: high-speed progressive die (such as electronic connector production) stamping line with high risk of waste winding long strip waste processing (such as heat sink punching) Advantages: prevent waste accumulation from causing mold jamming. Improve the operation stability of the automation line. Disadvantages: Increase mold complexity and blade wear points. The cutting knife needs regular maintenance (lifespan of about 1 million times). Design points: Cutting knife angle: 30°-45°, reduce shear force. Waste length: generally ≤200mm, too long and easy to sag and get stuck. 6. Combined Stripping Structure (Combined Stripping) Structural principle: combined elastic unloading + ejector device + pneumatic assistance, multi-stage collaborative stripping. For example: first stripping by the elastic unloading plate, then ejected by the ejector rod, and finally cleared by air blowing. Applicable scenarios: ultra-thin materials (t≤0.1mm, such as copper foil shielding cover) High viscosity materials (such as silicone gaskets) Micro parts stamping (such as medical needles) Advantages: Thorough stripping, adaptable to extreme working conditions. Redundant design improves reliability. Disadvantages: Complex structure, mold cost increased by 30%-50%. The timing of multi-mechanism action needs to be precisely controlled. Selection Recommendation Table Stripping Structure Applicable Plate Thickness Speed Accuracy Maintenance Cost Fixed Stripper ≥1.5mm Very High (>500spm) Medium Low Elastic Stripper 0.2-1.5mm High (200-400spm) High Medium Ejector Any Medium (<200spm) Very High High Pneumatic Assist ≤0.5mm Very High Very High High Scrap Cutting Knife Any High Low Low Composite Stripper Structure ≤0.2mm Medium Very High Very High Summary The design of the stripper structure needs to comprehensively consider four factors: material properties, stamping speed, precision requirements, and cost budget: High-speed stamping of thick plates: fixed stripper plates are preferred, supplemented by scrap cutting knives. High-precision punching of thin plates: elastic stripper + pneumatic assistance is the golden combination. Deep drawing complex parts: ejector + elastic stripper plate double protection. Micro-stamping extreme working conditions: composite stripper structure is the only choice. Future trends: Technologies such as intelligent stripping systems (such as pressure sensors that provide real-time feedback to adjust the ejector force) and self-lubricating stripping plates (with the life of graphene coating increased by 5 times) will further improve stripping efficiency and reliability.
