Case study: starter pinions (1) Established within the GROWTH project GRD "Improvement of Service Life and Reliability of Cold Forging Tools with respect to Fatigue Damage due to Cyclic Plasticity (COLT)", funded by the European Community. COLT Design Manual for Cold Forging Dies Case study: Cold forging of starter pinions for automotive starters Cold forged starter pinions
Case study: starter pinions (2) Established within the GROWTH project GRD "Improvement of Service Life and Reliability of Cold Forging Tools with respect to Fatigue Damage due to Cyclic Plasticity (COLT)", funded by the European Community. COLT Design Manual for Cold Forging Dies Typical failure mode in the lower die insert Vertical and horizontal fatigue cracks in the lower die insert
Case study: starter pinions (3) Established within the GROWTH project GRD "Improvement of Service Life and Reliability of Cold Forging Tools with respect to Fatigue Damage due to Cyclic Plasticity (COLT)", funded by the European Community. COLT Design Manual for Cold Forging Dies Tooling system for improved radial and axial prestressing (STRECON ® E + Axi-Fit)
Case study: starter pinions (4) Established within the GROWTH project GRD "Improvement of Service Life and Reliability of Cold Forging Tools with respect to Fatigue Damage due to Cyclic Plasticity (COLT)", funded by the European Community. COLT Design Manual for Cold Forging Dies FE analysis of the tooling system with regard to the vertical crack initiation Assumed process pressure distribution 2D FE model of the cross-section with the gear profile
Case study: starter pinions (5) Established within the GROWTH project GRD "Improvement of Service Life and Reliability of Cold Forging Tools with respect to Fatigue Damage due to Cyclic Plasticity (COLT)", funded by the European Community. COLT Design Manual for Cold Forging Dies Stress response in the prestressed condition Because of its higher stiffness, prestressing by the STRECON ® E + leads - despite the lower nominal interference - to a similar prestress level
Case study: starter pinions (6) Established within the GROWTH project GRD "Improvement of Service Life and Reliability of Cold Forging Tools with respect to Fatigue Damage due to Cyclic Plasticity (COLT)", funded by the European Community. COLT Design Manual for Cold Forging Dies Stress response in the condition at max. process load Prestressing by the STRECON ® E + reduces the tensile stress in the fillets at maximum process load
Case study: starter pinions (7) Established within the GROWTH project GRD "Improvement of Service Life and Reliability of Cold Forging Tools with respect to Fatigue Damage due to Cyclic Plasticity (COLT)", funded by the European Community. COLT Design Manual for Cold Forging Dies FE analysis of the tooling system with regard to the horizontal crack initiation Contact area
Case study: starter pinions (8) Established within the GROWTH project GRD "Improvement of Service Life and Reliability of Cold Forging Tools with respect to Fatigue Damage due to Cyclic Plasticity (COLT)", funded by the European Community. COLT Design Manual for Cold Forging Dies Contact stresses between upper and lower die insert in the prestressed condition By reducing the plane contact area, the maximum contact stress becomes higher and gets closer to the inner bore of the die
Case study: starter pinions (9) Established within the GROWTH project GRD "Improvement of Service Life and Reliability of Cold Forging Tools with respect to Fatigue Damage due to Cyclic Plasticity (COLT)", funded by the European Community. COLT Design Manual for Cold Forging Dies Axial stresses in the upper and lower die insert in the prestressed condition By reducing the plane contact area, the axial prestress in the shoulder (where the cracks actually occur) is increased
Case study: starter pinions (10) Established within the GROWTH project GRD "Improvement of Service Life and Reliability of Cold Forging Tools with respect to Fatigue Damage due to Cyclic Plasticity (COLT)", funded by the European Community. COLT Design Manual for Cold Forging Dies Axial prestress during assembly
Case study: starter pinions (11) Established within the GROWTH project GRD "Improvement of Service Life and Reliability of Cold Forging Tools with respect to Fatigue Damage due to Cyclic Plasticity (COLT)", funded by the European Community. COLT Design Manual for Cold Forging Dies Recommendations for the design of dies for the cold forging of tripods and cross-joints Recommended tooling system: STRECON ® E + Axi-Fit provides high stiffness and combines improved radial and axial prestressing Result: Die life for starter pinion dies improved by factor 2-3 (depending on the type of starter pinion)