Fall Technical Meeting 2025

In bevel and hypoid gears, as well as straight bevel gears, the pinion profile shift coefficient X1 and the gear profile shift coefficient X2 have the same absolute amount but opposite signs. In bevel gears, this prevents a shaft angle change. This means that a positive profile shift in both members of a bevel gearset would change the shaft angle by (X1 + X2) * mn / Mean Cone Distance. The new developed independent profile shift allows a positive profile shift in pinion and gear without a change of the shaft angle, yet having all the advantages like elimination of undercut, increased contact ratio, and improved NVH as well as stronger tooth profiles, especially in case near miter ratios with a low number of teeth.

Speaker: Hermann Stadtfeld
– Gleason Corporation
Bio: Dr. Hermann Stadtfeld received in 1978 his B.S. and in 1982 his M.S. in Mechanical Engineering at the Technical University in Aachen, Germany. In 1987, he received his Ph.D. Since the beginning of 1994, he has worked for The Gleason Works in Rochester, New York, first as Director of R&D, and from 1996 as Vice President R&D. Today the position of Vice President – Bevel Gear Technology and R&D. Dr. Stadtfeld published more than 300 technical papers and 10 books on Bevel Gear Technology. He holds more than 70 international patents on gear design, gear process as well as tools and machines. In 2025, he received the prestigious Ernst Blickle Award from the SEW-Eurodrive Foundation. Dr. Stadtfeld holds a Professorship at the University of Ilmenau, Germany. He has previously presented 17 papers at the AGMA Fall Technical Meeting.

This research focuses on addressing gear scuffing in electric vehicle (EV) transmission systems. Gear scuffing, caused by metal-to-metal contact under high load and speed, poses a significant challenge to EV gearbox durability. To tackle this, the study utilizes advanced software tools: Masta and Windows LDP. Masta uses ISO 6336 and empirical correlations, while Windows LDP employs an elastohydrodynamic lubrication (EHL) model for a physics-based approach. Despite improvements in scuffing temperature predictions, discrepancies exist between the tools due to variations in surface roughness, torque load, speed, and lubrication. The research proposes a dual approach, combining both tools and correlating results with physical testing on custom-designed rigs, enhancing EV transmission reliability and accelerating gearbox development.

Speaker: Zhiyuan Yu
– Drive System Design
Bio: Dr. Zhiyuan Yu is a mechanical engineer at Drive System Design (DSD) with expertise in gear technology. He earned his Ph.D. in Mechanical Engineering from Tennessee Technological University in 2017. Before joining DSD, he worked at American Axle (AAM) as a Senior Gear Design Engineer. At DSD, Dr. Yu is responsible for powertrain development and optimization projects, balancing technical and commercial responsibilities. He is skilled in software, such as Transmission 3D, MASTA, Ansys, and the Gleason Software Package. Dr. Yu also supports the engineering team, contributing to innovative and sustainable powertrain solutions.

The demand for more efficient gearboxes makes new types of gear sets increasingly interesting in order to realize such transmissions. The crown gear (also known as face gear) is not actually a new type of gear, but it has led a rather niche existence in the past. New manufacturing methods and new design and calculation options are bringing the crown gear back into focus. Today, crown gears are designed with the help of modern flank generators. With the help of the tooth model complex tooth contact analysis under load (LTCA) now can be carried out in the same way as for bevel gears. Two examples are used to show possible applications of crown gears in comparison with similar bevel gears.

Speaker: Joachim Thomas
– ZG Hypoid GmbH
Bio: Dr. Joachim Thomas currently works mainly as an independent developer and consultant with his company ZG Hypoid GmbH. After writing his doctoral thesis at FZG (Technical University of Munich), he worked for many years in industry as a gear expert specializing in bevel gears. He worked for MAN Truck & Bus, Klingelnberg and Voith. He has been a member of the ISO standardization working group for bevel gears (ISO /TC60 /SC2 /WG13) since it was founded more than 25 years ago and has headed this group as convenor since 2015. Joachim Thomas was co-author and co-editor of the textbook “Bevel Gear” by J. Klingelnberg and has given lectures and training courses at numerous events worldwide.

This paper introduces a practical framework for identifying and mitigating Tooth Interior Fatigue Fracture (TIFF) in straight-toothed, net-forged bevel gears used in automotive differentials. As drivetrain systems evolve to deliver higher torque in compact designs, subsurface failures like TIFF pose increasing challenges. Unlike well-understood surface failures, TIFF demands deeper insight into material behavior and internal stress. Drawing from real-world case studies, industry practices, and academic research, the paper evaluates diagnostic and preventative methods including visual inspection, MPI, SEM, microgeometry optimization, and heat treatment. It offers actionable strategies for both newcomers and seasoned engineers, aiming to enhance drivetrain reliability and gear performance. This work supports the ongoing advancement of high-performance gear systems by addressing complex, often-overlooked failure modes.

Speaker: Caleb Gurd
– Eaton Corporation
Bio: Caleb Gurd is a Lead Gear Engineer at Eaton’s Vehicle Group in Galesburg, MI, with over eight years of experience in the design and analysis of parallel axis and right-angle gearing systems. He holds a Bachelor’s degree in Physics from Kalamazoo College and a Master’s degree in Mechanical Engineering from Western Michigan University. Mr. Gurd bridges deep technical knowledge with real-world innovation, driving advancements in drivetrain technology for high-performance and commercial vehicle applications. He has been honored with the 2018 AGMA Foundation Scholarship and the 2024 AGMA Next Generation Award, recognizing his contributions to the advancement of the gear industry.

CAE-based micro geometry design of cylindrical gears enables to optimize the operational behavior of gearboxes and enhances the lifetime due to the reduction of root stress and flank pressure.In this paper, a tooth contact analysis software for planetary gears with a numerical contact algorithm is extended to calculate the damage accumulation both concerning pitting durability and tooth root bending fatigue strength. This approach is further used to design the micro geometry in lead direction based on the safety factors on flank and root as a design target for a load collective of a wind turbine gear stage. The method is then compared to a particle swarm optimization approach with higher calculation time yet being able to optimize the static transmission error additionally.

Speaker: Simon Nohl
– Laboratory for Machine Tools and Production Engineering (WZL) of RWTH Aachen University
Bio: Simon Nohl began working at the Laboratory for Machine Tools and Production Engineering (WZL) at RWTH Aachen University in 2017 as a student assistant during his mechanical engineering studies. He completed a project thesis on powder metallurgical gear simulation, a bachelor thesis on test rig design and simulation validation for automotive planetary gear trains, and a master thesis on modeling and verification of a tooth contact analysis for planetary gears—all at WZL. Since 2022, he is a research assistant at WZL, focusing on planetary gearboxes and condition monitoring. He also supervises the tooth contact analysis software “FE-Stirnradkette”, that is being developed at WZL since over 40 years.

International standards are essential for ensuring consistent, reliable, and high-quality engineering practices worldwide—and they serve as a common technical language. For cylindrical steel gears, typical damage modes and their corresponding safety factors are addressed in the ISO 6336 series. This series is developed and maintained by ISO/TC 60/SC 2/WG 6 “Gear Calculations,” active since 1994 with the goal of making state-of-the-art calculation methods widely accessible. Currently, the group is working on upgrading several key Technical Specifications to full International Standards, including ISO/TS 6336-4 (tooth flank fracture), ISO/TS 6336-20 and -21 (scuffing), and ISO/TS 6336-22 (micropitting). This presentation will provide an update on the standardization process and highlight recent technical developments of particular relevance to gear researchers, developers, and practitioners worldwide.

Speaker: Karsten Stahl
– Gear Research Center (FZG), Technical University of Munich (TUM)
Bio: Professor Karsten Stahl studied mechanical engineering at the Technical University of Munich (TUM) and served as a research associate at the Gear Research Centre (FZG) at TUM and received his Ph.D. degree (Dr.-Ing.). Then, he worked 10 years for BMW in different positions. He was head of the group “Prototyping, Gear Technology & Methods” in Dingolfing, department leader “Validation Driving Dynamics and Powertrain” at the MINI plant in Oxford, and Manager for “Predevelopment and Innovation Management” within BMW Driving Dynamics and Powertrain in Munich. Since 2011, Prof. Stahl has been head of the Institute for Machine Elements and director of the Gear Research Center (FZG) at TUM, and since 2024 has been head of the department of Mechanical Engineering at the School of Engineering and Design of TUM. The focus of his research is experimental and analytical investigations of endurance, tribology, NVH, materials, and condition monitoring on gears, transmission components, and drive systems, targeting to develop methods and tools for the reliable determination of fatigue life, efficiency, and vibration characteristics. Prof. Stahl is the author of several hundred scientific publications, a member of many scientific boards and associations, convenor of DIN and ISO working groups, editor of scientific journals, and chairman of different scientific conferences, including president of the VDI International Conference on Gears.

Additive manufacturing has been positioned in the manufacturing industry due to its capabilities to fabricate complex parts. The use of Laser Directed Energy Deposition (LDED) in repairs reduces considerably the lead times, and the gear industry could benefit from this advantage. However, there is a lack of research and data on the performance of gears repaired by LDED. In this work, we chose the martensitic tool steel Dievar to repair the teeth of a gear, damaged during the assembly process of a machine for aluminum parts production. We also investigate the bending fatigue response, and the corresponding S-N curve of gear teeth manufactured with Dievar. The results of the experiments demonstrate that LDED has large potential for being widely adopted in gear repair applications.

Speaker: Diego Montoya
– Ikergune, INZU Group
Bio: Diego Montoya-Zapata is an R&D Additive Manufacturing Engineer at Etxetar, INZU Group. He holds a PhD in Computational Geometry and a BSc in Mathematical Engineering from EAFIT University, Colombia. He has 7 years of experience in computational geometry and computational mechanics for Additive Manufacturing. His current research focuses on the evaluation of path-planning strategies for Laser-Directed Energy Deposition (LDED) in industrial applications, such as gear repair by LDED.