2024 Fall Technical Meeting (FTM)

10:00am – 5:00pm
Registration Open
Lindbergh Foyer

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10:00am – 12:00pm
SME Chicagoland Heat Treat Training
Coleman A
Registration for the pre-conference training is $200 per person and can be added to your FTM registration fee, or you can register for the training alone.

• The Heat Treat training is presented by SME (Chicago Chapter) and held in conjunction with the AGMA Fall Technical Meeting.
• Topics presented will focus on successful methods for heat treating of gears and managing distortion.

The training will consist of three presenters who are recognized experts in the area of heat treating. The presenters and their specific subject areas are as follows:

Dan Herring
Herring has spent his career in the heat treatment industry addressing heat treating, brazing and sintering problems. The author of over seven hundred (700) published papers and seven (7) books including Vacuum Heat Treatment (Volume 1 & 2) published in 2012/2015, Atmosphere Heat Treatment published in 2014/2016 as well as several e‐books entitled A Comprehensive Guide to Heat Treatment (Volume 1 & 2) released in 2018 and Metallurgical Fundamentals of Heat Treating released in 2021. “The Heat Treat Doctor” is dedicated to advancing the state‐ of‐the‐art in the thermal processing field.

Herring’s Presentation

• Gear materials and their heat treatment
• Critical considerations – microstructure & properties
• Preventing gear failures by intelligent heat treatment
• Ways in which to optimize gear heat treatment in atmosphere furnaces
• Ways in which to optimize gear heat treatment in vacuum furnaces

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Arvid Casler
Casler has a long history of applied expertise in the heat-treating sector for manufacturing. Previously, Casler was the Chief Metallurgist for Northstar Aerospace, and is now General Manager of Element Chicago which is a material testing laboratory. Casler is a Frost & Sullivan and Presidential Service Award recipient (2016), and his affiliations include the ASTM E28 Committee, the Rockford‐Stateline Chapter of ASNT, and several committees of ASM International while a current member of NACE, AIME/TMS, STLE and SAE.

Casler’s Presentation

• Review of starting material conditions, including basic product forms, forged, wrought, cold rolled, and hot rolled
  • Basic furnace designs and fixturing vs. furnace load
  • Sources of distortion ‐ brief review of the development of residual stress, stress relief, how to identify which is which (shape vs. size), and intermittent stress relief (inclusion of masking materials)
  • Quenching primer ‐ media vs. distortion, prediction methods, and quench phases
  • Quench press use

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Tom Hart
Hart is a seasoned Product Manager specializing in Vacuum Furnaces at SECO/VACUUM. Tom draws from the experience of his 20‐year career in precision manufacturing and heat treatment industries. In his role, Tom collaborates closely with partners, providing invaluable insights into heat treatment processes, equipment, and infrastructure specific to vacuum furnaces. His knowledge spans various heat treatment techniques, including hardening, annealing, low‐ pressure carburizing, tempering, sintering, vacuum brazing, and more.

Hart’s Presentation

• An overview focusing on gear heat treatment with low pressure carburizing and the three methods of quenching (batch oil, batch gas and 4DQ)
• A detailed look at the newer 4DQ process – which in most cases can eliminate the need for die press quenching

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1:00pm – 5:00pm
Session 1: Materials & Heat Treatment
Lindbergh Ballroom

The Role of In-Situ Techniques in Microstructure Optimization of Interstitially Alloyed Steels
Qianchen Zeng, Worcester Institute

Microstructure optimization of steel for improved performance requires detailed knowledge of the thermal response of the materials. When designing heat treatments of new materials, in-situ information about, for example, phase transformation, is pivotal. In this work, in-situ techniques are applied for mapping the heat treatment response of three technologically relevant materials systems. It is showcased how in-situ techniques can be applied to record the heat treatment response of these generically different special materials. It is also emphasized how nitrogen can be actively used in steels, which can pave the way for more widespread use of nitrogen containing steels. The topic of using high carbon steels in additive manufacturing is also addressed.

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Durability and Performance Rating Procedures for Plastic Spur Gears
Dr. Damijan Zorko, RD Motion, d.o.o.

High performance plastic gears are increasingly replacing metal gears in several applications due to their many advantages. Lower weight, no need for lubrication, cheaper mass production, significantly better NVH and chemical/corrosion resistance are just a few of these advantages. To ensure a reliable gearbox operation, gears need to be appropriately designed in order to avoid failure within the required lifespan. There is currently no international standard available for the mechanical design of plastic gears. The most up-to-date is VDI 2736, which provides the design rating procedures for all common failure modes. A significant lack of required material data is the major drawback preventing a larger adoption of plastic gears. The present study provides experimental methodologies, which can be employed to characterize the gear-specific material data.

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A Preliminary Study on a Novel Procedure for the Assessment of Fatigue Performance of PA6 Polymer Gears
Dr. Riccardo Longato, Longato Riccardo Srls

In the present study, experimental tests are conducted in accordance with the standard for both procedures and equipment, but a new procedure is conceptualized for the evaluation of plastic gears. For the test setup, the gears are installed in a climate chamber to achieve the correct temperature test control. With an infrared camera and temperature feedback software, the temperature is set at 30°C. From the triplet σ_FlimNi (fatigue strength) N_i (number of cycles) θ_i (temperature) data for each performed test, it is possible to determine a point on the temperature-dependent Wöhler curve. From this curve, the novel approach consists in the forecast of time to failure assuming a Weibull fault distribution. The obtained results are compared with the standard VDI 2736 approach.

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Bending Fatigue Strength of Gear Steels for Automotive Electric Drive Units
Christopher Aylott, Newcastle University

Gear bending fatigue tests were conducted on three commercially available carburizing steels to support the development of gearing for future automotive electric drive units, which requires increased power density, efficiency and reliability. 20MnCr5 was selected as the baseline steel, Ovako 236Q was selected to investigate the effect of inclusion content and Ovako 158Q (20NiMo9-7F) was selected to investigate the effect of reduced intergranular oxidation. Both candidate steels outperformed the baseline steel in the as-carburized condition with further improvements in finite life performance and/or mean strength achieved through the use of duplex shot peening or root grinding. The work outlined in this paper has therefore shown the ability for alternative steel selection to either achieve increased power density or decrease cost through reduction of manufacturing stages.

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Analysis of Tooth Bending Fatigue of AISI 9310 Gears Through Strain-Based Criteria
Dr. Lorenzo Pagliari, Free University of Bozen/Bolzano

This paper aims at assessing the applicability of strain-based criteria for the fatigue characterization of gears. Specifically, four different strain-based criteria based on the theory of critical plane were investigated. Experimental data on AISI 9310 spur gears using the single tooth bending method to achieve crack initiation was considered. Stress and strain tensors developed during the tests were calculated through a finite element model and were numerically elaborated through the selected criteria, obtaining different predictions. This study managed to demonstrate that strain-based criteria can also be employed for the fatigue analysis of gears, and that they have the capabilities of characterizing certain features of gear fatigue behavior with very high accuracy, representing a practical tool for companies to quickly estimate the fatigue behavior of gears.

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Experimental Study on the Performance of Plastic Worm Gears
Dr. Borut Černe, RD Motion, d.o.o.

Worm gears are a common type of plastic gears, employed in several actuators, ranging through different industries: automotive, appliances, medical. Despite the fact that plastic worm gears are very commonly used, there has been comparatively limited research done on their performance characteristics. Data on how different plastic materials perform in a worm gear transmission is almost non-existing. The majority of applications are designed based on an empirical know-how and by employing conservative methods leading to an overdesign. The study provides a comprehensive overview of the state-of-the art models available for conducting design rating procedures of plastic worm gears. Corresponding to the design models, experimental methods are proposed, which can be used to characterize materials performance under specific load conditions which arise in worm gear pairs.

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5:30pm – 6:30pm
Welcome Reception
Coleman Ballroom

7:00am – 5:00pm
Registration Open
Lindbergh Foyer

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7:00am – 8:00am
Breakfast
Coleman Ballroom

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8:00am – 12:00pm
Session 2: Applications
Lindbergh Ballroom

Design Alternative for a Helicopter Final Stage Planetary Gearbox, Introducing the Innovative Orbicular Gear Mechanism (OGM)
Mert Vardar, Tr Transmisyon Engineering

The Orbicular Gear Mechanism (OGM) is a promising alternative to traditional planetary gear systems, particularly in aerospace applications. Unlike conventional designs, OGM utilizes face gears for the sun and ring gears, resulting in superior compactness and weight reduction. Its unique configuration maximizes planet gears relative to reduction ratios, enabling smaller yet similarly efficient gearboxes. OGM also minimizes centrifugal effects on the planets, allowing for high-speed operation. Overall, OGM presents a promising solution for aerospace applications, offering enhanced load distribution, weight reduction, and compactness compared to traditional planetary gear configurations.

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Analytical Calculation of the Gear Body Stiffness of Face Gears
Jonas-Frederick Berger (b. Hochrein), Institute of Machine Elements, Gear Research Center (FZG), TUM School of Engineering and Design, Technical University of Munich

Due to the constantly increasing requirements, more and more transmissions are being adapted and developed for their specific application. It is of paramount importance to optimally exploit the potential of the gears. Target criteria can be the NVH behavior and/or the maximum carrying capacity. To evaluate these objectives, it is crucial to know the load distribution in the meshing. The load distribution is usually determined with loaded tooth contact simulation (LTCA), based on the stiffnesses of the machine elements in the gearbox. This paper presents and discusses a novel approach to determine the wheel body stiffness for disk-like gears. The face gear drive serves as a demonstrator, whereby the approach can be transferred to other angular gears (e.g. bevel gears) without any difficulty.

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Electric vs. Combustion: A Comparative Analysis of Gear Design for Commercial Vehicle Applications
Carlos Wink, Eaton Corporation

The automotive industry has seen a significant shift from Internal Combustion Engines (ICE) to Electric Vehicles (EV) over the past decade, primarily in passenger cars. Compared to that, the commercial vehicle sector is now beginning to explore EVs. The gear design approach for EV is different from conventional ICE. These gears run at higher speeds and are prone to issues like severe pitting, micropitting, scuffing, power loss, and gear whine. This paper explores the design of gears for commercial EV applications, compares it with conventional ICE gear design, and identifies critical parameters for risk mitigation and improved NVH.

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Gearbox NVH Analysis – An Engineering Approach
Timo Giese, FunctionBay GmbH

Enhancing acoustic comfort in gearbox engineering is crucial, necessitating advanced computational models and simulations for predicting and improving noise, vibration, and harshness (NVH) performances. Comprehensive evaluations require extensive experimental data to validate structural, dynamic, and acoustic characteristics. This paper presents an engineering approach for investigating gearbox NVH performances. Numerical and Experimental Modal Analysis (NMA/EMA) validate the natural frequencies of structural components, with data compared using the Modal Assurance Criterion (MAC). Simplified modeling guidelines for housing bolted connections are derived. A flexible multibody gearbox model is developed using modal reduction techniques and advanced gear and bearing contact formulations, validated through dynamic simulations. Finally, a time domain boundary element method (TD-BEM) is used for numerical acoustic analysis under dynamic conditions.

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Design Method of System Tolerances in Cylindrical Gearboxes for Cost-Efficient Optimization of the Excitation Behavior
Laurenz Roth, M.Sc, Laboratory for Machine Tools and Production Engineering (WZL) of RWTH Aachen University

The design of cylindrical gears is often carried out separately from the development of surrounding gearbox components. This applies in particular to the procedure for defining the tolerances. Mostly, experience is used when the tolerance limits of surrounding housing components, shaft shoulders, rolling bearing operating clearances or bores are defined. The definition of restrictive tolerance limits determines the appropriate manufacturing processes, that are suitable for achieving the tolerance requirements. That influences the total manufacturing costs. The aim of the paper is to develop a method that enables a tolerance design for various types of deviations within a gearbox with cylindrical gears. It takes into account the tolerance’s relevance for the noise excitation of the gears and the manufacturing costs resulting from the individual manufacturing requirement.

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Calculation of the Scuffing Load Capacity of Spur Gears Using a Local Thermophysical Approach
Mathis Steinrötter, Ruhr University Bochum

Efforts to achieve global climate targets require efficient drive systems with high power density, increased speed, and low-viscosity lubricants. However, these factors reduce scuffing load capacity, a key limitation in high-speed gearbox design. Scuffing is influenced by tribological stress, friction conditions, lubricant formulation, and materials. The flash temperature method (ISO 6336-20) verifies scuffing load capacity but is limited to speeds below 50 m/s, which current trends exceed. The standard method empirically models material influence, restricting technological progress. This article introduces a new calculation method for high-speed cylindrical gears, considering material thermophysical properties. Unlike ISO 6336-20, it uses a lubricant-specific characteristic curve, with permissible flash temperature based on the PECLET number, referencing conductive and convective heat properties. This method enhances power density in drive systems.

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12:05pm – 1:05pm
Awards Luncheon
Coleman Ballroom

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1:10pm – 5:00pm
Session 3: Design & Rating
Lindbergh Ballroom

Influence of Reverse Loading on the Tooth Flank Fracture Load Capacity
Johannes Rolzhäuser, Laboratory for Machine Tools (WZL) of RWTH Aachen University

Due to near surface optimization in the last years, tooth flank fractures are increasingly occurring. The influence of reverse loading (e.g. in planet gears) on the tooth flank fracture load capacity is currently only known to a limited extent. Hence, the aim of this report is the investigation of the influence of the reverse loading on the tooth flank fracture load capacity. For this purpose, a FE-based tooth flank fracture load capacity calculation is extended. Subsequently, a simulation study is carried out, in which the load capacity as well as the location of the crack initiation is investigated for reverse loading. Finally, first experimental tests are carried out on a reverse bending test rig.

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Categorization of Gear Stiffness Methodologies, Workflows and Software
Adam Foltz, Purdue University in Indianapolis

A comprehensive breakdown of the different methodologies, workflows and software used for the determination of gear stiffness in loaded tooth contact analysis (LTCA) is covered. A brief history of the most important papers in the field is presented. A breakdown of the different analytical formulations for the various components of gear stiffness is given, along with the papers they originated from. A total of ten different LTCA schemes seen in both commercial and academic software are covered, along with eight different workflows that can be used in the LTCA process. Fifteen different subtleties in the LTCA algorithms, and seven separate areas for research in the field were discussed. The references include all relevant work discussed sorted in chronological order.

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Evaluation of Gear Contact Fatigue Surface Integrity Aspects in Fatigue Lifetime Using the Barkhausen Noise Technique
Bruno Henrique Lima, M.Sc, Instituto Tecnológico de Aeronáutica

This study addresses the Magnetic Barkhausen Noise (MBN) technique to monitor contact fatigue early stages evolution in gears. Fatigue testing was conducted inducing a natural evolution of gear contact fatigue. Monitoring MBN signals at regular intervals during testing allowed for correlation with surface integrity degradation. Furthermore, the study delves into microstructural aspects related to contact fatigue. In-depth analyses of residual stresses, microstructure, and microhardness provided a comprehensive understanding of surface degradation. Early contact fatigue stages were characterized by surface softening in the near-surface region, up to approximately 40 µm depth, accompanied by a less compressive residual. Results revealed a significant variation in MBN signals influenced by operational loads during tests, with a noteworthy increase observed just before gear failure.

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Investigation of Gear Involute Deviations Under Press-Fit Conditions
Dr. Anusha Anisetti, Eaton Corporation

Tooth form is critical to gear performance. Intentional design modifications and manufacturing deviations of tooth flanks affect load distribution of the meshing teeth and consequently bending stress, contact stress, and gear noise. Gears are connected to the rotating shafts through different ways, such as splines, keyways, welding, and interference fit. Press/Shrink fit is largely used to assemble automobile gears; however, it causes deformation in gear teeth during the assembly process. In this paper, the main focus is to examine this assembly deviation of the tooth profile and its impact on gear contact fatigue life. A simple correction on gear teeth involute during design process is proposed to help improve the conjugate gear meshing conditions and consequently life while facilitating manufacturing of the design intended gears.

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Influence of Unbalanced Sliding Conditions on the Pitting Load Carrying Capacity of Internal Gears
Michael Geitner, Gear Research Center (FZG), Technical University of Munich

Macropitting occurs predominantly in contact areas of negative specific sliding. Positioning pitch point C outside of the active profile for internal gears allows to completely avoid negative sliding either on planet or ring gear. The pitting resistance of each partner can be affected by positioning of C and the resulting differences in specific sliding, allowing a lifetime optimization of the full gear stage. Systematic investigations on the pitting load capacity with representative internal gear geometries in different material pairings were performed. The results confirm a distinct influence of unbalanced sliding conditions, showing a significant increase of the pitting load capacity by avoiding areas of negative sliding on the ring gear, while an exposure to negative sliding only leads to a reduction of the pitting resistance.

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Influence of Nonlinear Cumulative Damage in Gear Lifetime Analysis
Riley Damm, The Ohio State University

In many gearing applications, the gearbox or transmission system is subject to complex load spectra and mission cycle loading. Many classical and contemporary studies have shown that damage accumulation in metals is nonlinear, and the order of the loading should not be ignored. Yet, standard calculation methods for gears such as ISO 6336-6:2019, ANSI/AGMA 2001-D04, and IEC 61400-4:2012 still employ a linear damage rule. In this study, various damage rules are leveraged to perform lifetime analyses of gears subject to variable loading. ISO 6336-6:2019 is utilized as an example realistic mission cycle for a gear. The influence of load spectra order, mission cycle length and load spectral content on estimated design life using nonlinear damage is explored.

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SPECIAL PRESENTATION: Design Automation for High Speed Gears
Dr. Burkhard Pinnekamp, RENK (retired)

High speed gears for industrial applications such as power generation or compressor drives are built according to general design rules but usually have specific performance parameters such as speed, ratio, and power. Moreover, the location of driving and driven equipment may vary. This is a typical engineer-to-order process, which is suitable to be assisted by design automation. This paper presents an advanced program system used to define design and performance parameters, create customer documents and develop data for the complete production cycle. All data are created in a short time, and before a quotation is made to the customer. This presentation describes different process types for different products and, as one example for improved digital processes, the development process for high-power, high-speed gears with design automation.

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6:00pm – 8:00pm
Networking Reception
Dave & Busters in Rosemont, IL

7:00am – 1:00pm
Registration Open
Lindbergh Foyer

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7:00am – 8:00am
Breakfast
Coleman Ballroom

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8:00am – 12:00pm
Session 4: Efficiency, Lubrication, & NVH
Lindbergh Ballroom

Advanced Gearbox Lubrication Analysis: A Virtual Lab for Design Optimization
Benjamin Beckelynck, B.ING, M.Sc, Optimec Consultants Inc.

This paper presents a workflow for gearbox lubrication analysis using advanced CFD and heat transfer simulations. Developed with a client transitioning to electric vehicles, the workflow addresses complex lubrication physics and bearing overheating issues. By creating a digital twin, we enabled a virtual lab environment for testing multiple scenarios, significantly reducing time and cost. Leveraging GPU power, the XFlow 2023 solver cuts computation times from weeks to days. This approach allows rapid iteration and optimization of gearbox designs, improving efficiency and lifespan while preventing flaws. Validated through visual comparisons, churning loss measurements, and temperature data, the workflow enhances product performance, accelerates development timelines, and reduces costs, providing a robust tool for engineering challenges.

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Nanocomposite Coatings for Gears
Dr. Peter Schmidt, PE, United Protective Technologies, LLC, UNCC PORTAL

Plasma-deposited nanocomposite coatings can offer substantial operational performance and durability improvements to interfaces in rolling or sliding contact without significantly adding to overall part volume or affecting heat treatment of the substrate. This work describes the development and initial testing of a thin film coating system designed for aerospace gear sets. The predecessor coating system was developed for use on racing hypoid gear sets and has been successfully deployed on automotive platforms. Dynamometer testing of vehicles employing this coating showed a nontrivial increase in brake horsepower available. Test results are reported. Gear surface finish data and photographs are also included, with examples shown prior to testing and after testing.

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CFD Simulation of Power Losses and Lubricant Flow in Gearboxes
Dr. Franco Concli, Prof.-Ing., Free University of Bozen/Bolzano

Efficiency has become an increasingly crucial factor. Being able to predict efficiency and lubrication in gearboxes remains an imperative engineering challenge. Existing mathematical models available in literature rely on empirical relations, providing accurate results only within narrow operating ranges.

The implementation of a computationally efficient mesh-handling strategy, along with the development of advanced solvers capable of addressing new phenomena like cavitation, aeration, oil suspension or unconventional lubrication (e.g., non-Newtonian fluids), has made CFD ready for an extensive industrial application for the simulation of lubricated systems. Compared to a decade ago, the computational effort has been slashed by 97%, enabling the simulation of complex systems.

This paper presents application examples across various gear types, showcasing the versatility of the developed approach showing some real case studies.

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How to Replace Oil as a Lubricant in Worm Gearboxes with Grease
Felix Müller, M.Sc, Chair of Machine Elements, Gears, and Tribology (MEGT), Rheinland-Pfälzische Technische Universität (RPTU)

This work explores the use of lubricating grease as an alternative to oil in worm gearboxes, driven by specific requirements and environmental conditions. Switching to grease necessitates new approaches to gearbox design, calculation, and tribological analysis. The study examines the rheological properties of greases, their tribological behavior, and lubricant distribution in gearboxes. Various lubricants are tested using tribometers, and their behavior in real worm gearboxes is analyzed. Experimental results, including film thickness, viscosity, and friction coefficient measurements, are compared with analytical methods. Tests also analyze grease distribution using fluorescent particles during operation. The findings highlight the potential of greases in worm gears, enabling the prediction of friction and informing gearbox design adjustments.

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Mitigation of Gear Whine Noise in Agricultural Tractor Application
Ketan Bhate, John Deere India

This study focuses on reducing gear whine noise in tractors through simulation and physical validation. It examines load-dependent noise in field operations, identifies two distinct gear orders, and enhances gear macro geometry, particularly helix angles and face width. The study also addresses gear manufacturing variations by shifting to advanced grinding methods. A system-level bench test calibrates the simulation model, and proto gears are developed for physical experimentation using Design of Experiments (DOE). These interventions lead to a significant noise reduction at the vehicle level. The research highlights the importance of precise geometric modifications in minimizing gear whine noise, ultimately improving tractor performance and user experience.

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Advanced Lubricant Technology for Open Gear Applications
Dr. Jennifer Clark, The Lubrizol Corporation

 Proper lubrication is critical for all open gear applications. These applications are extremely demanding and range from sugar mills to mining. Over time, asphaltic stock have been phased out in favor of physically cleaner and more visually appealing polyisobutylene, higher paraffinic base fluids and Polyalphaolefins. Recently, a new family of unique performance polymers were used to develop fluid lubricants for open gear applications. The primary focus of this work is to illustrated the development of a new fluid lubricant technology and their performance in real world applications. Our initial work focused on FZG testing, traction studies and other traditional bench tests to validate basic performance before we moved to a sugar mill and on to larger equipment including a ball mill.

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Efficient Numerical Assessment of Thermal Effects in a Gearbox Using Smoothed Particle Hydrodynamics
Benjamin Legrady, Dive Solutions GmbH

Using advanced computational fluid dynamics (CFD) and smoothed particle hydrodynamics (SPH) techniques, this approach streamlines early-stage gearbox design by simulating over 100 design variations in a single day. It optimizes cooling performance and reduces development time and costs without the need for extensive prototype testing. Key findings include improved cooling through optimized nozzle configurations. Leveraging a cloud-native platform enables quick, data-driven decisions, enhancing efficiency in gearbox engineering through virtual optimization.

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12:05pm – 1:00pm
Networking Lunch
Coleman Ballroom

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1:05pm – 5:00pm
Session 5: Manufacturing, Inspection, and Quality Control
Lindbergh Ballroom

Statistical Analysis of the Position Tolerances of Planet Pins in Planetary Gearboxes
Benjamin Abert, FVA GmbH

The simulation of planetary gearboxes is often based on a nominal geometry for the planet carriers. However, it is known that the position of the planet pin has an influence on the load distribution factor, as defined in ISO6336. Thus, the position tolerances also affect the load capacity. The primary objective of this work is to systematically analyze the position tolerances of the journal in the planet carrier. A Monte-Carlo simulation is used to evaluate the load capacity of a planetary gear stage under the influence of the tolerances. A correlation between the loads required by the customer and the deviations in the components due to manufacturing tolerances enables the use of components that would previously have been scrapped, especially in context of modular drives

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Review of the Gear Transmission Error
Dr. Zhaoyao Shi, Beijing Engineering Research Center of Precision Measurement Technology and Instruments, Beijing University of Technology

This paper traces the research history of transmission error (TE) over the past century, highlighting three cognitive stages of TE: geometric error, kinematic error, and dynamic error. The relationship between transmission error and individual gear error is investigated, leading to the classification of transmission error. Furthermore, the composition of transmission errors is clarified, emphasizing their dynamic nature. The application of transmission error in various areas, such as gear design, process error analysis, transmission chain accuracy characterization, and gear noise, vibration, and harshness (NVH) evaluation, is summarized. Finally, the limitations and deficiencies of transmission error are outlined, and a resolution to address these issues is proposed by considering gear pair integrated errors.

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Generating Gear Grinding in E-Mobility: Challenges and Solutions
Dr. Maximilian Zimmer, Reishauer AG

The topic of this paper is the changing focus in gear design and the resulting challenges in gear production, in particular for continuous generating gear grinding with the rising influence of the E-mobility in the automotive industry. Knowing the characteristics of the generating grinding process methods for optimizing the NVH-behavior of a gear will be presented. A comprehensive approach has to consider the whole process containing the gear design and all the involved manufacturing processes. In particular, the external excitation of components in the grinding machine which typically results in NVH issues will be discussed. In this context this paper will show the fundamental effect of external excitation frequencies in the grinding machine and an approach to solve the problem.

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Innovative Processes and Strategies for Increasing Machining Efficiency for Worms and Worm Gears
Jörg Lohmann, Dipl.-Ing., EMAG Koepfer GmbH

Recent increases in digitalization, connection and automation led to a demand for higher degrees of automation and flexibility. Industrial gearboxes, such as fractional horsepower and worm gearboxes, are increasingly important, since they significantly impact production of automation solutions, robots and other handling systems. This report shows how worms can be machined more efficiently by replacing the single index worm milling process with a more efficient hobbing process, using a special hobbing strategy. Additionally, this report offers a machining strategy for single index worm milling, avoiding deviations in the gear geometry caused by internal material tensions released during cutting. Moreover, the report explains how to increase efficiency by avoiding return strokes within the machining cycle.

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Cutting Tool Selection Criteria for Cylindrical Gear Manufacturing
Dr. Massimiliano Turci, Studio Tecnico Turci

This paper concludes the trilogy of articles about the relationship between design and production of gears. It has already examined the design with the available tools. It is the first step in answering the designer’s question, “Can I manufacture this gear?” The closed-loop relationship between design and production with mutual exchange of information has also been seen. The closed loop is the active and synchronous participation of production in design. These two scenarios are typical of companies that have both design and production. This third “episode” examines the typical situation of third-party manufacturers, who receive the design of a single gear and ask: How can I make this wheel? Particular attention will be paid to the choice of hob pressure angle.

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Influence of Material Removal Rate on Residual Stress State in Gear Grinding
Angelo Carvalho, M.Sc, Instituto Tecnológico de Aeronáutica

Residual stress plays a critical role in avoiding fatigue failure. Fatigue cracks nucleate and propagate under tensile stresses, a suitable compressive residual stress state is then desirable. Grinding, typically the last manufacturing process, induces residual stresses, which vary with material removal rate (MRR). The objective of this study is the comprehension of how the variation of MRR along the gear tooth profile influences the grinding-induced residual stresses. Case-hardened steel discs were ground with different MRRs, and their residual stress state was characterized in terms of surface distribution and in-depth profile. ITA Geometry gear samples were similarly assessed, showing good correlation between MRR and residual stress state. Results indicate that optimizing grinding parameters by MRR can enhance the residual stress state, improving gear durability.

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Micropitting Load Carrying Capacity of 5-Axis Milled Gears
Lennart Schierholz, M.Sc, Ruhr University Bochum

This article presents the results of tests performed on back-to-back test rig for large module gears and on a FZG gear test rig to investigate micropitting load carrying capacity using 5-axis milled gears. Tests revealed geometric deviations and significant wear, particularly profile form deviations and scrape marks, due to premature meshing impacts. 5-axis milled gears showed similar micropitting wear depths but larger wear surfaces. The resulting surface caused higher local contact stress which result in an early wear phenomena and larger worn surface. Lowering the injection temperature from 90°C to 60°C reduced micropitting due to better lubrication. Ensuring good geometric quality in gear manufacturing via 5-axis milling is crucial to prevent accelerated micropitting wear.