Gear Rolling for Production of High Gears

Gears are used to transmit mechanical workfrom one point to another. They are widely used in different mechanisms and they are the most important components of a transmission system. Thus, it is important that they are manufactured with high precision to deliver the work with highest possible efficiency. The dominant gear production method is metal cutting, like hobbing. The gear manufacturing industry aims to replace their traditional production lines with greener processes and thereby urge engineers to think about using metal forming methods instead of the traditional metal cutting solutions when possible. Gear rolling is an interesting metal forming method that can be an alternative method to fabricate gear wheels. Research on gear rolling firstly came into interest around 2000. Very few papers are published that covers the development of the method and its limitations and advantages. Almost all of these publications considered rolling of gear wheels with small modules. The focus of this study will be on application of gear rolling for gear wheels with large module (over 3 mm) where the amount of deformation is much larger than found in previous studies. In this thesis the Finite Element Method has been used to simulate and predict the results of rolling of high gears. In addition to that experiments were performed to validate the numerical results and develop the modelling technique for further investigations. The main topic of discussion is about the gear quality as a measure of the success for the process. Extra attention has been paid to the effects of friction and process planning in the result of process loads and also on the gear quality. The thesis structure is based on four published papers, and some additional results from the experiments which have not yet been published. According to the results of these papers, the effect of friction and process parameters are recognized in the final product quality. It is shown that FEM has a great potential in order to model and analyze the gear rolling process. A new approach to combine numerical methods with quality measurement to predict the process outcomes is also presented. The results show that gear wheels with a module of 4mm reach an ISO quality level between 11 and 12. This is substantially lower quality than can be obtained with metal cutting operations. The results of this thesis can be used as the starting point for future research to optimize the quality of gear rolling for high gears.QC 20150914</p

Gear Rolling for Production of High Gears

Gears are used to transmit mechanical workfrom one point to another. They are widely used in different mechanisms and they are the most important components of a transmission system. Thus, it is important that they are manufactured with high precision to deliver the work with highest possible efficiency. The dominant gear production method is metal cutting, like hobbing. The gear manufacturing industry aims to replace their traditional production lines with greener processes and thereby urge engineers to think about using metal forming methods instead of the traditional metal cutting solutions when possible. Gear rolling is an interesting metal forming method that can be an alternative method to fabricate gear wheels. Research on gear rolling firstly came into interest around 2000. Very few papers are published that covers the development of the method and its limitations and advantages. Almost all of these publications considered rolling of gear wheels with small modules. The focus of this study will be on application of gear rolling for gear wheels with large module (over 3 mm) where the amount of deformation is much larger than found in previous studies. In this thesis the Finite Element Method has been used to simulate and predict the results of rolling of high gears. In addition to that experiments were performed to validate the numerical results and develop the modelling technique for further investigations. The main topic of discussion is about the gear quality as a measure of the success for the process. Extra attention has been paid to the effects of friction and process planning in the result of process loads and also on the gear quality. The thesis structure is based on four published papers, and some additional results from the experiments which have not yet been published. According to the results of these papers, the effect of friction and process parameters are recognized in the final product quality. It is shown that FEM has a great potential in order to model and analyze the gear rolling process. A new approach to combine numerical methods with quality measurement to predict the process outcomes is also presented. The results show that gear wheels with a module of 4mm reach an ISO quality level between 11 and 12. This is substantially lower quality than can be obtained with metal cutting operations. The results of this thesis can be used as the starting point for future research to optimize the quality of gear rolling for high gears.QC 20150914</p

Innovative Manufacturing Method for Gears for Heavy Vehicle Application

The present thesis is a summary of research result on an innovative manufacturing method for production of PM gears for application in heavy vehicle. The method uses a powder metal densifications process route to ensure full density. The thesis addresses an innovative processing route where loosely packed powder goes through a double pressing followed by double sintering combined with hot isostatic pressing at the end of the chain in order to reach the full density for the PM gear. The thesis addresses three research questions. First the feasibility of reaching full density for a gear constructed of standard modules relevant for heavy vehicles is investigated. Then the effect of gear geometry on the PM processing is studied. It is revealed that gear geometry influences the density distributions hence the final result. Therefore, the part of the research focusing on the relationship between gear dimensions and the densification results is conducted. It is shown that specific gear geometrical parameters could be more suitable to reach full density. Finally, a prediction model is proposed which can be used in order to measure the density before HIP and exclude risky geometries. A combined numerical and experimental research methodology is implemented in order to address the research questions in the thesis. A verified hardening model for one sample powder mixture is developed in ABAQUS using experimental densification tests. The model helps us to simulate the first pressing and follow the density gradients generated during the first pressing step. The density gradient will be stored in the green component and modified after first sintering and then is used as the input for the second pressing simulation. The result of the second pressing simulation is then modified to include the second sintering effects and finally it is used as the input for HIP simulation. This chain of simulations helps us to understand the gear geometry influence on the density gradients and neutral zone formation during the pressing process. It also ensures that the transition of open pores to closed pores occurs before HIP as a requirement to reach fully density in the analysis. Physical experiments were performed in order to validate FE simulations predictions. Density measurement and dimensional measurement are used to compare the results of FE simulations and physical trial results in order to validate and support the final conclusions based on FE model. Using the validated FE model, a methodology to predict the density before HIP is designed where different gear geometries are modelled and then a regression model is extracted which can predict the minimum RD in neutral zone of the gear before performing costly experiments for a specific material and gear dimensions.Denna avhandling presenterar en sammanfattning av forskningsresultat om en innovativ tillverkningsmetod för produktion av PM-kugghjul, för användning i tunga fordon. Metoden utnyttjar pulvermetallförtätningsprocessvägar för att säkerställa full densitet. Avhandlingen behandlar en innovativ processväg där löst packat pulver genomgår dubbelpressning följt av dubbelsintring i kombination med varmisostatisk pressning i slutet av kedjan för att kunna uppnå full densitet för PM-kugghjulet. Avhandlingen behandlar tre forskningsfrågor. Först undersöks möjligheten att nå full densitet för ett kugghjul uppbyggt av standardmoduler som är relevanta för tunga fordon. Därefter studeras effekten av växelgeometri på PM-behandlingen. Det avslöjas att kugghjulsgeometrin påverkar densitetsfördelningen och följaktligen det slutresultatet. Därför undersöks den del av forskningen som fokuserar på sambandet mellan kugghjulets dimensioner och förtätningsresultaten. Det påvisas att specifika kugghjulgeometriska parametrar kan vara mer lämpliga för att erhålla full densitet. Slutligen föreslås en prediktionsmodell som kan användas för att mäta densiteten före HIP och utesluta riskabla geometrier. En kombinerad numerisk och experimentell forskningsmetodik implementeras för att behandla forskningsfrågorna i avhandlingen. En verifierad härdningsmodell för en provpulverblandning har utvecklats i ABAQUS genom att utnyttja experimentella packningstest. Modellen hjälper oss att simulera den första pressningen och följa densitetsgradienterna som genereras under det första pressningssteget. Densitetsgradienten lagras i grönakroppen och modifieras efter första sintringen och används sedan som ingång för den andra pressningssimuleringen. Resultatet av den andra pressningssimuleringen modifieras därefter för att inkludera de andra sintringseffekterna och slutligen används den som ingång för HIP-simulering. Denna kedja av simuleringar hjälper oss att förstå hur kugghjulets geometri inverkar på densitetsgradienter och neutral zonbildning under pressningsprocessen. Det säkerställer också att övergången av öppna porer till slutna porer inträffar före HIP som ett krav för att nå full densitet i analysen. Fysiska experiment utfördes för att validera förutsägelserna från FE-simuleringarna. Densitetsmätning och dimensionell mätning används för att jämföra resultaten av FE-simuleringar och fysiska testresultat för att validera och stödja de slutliga slutsatserna som baseras på FE-modellen. Med hjälp av den validerade FE-modellen designas en metod för att förutsäga densiteten före HIP där olika kugg-geometrier modelleras och sedan extraheras en regressionsmodell som kan förutsäga minsta RD i kuggens neutrala zon innan man utför dyra experiment för ett specifikt material och kugghjulsdimensionerDue to Covid 19 rules, the defence session would be online.</p

Innovative Manufacturing Method for Gears for Heavy Vehicle Application

The present thesis is a summary of research result on an innovative manufacturing method for production of PM gears for application in heavy vehicle. The method uses a powder metal densifications process route to ensure full density. The thesis addresses an innovative processing route where loosely packed powder goes through a double pressing followed by double sintering combined with hot isostatic pressing at the end of the chain in order to reach the full density for the PM gear. The thesis addresses three research questions. First the feasibility of reaching full density for a gear constructed of standard modules relevant for heavy vehicles is investigated. Then the effect of gear geometry on the PM processing is studied. It is revealed that gear geometry influences the density distributions hence the final result. Therefore, the part of the research focusing on the relationship between gear dimensions and the densification results is conducted. It is shown that specific gear geometrical parameters could be more suitable to reach full density. Finally, a prediction model is proposed which can be used in order to measure the density before HIP and exclude risky geometries. A combined numerical and experimental research methodology is implemented in order to address the research questions in the thesis. A verified hardening model for one sample powder mixture is developed in ABAQUS using experimental densification tests. The model helps us to simulate the first pressing and follow the density gradients generated during the first pressing step. The density gradient will be stored in the green component and modified after first sintering and then is used as the input for the second pressing simulation. The result of the second pressing simulation is then modified to include the second sintering effects and finally it is used as the input for HIP simulation. This chain of simulations helps us to understand the gear geometry influence on the density gradients and neutral zone formation during the pressing process. It also ensures that the transition of open pores to closed pores occurs before HIP as a requirement to reach fully density in the analysis. Physical experiments were performed in order to validate FE simulations predictions. Density measurement and dimensional measurement are used to compare the results of FE simulations and physical trial results in order to validate and support the final conclusions based on FE model. Using the validated FE model, a methodology to predict the density before HIP is designed where different gear geometries are modelled and then a regression model is extracted which can predict the minimum RD in neutral zone of the gear before performing costly experiments for a specific material and gear dimensions.Denna avhandling presenterar en sammanfattning av forskningsresultat om en innovativ tillverkningsmetod för produktion av PM-kugghjul, för användning i tunga fordon. Metoden utnyttjar pulvermetallförtätningsprocessvägar för att säkerställa full densitet. Avhandlingen behandlar en innovativ processväg där löst packat pulver genomgår dubbelpressning följt av dubbelsintring i kombination med varmisostatisk pressning i slutet av kedjan för att kunna uppnå full densitet för PM-kugghjulet. Avhandlingen behandlar tre forskningsfrågor. Först undersöks möjligheten att nå full densitet för ett kugghjul uppbyggt av standardmoduler som är relevanta för tunga fordon. Därefter studeras effekten av växelgeometri på PM-behandlingen. Det avslöjas att kugghjulsgeometrin påverkar densitetsfördelningen och följaktligen det slutresultatet. Därför undersöks den del av forskningen som fokuserar på sambandet mellan kugghjulets dimensioner och förtätningsresultaten. Det påvisas att specifika kugghjulgeometriska parametrar kan vara mer lämpliga för att erhålla full densitet. Slutligen föreslås en prediktionsmodell som kan användas för att mäta densiteten före HIP och utesluta riskabla geometrier. En kombinerad numerisk och experimentell forskningsmetodik implementeras för att behandla forskningsfrågorna i avhandlingen. En verifierad härdningsmodell för en provpulverblandning har utvecklats i ABAQUS genom att utnyttja experimentella packningstest. Modellen hjälper oss att simulera den första pressningen och följa densitetsgradienterna som genereras under det första pressningssteget. Densitetsgradienten lagras i grönakroppen och modifieras efter första sintringen och används sedan som ingång för den andra pressningssimuleringen. Resultatet av den andra pressningssimuleringen modifieras därefter för att inkludera de andra sintringseffekterna och slutligen används den som ingång för HIP-simulering. Denna kedja av simuleringar hjälper oss att förstå hur kugghjulets geometri inverkar på densitetsgradienter och neutral zonbildning under pressningsprocessen. Det säkerställer också att övergången av öppna porer till slutna porer inträffar före HIP som ett krav för att nå full densitet i analysen. Fysiska experiment utfördes för att validera förutsägelserna från FE-simuleringarna. Densitetsmätning och dimensionell mätning används för att jämföra resultaten av FE-simuleringar och fysiska testresultat för att validera och stödja de slutliga slutsatserna som baseras på FE-modellen. Med hjälp av den validerade FE-modellen designas en metod för att förutsäga densiteten före HIP där olika kugg-geometrier modelleras och sedan extraheras en regressionsmodell som kan förutsäga minsta RD i kuggens neutrala zon innan man utför dyra experiment för ett specifikt material och kugghjulsdimensionerDue to Covid 19 rules, the defence session would be online.</p

Numerical and Experimental Analysis of the Gear Size Influence on Density Variations and Distortions during the Manufacturing of PM Gears with an Innovative Powder Processing Route Incorporating HIP

The paper is the result of research intended to develop a process route for the manufacturing of powder metallurgical (PM) gears for application in transmissions units for heavy duty powertrain applications. The main problem of PM for such applications is that the generated pores that occur through conventional pressing and sintering processes reduce the gear strength, which reduces the capacity for power transmission by the gear. In prior work, removing the pores and reaching 100% density by adding Hot Iso-static Pressing (HIP) after two times pressing and two times sintering steps in the process route was suggested to solve the mentioned problem. During the investigations of this work it was revealed that the gear dimensions could influence the process results with respect to geometrical distortions. In this paper we have presented a finite element (FE) model based analysis on how the gear geometrical parameters influenced the distortions occurring in HIP. The simulation model is validated with experiments. Furthermore, the simulation model is used to create a prediction model for further investigations. The research showed that PM gears with different sizes during the proposed process route behaved differently in terms of distortions. This was illustrated with a series of simulations with different gear geometries. A regression model was developed based on the FE results for further practical predictive use. The distortions caused by HIP should be considered in the process design to prevent expensive post processes afterwards to reach the gear with accurate geometry and keep the costs of manufacturing low. It is concluded that it is possible to use the innovative process route including HIP to reach the full density and close all the open pores but not for all kind of gear geometries