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To meet the future goals of higher productivity and lower production costs, the cutting speeds and feeds in modern gear hobbing applications have to increase further. In several cases, coated carbide tools have replaced the commonly used high speed steel (HSS) tools.
Hobs, broaches, shaper cutters, shaver cutters, milling cutters, and bevel cutters used in the manufacture of gears are commonly made of high speed steel. These specialized gear cutting tools often require properties, such as toughness or manufacturability, that are difficult to achieve with carbide, despite the developments in carbide cutting tools for end mills, milling cutters, and tool inserts.
The power of high speed gears for use in the petrochemical industry and power stations is always increasing. Today gears with ratings of up to 70,000kW are already in service. For such gears, the failure mode of scoring can become the limiting constraint. The validity of an analytical method to predict scoring resistance is, therefore, becoming increasingly important.
Above all, a gear is not just a mechanical transmission, but is developed to a system fulfilling multiple demands, such as clutch integration, selectable output speeds, and controls of highest electronic standards. This paper shows the basics for high-speed gear design and a selection of numerous applications in detailed design and operational needs.
Are trains still a growth industry prospect for manufacturers?
In this paper a thermal network model is developed to simulate the thermal behavior of a high-speed, one-stage gear unit which is jet-lubricated.
For a high-speed gearbox, an important part of power losses is due to the mesh. A global estimation is not possible and an analytical approach is necessary with evaluations of three different origins of power losses: friction in mesh contact, gear windage and pumping effect between teeth.
The newer profile-shifted (long and short addendum) gears are often used as small size reduction gears for automobiles or motorcycles. The authors have investigated the damage to each cutting edge when small size mass-produced gears with shifted profiles are used at high speeds.
Depo provides all-in-one machining capabilities for the gear industry.
The main theme of this article is high-capacity, high-speed load gears in a power transmission range between 35 MW and 100 MW for generators and turbo-compressors driven by gas or steam turbines.
Gear designers face constant pressure to increase power density in their drivetrains. In the automotive industry, for example, typical engine torque has increased significantly over the last several decades. Meanwhile, the demands for greater fuel efficiency mean designers must accommodate these increased loads in a smaller, more lightweight package than ever before. In addition, electric and hybrid vehicles will feature fewer gears, with fewer transmission speeds, running at higher rpms, meaning the gears in those systems will have to endure life cycles far beyond what is typical with internal combustion engines.
Technology investments lead to product innovation at gear materials suppliers.
The manufacturing process to produce a gear essentially consist of: material selection, blank preshaping, tooth shaping, heat treatment, and final shaping. Only by carefully integrating of the various operations into a complete manufacturing system can an optimum gear be obtained. The final application of the gear will determine what strength characteristics will be required which subsequently determine the material and heat treatments.
Plane strain fracture toughness of twelve high-carbon steels has been evaluated to study the influence of alloying elements, carbon content and retained austenite. The steels were especially designed to simulate the carburized case microstructure of commonly used automotive type gear steels. Results show that a small variation in carbon can influence the K IC significantly. The beneficial effect of retained austenite depends both on its amount and distribution. The alloy effect, particularly nickel, becomes significant only after the alloy content exceeds a minimum amount. Small amounts of boron also appear beneficial.
QuesTek Innovations LLC is applying its Materials by Design computational design technology to develop a new class of high-strength, secondary hardening gear steels that are optimized for high-temperature, low-pressure (i.e., vacuum) carburization. The new alloys offer three different levels of case hardness (with the ability to “dial-in” hardness profiles, including exceptionally high case hardness), and their high core strength, toughness and other properties offer the potential to reduce drivetrain weight or increase power density relative to incumbent alloys such as AISI 9310 or Pyrowear Alloy 53.
This is part II of a two-part paper that presents the results of extensive test programs on the RCF strength of PM steels.
Corus Engineering Steels' formula for its new gear steels: Maintain achievable hardness while using fewer alloys, thereby cutting steel costs for gear manufacturers.
This study quantified the performance of a new alloy and has provided guidance for the design and development of next-generation gear steels.
The latest technology on display in Columbus, OH. October 24-26.
This article summarizes results of research programs on RCF strength of wrought steels and PM steels.
Sivyer Steel Corporation, Bettendorf, IA, an ISO-9002-certified casting specialist, is familiar with tackling tough jobs. The company has built an international reputation as a supplier of high-integrity castings, especially those which require engineering and/or full machining. Its not unusual for Sivyer's customers, especially those in the mining, recycling, power generation, valve and nuclear fields, to ask the foundry to produce a one-of-a-kind casting - often something revolutionary - but AnClyde Engineered Products' request was a special challenge, even for Sivyer.
The complete Industry News section from the August 2014 issue of Gear Technology.
Broaching is a machining technique commonly used to cut gear teeth or cam profiles for the high volume manufacture of power transmission parts used in vehicles (Refs. 1–2). This article shows how the right gear blank material can make all the difference if you want to get more parts out of each tool.
The increasing demands in the automotive industry for weight reduction, fuel efficiency and a reduced carbon footprint need to be addressed urgently. Up until now, widely used conventional steels have lived up to expectations. However, with more stringent emissions standards, demands on materials are increasing. Materials are expected to perform better, resulting in a need for increased fatigue strength. A possibility to increase torque on current generations without design changes can be achieved by selecting suitable materials.
It is becoming increasingly apparent that material properties can and will play a greater role than before in addressing the challenges most transmission manufacturers are facing today. Making use of materials' intrinsic fatigue properties provides a new design tool to support the market changes taking place.
Much of the existing guidelines for making large, high-performance gears for wind turbine gearboxes exhibit a need for improvement. Consider: the large grinding stock used to compensate for heat treatment distortion can significantly reduce manufacturing productivity; and, materials and manufacturing processes are two other promising avenues to improvement. The work presented here investigates quenchable alloy steels that, combined with specifically developed Case-hardening and heat treatment processes, exhibits reduced distortion and, in turn, requires a smaller grinding stock.
Natural resources—minerals, coal, oil, agricultural products, etc.—are the blessings that Mother Earth confers upon the nations of the world. But it takes unnaturally large gears to extract them.
Manufacturers focus on tool design, materials, coating, machine tool options and cutting parameters.
Using the DANTE software, a finite element simulation was developed and executed to study the response of a carburized 5120 steel helical gear to quenching in molten salt. The computer simulation included heat-up, carburization, transfer and immersion in a molten salt bath, quenching, and air cooling. The results of the simulation included carbon distribution of phases, dimensional change, hardness, and residual stress throughout the process. The predicted results were compared against measured results for hardness, dimensions and residual stress. The excellent agreement between predictions and measured values for this carburized 5120 steel gear provides a basis for assessing the various process parameters and their respective importance in the characteristics of not only these heat-treated parts, but of other compositions and shapes.
The selection of the proper steel for a given gear application is dependent on many factors. This paper discusses the many aspects related to material, design, manufacture, and application variables. The results of several studies on the optimization of alloy design for gas- and plasma- carburization processing and reviewed.
Industry battles it out for World's Largest Gear title.
Surface-hardened, sintered powder metal gears are increasingly used in power transmissions to reduce the cost of gear production. One important problem is how to design with surface durability, given the porous nature of sintered gears. Many articles have been written about mechanical characteristics, such as tensile and bending strength, of sintered materials, and it is well-known that the pores existing on and below their surfaces affect their characteristics (Refs. 1-3). Power transmission gears are frequently employed under conditions of high speed and high load, and tooth surfaces are in contact with each other under a sliding-rolling contact condition. Therefore it is necessary to consider not only their mechanical, but also their tribological characteristics when designing sintered gears for surface durability.
Multiple possibilities are available to increase the transmissible power of girth gears. These solutions include: using a larger module, increasing of the gear diameter through the number of teeth, enlarging the face width, and increasing the hardness of the base material. The first three parameters are mostly limited by cutting machine capability. Module, outside diameter, and face width (for a cast gear) can theoretically be increased to infinity, but not the cutting machine dimensions. There are also practical limits with respect to the installation of very large diameter/large face width gears.
Super-reduction hypoid gears (SRH) are bevel worm gears with certain differences regarding hypoid gears. If two axes are positioned in space and the task is to transmit motion and torque between them using some kind of gears with a ratio above 5 and even higher than 50, the following cases are commonly known. Tribology Aspects in Angular Transmission Systems, Part VIII.
This paper presents how low pressure carburizing and high pressure gas quenching processes are successfully applied on internal ring gears for a six-speed automatic transmission. The specific challenge in the heat treat process was to reduce distortion in such a way that subsequent machining operations are entirely eliminated.
A major source of helicopter cabin noise (which has been measured at over 100 decibels sound pressure level) is the gearbox. Reduction of this noise is a NASA and U.S. Army goal. A requirement for the Army/NASA Advanced Rotorcraft Transmission project was a 10 dB noise reduction compared to current designs.
Two-shaft planetary gear drives are power-branching transmissions, which lead the power from input to output shaft on several parallel ways. A part of the power is transferred loss-free as clutch power. That results in high efficiency and high power density. Those advantages can be used optimally only if an even distribution of load on the individual branches of power is ensured. Static over-constraint, manufacturing deviations and the internal dynamics of those transmission gears obstruct the load balance. With the help of complex simulation programs, it is possible today to predict the dynamic behavior of such gears. The results of those investigations consolidate the approximation equations for the calculation of the load factors...
This paper deals with analysis of the load sharing percentage between teeth in mesh for different load conditions throughout the profile for both sun and planet gears of normal and HCR gearing—using finite element analysis. (FEA).
Hofler Rapid 6000 Makes North American Debut at Highway Machine Company.
Often, the required hardness qualities of parts manufactured from steel can only be obtained through suitable heat treatment. In transmission manufacturing, the case hardening process is commonly used to produce parts with a hard and wear-resistant surface and an adequate toughness in the core. A tremendous potential for rationalization, which is only partially used, becomes available if the treatment time of the case hardening process is reduced. Low pressure carburizing (LPC) offers a reduction of treatment time in comparison to conventional gas carburizing because of the high carbon mass flow inherent to the process (Ref. 1).
Our question this issue deals with high-ratio hypoid gears, and it should be noted here that this is a tricky area of gearing with a dearth of literature on the topic. That being the case, finding “experts” willing to stick their necks out and take on the subject was not a given.
High demands for cost-effectiveness and improved product quality can be achieved via a new low pressure carburizing process with high pressure gas quenching. Up to 50% of the heat treatment time can be saved. Furthermore, the distortion of the gear parts could be reduced because of gas quenching, and grinding costs could be saved. This article gives an overview of the principles of the process technology and the required furnace technology. Also, some examples of practical applications are presented.
This paper will demonstrate that, unlike commonly used low-contact-ratio spur gears, high-contact-ratio spur gears can provide higher power-to-weight ratio, and can also achieve smoother running with lower transmission error (TE) variations.
Carburized helical gears with high retained austenite were tested for surface contact fatigue. The retained austenite before test was 60% and was associated with low hardness near the case's surface. However, the tested gears showed good pitting resistance, with fatigue strength greater than 1,380 MPa.
In high precision and heavily loaded spur gears, the effect of gear error is negligible, so the periodic variation of tooth stiffness is the principal cause of noise and vibration. High contact ration spur gears can be used to exclude or reduce the variation of tooth stiffness.
The purpose of this paper is to present a method of designing and specifying gear teeth with much higher bending and surface contact strength (reduced bending and surface contact stresses). This paper will show calculation procedures, mathematical solutions and the theoretical background equations to do this.
New material technology allows for more efficient and flexible hobbing.
When a gear set is to be designed for a new application, the minimum size gears with the required capacity are desired. These gears must be capable of meeting the power, speed, ratio, life, and reliability requirements.
In several applications like hoisting equipment and cranes, open gears are used to transmit power at rather low speeds (tangential velocity < 1m/s) with lubrication by grease. In consequence those applications have particularities in terms of lubricating conditions and friction involved, pairing of material between pinion and gear wheel, lubricant supply, loading cycles and behavior of materials with significant contact pressure due to lower number of cycles.
under pressure from numerous market forces. The oil sector’s decline, weakened global economies (particularly China) and local government policies outnumber and outweigh relieving forces such as the FAST Act, leaving the industry in a general downturn. The outlook has yet to become truly grim, but companies are beginning to scale back.
Andantex USA is a part of the worldwide Redex group, a longtime provider of high-precision motion control components and systems
Market needs push in 2013, but will it get one? The construction/off-highway industries have been here before. New equipment, technologies and innovations during an economic standstill that some have been dealing with since 2007.
What gear material is suitable for high-temperature (350 – 550 degree C), high-vacuum, clean-environment use?
Faith — paraphrasing the gospels of Matthew and Mark — can move mountains. But it helps if you have precision geared equipment.
The performance of carburized components can be improved simply by changing the alloy content of the steel.