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Modern manufacturing processes have become an ally of the product designer in producing higher quality, higher performing components in the transportation industry. This is particularly true in grinding systems where the physical properties of CBN abrasives have been applied to improving cycle times, dimensional consistency, surface integrity and overall costs. Of these four factors, surface integrity offers the greatest potential for influencing the actual design of highly stressed, hardened steel components.
The merits of CBN physical characteristics over conventional aluminum oxide abrasives in grinding performance are reviewed. Improved surface integrity and consistency in drive train products can be achieved by the high removal rate of the CBN grinding process. The influence of CBN wheel surface conditioning procedure on grinding performance is also discussed.
The quality of a gear and its performance is determined by the following five parameters, which should be specified for each gear: Pitch diameter, involute form, lead accuracy, spacing accuracy, and true axis of rotation. The first four parameters can be measured or charted and have to be within tolerance with respect to the fifth. Pitch diameter, involute, lead, and spacing of a gear can have master gear quality when measured or charted on a testing machine, but the gear might perform badly if the true axis of rotation after installation is no longer the same one used when testing the gear.
Grinding is a technique of finish-machining, utilizing an abrasive wheel. The rotating abrasive wheel, which id generally of special shape or form, when made to bear against a cylindrical shaped workpiece, under a set of specific geometrical relationships, will produce a precision spur or helical gear. In most instances the workpiece will already have gear teeth cut on it by a primary process, such as hobbing or shaping. There are essentially two techniques for grinding gears: form and generation. The basic principles of these techniques, with their advantages and disadvantages, are presented in this section.
In conventional gear grinders, grinding wheels with Alundum grains and a hardness of about 2000 HV have been used for finishing steel gears with hardnesses up to about 1000HV. In this case, the accuracy of the gears ground is greatly affected by wear of the grinding wheel because the difference in hardness is comparatively small when the gears are fully hardened.
Until recently, form gear grinding was conducted almost exclusively with dressable, conventional abrasive grinding wheels. In recent years, preformed, plated Cubic Boron Nitride (CBN) wheels have been introduced to this operation and a considerable amount of literature has been published that claim that conventional grinding wheels will be completely replaced in the future. The superior machining properties of the CBN wheel are not disputed in this paper.
Modern gearboxes are characterized by high torque load demands, low running noise and compact design. In order to fulfill these demands, profile and lead modifications are being applied more often than in the past. This paper will focus on how to produce profile and lead modifications by using the two most common grinding processes—threaded wheel and profile grinding. In addition, more difficult modifications—such as defined flank twist or topological flank corrections—will also be described in this paper.
Borazon is a superabrasive material originally developed by General Electric in 1969. It is a high performance material for machining of high alloy ferrous and super alloy materials. Borazon CBN - Cubic Born Nitride - is manufactured with a high temperature, high pressure process similar to that utilized with man-made diamond. Borazon is, next to diamond, the hardest abrasive known; it is more than twice as hard as aluminum oxide. It has an extremely high thermal strength compared to diamond. It is also much less chemically reactive with iron, cobalt or nickel alloys.
A considerable improvement in the performance of the machining of hard to grind materials can be achieved by means of CBN wheels.
New freedom of motion available with CNC generators make possible improving tooth contact on bevel and hypoid gears. Mechanical machines by their nature are inflexible and require a special mechanism for every desired motion. These mechanisms are generally exotic and expensive. As a result, it was not until the introduction of CNC generators that engineers started exploring motion possibilities and their effect on tooth contact.
Because of the better thermal conductivity of CBN abrasives compared to that of conventional aluminum oxide wheels, CBN grinding process, which induces residual compressive stresses into the component, and possibly improves the subsequent stress behavior. This thesis is the subject of much discussion. In particular, recent Japanese publications claim great advantages for the process with regard to an increased component load capacity, but do not provide further details regarding the technology, test procedures or components investigated. This situation needs clarification, and for the this reason the effect of the CBN grinding material on the wear behavior and tooth face load capacity of continuously generated ground gears was further investigated.
Grinding in one form or another has been used for more than 50 years to correct distortions in gears caused by the high temperatures and quenching techniques associated with hardening. Grinding improves the lead, involute and spacing characteristics. This makes the gear capable of carrying the high loads and running at the high pitch line velocities required by today's most demanding applications. Gears that must meet or exceed the accuracy requirements specified by AGMA Quality 10-11 or DIN Class 6-7 must be ground or hard finished after hear treatment.
The latest machines, tooling and technology for gear grinding were featured at IMTS 2012.
This machine concept facilitates highly productive profile grinding for large workpieces. The range for external and internal gears comprises models for manufacturing workpieces up to 2,000 millimeters – for industrial gear units, wind power, and marine propulsion applications
It isn't for everyone, but... Within the installed base of modern CNC gear profile grinding machines (approximately 542 machines worldwide), grinding from the solid isn't frequent, but a growing number of gear profile grinder users are applying it successfully using CBN-plated wheels.
Gear grinding is one of the most expensive and least understood aspects of gear manufacturing. But with pressures for reduced noise, higher quality and greater efficiency, gear grinding appears to be on the rise.
Power train designs which employ gears with cone angles of approximately 2 degrees to 5 degrees have become quite common. It is difficult, if not impossible, to grind these gears on conventional bevel gear grinding machines. Cylindrical gear grinding machines are better suited for this task. This article will provide an overview of this option and briefly introduce four grinding variation possibilities.
Whether you spent time at Gear Expo in Indianapolis or EMO in Hannover, there was certainly new technology attracting attention. Machine tools are faster, more efficient and can integrate numerous functions in a single setup. Grinding technology is turning science upside down and inside out with high-speed removal rates and increased throughput.
In the quest for ever more exacting and compact commercial gears, precision abrasives are playing a key production role - a role that can shorten cycle time, reduce machining costs and meet growing market demand for such requirements as light weights, high loads, high speed and quiet operation. Used in conjunction with high-quality grinding machines, abrasives can deliver a level of accuracy unmatched by other manufacturing techniques, cost-effectively meeting AGMA gear quality levels in the 12 to 15 range. Thanks to advances in grinding and abrasive technology, machining has become one of the most viable means to grind fast, strong and quiet gears.
This paper intends to determine the load-carrying capacity of thermally damaged parts under rolling stress. Since inspection using real gears is problematic, rollers are chosen as an acceptable substitute. The examined scope of thermal damage from hard finishing extends from undamaged, best-case parts to a rehardening zone as the worst case. Also, two degrees of a tempered zone have been examined.
Machine tool companies are expanding capabilities to better accommodate the changing face of manufacturing. Customers want smaller-sized equipment to take up less valuable floor space, multifunctional machines that can handle a variety of operations and easy set-up changes that offer simplified operation and maintenance.
This paper presents the results of a study performed to measure the change in residual stress that results from the finish grinding of carburized gears. Residual stresses were measured in five gears using the x-ray diffraction equipment in the Large Specimen Residual Stress Facility at Oak Ridge National Laboratory.
When gears are case-hardened, it is known that some growth and redistribution of stresses that result in geometric distortion will occur. Aerospace gears require post case-hardening grinding of the gear teeth to achieve necessary accuracy. Tempering of the case-hardened surface, commonly known as grinding burn, occurs in the manufacturing process when control of the heat generation at the surface is lost.
Flexibility and productivity are the keywords in today’s grinding operations. Machines are becoming more flexible as manufacturers look for ways to produce more parts at a lower cost. What used to take two machines or more now takes just one.
The fundamental purpose of gear grinding is to consistently and economically produce "hard" or "soft" gear tooth elements within the accuracy required by the gear functions. These gear elements include tooth profile, tooth spacing, lead or parallelism, axial profile, pitch line runout, surface finish, root fillet profile, and other gear geometry which contribute to the performance of a gear train.
Recent breakthroughs in profile grinding software are helping Anderson Precision Gears and others meet wind power’s insatiable appetite for faster production of large, high-quality gears.
When you push 850 horsepower and 9,000 rpm through a racing transmission, you better hope it stands up. Transmission cases and gears strewn all over the racetrack do nothing to enhance your standing, nor that of your transmission supplier.
This article shows the newest developments to reduce overall cycle time in grinding wind power gears, including the use of both profile grinding and threaded wheel grinding.
The benefits of ground gears are well known. They create less noise, transmit more power and have longer lives than non-ground gears. But grinding has always been thought of as an expensive process, one that was necessary only for aerospace or other high-tech gear manufacturing.
The bevel gear grinding process, with conventional wheels, has been limited to applications where the highest level of quality is required.
This paper acknowledges the wide variety of manufacturing processes--especially in grinding--utlized in the production of bevel gears...
Instances of damage to discontinuous form ground and surface-hardened gears, especially of large scale, have recently increased. This may be attributed partly to a faulty grinding process with negative effects on the surface zones and the surface properties.
Guidelines are insurance against mistakes in the often detailed work of gear manufacturing. Gear engineers, after all, can't know all the steps for all the processes used in their factories.
Bevel gear manufacturers live in one of two camps: the face hobbing/lapping camp, and the face milling/grinding camp.
Hofler Rapid 6000 Makes North American Debut at Highway Machine Company.
Tom Lang of Kapp Technologies shares his views on the trends affecting ground gears.
New machine promises DIN 2 accuracy and unique features at low cost.
The GS:TE-LM thread grinder from Drake Manufacturing is fitted with a robot load/unload system that provides maximum throughput for high-volume production of ground threads.
In order to grind gears burn-free and as productively as possible, a better understanding of the process is required.
The essence of designing gears is often by necessity risk-averse, given that many of them are used in applications where loss of life is a distinct possibility. The Gear Research Institute (GRI) at The Pennsylvania State University conducts risk reduction testing with the same goal in mind - whether it be gears in fighter jets, Ferris wheels, tanks, or countless other gear-reliant vehicles and machinery.
The complete Product News section from the June/July 2013 issue of Gear Technology.
Cubitron II wheels are put to the test in this case study.
For two days in Saline, Michigan, Liebherr's clients, customers and friends came together to discuss the latest gear products and technology. Peter Wiedemann, president of Liebherr Gear Technology Inc., along with Dr.-Ing. Alois Mundt, managing director, Dr.-Ing. Oliver Winkel, head of application technology, and Dr.-Ing. Andreas Mehr, technology development shaping and grinding, hosted a variety of informative presentations.
Every so often manufacturing is jolted out of its inertia by a transformative technology – one that fundamentally changes not only the way products are made, but also the economics of the business.
Dressable vitrified bond CBN grinding tools combine the advantages of other common tool systems in generating gear grinding. Yet despite those technological advantages, there is only a small market distribution of these grinding tools due to high tool costs. Furthermore, scant literature exists regarding generating gear grinding with dressable CBN. This is especially true regarding the influence of the grinding tool system on manufacturing-related component properties. The research objective of this report is to determine the advantages of dressable CBN tools in generating gear grinding.
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.
The grinding/abrasives market is rapidly changing, thanks to new technology, more flexibility and an attempt to lower customer costs. Productivity is at an all-time high in this market, and it’s only going to improve with further R&D. By the time IMTS 2014 rolls around this September, the gear market will have lots of new toys and gadgets to offer potential customers. If you haven’t upgraded any grinding/abrasives equipment in the last five years, now might be a good time to consider the investment.
When a customer needed gears delivered in three weeks, here’s how Brevini Wind got it done.
Gear Technology was founded 22 years ago on a very simple principle: to provide the best possible educational articles and information for the gear industry.
This paper initially defines bias error—the “twisted tooth phenomenon.” Using illustrations, we explain that bias error is a by-product of applying conventional, radial crowning methods to produced crowned leads on helical gears. The methods considered are gears that are finished, shaped, shaved, form and generated ground. The paper explains why bias error occurs in these methods and offers techniques used to limit/eliminate bias error. Sometimes, there may be a possibility to apply two methods to eliminate bias error. In those cases, the pros/cons of these methods will be reviewed.
Non-uniform gear wear changes gear topology and affects the noise performance of a hypoid gear set. The aggregate results under certain vehicle driving conditions could potentially result in unacceptable vehicle noise performance in a short period of time. This paper presents the effects of gear surface parameters on gear wear and the measurement/testing methods used to quantify the flank wear in laboratory tests.
Hard Gear Finishing (HGF), a relatively new technology, represents an advance in gear process engineering. The use of Computer Numerical Controlled (CNC) equipment ensures a high precision synchronous relationship between the tool spindle and the work spindle as well as other motions, thereby eliminating the need for gear trains. A hard gear finishing machine eliminates problems encountered in two conventional methods - gear shaving, which cannot completely correct gear errors in gear teeth, and gear rolling, which lacks the ability to remove stock and also drives the workpiece without a geared relationship to the master rolling gear. Such a machine provides greater accuracy, reducing the need for conventional gear crowning, which results in gears of greater face width than necessary.
This article investigates fillet features consequent to tooth grinding by generating methods. Fillets resulting from tooth cutting and tooth grinding at different pressure angles and with different positions of grinding wheel are compared. Ways to improve the final fillet of the ground teeth with regard to tooth strength and noise, as well as the grinding conditions, are shown. "Undergrinding" is defined and special designs for noiseless gears are described.
Previews of manufacturing technology related to gears that will be on display at IMTS 2012.
When designing hardened and ground spur gears to operate with minimum noise, what are the parameters to be considered? should tip and/or root relief be applied to both wheel and pinion or only to one member? When pinions are enlarged and he wheel reduced, should tip relief be applied? What are the effects on strength, wear and noise? For given ratios with enlarged pinions and reduced wheels, how can the gear set sized be checked or adjusted to ensure that the best combination has been achieved?
For over 50 years, grinding has been an accepted method of choice for improving the quality of gears and other parts by correcting heat treat distortions. Gears with quality levels better than AGMA 10-11 or DIN 6-7 are hard finished, usually by grinding. Other applications for grinding include, but are not limited to, internal/external and spur/helical gear and spline forms, radius forms, threads and serrations, compressor rotors, gerotors, ball screw tracks, worms, linear ball tracks, rotary pistons, vane pump rotators, vane slots, and pump spindles.
Analysis of helical involute gears by tooth contact analysis shows that such gears are very sensitive to angular misalignment leading to edge contact and the potential for high vibration. A new topology of tooth surfaces of helical gears that enables a favorable bearing contact and a reduced level of vibration is described. Methods for grinding helical gears with the new topology are proposed. A TCA program simulating the meshing and contact of helical gears with the new topology has been developed. Numerical examples that illustrate the proposed ideas are discussed.
The grinding of gears with dish wheels (Maad type grinding machines) is widely viewed as the most precise method of gear grinding because of the very short and simple kinematic links between the gear and the tool, and also because the cutting edges of the wheels represent planar surfaces. However, in this grinding method, depending on the parameters of the gears and one of the adjustments (such as the number of teeth encompassed by the grinding wheels), so-called overtravel at the tip or at the root of the teeth being ground generally occurs. When this happens, machining with only one wheel takes place. As a result, the profile error and the length of the generating path increases while productivity decreases.
The goal of gear drive design is to transit power and motion with constant angular velocity. Current trends in gear drive design require greater load carrying capacity and increased service life in smaller, quieter, more efficient gearboxes. Generally, these goals are met by specifying more accurate gears. This, combined with the availability of user-friendly CNC gear grinding equipment, has increased the use of ground gears.
This article deals with certain item to be taken into consideration for gear grinding, common problems that arise in gear grinding and their solutions. The discussion will be limited to jobbing or low-batch production environments, where experimental setup and testing is not possible for economic and other reasons.
When hardened steel components are ground, there is always the possibility of damage to the steel in the form of residual stress or microstructural changes. Methods for detecting this sort of damage have always had one or more drawbacks, such as cost, time, complexity, subjectivity, or the use of hazardous chemicals.
In the wide, wide world of moving parts, the gears required for the big jobs—the really big jobs—often experience big problems. Proper lubrication of these gears is paramount in industrial applications such as wind turbines, kilns, sugar mills, crushers, heavy construction, offshore drilling rigs, mining and quarrying.
The quality of molded plastic gears is typically judged by dimensional feature measurements only. This practice overlooks potential deficiencies in the molding process.
Capacity is key today, and the best way to ensure that you are squeezing every dime out of that new machine is to complement it with innovative workholding.
An analysis of possibilities for the selection of tool geometry parameters was made in order to reduce tooth profile errors during the grinding of gears by different methods. The selection of parameters was based on the analysis of he grid diagram of a gear and a rack. Some formulas and graphs are presented for the selection of the pressure angle, module and addendum of the rack-tool. The results from the grinding experimental gears confirm the theoretical analysis.
In his Handbook of Gear Design (Ref.1), Dudley states (or understates): "The best gear people around the world are now coming to realize that metallurgical quality is just as important as geometric quality." Geometric accuracy without metallurgical integrity in any highly stressed gear or shaft would only result in wasted effort for all concerned - the gear designer, the manufacturer, and the customer - as the component's life cycle would be prematurely cut short. A carburized automotive gear or shaft with the wrong surface hardness, case depth or core hardness may not even complete its basic warranty period before failing totally at considerable expense and loss of prestige for the producer and the customer. The unexpected early failure of a large industrial gear or shaft in a coal mine or mill could result in lost production and income while the machine is down since replacement components may not be readily available. Fortunately, this scenario is not common. Most reputable gear and shaft manufacturers around the world would never neglect the metallurgical quality of their products.
Gear noise associated with tooth surface topography is a fundamental problem in many applications. Operations such as shaving, gear grinding and gear honing are usually used to finish the gear surface. Often, gears have to be treated by a combination of these operations, e.g. grinding and honing. This is because gear honing operations do not remove enough stock although they do create a surface lay favorable for quiet operation. See Fig. 1 for typical honing process characteristics. Gear grinding processes, on the other hand, do remove stock efficiently but create a noisy surface lay.
Okay. You've been convinced. You've gritted your teeth and decided to spend the money to launch a company Web site. Everybody from your teenage propeller-head to the girl in the mail room and the salesman in the flashy suit who gave you "such a deal" on Web site services has promised that your site will be the best thing that's happened to your business since the advent of CNC machines.
The capabilities and limitations of manufacturing gears by conventional means are well-known and thoroughly documented. In the search to enhance or otherwise improve the gear-making process, manufacturing methods have extended beyond chip-cutting - hobbing, broaching, shaping, shaving, grinding, etc. and their inherent limitations based on cutting selection and speed, feed rates, chip thickness per tooth, cutting pressure, cutter deflection, chatter, surface finish, material hardness, machine rigidity, tooling, setup and other items.
When it comes to setting the standard for gear making, the auto industry often sets the pace. Thus when automakers went to grinding after hardening to assure precision, so did the machine shops that specialize in gearing. But in custom manufacturing of gears in small piece counts, post-heat treat grinding can grind away profits too.
"A Decade of Performance" is the theme of the American Gear Manufacturers Association Gear Expo 97, to be held October 19-22 at Detroit's Cobo Hall. Products and services related to every aspect of the gear manufacturing process, from turning and grinding the blanks to coating and inspection of the gears,will be represented at the show.
Traditionally, high-quality gears are cut to shape from forged blanks. Great accuracy can be obtained through shaving and grinding of tooth forms, enhancing the power capacity, life and quietness of geared power transmissions. In the 1950s, a process was developed for forging gears with teeth that requires little or no metal to be removed to achieve final geometry. The initial process development was undertaken in Germany for the manufacture of bevel gears for automobile differentials and was stimulated by the lack of available gear cutting equipment at that time. Later attention has turned to the forging of spur and helical gears, which are more difficult to form due to the radial disposition of their teeth compared with bevel gears. The main driver of these developments, in common with most component manufacturing, is cost. Forming gears rather than cutting them results in increased yield from raw material and also can increase productivity. Forging gears is therefore of greater advantage for large batch quantities, such as required by the automotive industry.
Vibration and noise from wind turbines can be significantly influenced - and therefore reduced - by selecting suitable gearing modifications. New options provided by manufacturers of machine tools and grinding machines, and especially state-of-the-art machines and controls, provide combined gearing modifications - or topological gearing corrections - that can now be reliably machined. Theoretical investigations of topological modifications are discussed here with the actual machining and their possible use.
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.
It's an ideal time for a pilgrimage to AGMA’s Fall Technical Meeting and Gear Expo, which take place in Indianapolis.
Big gears, They drive the machinery that rolls steel, grinds limestone, pulverizes coal, pumps mud, mixes rubber, raises bridges and does many other heavy-duty industrial jobs. For 117 years, big gears have also driven the business of Horsburgh & Scott of Cleveland, OH.
In order to increase the load carrying capacity of hardened gears, the distortion of gear teeth caused by quenching must be removed by precision cutting (skiving) and/or grinding. In the case of large gears with large modules, skiving by a carbide hob is more economical than grinding when the highest accuracy is not required.
In the past, the blades of universal face hobbing cutters had to be resharpened on three faces. Those three faces formed the active part of the blade. In face hobbing, the effective cutting direction changes dramatically with respect to the shank of the blade. Depending on the individual ratio, it was found that optimal conditions for the chip removal action (side rake, side relief and hook angle) could just be established by adjusting all major parameters independently. This, in turn, results automatically in the need for the grinding or resharpening of the front face and the two relief surfaces in order to control side rake, hook angle and the relief and the relief angles of the cutting and clearance side.
I'm a big believer in the value of IMTS as a marketplace where gear manufacturers can go and look at the latest machine tools and processes; compare hobbing machines, gear grinders and inspection equipment; see turning, milling or grinding machines in action; and ask questions of the various vendors all in one place. This year's IMTS promised to be the biggest ever, and I have no doubt that it will be a valuable experience to those who go there looking for ways to improve the way they manufacture products.
When parts you manufacture pass through numerous processes such as deep hole drilling, machining, hobbing and grinding, a CMM is essential when your customers require 100 percent in-process and final inspection.
The complete product news section from the January/February 2009 issue of Gear Technology, featuring giant-sized David Brown girth gears, gear inspection up to 4.5 meters and the latest Gleason gear grinder.
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.
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.
Custom Gear and Machine, Inc., of Roscoe, IL, recently purchased a Reishauer RZ400 gear grinder and, on one job, has seen the cycle time drop from 40 minutes to six minutes, according to Tim Rose, vice president of manufacturing, who runs the business with co-owners Dave Patterson and Mike Rasmann.
Beveloid gears are used to accommodate a small shaft angle. The manufacturing technology used for beveloid gearing is a special setup of cylindrical gear cutting and grinding machines. A new development, the so-called Hypoloid gearing, addresses the desire of gear manufacturers for more freedoms. Hypoloid gear sets can realize shaft angles between zero and 20° and at the same time, allow a second shaft angle (or an offset) in space that provides the freedom to connect two points in space.
Indexable carbide insert (ICI) cutting tools continue to play a pivotal role in gear manufacturing. By offering higher cutting speeds, reduced cycle times, enhanced coatings, custom configurations and a diverse range of sizes and capabilities, ICI tools have proven invaluable for finishing and pre-grind applications. They continue to expand their unique capabilities and worth in the cutting tool market.
Undue vibrations, power spikes and grit give NASA pause.
The higher load carrying capacities, compact dimensions and longer life of hardened gears is an accepted fact in industry today. However, the costs involved in case hardening and subsequent finishing operations to achieve these advantages are considerable. For example, in order to achieve desired running properties on larger gears, it has been necessary to grind the tooth flanks. This costly operation can now be replaced, in many cases, by a new Hard Cutting (HC) process which permits the cutting of hardened gears while maintaining extremely low tooling costs.
Cubic boron nitride (CBN) finishing of carburized gearing has been shown to have certain economic and geometric advantages and, as a result, it has been applied to a wide variety of precision gears in many different applications. In critical applications such as aerospace drive systems, however, any new process must be carefully evaluated before it is used in a production application. Because of the advantages associated with this process, a test program was instituted to evaluate the load capacity of aerospace-quality gears finished by the CBN process as compared to geometrically identical gears finished by conventional grinding processes. This article presents a brief description of the CBN process, its advantages in an aerospace application, and the results of an extensive test program conducted by Boeing Helicopters (BH) aimed at an evaluation of the effects of this process on the scoring, surface durability, and bending fatigue properties of spur gears. In addition, the results of an x-ray diffraction study to determine the surface and subsurface residual stress distributions of both shot-peened and nonshot-peened CBN-ground gears as compared to similar conventionally ground gears are also presented.
Question: When evaluating charts from a gear inspection machine, it is sometimes found that the full length of the profile traces vary, and that sometimes they are less than the length of active profile (above start of active profile-SAP) by up to 20%. This condition could be caused by a concentricity error between tooth grinding and shaping, or by unequal stock removal when grinding. (See Fig. 1.) Is it possible that some of the variation is coming from the inspection machine? How can variation from the inspection machine be reduced?
Spur gear surface endurance tests were conducted to investigate CBN ground AISI 9310 spur gears for use in aircraft applications, to determine their endurance characteristics and to compare the results with the endurance of standard vitreous ground AISI 9310 spur gears. Tests were conducted with VIM-VAR AISI 9210 carburized and hardened gears that were finish ground with either CBN or vitreous grinding methods. Test conditions were an inlet oil temperature of 320 K (116 degree F), an outlet oil temperature of 350 K (170 degree F), a maximum Hertz stress of 1.71 GPa (248 ksi), and a speed of 10,000 rpm. The CBN ground gears exhibited a surface fatigue life that was slightly better than the vitreous ground gears. The subsurface residual stress of the CBN ground gears was approximately the same as that for the standard vitreous ground gears for the CBN grinding method used.
At the time I'm writing this editorial, the new year is barely two weeks old. The air and the papers are still full of those inevitable end-of-the-year estimates of how far we've come in one area or another and how far we have to go. Analyses of the future, both grim and humorous, abound. There are even more of these laundry lists of PROBLEMS TO BE SOLVED IMMEDIATELY than usual, since a new president will be inaugurated in a week or so. Everyone had advice for George Bush on what to do first and how to do it. Some of the advice is sound, and I hope he's listening; however, reading all these position papers can be a depressing exercise.
Traditionally, a worm or a multi-stage gear box has been used when a large speed ratio is required. However, such boxes will become obsolete as size and efficiency become increasingly important considerations for a modern transmission. The single-enveloped worm gear has a maximum speed ratio of only 40 to 60. Its efficiency is only 30 to 60 per cent. The necessity of using bronze for the worm gear and grinding nitoalloy steel for the worm drives up material and manufacturing costs.
A few years ago, during a presidential election campaign, I saw an editorial cartoon that depicted a man standing outside a voting booth with a bemused expression on his face. Over the door to the booth was a quotation from Dante: "Abandon hope, all ye who enter here." Unfortunately for all of us, the grim jest is just as timely now. Once again, when we make our choice for president this year, the pick seems to be between Mr. Well-He's-Not-Actually-Awful and Mr. At-Least-He's-Not-The-Other-Guy. A candidate who can arouse truly positive and hopeful feelings in the electorate is once again not on the ballot.
For this interview, we spoke with George Wyss, president, and Dennis Richmond, vice president of Reishauer Corporation about gear grinding and its place in gear manufacturing today.
News Items About GRI
1 Gleason Improves Quality for Large Gear Grinding (April 23, 2010)
Gleason's latest generation of Profile Grinding Machines now can be equipped to perform a new process called OPTI-GRIND that signific... Read News
2 Grinding Wheel Improves Surface Finish (October 29, 2009)
The SK23w ceramic grinding wheel specification from Burka-Kosmos drastically increases the Q'w and V'w rates. This type of grindi... Read News
3 Versatile Reishauer Grinder Adapted for Larger Gears (December 28, 2009)
The RZ 260 gear grinding machine from Reishauer is based on the successful RZ 150 series, but not only has size been increased, but all c... Read News
4 Wenzel Introduces New Grind Burn Detection Capability (March 15, 2010)
In a continuing effort to enhance the capabilities of its gear measuring equipment, Wenzel has introduced a new feature that detects any ... Read News
5 MHI Grinder Hones Four Times Faster (September 30, 2009)
The ZI20A from Mitsubishi Heavy Industries is an internally toothed ring gear grinding machine capable of high-speed and precision with l... Read News
6 SCHUNK Offers New Sealed DRG Two-Finger Radial Gripper (June 1, 2010)
The new DRG Two-Finger Radial Gripper from SCHUNK is utilized for difficult handling tasks. The gripper is used in dirty working environm... Read News
7 Surface Grinder Operates with Maximum Productivity, Minimum Cycle Times (February 4, 2009)
The TechMaster 844, from Jones and Shipman, offers 800 mm x 400 mm grinding capacity with a vertical capacity of 360 mm. The machine is ... Read News
8 Philadelphia Gear’s Birmingham Facility Installs Hofler Grinder (July 10, 2007)
Philadelphia Gear Corp. announced that its Birmingham Regional Service Center installed a 1.5 meter Höfler grinder. ... Read News
9 Grieves New Oven Burns Hydrocarbons from Machined Metal Parts (July 19, 2007)
The new No. 875 oven from Grieve is a gas-fired, 1600ºF (871ºC) specialty furnace from Grieve, currently used for burning off h... Read News
10 Bryant Celebrates 100 Years of Grinding (November 24, 2008)
Bryant Grinder, a division of Vermont Machine Tool Corporation, is celebrating its 100th anniversary in 2009, making it one of the olde... Read News
11 Gleason Grinder Cuts Production Times (February 4, 2009)
The Genesis 160TWG threaded wheel grinder from Gleason is capable of hard finish grinding of cylindrical gears with diameters up to 160 m... Read News
12 Supertec to Present Seven New Grinding Machines at IMTS (June 16, 2010)
Supertec Machinery will exhibit seven new grinding machine models/types at this year's IMTS. They will be located in the Grinding Pav... Read News
13 Drake Grinders Upgrade China Gage Capabilities (September 23, 2010)
Drake Manufacturing Services Co. recently shipped another in a series of high precision gage grinding machines to one of China's emer... Read News
14 Drake Manufacturing Enjoys Export Surge with Thread Grinder (May 23, 2011)
Drake Manufacturing Services Co. is enjoying a surge in exports to Chinese manufacturers, with orders in hand for more than 25 machines. ... Read News
15 CIMCOOL 609 Designed for Grinding Performance (June 29, 2011)
CIMCOOL Fluid Technology has created CIMTECH 609, an innovative hybrid developed for superior grinding performance and excellent machinin... Read News
16 Dapra Offers Grinding and Deburring Tools (October 3, 2011)
Dapra's series of Biax hand-held, air-powered tools include lightweight grinders and variable-speed deburring machines. The SRD 3-55/... Read News
17 PHL Gripper Increases Module Efficiency (October 14, 2011)
With the PHL, Schunk launches a new generation of long stroke grippers. The PHL from Schunk alternatively disposes of a multi-tooth guida... Read News
18 Duo Plus Boasts Efficient Grip System (April 26, 2011)
One of the most important keys to success in modern workpiece production is efficiency. Machines are supposed to perform more than just o... Read News
19 Northfield Chuck Enhances Grip Force (April 25, 2011)
Northfield Precision Instrument Corporation, a designer and manufacturer of precision workholding chucks, introduces their Model DPH-500-... Read News
20 Grieve Corp. Releases Gas-Heated Box Furnace (September 23, 2010)
No. 871 is an electrically-heated 2000 degrees F gas-heated box furnace from Grieve, currently used for heat treating and high temperatur... Read News
21 Luren's LFG-8040 Grinds Spur and Helical Gears (January 19, 2011)
The most recent development from Luren Precision Co., Ltd. is the vertical type CNC gear profile grinding machine, LFG-8040, th... Read News
22 Grieve Releases 863 Box Furnace (January 26, 2011)
No. 863 is an electrically-heated 1400 degrees F(~760 degrees C) box furnace from Grieve, currently used for preheating molds. 52 kW are ... Read News
23 Northfield Releases Rubber Grip Chuck (April 4, 2011)
Northfield Precision Instrument Corporation, a designer and manufacturer of precision workholding chucks, introduces their Automobile Rub... Read News
24 Highway Machine Co. Acquires North America's First Six-Meter Form Grinder (July 3, 2007)
HMC announced its recent acquisition of the first six Meter, (240"), Hofler Form Grinder in NorthAmerica, which will be in... Read News
25 Kapp's Rotor Grinding Technology Improves Efficiency by 30 Percent (June 15, 2007)
The Kapp RX 59 allows the rotors used in air compressors to be manufactured on the machines by using a high precision grinding process.Ro... Read News
26 Landis Introduces New Grinders at IMTS (April 6, 2006)
Landis Grinding Systems new LT1-1200 flexible CNC grinder with variable swiveling wheelhead will be displayed for the first time at... Read News
27 New Depressed Center Wheels Introduced by Camel Grinding Wheels (April 6, 2006)
CGW-Camel Grinding Wheels has introduced Fast Cut Series Aluminum Oxide Type 27 Depressed Center Wheels with N-grade bond for right angle... Read News
28 Nortons New Gear Grinding Wheels Increase Life of Parallel Axis Spur Gears (April 11, 2006)
The new BRGg VPHS high speed grinding wheels from Saint Gobain are designed to reduce cycle times by increasing metal removal rates. The ... Read News
29 Drakes Newest Thread Grinder Utilizes Robot Load/Unload System (April 11, 2006)
The GS: TE-LM thread grinder from Drake Manufacturing is fitted with a robot load/unload system that provides maximum throughput for high... Read News
30 Marposs New Gage Head Designed for Internal Grinders (April 11, 2006)
The Thruvar from Marposs is a through-the-spindle gage for in-process measurement application on internal grinding machines and was intro... Read News
31 Bryan Grinder Releases New Software (April 3, 2006)
Bryant? Grinder, a division of Vermont Machine Tool, released Revelations? software, a Microsoft Windows-based, CNC control software that... Read News
32 United Gear Buys Tooth Grinder (February 22, 2006)
United Gear & Asssembly installed a new Kapp KX 300P grinder. The machine is designed for grinding external spur and helical gears. Si... Read News
33 New Grinder for Gear Cutter Blades (January 19, 2004)
The SBG cutter grinder from ANCA can grind parts to +/ ?5 microns, and it includes a chuck and palletized auto load that is specifically ... Read News
34 Sigma Pool Merges All Grinding Activities (February 7, 2005)
Sigma Pool partners have merged all activities in the field of cylindrical gear grinding under the roof of Liebherr-Verzahntechnik GmbH i... Read News
35 New Furnace from Grieve (March 9, 2005)
The No. 943 pit furnace from Grieve is an electrically heated, top loading pit furnace capable of 2,000 degrees F and is suitable for hea... Read News
36 Samputensil Introduces High Capacity Grinding Machine (January 6, 2006)
The new 250G generating grinding machine from Samputensili, introduced at EMO 2005 was developed to achieve a shorter cycle time. Acco... Read News
37 United Grinding?s Newest Machine Grinds Shafts and Chucked Workpieces (April 11, 2006)
[photo] The Studen S242 from United Grinding is designed for the hard turning and grinding of high-precision applications for both shaf... Read News
38 Service Network and Worcester Polytechnik Launch Grinding Consortium (April 14, 2006)
Service Network is spearheading an effort with Worcester Polytechnic Institute to form a grinding research center located in Worcester, M... Read News
39 Marposs Introduces Gauge Head for In-Process Grinder Control at Eastec (February 26, 2007)
Marposs Corp. will show its new NanoUnimar ultra-compact gauge head for in-process grinder control in Booth #3006 at the EASTEC APEX 2007... Read News
40 Schafer Gear Adds New Grinding Equipment (May 24, 2007)
Schafer Gear Works invested in new production equipment, including new gear grinding machines in the company's South Bend, IN, and Ro... Read News
41 Cinetec Grinding Moves Headquarters to Hagerstown, Maryland (May 29, 2007)
Cinetic Landis Grinding Corp. relocated its headquarters and manufacturing/assembly facility approximately 15 miles to Hagerstown, MD. ... Read News
42 Drakes New Mini External Thread Grinder Targets Small Parts Makers (May 31, 2007)
With a work envelope of 100 mm x 100 mm, Drake's GS:TEM mini three-axis thread grinder is aimed at higher volume, precision threaded ... Read News
43 Schunk Releases New Electrical Miniature High-Speed Parallel Gripper (February 14, 2007)
Schunk Workholding's miniature high-speed parallel gripper (MHP) is the two-finger counterpart to the centric gripper SMG. Accord... Read News
44 Gleasons Newest Threaded Wheel Grinder Delivers Faster Floor-to-Floor Times for Cylindrical Gears up to 300 mm (February 13, 2007)
The 300 TWG from Gleason Corp. is designed to deliver fast floor-to-floor times for grinding of cylindrical gears with a diameter up to 3... Read News
45 Accura Technics New Grinder Works on Multiple Surfaces (April 22, 2006)
Accura Technics newest product is designed for precision grinding applicable to aerospace, automotive, bearing and optics manufactu... Read News
46 Walter Grinders New Tool Grinder Offers Shorter Cycle Times (April 22, 2006)
Walter Grinders unveiled its Helitronic Vision CNC tool grinder at IMTS. According to the companys press release, the grinder offer... Read News
47 Gleasons New Threaded Grinder Optimizes Fine Finishing of Hard Spur and Helical Gears (January 2, 2007)
Gleasons new Genesis 130TWG High Speed Threaded Wheel Grinder features a new design that reduces floor space requirements and impro... Read News
48 Makinos New Grinding Machining Center Grinds, Drills, Bores and Mills on the Same Machine (January 9, 2007)
Makino introduced the G5 Grinder horizontal machining center, capable of grinding, drilling, boring and milling all on the same machine.... Read News
49 Klingelnberg Opens Blade Grinding Center in Mexico (October 27, 2011)
In August 2011, Klingelnberg's Mexico site was moved to a new facility in Querétaro City. This investment is part of the compa... Read News
50 Holroyd Sells Grinding Machines to Chinese Company (December 20, 2011)
U.K.-based Holroyd Machine Tools and Components of Milnrow, Lancashire, a division of the Precision Technologies Group, has announced the... Read News
51 C&B Machinery Offers Clamp Bore Disc Grinding Machine (November 22, 2013)
C & B Machinery has received multiple orders for its latest generation Model CBV-3 Clamp Bore disc grinding machine. The automotive i... Read News
52 Forkardt Offers OmniGrip Collet System (November 19, 2013)
Forkardt OmniGrip Collet Systems are flexible, sealed collet heads that interchange in seconds and are available with spindle mounts for ... Read News
53 IDC Installs Niles ZP24 Gear Grinder (December 26, 2013)
IDC Industries is installing their new Niles ZP24 gear grinder. This new machine, the largest of its type in Michigan, will allow IDC to ... Read News
54 Grieve Releases High-Temp Atmosphere Furnace (January 6, 2014)
No. 854 is a special high-temperature, 2,200 degrees F electrically-heated, inert atmosphere floor furnace from Grieve, currently used fo... Read News
55 Oelheld Develops HSS Grinding Oil (January 24, 2014)
SintoGrind HSS was especially developed for profile and flute grinding of steel alloys and in particular for High-Speed-Steel and medical... Read News
56 Körber Schleifring Becomes United Grinding (November 12, 2013)
Körber Schleifring, a global provider of grinding machine technology and its North American arm United Grinding Techologies are now ... Read News
57 3M Introduces Cubitron II Conventional Wheels for Gear Grinding (November 1, 2013)
3M Abrasive Systems is introducing 3M Cubitron II Conventional Wheels for Gear Grinding, giving engineers new tools to take the manufactu... Read News
58 Bryant Offers Miniature Grinder (June 21, 2013)
The new Bryant Miniature precision grinder (Model RU1) with standard 4.0 inch (100 mm) travel in both “X” and “Z”... Read News
59 Grieve Furnace Treats Large Gears (July 24, 2013)
No. 1030 is a 550ºF floor-level electric cabinet oven from Grieve, currently used for heating large gears at the customer’s fa... Read News
60 Grieve Offers High-Temp Bench Oven (August 23, 2013)
No. 1017 is a 1000ºF high-temperature bench oven from Grieve, currently used for various heat processings at the customer’s fa... Read News
61 Schunk Integrates Grippers with Sensing Technology (October 31, 2013)
Schunk has enlarged its number of available sensors for the modular system of grippers with the new OAS sensor. When grippers such as the... Read News
62 United Grinding to Display Innovations at GrindTec 2014 (January 27, 2014)
United Grinding, the largest single-source provider of complete and integrated grinding solutions, will showcase its latest grinding, ero... Read News
63 Oelheld Introduces SintoGrind 353 (January 31, 2014)
Oelheld U.S. introduces SintoGrind 353, a premium gear grinding fluid formulated from pure synthetic base stocks. SintoGrind 353 was espe... Read News
64 Grieve Releases Heavy-Duty Box Furnace (May 5, 2014)
No. 954 is an electrically-heated 2000°F(~1093°C) inert atmosphere heavy-duty box furnace from Grieve, currently used for heat treating titanium at the customer’s facility... Read News
65 Gear Grinders Find Value in RUF Briquetting Systems (May 7, 2014)
Briquetting is a way to regain value from the materials you already have, and gear grinding operations are finding the value they thought was lost in their grinding sludge... Read News
66 Vomat Offers Temp Stability During Grinding (May 23, 2014)
In order to produce high-performance cutting tools, tool manufacturers go to great lengths to get all manufacturing parameters right. Production conditions have tremendous influence on the final quality of the tool... Read News
67 DiaGrind 535-5 Offers Advantages in Gear Honing and Grinding (June 11, 2014)
The multifunctional metalworking fluid DiaGrind 535-5 has many enthusiastic users all over the world. They range from small shops to mult... Read News
68 EMAG Introduces Small Grinding Center (April 15, 2014)
Demand for components such as gearwheels, planetary gears, chain gears or flanged components for cars typically runs in quantities of millions... Read News
69 Grieve Introduces Latest Oven (April 10, 2014)
No. 839 is an electrically-heated, 850°F walk-in oven from Grieve, currently used for heat treating and high-temperature batch paint baking... Read News
70 Burka-Kosmos Offers Latest Grinding Wheel (February 3, 2014)
The Mira Ice product line of gear grinding wheels was developed in order to meet the requirements of profile grinding larger gears. A new... Read News
71 PTG to Showcase Grinding in Germany (February 12, 2014)
PTG Deutschland GmbH, the German-based division of Britain’s Precision Technologies Group, has chosen GrindTec 2014 to showcase its... Read News
72 United Grinding Invites Customers to Grinding Symposium (March 5, 2014)
The United Grinding Group – Körber Schleifring up until EMO 2013 – has clearly understood the signs of the times in the ... Read News
73 United Grinding Announces New President (March 27, 2014)
United Grinding North America, Inc. recently announced that current president and CEO, Rodger Pinney, has been elected as vice chairman... Read News
74 Norton Grinding Abrasives Feature Bond Technology (June 20, 2013)
Norton Abrasives, a brand of Saint-Gobain, has developed and launched Norton Vitrium3, the next generation of bonded abrasives prod... Read News
75 Grieve Introduces Electric Rotary Hearth Oven (June 7, 2013)
Grieve Corporation introduces No. 815, a 500°F electric rotary hearth oven, currently in use for preheating gears at a customer&rsquo... Read News
76 Schunk Expands Gripping Modules (June 14, 2012)
Schunk is further expanding its program of universal gripping modules: After the parallel gripper PGN-plus, the centric gripper PZN-plus,... Read News
77 LMT Tools Assist China Agricultural Machinery Market (May 7, 2012)
Although the general market environment has become more difficult, the production of agricultural machinery in China is booming more than... Read News
78 Drake Ships Steering Worm Grinder to Europe (June 26, 2012)
Drake Manufacturing Services Co. has recently shipped a GS:TE-LM 200 Steering Worm Grinder to a European automotive parts supplier. The m... Read News
79 Ultra Grind Offers Two Meter Grinding Capacity (July 31, 2012)
The Hardinge Grinding Group introduces a new 2-meter capacity, UltraGrind 2000 grinding machine manufactured by Jones & Shipman, a Ke... Read News
80 Saint-Gobain Introduces Grinding App (August 27, 2012)
Saint-Gobain Abrasives has recently introduced a Norton Abrasives Grinding App. This application includes three calculators includi... Read News
81 Kapp Offers Advancements in Gear Grinding (April 23, 2012)
Two grinding machines with flexible process capabilities will be on display at booth N-7036 at the IMTS in Chicago, Illinois, September 1... Read News
82 Mechatronic Gripper Offers Rapid Small Part Handling (April 17, 2012)
The conversion from pneumatic to electric gripping modules has been made much simpler, thanks to the electrically driven small parts grip... Read News
83 Micro Precision Gear Utilizes Holroyd Grinder (February 6, 2012)
Holroyd Precision, a division of the Precision Technologies Group, has recently completed a customer satisfaction survey with major custo... Read News
84 Grieve Offers Inert Atmosphere Cabinet Oven (February 21, 2012)
No. 855 is a 1250 degree Fahrenheit electrically-heated, inert atmosphere cabinet oven from Grieve, currently used for heat treating at t... Read News
85 Long Stroke Gripper Offers Efficient Alternative (March 15, 2012)
When components of different sizes have to be handled alternately, conventional centric grippers quickly reach their limits. In order to ... Read News
86 Drake Ships Two Thread Grinders to China (April 2, 2012)
Drake Manufacturing Services Co. has recently shipped two linear motor 4-axis CNC thread grinders to a Chinese petroleum company manufact... Read News
87 Hardinge Offers Super-Grip Power Chucks (August 30, 2012)
Hardinge Inc. manufactures a premiere line of lever-operated, counter-centrifugal and dynamically balanced Sure-Grip Power Chucks. The le... Read News
88 Grieve Offers High Temp, Walk In Oven (December 6, 2012)
No. 893 is an 850ºF, electrically-heated walk-in oven from Grieve, currently used for heat treating parts on rollout shelves at the ... Read News
89 ANCA to Demonstrate CNC Tool and Cutter Grinder (March 25, 2013)
The new, affordable ANCA MX5 CNC tool and cutter grinder will be demonstrated at EASTEC Booth 1152. Designed with the volume end-mill pro... Read News
90 Gleason Offers Profile Grinding on Threaded Wheel Gear Grinding Machines (March 27, 2013)
Gleason Corporation recently announced the availability of a Profile Grinding option for its 300TWG Threaded Wheel Grinding Machine... Read News
91 Grieve Furnace Used for Gear Preheats (April 26, 2013)
Grieve Corporation introduces No. 815, a 500°F electric rotary hearth oven, currently in use for preheating gears at a customer&rsquo... Read News
92 Holroyd Launches Worm Gear Grinding Stations (May 31, 2013)
Holroyd Precision Limited has launched a brand new, full CNC machine range that is specifically designed to provide ultra-high levels of ... Read News
93 Tool Grind Workholding System Limits Runout (March 20, 2013)
MicroPlus, ANCA's new high accuracy workholding and tool support system, significantly reduces tool runout during grinding, enabling ... Read News
94 EMAG Offers Hard Turning and Grinding Advantages (March 12, 2013)
The advantages of the process combination hard turning + grinding lie in process stream consolidation, improved component quality and gre... Read News
95 Refrigeration Company Invests in Holroyd Grinder (December 13, 2012)
Holroyd Precision Ltd., the specialist machine tool design, manufacture and supply division of U.K.-based Precision Technologies Group (P... Read News
96 Gleason Offers Wobble Compensation in Gear Grinding (December 27, 2012)
Conventional grinding cycles for cylindrical gears typically involve a significant amount of time dedicated to the manual alignment of th... Read News
97 Ingersoll Switches to SintoGrind IG (January 15, 2013)
To advance its grinding capabilities and improve the working environment, Ingersoll Cutting Tools has switched to SintoGrind IG, a synthe... Read News
98 Oelheld Releases DiaGrind 535-15 (March 4, 2013)
oelheld U.S. recently announced the availability of domestically manufactured DiaGrind 535-15. The multifunctional DiaGrind 535-15 is bee... Read News
99 Industry Gathers for United Grinding Symposium (June 24, 2014)
The world's largest event in the grinding machine industry drew to a close in Thun (Switzerland) with an enthusiastic audience. Every... Read News