Dec. 02, 2024
Experts with Norton | Saint-Gobain Abrasives discuss the challenges of gear grinding and how advances in technology are improving the efficiency of grinding methods.
For more information, please visit SINOTOOLS.
Methods of gear grinding have changed over the years. As manufacturing standards get tighter, the right machines and abrasives needed to meet specifications have become even more critical. Product Manager Josh Fairley and Senior Application Engineer Phil Plainte with Norton | Saint-Gobain Abrasives share their expertise on how gear grinding &#; as well as using the correct grinding wheel &#; plays an important role in gear manufacturing. They also reveal how their company is addressing this essential process.
What changes have you seen in terms of what gear manufacturers need for grinding wheels?
PLAINTE: High-volume automotive manufacturing has made the greatest impact for changing and transforming the way gears are mass produced. Automotive manufacturers are building transmissions with &#;aircraft quality&#; gears, which meet the highest quality standards. The newer transmissions are a fraction of the size of the older designs and handle significantly higher torque, horse power, and higher RPMs. The efficiency of these transmissions has increased miles per gallon tenfold. These changes have pushed machine builders and grinding wheel manufacturers to develop products that meet the new requirements.
Gear manufacturers did not always need grinding wheels to provide the final surface finish and form required. They could get by with hobbing and shaving, and on special jobs they might use lapping ring and pinion sets. Aerospace was the first industry to embrace grinding gears, but the aerospace industry was not as cost focused as automotive.
FAIRLEY: Quality standards have increased dramatically over the years for all gear applications. The need to improve efficiency while maintaining high quality and driving down the cost per piece has made choosing the right grinding wheel for the job much more important. Depending on the goals of the gear manufacturer, different grinding wheel specifications are needed to optimize the desired metrics.
What are the most common gear-grinding challenges you see from gear manufacturers? (i.e. higher speeds, burring, finishes etc.?)
FAIRLEY: The most common challenges in gear grinding stem from the strict quality standards and efficiency/flexibility needs of gear manufacturers. Gear manufacturers are looking for very fine finishes and excellent gear geometry results from using their grinding wheels. They are also looking for precise form holding and reduced dimensional variation along with significant cycle time reductions. These quality metrics are more challenging to obtain because of the risk of burning gears. High-grinding area of contact, fine surface finish requirements, and tight form-holding requirements all work against a burn-free grind. Therefore, it is critical to specify the best grinding wheel matrix and grinding parameters for the job.
Another big challenge is operator and engineering knowledge of grinding. Norton | Saint-Gobain offers on-site technical training through our &#;Norton School of Grinding,&#; as well as our Precision Customer Seminars in Worcester, Massachusetts. These training classes give gear manufacturers the opportunity to learn grinding theory and ask application specific questions to our grinding experts.
When evaluating a grinding solution for gear manufacture, what are the top five key tips for determining a suitable grinding wheel?
FAIRLEY: 1) Identify the goal and what the key metrics are for the grinding process: If you are looking for high quality, high efficiency, or both, different grinding wheel specifications will get you there. We offer different specifications for each of these performance metrics in order to provide the most optimized solution for the customer, rather than one specification for everything.
2) Know your application: There are different types of gear grinding, and depending on the type, different grinding wheel specifications and sizes should be used.
3) Gear information: To pick the optimal grinding wheel for your gear grinding process, all aspects of the gear should be communicated. The material being ground, the desired surface finish, and profile to hold are all critical to picking the right wheel.
PLAINTE: 4) Coolant delivery and machine characteristics: It is well known how critical coolant is in the gear-grinding process. In an ideal scenario, coolant temperature, flow, targeting, pressure, and filtration are all set up properly. However, if one of these is not at an ideal condition, a modification to the grinding wheel specification or grinding parameters can alleviate those issues.
5) Dressing methodology: The dresser technology, application, and dressing parameters have a huge impact on grinding performance. Different grinding wheel technologies will be optimized depending on the dressing tool and parameters used.
In terms of technology and application support, what should gear manufacturers expect from their grinding wheels manufacturer/supplier?
PLAINTE: We work with the customer at all levels, from design to manufacture. We have excellent relationships with machine-tool builders and are happy to begin at Day 1 during the gear-grinding application design process. We also get involved when gear manufacturers are faced with challenges and are looking for new ways of producing gears and developing processes.
In what ways is Norton tackling the future of gear grinding?
PLAINTE: Norton | Saint-Gobain is a world leader in the abrasives industry that is focused on engineered material development. A considerable percentage of gross sales is reinvested in R&D. We have six grinding technology centers located throughout the world.
FAIRLEY: Dedication to innovation. Advancements in grain, bond, and engineered porosity, all developed in-house. Norton was the first to develop ceramic, micro-structured grains, changing the game in terms of what grinding processes could achieve. We were the first to develop shaped grains, allowing for unprecedented removal rates. As the gear industry quickly evolved, we too evolved to support the market.
Norton | Saint-Gobain is at the forefront of grinding wheel technology and expertise. We also have a large and diverse team of experienced sales personnel and application support, both locally and globally.
We recently introduced the Norton Xtrimium&#; range of gear solutions designed for high-performance gear grinding in extreme, tight tolerance environments. The newly structured portfolio of gear-grinding products is specifically designed by category to provide higher-profile accuracy, supreme form holding, and burn-free grinding in worm, profile, and bevel applications. Highlighting the new range is an innovative dual-worm wheel design that enables two operations in one grinding wheel, substantially saving time and cost.
How is Norton | Saint-Gobain addressing Industry 4.0 initiatives?
FAIRLEY: To address Industry 4.0 initiatives, we have introduced Norton 4Sight process monitoring and diagnostic system, which provides real-time monitoring and improved vision of the machine and operation, as well as in-depth insight into the grinding cycle for optimization and troubleshooting. This also enables customers to work with Norton application engineers remotely to provide real time troubleshooting and optimization. We are also investigating the use of QR coding and RFID technologies in collaboration with customers, to help gear manufacturers achieve their Industry 4.0 goals.&#;
More info www.nortonabrasives.com; 800-551-
Photo Credit: Getty Images
The grinding wheel is a cutting tool. It's an abrasive cutting tool.
In a grinding wheel, the abrasive performs the same function as the teeth in a saw. But unlike a saw, which has teeth only on its edge, the grinding wheel has abrasive grains distributed throughout the wheel. Thousands of these hard, tough grains move against the workpiece to cut away tiny chips of material.
Abrasive suppliers offer a wide array of products for a variety of grinding applications in metalworking. Choosing the wrong product can cost the shop time and money. This article presents some of the fundamentals of selecting the best grinding wheel for the job.
Grinding wheels and other bonded abrasives have two major components: the abrasive grains that do the actual cutting and the bond that holds the grains together and supports them while they cut. The percentages of grain and bond and their spacing in the wheel determine the wheel's structure.
The particular abrasive used in a wheel is chosen based on the way it will interact with the work material. The ideal abrasive has the ability to stay sharp with minimal point dulling. When dulling begins, the abrasive fractures, creating new cutting points.
Each abrasive type is unique with distinct properties for hardness, strength, fracture toughness and resistance to impact.
Aluminum oxide is the most common abrasive used in grinding wheels. It is usually the abrasive chosen for grinding carbon steel, alloy steel, high speed steel, annealed malleable iron, wrought iron as well as bronzes and similar metals. There are many different types of aluminum oxide abrasives, each specially made and blended for particular types of grinding jobs. Each abrasive type carries its own designation, usually a combination of a letter and a number. These designations vary by manufacturer.
Zirconia alumina is another family of abrasives, each one made from a different percentage of aluminum oxide and zirconium oxide. The combination results in a tough, durable abrasive that works well in rough grinding applications, such as cut-off operations, on a broad range of steels and steel alloys. As with aluminum oxide, there are several different types of zirconia alumina from which to choose.
Silicon carbide is an abrasive used for grinding gray iron, chilled iron, brass, soft bronze and aluminum, as well as stone, rubber and other nonferrous materials.
Ceramic aluminum oxide is another major development in abrasives. This is a high-purity grain manufactured in a gel sintering process. The result is an abrasive with the ability to fracture at a controlled rate at the submicron level, constantly creating thousands of new cutting points. This abrasive is exceptionally hard and strong. It is primarily used for precision grinding in demanding applications on steels and alloys that are the most difficult to grind. The abrasive is normally blended in various percentages with other abrasives to optimize its performance for different applications and materials.
Once the grain is known, the next question relates to grit size. Every grinding wheel has a number designating this characteristic. Grit size is the size of individual abrasive grains in the wheel. It corresponds to the number of openings per linear inch in the final screen size used to size the grain. In other words, higher numbers translate to smaller openings in the screen the grains pass through. Lower numbers (such as 10, 16 or 24) denote a wheel with coarse grain. The coarser the grain, the larger the size of the material removed. Coarse grains are used for rapid stock removal where finish is not important. Higher numbers (such as 70, 100 and 180) are fine grit wheels. They are suitable for imparting fine finishes, for small areas of contact and for use with hard, brittle materials.
To allow the abrasive in the wheel to cut efficiently, the wheel must contain the proper bond. The bond is the material that holds the abrasive grains together so they can cut effectively. The bond must also wear away as the abrasive grains wear and are expelled so new, sharp grains are exposed.
There are three principal types of bonds used in conventional grinding wheels. Each type is capable of giving distinct characteristics to the grinding action of the wheel. The type of bond selected depends on such factors as the wheel operating speed, the type of grinding operation, the precision required and the material to be ground.
Most grinding wheels are made with vitrified bonds, which consist of a mixture of carefully selected clays. At the high temperatures produced in the kilns where grinding wheels are made, the clays and the abrasive grain fuse into a molten glass condition. During cooling, the glass forms a span that attaches each grain to its neighbor and supports the grains while they grind.
Grinding wheels made with vitrified bonds are very rigid, strong and porous. They remove stock material at high rates and grind to precise requirements. They are not affected by water, acid, oils or variations in temperature.
Vitrified bonds are very hard, but at the same time, they are brittle like glass. These bonds are broken down by the pressure of grinding.
Some bonds are made of organic substances. These bonds soften under the heat of grinding. The most common organic bond type is the resinoid bond, which is made from synthetic resin. Wheels with resinoid bonds are good choices for applications that require rapid stock removal, as well as those where better finishes are needed. They are designed to operate at higher speeds, and they are often used for wheels in fabrication shops, foundries, billet shops and for saw sharpening and gumming.
Another type of organic bond is rubber. Wheels made with rubber bonds offer a smooth grinding action. Rubber bonds are often found in wheels used where a high quality of finish is required, such as ball bearing and roller bearing races. They are also frequently used for cut-off wheels where burr and burn must be held to a minimum.
The strength of a bond is designated in the grade of the grinding wheel. The bond is said to have a hard grade if the spans between each abrasive grain are very strong and retain the grains well against the grinding forces tending to pry them loose. A wheel is said to have a soft grade if only a small force is needed to release the grains. It is the relative amount of bond in the wheel that determines its grade or hardness.
Hard-grade wheels are used for longer wheel life, for jobs on high-horsepower machines and for jobs with small or narrow areas of contact. Soft grade wheels are used for rapid stock removal, for jobs with large areas of contact, and for hard materials such as tool steels and carbides.
The wheel itself comes in a variety of shapes. The product typically pictured when one thinks of a grinding wheel is the straight wheel. The grinding face&#; the part of the wheel that addresses the work &#; is on the periphery of a straight wheel. A common variation of the straight wheel design is the recessed wheel, so called because the center of the wheel is recessed to allow it to fit on a machine spindle flange assembly.
On some wheels, the cutting face is on the side of the wheel. These wheels are usually named for their distinctive shapes, as in cylinder wheels, cup wheels and dish wheels. Sometimes bonded abrasive sections of various shapes are assembled to form a continuous or intermittent side grinding wheel. These products are called segments. Wheels with cutting faces on their sides are often used to grind the teeth of cutting tools and other hard-to-reach surfaces.
If you want to learn more, please visit our website abrasive grinding wheel manufacturers.
Related links:Mounted wheels are small grinding wheels with special shapes, such as cones or plugs, that are permanently mounted on a steel mandrel. They are used for a variety of off-hand and precision internal grinding jobs.
Grinding wheels are generally labeled with a maximum safe operating speed. Don't exceed this speed limit. The safest course is not even to mount a given wheel on any grinder fast enough to exceed this limit.
These diamond metal bond wheels offer superior performance in round tool grinding.
A number of factors must be considered in order to select the best grinding wheel for the job at hand. The first consideration is the material to be ground. This determines the kind of abrasive you will need in the wheel. For example, aluminum oxide or zirconia alumina should be used for grinding steels and steel alloys. For grinding cast iron, nonferrous metals and non-=metallic materials, select a silicon carbide abrasive.
Hard, brittle materials generally require a wheel with a fine grit size and a softer grade. Hard materials resist the penetration of abrasive grains and cause them to dull quickly. Therefore, the combination of finer grit and softer grade lets abrasive grains break away as they become dull, exposing fresh, sharp cutting points. On the other hand, wheels with the coarse grit and hard grade should be chosen for materials that are soft, ductile and easily penetrated.
The amount of stock to be removed is also a consideration. Coarser grits give rapid stock removal since they are capable of greater penetration and heavier cuts. However, if the work material is hard to penetrate, a slightly finer grit wheel will cut faster since there are more cutting points to do the work.
Wheels with vitrified bonds provide fast cutting. Resin, rubber or shellac bonds should be chosen if a smaller amount of stock is to be removed, or if the finish requirements are higher.
Another factor that affects the choice of wheel bond is the wheel speed in operation. Usually vitrified wheels are used at speeds less than 6,500 surface feet per minute. At higher speeds, the vitrified bond may break. Organic bond wheels are generally the choice between 6,500 and 9,500 surface feet per minute. Working at higher speeds usually requires specially designed wheels for high speed grinding.
In any case, do not exceed the safe operating speed shown on the wheel or its blotter. This might be specified in either rpm or sfm.
The next factor to consider is the area of grinding contact between the wheel and the workpiece. For a broad area of contact, use a wheel with coarser grit and softer grade. This ensures a free, cool cutting action under the heavier load imposed by the size of the surface to be ground. Smaller areas of grinding contact require wheels with finer grits and harder grades to withstand the greater unit pressure.
Next, consider the severity of the grinding action. This is defined as the pressure under which the grinding wheel and the workpiece are brought and held together. Some abrasives have been designed to withstand severe grinding conditions when grinding steel and steel alloys.
Grinding machine horsepower must also be considered. In general, harder grade wheels should be used on machines with higher horsepower. If horsepower is less than wheel diameter, a softer grade wheel should be used. If horsepower is greater than wheel diameter, choose a harder grade wheel.
More: 7 Key Factors in Choosing a Grinding Wheel
Grinding wheels must be handled, mounted and used with the right amount of precaution and protection.
They should always be stored so they are protected from banging and gouging. The storage room should not be subjected to extreme variations in temperature and humidity because these can damage the bonds in some wheels.
Immediately after unpacking, all new wheels should be closely inspected to be sure they have not been damaged in transit. All used wheels returned to the storage room should also be inspected.
Wheels should be handled carefully to avoid dropping and bumping, since this may lead to damage or cracks. Wheels should be carried to the job, not rolled. If the wheel is too heavy to be carried safely by hand, use a hand truck, wagon or forklift truck with cushioning provided to avoid damage.
Before mounting a vitrified wheel, ring test it as explained in the American National Standards Institute's B7.1 Safety Code for the Use, Care and Protection of Grinding Wheels. The ring test is designed to detect any cracks in a wheel. Never use a cracked wheel.
A wise precaution is to be sure the spindle rpm of the machine you're using doesn't exceed the maximum safe speed of the grinding wheel.
Always use a wheel with a center hole size that fits snugly yet freely on the spindle without forcing it. Never attempt to alter the center hole. Use a matched pair of clean, recessed flanges at least one-third the diameter of the wheel. Flange bearing surfaces must be flat and free of any burrs or dirt buildup.
Tighten the spindle nut only enough to hold the wheel firmly without over-tightening. If mounting a directional wheel, look for the arrow marked on the wheel itself and be sure it points in the direction of spindle rotation.
Always make sure that all wheel and machine guards are in place, and that all covers are tightly closed before operating the machine. After the wheel is securely mounted and the guards are in place, turn on the machine, step back out of the way and let it run for at least one minute at operating speed before starting to grind.
Grind only on the face of a straight wheel. Grind only on the side of a cylinder, cup or segment wheel. Make grinding contact gently, without bumping or gouging. Never force grinding so that the motor slows noticeably or the work gets hot. The machine ampmeter can be a good indicator of correct performance.
If a wheel breaks during use, make a careful inspection of the machine to be sure that protective hoods and guards have not been damaged. Also, check the flanges, spindle and mounting nuts to be sure they are not bent, sprung or otherwise damaged.
The grinding wheel is one component in an engineered system consisting of wheel, machine tool, work material and operational factors. Each factor affects all the others. Accordingly, the shop that wants to optimize grinding performance will choose the grinding wheel best suited to all of these other components of the process.
About the author: Joe Sullivan was a senior product manager for Norton Company, Worcester, Massachusetts.
Superabrasives make up a special category of bonded abrasives designed for grinding the hardest, most challenging work materials.
Because carbides, high speed steels, PCD, PCBN, ceramics and some other materials used to make cutting tools can be nearly as hard as conventional abrasives, the job of sharpening them falls to a special class of abrasives-diamond and the CBN, the superabrasives.
These materials offer extreme hardness, but they are more expensive than conventional abrasives (silicon carbide and aluminum oxide). Therefore, superabrasive grinding wheels have a different construction than conventional abrasive wheels. Where a conventional abrasive product is made up of abrasive all the way through, superabrasive wheels have abrasive on the cutting edge of the wheel that is bonded to a core material, which forms the shape of the wheel and contributes to the grinding action.
Superabrasive wheels are supplied in the same standard grit range as conventional wheels (typically 46 through 2,000 grit). Like other types of wheels, they can be made in a range of grades and concentrations (the amount of diamond in the bond) to fit the operation.
There are four types of bond used in superabrasive wheels. Resinoid bond wheels are exceptionally fast and cool cutting. They are well-suited to sharpening multi-tooth cutters and reamers, and for all precision grinding operations. Resin is the "workhorse" bond, most commonly used and most forgiving. Vitrified bond wheels combine fast cutting with a resistance to wear. They are often used in high-volume production operations. Metal bond wheels are used for grinding and cutting nonmetallic materials, such as stone, reinforced plastics and semiconductor materials that cannot be machined by other cutting tools. Single-layer plated wheels are used when the operation requires both fast stock removal and the generation of a complex form.
For more plier and cutter manufacturerinformation, please contact us. We will provide professional answers.
If you are interested in sending in a Guest Blogger Submission,welcome to write for us!
All Comments ( 0 )