Creep feed grinding
Manufacturing engineering student
Islamic Azad univercity of Najafabad
GRINDING IS ONE OPERATION WHERE today's technologies are impacting what used to be considered a finishing process and adding the flexibility to do more operations over a variety of processes.
In order to take advantage of what is becoming available in grinding technology and to justify its purchase, it is critical to know the actual cost of manufacturing a part. Competitive companies are no longer purchasing grinding machines to replace worn out grinders to perform the same operation. They are evaluating manufacturing methods and adopting new practices to achieve higher quality parts at lower piece part costs.
A creep-feed grinding operation, for example, could replace a number of milling and broaching operations. Apart from the improvement in workpiece quality, the abrasive machining process will off-set the cost of capital equipment, consumable tools, resharpening, inspection and inventory of cutters, fixture cost, tool changeover and part handling times, and post-process deburring/finishing operations.
New bond systems. Superabrasives, particularly CBN (cubic boron nitride), appeared in the late 1960s. Great strides have been made since then to improve bond systems and techniques to eliminate or at least better control wheel trueing and dressing operations. Resin bond diamond and CBN wheels, which require a certain amount of finesse to prepare for grinding, are facing strong competition in the new vitrified and electroplated wheels.
Vitrified bond superabrasive wheels are similar to the vitrified bond conventional abrasive, aluminum oxide and silicon carbide wheels. Wheel preparation is simplified, in that traditional wheel trueing methods, like crush form dressing and single point diamond dressing, can be applied to true and form the wheel periphery. However, all vitrified superabrasive wheels are not so easy to use, as a certain amount of peripheral wheel conditioning (sticking with an aluminum oxide stick) may be required prior to grinding.
The vitrified bond superabrasive wheels available today provide better chip clearance and better cutting fluid application over resin and metal bond wheels. Vitrified superabrasive wheels are particularly suited to, and are finding the most application in, ID (internal diameter) grinding where the wheel wear and redressing time associated with conventional wheels drastically affects the productivity and precision of the process.
Resin and metal bond superabrasive wheels can have very strong grain retention properties, yet to achieve that strength, they are very closed in structure and therefore limit the efficiency of the process.
New abrasives. Not all grinding will be with superabrasives in the future. Particularly when batch quantities are low and a variety of form profiles are required, economic justification can be made for the use of conventional grinding wheels. The advent of ceramic abrasives, like Cubitron by The 3M Company (St. Paul, MN) and SG (Seeded-Gel) Abrasive by Norton (Worcester, MA), has greatly enhanced the wear characteristic of the grains so that they stay sharp and cool cutting, extending the life of coated abrasive media (in the case of Cubitron), and extending the time between wheel dressings (as with Norton's SG abrasive).
Conventional aluminum oxide is fused from bauxite. After crushing in a ball mill, the result is a very random shape grain with a very brittle structure. This is in contrast with the very dense and hard structure of the SG abrasive. However, a balance has to be struck between the properties of the SG grain and the "fracturability" and ease of bonding of the conventional fused alumina. This is why SG wheels are being produced with a variety of percentage mix of both the SG and alumina grain.
An exciting aspect in the manufacturing process of the SG abrasive is that the shape and aspect ratio of the grains can be controlled. Perhaps we might one day see a grinding wheel made of grains which are the same size and shape as well as oriented in the wheel to perform at maximum efficiency.
Machining the materials of tomorrow. Ceramic materials are the greatest challenge to the machining industry today. Grinding, using diamond grinding wheels, is the only economically viable method for the precision machining of ceramic materials in their sintered state. Ceramic materials are generally very hard and prone to edge chipping. The mechanism for machining ceramics is different from machining metals.
Ceramic materials are machined in a manner which resembles the chipping of ice from a driveway. The surface is pitted with craters the size of which depends on the size of the grain being used. The diamonds on the grinding wheel periphery act more like a series of hammer blows to the surface rather than as cutting edges causing chips to form.
Work that is being conducted on laboratory research machines in Japan has shown that, with very small infeeds and a very rigid machine, ceramic materials can be machined within their plastic regime. This yields excellent structural surfaces with high surface integrity.
Abrasive machine tool design. High precision and the ability to produce consistently high quality workpieces in state-of-the-art materials is a technological challenge. To perform this economically is another challenge and is directly related to the employment of the latest technology.
Lawrence Livermore National Laboratories (Livermore, CA) is synonymous with ultra-precision machining. Its search for an ultra-precision grinding machine took it to Italy where it was able to commission the most accurate creep-feed grinding machine ever built. Cimat-Camut produced the Gamma 625 machine. Standing on a giant block of stone and in an environmentally controlled room, this machine surpassed the expected values of slideway straightness, squareness, positioning and stiffness expected by the engineers at Lawrence Livermore.
Flexibility and versatility have been built into the Ceratech T-25 grinding machine by Mazak (Florence, KY). This fully CNC machine has been specifically designed for machining ceramics. It has automatic wheel changing capability from a magazine of wheel heads, wheel position sensing and an unusual method for trueing metal bond diamond grinding wheels. The CNC control is used to turn the inverse shape of the grinding wheel profile in a graphite electrode, on the machine. That electrode is then used to EDM the profile into the metal bond diamond grinding wheel. This concept allows virtually any shape to be formed into the grinding wheel in as short a time as it takes to turn the electrode.
Equipment is changing. Advanced Science and Technology has developed a machine that looks nothing like a grinding machine, but the advantages easily outweigh its peculiar appearance. Basically, it has a stationary wheelhead concept, but supported equally from both sides of the grinding wheel. The wheelhead does not move; it is isolated and de-coupled from the workpiece manipulation system so that minimal process vibration is transmitted through the structure, providing more stability for high-speed grinding operations. The dynamic stiffness of the system will approach 10,000,000 lbs/in. How the workpiece is presented to the grinding wheel is what makes the machine a plane, cylindrical, or contour grinder.
A new era. Electroplated superabrasive grinding wheels are taking us into high-speed grinding. High speed refers to the peripheral wheel speed. Conventional wheel speeds range from about 2,000 to 7,000 sfm. High speed grinding is in the range of 20,000-50,000 sfm. At these speeds, stock removal capability increases, wheel life may be extended and part surface integrity can be improved. The electroplated grinding wheel is a metal hub with a single layer of superabrasive plated to an accurately machine rim. The wheel needs no dressing, only trueing on the machine spindle. As the electroplated wheel is basically a metal disc, it can withstand very high rotational speeds without bursting.
Competitive advantage. These new abrasives technologies should be viewed as a significant element in an approach to strategic manufacturing. Advancing abrasives technology, plus grinding machine tool development and refinement, can be coupled to provide a serious competitive advantage in material removal operations. The enlightened grinding practitioner will keep a close eye on both machine tool and abrasives technology to turn their rapid advancement to individual and corporate advantage
Catching up to creep-feed grinding
Creep-feed grinding (CFG) is undoubtedly the fastest growing abrasive-technology process in the US, along with the use of superabrasives. To machine materials of the future---ceramics, cermets, monocrystal ceramics, whisker-reinforced metals, nonmetals, etc---grinding will be the only process available. CFG will be the only economical solution for ceramics. Conventional milling, broaching, planing, and turning---even in their most up-to-date forms---will not be able to cut tomorrow's materials. Grinding will be the only way for cutting tool technology to catch up to material science.
Unfortunately, the US machine tool industry has not kept abreast of this evolving technology and has lost market share to off-shore competition. US industry, until recently, has depended on foreign machine tool builders to produce creep-feed grinding machines and modern grinding systems. US builders have had to play catch-up, with few companies fully embracing the new technology, because of the significant investment commitment required---both financially and technically in the machine-tool designs suitable for creep-feed and superabrasive grinding.
CFG is a high-precision, high stock-removal abrasive process. Even the most difficult-to-machine materials can be machined relatively burr-free with excellent surface integrity. Metallics are being machined at rates much faster than milling and in the hardened state. The savings are not just the result of fast stock removal. Add to this the elimination of costly deburring operations, straightening after heat treatment, inventorying of raw material and consumable tooling, risk of thermal or metallurgical damage to part surfaces, or the need for expensive near-net-shape technologies. This is why CFG is the choice of the aerospace industry.
New machine requirements
CFG has been in use for almost 30 years. The 1990's will be an opportune time to reassess the CFG process and develop a completely new concept in machine-tool design, a new generation addressing these present and future industry needs:
Higher speeds: Industry recognizes the need for higher peripheral wheel speeds, particularly with superabrasives. This expertise lies predominately in Europe, and US safety standards for use of high wheel speeds lag those in Europe. Major high-speed advantages are being lost here due to inadequate machine designs and lack of initiative to improve wheel-safety standards.
Higher precision: Precision is directly affected by machine-tool design. Although CNCs and pseudo-adaptive controls allow poor machine designs to perform somewhat satisfactorily, the only path to an advanced, more precise machine is through its basic design.
A significant contributor is the epoxy/concrete machine base, such as the Granitan patent held by Studer in Switzerland. US builders are relying heavily on the Swiss for machine-base technology, as well as its fabrication and manufacture.
Wheel technology: The latest abrasive technologies require superior machine tools from the standpoint of thermal and vibrational stability, as well as truing and dressing methods. Whether the raw grains are manufactured by GE or DeBeers, the majority of superabrasive wheels are made by foreign sources. The latest grinding wheel technologies are vitrified superabrasive wheels and high induced-porosity conventional wheels. Japan leads the way in superabrasive wheel technology, followed closely by the Europeans. Domestic wheels have improved dramatically in recent years with some wheel specifications equal to European. Although the dollar decline has made foreign products less attractive, European wheel vendors remain highly competitive.
Materials technology: Machining the latest materials-high-temperature alloys, ceramics, and nonmetals-requires machine tools with high stiffness and superior control and resolution. As this technology accelerates, it is leaving behind those grinding machines that have been on the shop floor for years and are now either technically or economically unable to machine these latest materials.
Continuous-dress capability: Continuous-dress creep-feed grinding (CDCF) is an additional need for US industry, beyond CNC creep-feed and CNC surface grinding. Other than companies such as Brown & Sharpe, Roberts, and Gallmeyer & Livingston in the US; CFG and CDCF machine-tool expertise lies in Europe with companies such as Elb, Maegerle, and Hauni-Blohm. The Japanese are closely following the creep-feed process with Niigata and Okamoto offering machines capable of CFG and ceramic grinding.
Controls and automation
Control systems need to be developed to perform complex multiaxis contouring of shapes on CFG machines. Very high resolution is required. Contouring has opened a new market for CFG, but needs the development of user-friendly controls. For CFG to machine a wide variety of materials and profiles, it will need machines designed for faster and easier setups and economical small-lot production. Today's just-in-time concepts are completely different from those for the CFG machines of even a short time ago.
Even in Europe, makers of CFG machines still rely on the traditional surf ace-grinder approach to their machine designs; i.e., a century-old concept of manual operation. A major disadvantage of CFG today is that cut time is such a small portion of floor-to-floor time.
Automation of part loading/unloading, and wheel and dresser changing is of paramount importance. A newer surface grinder concept is needed that is uncompromising in capitalizing on the potential of the creep-feed process. The move is away from dedicated automated grinding cells (ably suited for producing turbine blades in high volume) to more flexible systems that allow economical production of medium to small batches of a wide variety of workpiece shapes and materials.
Research in creep-feed machineability is presently being conducted in the US, and accelerated to encompass wider fields of materials, grinding wheels, dressing systems, and cutting fluids. With so little CFG expertise in the US, the process desperately needs a source of definitive machineability data, and users need confidence in what is very much a foreign process-in both senses of the word.
Process adaptive control is not presently a reality for CFG. Although machining to a predetermined algorithm is possible, true adaptive control is beyond the realm of present-day technologies.
With these industry needs, there is enormous potential for the US machine-tool industry to build a new generation of CFG equipment. With little to be gained from equaling the competition, the effort should be to surpass it. A new approach would not only offer a competitive alternative, but boost export sales. This calls for a cooperation between user and machine builder, and input from independent sources to keep the design universal and not particular to one industry or application.
A concept I have long proposed for a whole new generation of grinding machines is based on bringing the part to the wheel, instead of the wheel to the part. This, after all, is how our ancestors sharpened their knives and tools: they held them against a stable, spinning wheel. They never attempted to do it the other way around!
My approach incorporates a wheelhead and dressing system more rigid and vibrationally stable than any existing production machine. Theoretical stiffness is in the order of 6 million lb/in. The principle of this patented design is a stationary, dual-supported grinding wheel. A special hydrostatic bearing allows the wheel and dresser to be changed easily, automatically, and accurately without sacrificing the mechanical stiffness of the system. The result is a single grinding machine capable of flat, form, contour,, cam, and OD cylindrical grinding. This concept of versatility, stiffness, and stability would take abrasive machining into the next generation.
ADVANTAGES OF CREEP-FEED (FULL-DEPTH) GRINDING
vs CONVENTIONAL MACHINING
• Increased productivity and quality of parts requiring slots and/or profiles.
• Eliminates costly first operations such as milling, broaching or turning. The form or slot can be creep-feed ground to full depth from the solid.
• Fully hardened parts can be creep-feed ground from the solid--thus, in many cases eliminating the need for straightening operations required prior to conventional reciprocation grinding after milling and heat treating.
• Reduced handling time and cost. For example, a conventional machining process of a part may require:
3. Heat Treat
5. Reciprocating Grinding.
Whereas with creep-feed, the milling, deburring, straightening, and extra handling operations can be eliminated.
• Reduced set-up time and costs due to combined operations.
• Reduced tooling costs (i.e., formed milling cutters, broaching tools, etc. as compared to grinding wheels).
• More parts processed per wheel life due to less wheel breakdown when compared to reciprocation grinding.
• Reduced wear on dressing tools due to the use of softer wheels.
• Wheel form maintained longer--thus, requiring less redressing and resulting in increased productivity.
• Reduced grinding wheel cost due to less wear and fewer number of dressing operations required.
• Improved tolerances and surface integrity as opposed to milling, broaching or turning.
THE WHEEL & CREEP FEED GRINDING
It is widely accepted that grinding wheels with a high percentage of porosity are an absolute necessity for Creep Feed grinding. It is the purpose of this paper to understand why and to, highlight possible areas for thought when selecting the appropriate wheel.
There's no "Buzz Word" in the grinding industry today that sparks the interest and excitement of "CREEP FEED".
It is impossible to attend a seminar on Creep Feed without hearing the phrase "very soft very open" when referring to the grinding wheel without any real explanation of why or compared to what? Compared to conventional grinding, and what is actually going on. In contrast to conventional reciprocating grinding, Creep Feed is characterized by increased depths of cut and much slower table speeds.
Increasing the depth of cut or infeed is an easily observable change to any grinding system. Increasing the depth of cut also increases the length of arc of contact. In this example "length of arc" will refer to the distance an abrasive particle must follow while in contact with the work piece. For our example we will be using a 16" diameter grinding wheel. Setting the machine for a depth of cut of .001", will generate an arc of contact between the wheel and the work piece of .126". Increasing the depth of cut to .110" will increase this arc of contact from .126 to 1.266". (Figure #1).
Using the same 16" diameter grinding wheel of any given width and depth of cut .001" we have a given area of contact. By "area of contact" we mean that portion of the wheel actually in contact with the work piece during the grind. (Length of arc x width of wheel) (Figure #2). Within this area, based on abrasive size and structure there will be a given amount of abrasive particles. Increasing the depth of cut (Figure #3) will proportionately increase this area of contact. Again, keeping abrasive size and structure constant, we can expect an increase in the amount of active abrasive particles in contact with the material.
Applying a given force of the same amount to both areas results in the amount of force per individual abrasive particle within the larger area to decrease (Figure #4). This decrease in unit pressure per abrasive particle is the same principle we see in conventional grinding. One should be able to visualize at this time that changing the depth of cut directly effects the area of contact between the wheel and the work piece. Changing the area of contact in turn effects the unit pressure per abrasive particle causing the grinding wheel to act harder or softer.
As in conventional reciprocating grinding it is an accepted f act that as you increase the area of contact, you must adjust the grade to maintain the same performance. Changing the depth of cut although very obvious is not the only element to influence the number of active abrasive particles in relation to area. Form must also be taken into consideration.
Unlike conventional surface grinding where form has a less noticeable effect on the number of active abrasive grinding particles, Creep Feed with full depth grinding has a much more pronounced affect. For example, a straight faced grinding wheel has a fixed number of active abrasive particles for a given horsepower (Figure #9A), unless Figure B has a depth of cut greater than that of the formed area, the effect is the same as removing 1/4 the amount of material with the same horsepower. A wheel that might work well with the given horsepower in 9A could possibly grind unsatisfactory in condition 9B. Another thing to remember here is that the sides of the form sections are not actively grinding, but rather have a polishing effect. Keeping horsepower constant from form 9A to 9B would result in more force per active abrasive particle, or we would expect the wheel to act softer than in 9A.
The extreme example of a forms affect on the active abrasives grinding particles is represented in Figure 9C. In this case only 1/2 the material is now being removed by twice the active abrasive particles. Again maintaining the same horsepower as in 9A would result in a much lower force per active abrasive particle and in this instance we would expect the wheel to act harder. From these examples it becomes easier to visualize that when we say very soft it is relative to performing the same operation by conventional reciprocation with it's greatly reduce area of contact. And that a wheel that works very well on a particular material with set machine parameters would possibly require readjusting these parameters, as the depth of cut or form on the grinding wheel is changed to optimize results.
When referring to the cavities or porosity within a grinding wheel what we are actually referring to is the wheels structure. Structure is the relationship of abrasive grain and bonding material to the voids or spaces within the wheel Figure #5. For each grit size and grade combination there is an optimum structure. In creep feed it is confirmed that increased porosity is absolutely necessary. Testing has also indicated that it is beneficial if the cavities have a size relatively close to the size of the abrasive particles. Extremely large pore size is undesirable because the number of active abrasive particles at the interface of the grinding wheel and workpiece becomes extremely erratic which can have a direct result on performance and wheel wear. As pore size increases, uniform distribution throughout the grinding wheel also becomes extremely difficult to control (Figure #6).
As pore size decrease control of distribution increases and improved bond to pore relationships are possible. Unduly small pore sizes are also not highly desirable. If the pore size becomes too fine relative to the abrasive particle-size the wheels will not transport sufficient coolant or allow for ample chip clearance and grindability will decrease.
Pore size also has a direct bearing on the grinding wheels form holding capabilities. As pore size increases without regard for abrasive size it becomes increasingly difficult to maintain form. Although bond posts between individual abrasive particles strengthen, the large honeycomb matrix of the wheel oftentimes will leave the truing device trying to impart a form into air (Figure #7). This is especially observable on the edges of the wheels where large chunks of abrasive material may separate from the grinding wheel. Smaller cavities reduce the size of the honeycomb matrix and bond posts between individual abrasive particles becomes less random. This finer more uniformly distributed matrix means that the truing device will have an increased probability of imparting the form into the grinding wheel. The wheel will also accept more intricate forms and tend to maintain the form longer.
To summarize, although grinding wheels with very large pores and obviously open honeycomb structures are very impressive visually, they may not be the best choice for all grinding operations. Quality in a Creep Feed grinding wheel is:
• Proper size relationship between abrasive grains and wheel cavities - for chip clearance and coolant transportation.
• Controlled abrasive and pore distribution - for high dynamic balance.
• Greater bond strength - to accept the higher total forces with higher concentrations of porosity.
• Controlled bond degradation - at the interface of wheel and piece part.
Three Faces of Creep-Feed Grinding
Creep-feed grinding is an abrasive machining process mainly used to produce slots or intricate forms in difficult-to-grind materials such as prehardened tool steels and high-temperature nickel-base aerospace alloys. The process utilizes a grinding wheel to impart forms previously associated with milling or broaching operations into a workpiece in one pass, at full depth of cut and very slow table speeds. The use of creep-feed grinding has grown to meet the need for increased productivity and greater production efficiencies.
Creep-feed grinding has two main advantages over machining. First, it can work materials that are difficult and costly to shape by other methods. Second, it is easier to modify the form on a grinding wheel than it is on a broach or milling cutter, enabling rapid design alterations and changeovers.
The process also has several advantages over conventional reciprocating surface grinding:
More actual grinding time. Time lost with the wheel not in contact with the workpiece while reversing the table in conventional grinding, can exceed the actual time required to grind the part.
Less tendency to chatter. The increased depth of cut associated with creep-feed grinding produces a grater interface between the wheel and the workplace. This increased interface, combined with slower table speeds, has a tendency to stabilize any vibration generated during the grinding process.
Increased form-holding characteristics. The wheel enters the workpiece slowly and only once, generating complete form that equalizes the load over the entire wheel face. Entering slowly and only once eliminates the shearing of abrasive particles that occurs as the wheel repeatedly strikes the edge of the workpiece in conventional reciprocating grinding.
Less thermal damage. In conventional surface grinding, with higher depths of cut and increased spindle and table speeds, heat is generated (and transferred into the workpiece) in impulses. But in creep-feed grinding, the heat is a constant moderate influx distributed over a much grater area. The result is that a greater volume of the workpiece material is heated to lower average and maximum temperatures. Although the maximum temperature may reach a point high enough to cause thermal damage ahead of the grinding wheel, the disturbed material will be removed during, the grinding process.
Types of Creep-feed Grinding
Three basic types of creep-feed grinding are used in U.S. industry today: Pseudo creep feed, true creep feed, and continuous-dress creep feed. Each method is utilized for specific grinding applications.
Pseudo creep-feed grinding is used for workplaces with narrow cross sections. The piece is ground at full depth, but because of the narrow cross section the full length arc contact experienced in true creep-feed grinding is not generated.
The narrow cross section of the workplace allows the use of conventional grinding machines with hydraulic drives. Table speeds, although slow by conventional reciprocating standards, do not require the precise mechanical drives of true creep-feed grinders. Pseudo creep-feed grinding can provide greater productivity than conventional reciprocating grinding, but it cannot compete with true creep-feed grinding.
Wheels used for pseudo creep-feed grinding need not be as highly porous as true creep-feed wheels, because the coolant application and swarf removal requirements are not as demanding. In some cases, conventional wheels will perform acceptably, although very porous wheels will provide the best performance. Wheel speeds for pseudo creep-feed grinding are typically in the area of 6500 sfm.
True creep-feed grinding, utilizing machines especially designed for the process, offers high metal-removal rates with full-depth-of-cut, one-pass grinding. It offers great potential for increased productivity and accuracy. The workpiece can start out as hardened blank stock, be fixtured only once, and end up as a finished part. The process also offers improved dimensional stability and freedom from adverse thermal effects in the workpiece.
True creep-feed grinding maximizes the length of arc of contact between the wheel and the workpiece. For this reason it demands a specially designed grinding wheel and machine tool specifically built for creep-feed grinding. In pseudo creep-feed grinding, a surge in the table can cause the wheel to exit the part; in true creep-feed grinding, a table surge can actually cause the wheel to burst.
Because of the increased area of contact, wheels for true creep-feed should be softer than conventional wheels. In addition, high metal removal rates and increased demand to transport coolant into the grinding interface require as open a wheel structure as possible.
Rigidity is essential to creep-feed grinding machines. They must withstand increased forces resulting from crush forming the grinding wheel for close-tolerance, form-grinding repeatability. Wheel speeds should be variable, while table speeds should be mechanically driven to ensure stick-free, slip-free operation.
In continuous-dress grinding, the wheel is sharpened and profiled while actively grinding the workpiece rather than between grinding cycles. This type of grinding can provide greater metal removal rates than those of true creep feed. More important, continuous-dress grinding increases form-holding and dimensional stability.
Continuous-dress grinding requires specially designed machines. They must have all the attributes of true creep-feed grinding machines and also be equipped with compensating-speed wheel spindles. These are necessary to automatically increase the speed of the wheel as its diameter decreases during operation. The compensating spindles ensure that the grinding wheel operates at a constant surface speed.
The rate at which the dressing device is fed into the wheel and the rate at which the wheel is fed into the workplace must also be perfectly synchronized to compensate for wheel wear, otherwise it will be impossible to grind the workpiece parallel.
The dressing operation resharpens dull abrasive grains or releases them from the bond system. Selection of the type of diamond roll dressing device to use----hand-set or reverse-platted---depends upon the desired form, grit size, and wheel grade. Although diamond roll dressing will not produce as aggressive a wheel as will crush-truing, continuous dressing will maintain the wheel at a constant percentage of its full potential. This produces steadier and lower average grinding forces, resulting in more efficient use of abrasive materials and shorter cycle times.
In review, creep-feed grinding can provide significant productivity improvements without requiring investment in specialized machinery. The process can be implemented on conventional machines for workpieces that have narrow cross sections.
True creep-feed grinding requires specially designed machinery, but can provide high metal-removal rates while producing a workpiece of better quality. The process is especially beneficial in applications where close tolerances and repeatability are important.
Continuous-dress creep-feed grinding offers the highest metal removal rates and the best form-holding and dimensional stability. The grinding system must be carefully controlled, however, to ensure successful operation.
All of these grinding techniques require consideration of the total grinding system. Factors that can affect system performance and productivity include workplace fixturing; wheel types and speeds; infeed rates; coolant placement, volume and pressure; truing and dressing systems;and, most important, the grinding machine itself. Careful coordination of these elements into a total creep-feed grinding system can yield substantial quality and productivity benefits for manufacturers of difficult-to-grind components