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To get shops started, Dan Pheil, president of Landis Grinding Systems in Waynesboro, Pa., recommends grinding-machine shoppers define the life-cycle cost expectations for the grinder and then determine if the intended machine meets that criteria. Pheil also suggests evaluating the machine builders support capacity. Ed Sinkora of Walter Grinders in Fredericksburg, Va., further recommends shoppers request suppliers prove the cycle times they claim through a machine, software, and support demonstration. Also suppliers should spell out the cost of running the machine and exactly how much it will produce. Machine designs According to David Drechsler, vice president of sales & marketing at Huffman Corp. in Clover, S.C., grinding-machine customers should look for a machine design that best fits their application. A modular design, for instance, lets a builder draw from a pool of proven, reliable modules to configure a grinder thats for either a specific, dedicated, high-production application or a flexible one for a variety of jobs. Both machine types can include anywhere from 3 to 6 simultaneouscontouring axes, and their modularity means the builder didnt waste time developing and debugging a completely new design. Whenever possible, shoppers should seek machine designs that combine operations for lean manufacturing. Several builders offer machines with multiple grinding wheels and multiple part fixtures, and some even combine grinding with milling. The results are higher-quality parts, less work-in-progress and inventory, and lower costs. Combining multiple operations in a single machine, says Russ Kaiser, vice president of engineering at Landis Grinding Systems, responds to a shops need to minimize its number of machines and reduce capital expenditures. For physical machine qualities, Drechsler of Huffman believes total system stiffness is critical. Often, the workpiece or the fixture is the weak link in the system-stiffness chain, he says. Along with being stiff, a grinding system must be accurate. Randy Ragnini, regional manager at Toyoda Machinery USA in Arlington Heights, Ill., says that most CNC grinders accommodate such things as inprocess gaging, special width and outer-diameter-combination gages, and lateral locators also known as flagging for enhancing machine accuracy. Grinding-machine shoppers looking for even more machine accuracy may want to add other features such as dynamic wheel balancing, acoustical-vibration detection and compensation, coolant chillers, and special wheelhead or workheadbearing components. John Drake, president of Drake Manufacturing in Warren, Ohio, concurs and encourages shoppers to look for grinders with interlocking accuracy systems that include linear scales, rotary encoders, millioncount servo feedback, and acoustic sensing. A properly specified coolant system is also important, adds Ragnini of Toyoda. Aside from delivering adequate coolant to the grinding wheel, coolant systems with bed wash and filtration enhance grinding accuracy and reduce setup time. When contemplating grinding-machine capacity, Gerry Sandstrom, sales engineer at Service Network Inc. in Worcester, Mass., advises that buyers focus not only on part size, but also weight. A combination of heavy grinding chuck and hefty workpiece may cause an improperly engineered or light-duty workhead to sag, resulting in accuracy and machinemaintenance problems. The shifting of heavy weights on long-stroke slides, likewise, affects part accuracy. Sandstrom also offers advice on machine horsepower. With modern drives and spindles, many shops, especially those doing I.D. grinding, tend to select one spindle and drive to handle all machine operations. This is a risky approach related to the drive motors horsepower curve. A linear-shaped horsepower curve may compromise speed or horsepower depending on the range of operation. This, in turn, negatively affects grinder productivity. Dedicated or universal For small-to-medium batchproduction work in a jobshop environment, universal-type grinders Several grinding machine builders offer machines with multiple grinding wheels and multiple part fixtures, and some even combine grinding with milling. Hardinge in Elmira, N.Y. These machines quickly and accurately do I.D., O.D., and surface grinding, but for high-volume production work, a shop might want to consider a dedicated grinding system, he advises. Dedicated systems, according to Winstanley, have only the components necessary for a particular application, which makes for extremely fast cycle times. However, choosing a universal grinder is not a compromise in accuracy. The machines are just as accurate and reconfigure in less time if the part changes. offer the best flexibility, says Robert Winstanley, North American sales manager, grinding, at cause their heads accommodate multiple grinding wheels. Jobs that often take up to 5 setups are usually completed in one or two. Universal heads come in various configurations. For instance, shoppers can equip heads with four O.D. wheels, three O.D.s and one I.D., or one O.D. and two I.D. While these heads are dedicated in a sense, the machine itself is still extremely flexible, says Winstanley of Hardinge. Wheel dressing on a universal is versatile. Shops can locate dressing units at the tailstock, behind the wheelhead, on the workhead, sliding up and down the worktable length, or anywhere convenient for a particular job, says Winstanley. Where and how a shop dresses its wheels greatly influences part cycle times, he adds. Taking dewater out of grinding swarf Handling grindingswarf sludge is an often-troublesome and costly aspect of highvolume operations. If not dewatered, sludge is hazardous waste under both federal and state regulations and must go to designated waste sites. Without proper disposal, the wet-waste generator faces fines and penalties. By producing dry swarf, shops avoid such liability. A high-density extruder (HDE) such as the National-Sebright HDE from National Conveyors, East Granby, Conn., provides an efficient and versatile method for dewatering grinding swarf. The unit uses a hydraulically powered ram box that moves forward and back. In the forward position, the ram-box top is the bottom surface for the feed hopper that accepts loads of wet swarf. During forward motion, the ram presses the newly deposited wet swarf with progressively increasing force, partially compressing and dewatering it. The discharge gate then closes partially. A separate hydraulic accumulator remains charged until remaining swarf solids are compressed, dewatered, and ready for discharge. The unit then ejects a dry swarf cake.

Lift-up wheel-dressing units quickly drop into position for dressing and lift clear during grinding, so machine slides dont have to traverse to and from remotely positioned dressing stations. canned cycles. Some controls house extensive libraries of easytouse conversational programs that walk operators through most common grinding and wheeldressing programs. Ragnini of Toyoda recommends simple conversational-programming features like pictogram sequencing, automatic grinding-conditions determination, position memory teach-in capabilities, copy and edit functions, and access to machine and programming-maintenance functions. Other desirable capabilities are contour dressing and simple program back up. According to Drake of Drake Manufacturing, shoppers may want to consider machine builders that incorporate a customers part programming into menu-driven control software. For complex parts, this software reduces setup and changeover times from hours to minutes. And since all process parameters are built-in, the machine is easy to operate. Setups and changeovers What buyers often neglect to investigate are grinding machine setup and changeover times, points out Merk Roland of Agathon in Bethel, Conn. Pertinent questions include: how long does it take to set up the machine from scratch, and how long does it take to change the machine over to a new job? Machine accessibility influences setup time. Shops should choose a grinder that provides operator comfort. Machine doors should swing open and provide plenty of room at the wheel and work envelope, says Winstanley of Hardinge. Also, automated touch-off mechanisms that locate wheels to workpieces speed setup. By Patricia L. Smith, executive editor Behind the grinding wheel Time to pick a grinding wheel? Dont judge products on price tags alone. Instead, focus on grinding efficiency. The best way to match appropriate wheels to applications is to evaluate machine tool, work material, abrasive, and operational factors separately and in relation to one another. Using such a systems approach helps curb costs, improve workpiece quality, and extend wheel life. End users should begin the wheel-selection process by evaluating priorities, cost drivers, and constraints, says Bob Smith, Saint-Gobains technical director, application engineering. Thats because low, medium, and high-volume producers have different needs. For instance, productivity may be the most important consideration for one company, while another may focus on versatility or precision. And different companies have varied capacities and costs in terms of material, abrasive, and manpower. Prioritizing these factors and recognizing their constraints is an essential step in the wheel-selection process. Grinding grits and grades Grinding wheels come in two general grit categories: conventional abrasives, which include aluminum oxide and silicon carbide, and superabrasives such as diamond and cubic boron nitride (CBN). In general, what grit size and grade to use depends on the workpiece material. Soft, ductile