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Fig. 3 - Parameter Case Angular Contact Ball Bearing Cylindrical Roller Bearing Tapered Roller Bearing Abbreviation ACBB CRB TRB Ring Outer Outer Inner Image Outer Diameter 250 mm 400 mm 232 mm Roundness - OD <1.5 μm <2 μm <1 μm Straightness - OD <0.5 μm <0.5 μm <0.5 μm Cylindricity - OD <2 μm <2.5 μm - Diameter Raceway - ID 227 mm 364 mm 190 mm Roundness Raceway - ID <1.5 μm <2 μm <1 μm Straightness ID - <0.8 μm <1.5 μm Profile of line - ID <0.5 μm - - Concentricity OD/ID <2 μm <2 μm <1.5 μm * radius dresser several usefully graded sizes and cover the diameter range from 10 to 460 mm. In parallel to the universal shoe grinding fixtures shown, there are also versions for the mass production of part families, which allow quick resetting to a new workpiece using quick-release plates. Electromagnetic Chuck Design e electromagnetic chuck drives the workpiece in the direc- tion of rotation, thus generating the workpiece speed. e chuck also holds the workpiece in its nominal position, as it lies against the front surface of the workpiece. A small relative movement takes place here between chuck (pole booster, pole ring) and workpiece end surface, as the supporting shoes position the workpiece eccentrically. Annular pole or radial pole pitches are selected depending on the workpiece size, with the annular pole pitch tending to be used for small workpieces 80 mm and smaller). Annular pole electromagnets can have different mounting hole patterns, which match a customer's product range. e driving or holding force of the electro- magnetic chuck can be programmed in many different stages. e holding force can thus be temporarily reduced for particularly delicate operations via CNC program commands, enabling stronger clamping afterwards in the same program. e magnetic force can be individually programmed in up to 16 stages on the magnet controller. If :: Fig. 2 - Studer's shoe grinding fixtures are available in six ranges covering diameters from 0.4 to 18.1 inch. several different electromagnetic chucks have to be used, the electrical connection is provided by plug-in contacts directly behind the chuck. Grinding Head Configurations e top priority is to finish-grind a roller bearing ring exter- nally and internally: perfect concentricity externally/ internally; same manufacturing temperature, so more dimen- sionally stable; reduction of quantity of "work in progress" (working capital) and so on. e grinding head should there- fore be equipped with the grinding tools required for the complete process: external grinding wheel(s), internal grinding wheel(s) and a measuring probe. And naturally on an infinitely variable, high-preci- sion B-axis with a swivel angle repetition accuracy of less than 1 inch is available for Studer S41. Achievable Accuracies e chart (Figure 3) provides information on what can be achieved with a shoe grinding fixture on a Studer cylindrical grinding machine. ese values have been confirmed in various customer projects and internal trials, but the blanks on the system side (frontal surface left) must be perfectly flat. Shoe grinding allows for high volume, accurate grinding of difficult to hold, thin-walled workpieces. Eliminating the stresses of conven- tional clamping methods makes this process an ideal solution for such applications. For more information from United Grinding (Studer) North America, call 937-859-1975 or visit grinding.com. TECH BRIEF productionmachining.com :: 29