Grinding Journal - Fall 2007 - (Page 27)

and one of the key features of the Mägerle is its ability to easily move the roll to grind the crown in the right place. The roll journals ride on bearings in the Mägerle in exactly the same way they would in a corrugating machine, plus the indexer is height adjustable to correct any skew. The roll is also low and easily accessible in the Mägerle, greatly facilitating setup. Leaving that door closed also contributes to temperature and process stability. With a part this big a small fluctuation in temperature would have a significant impact on size. Two chillers maintain the coolant temperature to within two degrees of the target. Maintaining the wheel form Continuous dressing is a key factor enabling Doug to grind for hours without interruption. The Mägerle boasts an overhead rotary dresser for use with a fullform wheel, a table mounted rotary dresser for CNC dressing with a standard diamond roll, and a table mounted point dresser. Doug reports that he can dress many different forms on many wheels with one standard 1 mm radius roll. But he sometimes uses rolls with a radius as small as a 0.45 mm which admittedly doesn’t last as long. If the flute geometry from roll to roll is very different (e.g. “A” style versus “B” style), he’ll change wheels rather than dress a completely different form into the wheel. This saves both wheel wear and dressing roll wear. Whatever method he chooses, Doug finds programming the Mägerle to create and maintain the necessary profile to be straightforward. He also gets very good wheel life, losing only 8-9 mm in wheel diameter in a regrinding operation. Of course roll material and coating affects wheel life. Wheel speeds average about 35 meters/second at 900-1100 RPM. A corrugating machine feeds paper between fluted rolls to create the folds. Optimum flute profiles vary based on speed, material, and other factors. (Operating speeds can reach 1,200 feet per minute.) The end product is used in packaging, displays, and even book covers. Mägerle power contributes to fast turnaround With a 100 HP (75 kW) grinding head and wrap-around hydrostatic ways to dampen any vibrations, the Mägerle MGC grinds even the biggest rolls in a day – which is considerably faster than Tiruna’s previous approach. For example, Doug might run a triple flute C-profile wheel at 31 inches/minute at full depth of cut (0.15 inches) into solid core. But he doesn’t rush. Once the machine is up and running and Doug has confirmed how many passes he’ll make before dressing, “we close the door and leave it running, and that could be as much as sixteen hours, all by itself just running. The longer it runs the better the product at the end. If you push it you might get a little TIR or a little jump at the end. You can’t rush grinding.” Or as his colleague, Sales Manager Chris Charette puts it: “Doug is…I’ll say it nicely a perfectionist.” They look more similar than they really are. Besides variation in size, there are subtle differences in flute profile, material, coating, and the linear profile. Grinding Journal 27

Table of Contents Feed for the Digital Edition of Grinding Journal - Fall 2007

Grinding Journal - Fall 2007 Contents From Virginia: Apparently no credit crunch for machine tools Why measure cutting tools Other perspectives on CNC tool measuring Productive grinding of superalloys SUPER service grinding BIG rolls Problem Solver

Grinding Journal - Fall 2007

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