subject: Perspective About Multitasking Grinder [print this page] Accepting this seeming inefficiency within the machining cycle, for the sake of a more efficient process overall, is part of the recipe for implementing these machines effectively.
Different manufacturing organizations view their costs differently, and the need for this process-wide outlook is part of why identifying the right applications for these machines is not necessarily cut and dried.
A traditional manufacturing mindset looks at a part's features and tolerances to see the particular machine tools best suited to produce all of that geometry. This part-centered perspective may optimize machining time and machining cost, but it may do so at the expense of less easily quantifiable costs related to handling the part.
Mr. Stine says a different mindset focuses on a particular unit cost. The part has to be produced to meet a certain price, after all of the costs both on and off the machine tool have been factored in. In this view, the efficiency with which each feature is machined is less significant as long as the overall process is as efficient as it can be. This latter view, he says, is the one that is more likely to realize the of consolidating the work of various diverse machine tools into one.
Turning On A Grinding Machine
"Hard turning" usually refers to the turning of workpieces that have Rockwell C hardness in the range of 50 or 60. It typically involves a rigid lathe and a hard cutting tool material such as PCBN. The S242 machine from Studer (represented by United Grinding Technologies) is the latest machine from this company able to perform OD grinding and hard turning within a single cycle.
John Richard, senior sales manager for Studer, explains why the two processes are complementary. If the tolerance is tight enough, he says, then turning will not do. A turning insert's dimensions slowly change while the insert cuts, affecting machining accuracy and finish. A grinding wheel is continually reconditioned while it machines, but this is not the case with a turning insert.
On the other hand, the turning insert can deliver a performance advantage that a grinding wheel can't. If heat treating introduces variations in the geometry of a rotating part, then a grinding wheel is going to begin by finding the high spot of the workpiece every time. The grinding cycle will vary. By contrast, a turning insert can withstand a slightly varying depth of cut for the sake of beginning the machining at the same diameter every time, to make the machining time consistent from piece to piece.
