Tech Talk
Explain the significance of "Spindle Integrity (Balance & Run-Out)"?
Balance and run-out of the grinding wheel are mechanical properties that must be addressed at the time of each grinding wheel mounting. Regardless of the overall rigidity of the machine, surface finish and grinding performance will not be maximized if the grinding wheel is not running true and is not dynamically balanced. Static balancing will not cut it! Balancing the wheel should always be performed on the wheel spindle using dynamic balancer. The balance can be either portable or permanent. To achieve consistency of balance throughout the life of the wheel, a permanent balancer is paramount. In other words if you are trying to achieve a specific sigma or cpk this is one less concern for understanding and controlling process.
I would always recommend ordering any grinder with a permanent balancer as part of the purchase. This can be an O.E.M. purchase or a third party purchases, Just order it! You can retrofit existing machines with a permanent balancer implanting the unit into existing or fabricated hubs. This will allow for one or two side plane balance, depending on the width of the grinding wheel. Wheel widths of four inches or more should be balanced from both sides using a two plane balancer.
For truing, the wheel should be mounted and trued to within 0.0005 to 0.001 of an inch. Sometimes the O.D. to I.D. tolerance of the wheel will not allow the wheel to be trued to the recommended levels. This will mean more dressing after the truing process is maximized. Truing is accomplished by finding the high spot on the wheel with an indicator. Then using a soft mallet and/or piece of wood (such as a 2x4) tap the wheel at the marked high spot (marking the position with a marker on the body of the wheel just behind the high position on the indicator), until the indicator is at zero. Repeat this process until you can hold the indicator to <0.001 around the periphery of the wheel.
When you have completed the run-out procedure and completed the dressing procedure, the wheel is ready for balancing. With a good bearing and mass the balance should be <0.1 micro metre displacement. The smaller the displacement the more the part will mirror the geometric tolerance capabilities of the grinder and the better the surface finish. Chatter created from imbalance can not be dressed out of the wheel face. The limit of the balance will depend on the balancer but, more important, on the limitations of the spindle bearing.
