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Tuesday, 26 November 2013

Grinding Problems

Grinding Problems Points : Grinding Problems, Irregular table movement or non table movement, Irregular scratches, Waviness on the work surface, Chatter or vibration marks, Burning or checking of the work surface, Wheel glazing or loading, Deep irregular marks, Work not flat, Work that is not parallel There are many problems peculiar to precision' surface grinding. A few of the more common problems, with suggestions for solution, are as follows: 1. Irregular table movement or non table movement (Hydraulic type machines) It may be caused by' clogged hydraulic lines" insufficient hydraulic fluid hydraulic pump not functioning properly or inadequate table lubrication. A cold hydraulic system may also cause these symptoms. Let the machine warm up for at least fifteen minutes before use. Air in the hydraulic lines can cause erratic table movement. 2. Irregular scratches It is caused by a dirty coolant system, or by particles becoming loosened in the wheel guard. This could also mean that the grinding wheel is too soft, and the abrasive particles .are carried to the wheel by the 'coolant system.' 3. Waviness on the work surface It can be caused by a wheel being out of round and can be corrected by truing the wheel. 4. Chatter or vibration marks It may he caused by a glazed or loaded grinding wheel. There is a slipping action between the wheel and the work surface the wheel cuts until the glazed, section comes into position and slides, rather than cuts, over the work. Correct by redressing the grinding wheel. The same effect can also be caused by a grinding machine that is not mounted solidly or by a wheel that is loose on the spindle. Check for these conditions and make corrections if necessary. 5. Burning or checking of the work surface This may be caused by insufficient cooling reaching the work surface a wheel that is too hard, or a wheel with grain that is too fine. Make corrections 'as indicated by inspection. 6. Wheel glazing or loading Often indicates that the-wrong coolant is being used. A dull diamond on the wheel dresser can also cause this condition. 7. Deep irregular marks These marks on the work surface may be caused by loose grinding wheel. 8. Work not flat 2It may be caused by insufficient coolant, a nicked or dirty chuck surface or a wheel that is too hard. Check and make necessary corrections. 9. Work that is not parallel This is frequently caused by a chuck that has not been "ground in" the last time it 'was mounted on the machine. A nicked or dirty chuck can also cause the same condition. Insufficient coolant may allow the work to expand in the center of the cut permitting more material to be removed in the center than at each end. As the piece cools, the center is depressed. Correct by directing more fluid to the cutting surface.

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