Machinery's Handbook, 31st Edition
CYLINDRICAL GRINDING 1319 grinding wheels, even temporarily, at higher than approved speed constitutes a grave safety hazard. Areas and Degrees of Automation in Cylindrical Grinding.— Power drive for the work rotation and for the reciprocating table traverse are fundamental machine move ments that, once set for a certain rate, will function without requiring additional attention. Loading and removing the work, starting and stopping the main movements, and applying infeed by hand wheel are carried out by the operator on cylindrical grinding machines in their basic degree of mechanization. Such equipment is still frequently used in tool room and jobbing-type work. More advanced levels of automation have been developed for cylindrical grinders and are being applied in different degrees, particularly in the following principal respects: a) Infeed, in which different rates are provided for rapid approach, roughing and finish ing, followed by a spark-out period, with presetting of the advance rates, the cutoff points, and the duration of time-related functions. b) Automatic cycling actuated by a single lever to start work rotation, table reciprocation, grinding-fluid supply, and infeed, followed at the end of the operation by wheel slide retraction, the successive stopping of the table movement, the work rotation, and the fluid supply. c) Table traverse dwells (tarry) in the extreme positions of the travel, over preset periods, to assure uniform exposure to the wheel contact of the entire work section. d) Mechanized work loading, clamping, and, after termination of the operation, unload ing, combined with appropriate work-feeding devices such as indexing-type drums. e) Size control by in-process or post-process measurements. Signals originated by the gage will control the advance movement or cause automatic compensation of size varia tions by adjusting the cutoff points of the infeed. f) Automatic wheel dressing at preset frequency, combined with appropriate compensa tion in the infeed movement. g) Numerical control obviates the time-consuming setups for repetitive work performed on small- or medium-size lots. As an application example: shafts with several sections of different lengths and diameters can be ground automatically in a single operation, grinding the sections in consecutive order to close dimensional limits, controlled by an in-process gage, which is also automatically set by means of the program. The choice of the grinding machine functions to be automated and the extent of automa tion will generally be guided by economic considerations, after a thorough review of the available standard and optional equipment. Numerical control of partial or complete cycles is being applied to modern cylindrical and other grinding machines. Cylindrical Grinding Troubles and Their Correction.— Troubles that may be encoun tered in cylindrical grinding may be classified as work defects (chatter, checking, burning, scratching, and inaccuracies), improperly operating machines (jumpy infeed or traverse), and wheel defects (too hard or soft action, loading, glazing, and breakage). The Landis Tool Company has listed some of these troubles, their causes, and corrections as follows: Chatter: Sources of chatter include: 1) faulty coolant; 2) wheel out of balance; 3) wheel out of round; 4) wheel too hard; 5) improper dressing; 6) faulty work support or rotation; 7) improper operation; 8) faulty traverse; 9) work vibration; 10) outside vibration trans mitted to machine; 11) interference; 12) wheel base; and 13) headstock. Suggested procedures for correction of these troubles are: 1) Faulty coolant: Clean tanks and lines. Replace dirty or heavy coolant with correct mixture. 2) Wheel out of balance: Rebalance on mounting before and after dressing. Run wheel without coolant to remove excess water. Store a removed wheel on its side to keep retained water from causing a false heavy side. Tighten wheel mounting flanges. Make sure wheel center fits spindle.
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