Method and device for grinding large crankshafts

A grinding machine for completely machining large crankshafts of truck engines, ship engines or stationary engines, comprising a machine bed, which has the following arranged on said machine bed:

• a) a first work headstock and a second work headstock which are each arranged on a grinding table and have respective CNC-controlled first and second rotary drives (C1 and C2), wherein the crankshaft to be ground is clamped between the work headstocks and the first and second rotary drives drive the crankshaft in a rotatory manner at two ends synchronously with respect to each other;
• b) a first grinding headstock with at least one first cubic boron nitride grinding wheel with CNC-controlled drives of a first axis (X1) bringing about an infeed of the first grinding wheel perpendicularly to a longitudinal axis of a main bearing or crank pin bearing and a second axis (Z1) bringing about a movement of the first grinding wheel parallel to said longitudinal axis of the main bearing or crank pin bearing, for rough-grinding and finish-grinding at least one of the main bearings and crank pin bearings of the crankshaft, wherein the first grinding wheel has a further CNC-controlled drive for a first pivot axis (WK1) constituting a pivot axis of the first grinding wheel, said first pivot axis running through the grinding wheel and an engagement point of the grinding wheel with a longitudinal axis of the crankshaft, and the first axis, second axis and first pivot axis are controllable dependently on one another in such a manner that a desired lateral surface contour of the at least one of the main bearings and crank pin bearings can be achieved;
• c) steady rests which are arranged on respective bearings and are movable up to a respective crankshaft main bearing in a manner contacting the latter, and in which a steady rest seat has been ground with the first grinding wheel;
• and
• d) a measurement device which is arranged at least on the first grinding headstock and having an additional dedicated CNC-controlled displacement axis drive which runs parallel to the longitudinal axis of the main bearings or the crank pin bearing, the additional dedicated CNC-controlled displacement axis drive being adapted to move the measurement device independently from the movement of the grinding wheel along the second axis and configured to perform a measurement operation during grinding including measuring a first current diameter of at least one bearing of the main bearings or crank pin bearings at a first measurement location, moving the measurement device independently from the grinding wheel and parallel to the longitudinal axis of the at least one bearing via the additional dedicated CNC-controlled displacement axis drive, and measuring at least a second current diameter of the at least one bearing at a second measurement location spaced apart from the first measurement location along an axial length of the at least one bearing, wherein the first and second axes of the first grinding wheel and further the first pivot axis of the first grinding wheel are configured to be controlled based on the first and second current diameters measured in the measurement operation in order to achieve the desired lateral surface contour, including a contour differing from a cylindrical outer contour, in the at least one bearing.

A method for completely grinding large crankshafts of truck engines, ship engines or stationary engines comprising a) rough-grinding and finish-grinding at least main bearings and crank pin bearings of the crankshaft with at least one first cubic boron nitride grinding wheel with CNC-controlled drives of a first axis (X1) and a second axis (Z1), and a further CNC-controlled drive for a first pivot axis (WK1);

• b) at least two end regions of the crankshaft are rough-ground and finish-ground;
• c) all of the rough-grinding and finish-grinding take place in a single setup of the crankshaft;
• d) the main bearings of the crankshaft including steady rest seats are rough-ground;
• e) one steady rest is lined up with each of the ground steady rest seats;
• f) the crankshaft is driven at two clamping ends by means of first and second electric drives (C1 and C2) operating synchronously to each other;
• g) a desired shape of a lateral surface of the crank pin bearings or main bearings is produced by movement of the first grinding wheel with the CNC-controlled axis drives:
• the first axis bringing about an infeed of the first grinding wheel perpendicularly to a longitudinal axis of the main bearings or crank pin bearings,
• the second axis bringing about a movement of the first grinding wheel parallel to the longitudinal axis of the main bearings or crank pin bearings, and
• the first pivot axis constituting a pivot axis of the first grinding wheel, said first pivot axis running through the grinding wheel and an engagement point of the grinding wheel with a longitudinal axis of the crankshaft, wherein the first grinding wheel has a width which is smaller than an axial length of the main bearings or the crank pin bearings of the crankshaft;
• h) pivoting a measurement device onto at least one bearing of the main bearings or crank pin bearings, in a measurement operation performed during grinding, measuring a first current diameter of the at least one bearing at a first measurement location, moving the measurement device independently from the grinding wheel and parallel to the longitudinal axis of the at least one bearing via an additional dedicated CNC-controlled drive, and measuring at least a second current diameter of the at least one bearing at a second measurement location, the first and second measurement locations spaced apart from each other along the axial length of said at least one bearing, wherein the first and second axes of the first grinding wheel and further the first pivot axis of the first grinding wheel are controlled based on the first and second current diameters measured in the measurement operation in order to obtain a desired contour of the lateral surface of said at least one including a cylindrical shape.