External grinding method:
First, the longitudinal grinding method.
Longitudinal grinding method is the most commonly used grinding method. During grinding, the table is reciprocated longitudinally and the grinding wheel is periodically reciprocated. The grinding allowance of the workpiece is ground in multiple reciprocating strokes.
Features of longitudinal grinding method (abbreviated as longitudinal method):
①. The working conditions of the abrasive grains are different on the whole width of the grinding wheel. The sharp corner of the left end face (or right end face) of the grinding wheel bears the main cutting effect. Most of the abrasive grains on the width of the grinding wheel are responsible for reducing the surface roughness value of the workpiece.
②. The longitudinal grinding method has small grinding force and good heat dissipation conditions, and can obtain higher processing accuracy and smaller surface roughness value.
③. Low labor productivity.
④. Grinding force is small, suitable for grinding slender, precision or thin-walled workpieces.
2. Cut-in grinding method.
Cut-in grinding method is also called lateral grinding method. The length of the outer circle of the workpiece to be ground should be less than the width of the grinding wheel. During grinding, the grinding wheel makes continuous or intermittent lateral feed movements until the entire balance is removed.
There is no longitudinal feed movement during grinding. A higher cutting speed can be used for rough grinding, and a lower cutting speed for fine grinding to prevent burns and heat deformation of the workpiece.
Features of the plunge-cut grinding method (referred to as plunge-cut method):
①. The working conditions of the abrasive grains are the same across the width of the grinding wheel, giving full play to the grinding effect of all abrasive grains. At the same time, because of the continuous lateral feed, the basic time of grinding is shortened, so it has high production efficiency.
②. The radial grinding force is large, and the workpiece is prone to bending deformation, which is generally not suitable for grinding thin workpieces.
③. A large amount of grinding heat is generated during grinding, and the workpiece is prone to burn and heat deformation.
④. The surface shape (dressing marks) of the grinding wheel will be copied to the workpiece surface, which will affect the surface roughness of the workpiece. In order to eliminate the above defects, a small longitudinal movement can be made at the end of the cutting method.
⑤. The cut-in method is only suitable for grinding the outer surface with a shorter length due to the limitation of the width of the grinding wheel.
