There are two basic applications of abrasive belt grinding, namely light grinding and heavy grinding. Light grinding removes very little material and can only play a role in surface premachining or workpiece finishing, such as polishing, deburring, etc. The belt grinding speed is faster when performing light grinding. Weight grinding plays a role in rough and fine machining of the workpiece. Its advantages are high cutting rate, low cutting heat, small deformation of the workpiece, and easy control of flatness and surface roughness.
Contact wheel grinding and free grinding are the two major processes of abrasive belt grinding. The former is suitable for rough grinding, semi-fine grinding and fine grinding, while the latter is also used for semi-fine grinding and fine grinding, but mainly plays a polishing role.
Abrasive belt grinding can improve machining accuracy, and it uses profiling methods and fixed-length machining methods for control. Profiling control uses a master template to appropriately control the feed speed in the tangential direction during grinding within a certain range, so that the workpiece can be ground corresponding to the master template; fixed-length processing is based on changes in the width of the workpiece and the machining allowance, appropriately control the feed speed of the workpiece, control the normal grinding resistance to a certain level, and maintain the grinding residual amount to a certain value (not zero).
The following matters should be paid attention to when grinding abrasive belts:
(1) Grinding depth During belt grinding, due to the elasticity of the contact wheel, the feed depth is different from the actual depth. The ratio is about 3:10.
(2) The initial grinding position of the new abrasive belt. Since the new belt removes more than the old belt, the initial grinding position of the new belt cannot be fixed, but the initial feed needs to be rotated from the left and right ends of the workpiece to avoid taper in the workpiece. Geometric accuracy can be improved by frequently measuring the outer diameter to identify the largest outer circle, where the new belt will initially feed, or by repeatedly grinding there.
(3) In order to improve the surface roughness of the workpiece using non-feed grinding, you can use non-feed grinding back and forth 3 to 4 times at the end of fine grinding, and the effect is very good.
(4) The machining allowance is generally 0.04 to 0.08 mm for abrasive belt grinding. When the surface roughness value before grinding is higher than Ra2.55m, the machining allowance can be slightly larger. The surface roughness value before free polishing is Ra 1.255m-RaO.635m, and the machining allowance is 0.01-0.02mm.
In addition, because the abrasive cutting edge of the new belt is very sharp and has different heights, only part of the cutting edge works, which affects the surface roughness of the workpiece. Therefore, the abrasive belt must be trimmed so that all cutting edges can be processed. There are two ways to trim it:
① Wrap the old belt around the round wooden rod, hold the wooden rod with your hand, and grind the new belt rotating on the contact wheel. At this time, the force should be appropriate;
② In semi-precision grinding during the process, the selected new belt is used for grinding work. After the cutting edge is slightly blunted, it is replaced for final fine grinding.
