The abrasive tools (or abrasives) used for grinding have the characteristics of small particles, high hardness and good heat resistance, so they can process hard metal materials and non-metal materials, such as hardened steel, cemented carbide props, ceramics, etc; In the machining process, there are many particles participating in the cutting movement at the same time, which can remove extremely thin and fine chips, so the machining accuracy is high and the surface roughness value is small. As a finishing method, grinding is widely used in production. At present, due to the development of strong grinding, the blank can also be directly ground to the required size and accuracy, thus obtaining a higher productivity.
1、 Common methods of cylindrical surface grinding
(1) Longitudinal grinding method
The high-speed rotation of the grinding wheel plays a cutting role, and the workpiece rotates to make a circular feed motion, and makes a longitudinal reciprocating linear feed motion together with the workbench. Each time the workbench reciprocates, the grinding wheel completes a transverse feed along the grinding depth direction. Each feed (cutting depth) is very small, and all grinding allowance is completed in multiple reciprocating strokes. When the workpiece is grinded close to the final size (with a margin of 0.005-0.01mm), it shall be polished several times without transverse feed until the spark disappears. The longitudinal grinding method has high machining accuracy and surface quality and strong adaptability. The same grinding wheel can be used to grind workpieces with different diameters and lengths, but the productivity is low. It is widely used in single piece, small batch production and fine grinding, especially for grinding workpieces with poor rigidity such as slender shafts.
(2) Horizontal grinding method (cutting method)
The workpiece will not make longitudinal reciprocating motion, and the grinding wheel will make transverse feed motion to the workpiece continuously or intermittently at a slow speed until all the allowance is removed. During horizontal grinding, the contact area between the workpiece and the grinding wheel is large, the grinding force is large, and the calorific value is large and concentrated, so workpiece deformation, knife burning and annealing are easy to occur. The horizontal grinding method has high production efficiency and is suitable for batch or mass production. It is suitable for grinding cylindrical surfaces with short length, good rigidity and low precision and shaft diameters with shoulders on both sides. If the grinding wheel is trimmed to shape, the formed surface can also be ground directly.
(3) Comprehensive grinding method
First, use the horizontal grinding method to rough grind the workpiece in sections, with 5-15mm overlap between adjacent sections, and leave 0.01-0.03mm fine grinding allowance on each section. During fine grinding, use the longitudinal grinding method. This grinding method combines the advantages of longitudinal grinding and transverse grinding, and is suitable for workpiece with large grinding allowance (allowance 0.7-0.6mm).
(4) Deep grinding method
When grinding, use a small longitudinal feed (1-2mm/r) and a large cutting depth (0.2-0.6mm) to grind all the allowance in one cutting. In order to avoid concentrated cutting load and rapid blunt grinding of the outer edges and corners of the grinding wheel, the grinding wheel should be trimmed into a cone or step shape. The steps with small outer diameter play the role of rough grinding, which can be roughened; Those with large outer diameter play the role of fine grinding, and they should be trimmed. The deep grinding method can obtain high precision and productivity, and the surface roughness value is small. It is suitable for processing rigid stub shafts in mass production.
