Under certain pressure, abrasive particles coated or pressed on the machined surface are finished by the relative motion of the tool and the workpiece. Grinding can be used to process all kinds of metal and non-metal materials, surface shape for plane, inside and outside cylindrical surface, conical surface, convex and concave ball, thread, tooth surface, etc. The machining accuracy can be up to IT5~01, the highest up to R0.63≤0.01 micron.
Lapping methods can be divided into wet lapping, dry lapping and semi-dry lapping.
(1) Wet grinding: also known as abrasive grinding, continuous injection or coating of liquid grinding agent on the grinding surface, the formation of abrasive slider and roller between the workpiece and the tool, the formation of cutting motion.
(2) Wet grinding is generally used for coarse grinding, and the particle size of fine abrasive is greater than W7.
(3) Dry grinding: also known as sanding grinding, abrasive evenly embedded in the surface of the tool, only a small amount of stearic acid mixed grease and other auxiliary materials applied to the tool surface. In the fine grinding process, the dry method is often used to study the particle size of fine powder abrasive is less than that of W7 abrasive.
(4) semi-dry grinding: similar to wet grinding, the grinding agent used is paste grinding paste. Grinding can be done by hand or on a grinder. Before grinding, the workpiece must be processed by other processing methods in order to obtain higher pre-machining accuracy, and the grinding allowance is generally 5≤30 microns.
Research tool is used for workpiece grinding and forming tools, is also the carrier of grinding agent. Hardness should be lower than that of the workpiece and have some wear resistance, which is usually made of gray cast iron. The metallographic structure of wet grinding tools is mainly ferrite, while that of dry grinding tools is mainly uniform fine pearlite. Mild steel tools are usually used when grinding threads below M5 and small pieces with complex shapes.
They mostly use brass and copper lashing tools when grinding small holes and soft metal materials. The working surface of the research tool should have sufficient stiffness and high geometric accuracy. The tool is also cut and worn during grinding. If done properly, its accuracy can also be increased so that the workpiece can be machined with a higher precision than the tool's original accuracy.
It is an important condition to improve grinding quality to deal with grinding motion path correctly. In surface grinding, the general requirements are:
(1) The workpiece's motion relative to the tool should be as close as possible to ensure the grinding length of each point on the workpiece;
(2) The motion trajectory of the workpiece is evenly distributed on the whole surface of the tool, so as to facilitate uniform wear of the tool;
(3) the curvature change of the motion trajectory should be small to ensure the smooth motion of the workpiece;
(4) The motion path of the workpiece at any point should be avoided as far as possible to avoid premature periodic repetition. In order to reduce cutting heat, grinding is usually done at low pressure and low speed. The pressure of rough study is not more than 0.3MPa, and the pressure of intensive study is 0.03~ 0.05MPa. The rough study speed is generally 20×120 m/min, and the intensive study speed is generally 10×30m/min.
Matching research methods are usually compatible with each other. Before matching, the two pieces need to be ground one piece at a time, and then the grinding agent is added between the surfaces of the two pieces. These two artifacts are each other's tools. Through matching research, the micro peaks that hinder accurate coordination are eliminated and the matching surfaces are made to coincide with each other.