Discussion and Analysis of Repair Technology for Defects on Lathe Guide Surface
The surface of the guide rail of the lathe is a very important structural surface for the machine tool. It relates to the accuracy and life of the machine tool. Generally, the precision of the machine tool guide rail surface depends on the surface roughness, straightness and parallelism of the guide rail. Therefore, when the surface of the guide rail is damaged, it should be repaired in time to ensure accurate mechanical performance.
Repair technology of the guide rail surface of the lathe is divided into hot repair and cold repair according to different conditions. Generally, hot repairing technology is mainly used in the case of light wear, conversion of wear and fatigue (lapping, grinding or cutting). The cold repairing technology is mainly used for local repairs in cases of burn-in, pitting, broken teeth, scratch, notch and other forms, such as soldering, welding, high-frequency surfacing, HVOF thermal spraying, laser cladding and precision machining.
The hot repairing technology of the lathe guide rail surface mainly includes lapping, grinding, cutting and other processing methods. Among them, lapping is the most widely used. The advantage of the lapping is that compared with the grinding, the lapping processes the entire surface and does not leave the stress concentration under the guide rail. In addition, its processing efficiency is much faster than grinding and cutting. The disadvantage is that its surface quality depends on the quality of the material, the surface of the iron-based guide rail will produce huge peak errors due to the uneven hardness of crystalline structure, while the surface accuracy of the non iron-based guide rail will be affected by the hardness and wear resistance of the alloy materials.
Grinding can be used to remove large craters and other large defects, but due to the great stress concentration on the side of the guide rail, special attention should be paid to the improvement of the guide rail surface roughness and thermal damage level. When cutting is used, a suitable tool material must be selected according to the actual guide rail surface material, and the cutting speed, depth and number of passes should be appropriately selected. In order to prevent thermal deformation during the repair process and ensure the accuracy of the guide rail surface, cooling should be added by necessary means such as water spray.
The technological process of cold repair for the lathe guide rail surface mainly contains soldering, welding, high-frequency surfacing, HVOF thermal spraying, laser cladding and precision machining.
The welding of the guide rail surface mainly adopts manual arc welding or oxyacetylene welding. The advantage of these methods is that they are simple, common and easy to operate. However, owing to the large heat input, large deformation will be generated in the welding process, resulting in the decrease of the accuracy of the guide rail surface. In addition, residual stress and inaccurate machining size of the guide rail surface may cause radial vibration of the guide rail surface during the machining process.
High-frequency surfacing technology is also a welding process, which makes up for some of the shortcomings of traditional welding technology by using high-frequency power supply to supply welding current. Due to the advantage of small heat input, the deformation of the guide rail surface caused by this process is relatively small. However, the application of this technology is limited due to the expensive cost and permeability of the welding wire.
HVOF thermal spraying is a kind of thermal spray technology. By using the energy generated by the combustion of mixture gas and powder, the pores in the sprayed layer can be reduced and the adhesion of the sprayed layer can be enhanced. Compared with traditional thermal spraying, HVOF thermal spraying has higher coating adhesion and less deformation. The primary limitation of this technology is the high cost of equipment and powder material.
Laser cladding is a kind of cooling powder welding technology. Its advantage is that the welding speed is fast and the deformation is small. Its disadvantage is that the depth of the weld is shallow, The welding defects may be generated.
Precision machining is an important method for the lathe guide rail surface processing. Compared with other repair methods, the advantage of precision machining is that it can process and restore the surface integrity of the guide rail, and that it is also suitable for more complicated shapes of guide rail. However, the complexity of the machining process and the difficulty of machining accuracy control in a short time limit its application in practice.
In summary, understand the performance and features of the guide rail surface of the lathe, according to the specific conditions of the damage, select the suitable hot repairing technology or cold repairing technology and process in the right way in order to repair the large, small and various defects of the guide rail surface. Make sure that these defects are completely removed, and the guide rail is re-polished and grinded to ensure its surface accuracy, in order to further guarantee its machining performance, such as the accuracy and life of the machine tool.
