Introduction
Metal cutting machine tools are widely used in modern mechanical parts processing and manufacturing. In order to improve the cutting efficiency and reduce the cost, the quality of the machined surface and the accuracy of the parts are strictly requirements. Surface scratches and scratches are an important indicator of the machining accuracy of the workpiece, which reflects the quality of the machining. Therefore, it is necessary to analyze the cause of the scratch, and come up with the corresponding prevention and control measures.
1 Causes of Abnormal Scratch
Scratches are the most common defect in the machining of metal cutting machines. It can be divided into two categories: one is due to the working wear of the cutting edge caused by the long-term cutting; the other is the surface scratch due to the poor machining process.
1.1 Cutting Tool wear
The wear of the cutting edge of the cutting tool is the main factor of the surface scratch on the workpiece. As the cutting tool wear increases, the rake angle and clearance angle of the blade will change, which will reduce the cutting fluid film on the blade surface, increase the cutting temperature, and cause wear on the rake angle and clearance angle at the edge of the cutting tool, resulting in reduced cutting ability and scratch on the workpiece.
1.2 Abnormal Conditions in Machining
The normal state of the workpiece surface cannot meet the requirements of no scratches. The scratch also occurs due to the abnormal conditions of the cutting process. Low cutter margin, inappropriate cutting parameters, unreasonable cutting tool materials and sharpening method, processing of brittle materials, small designed cutting radius and corner cutting, poor lubrication and cooling performance of the cutting fluid, the material of the cutting tool itself is too hard, etc., it is easy to cause the workpiece surface to produce scratches.
2 Exclusion measures
In order to make the machining process of metal cutting machine tools smoothly and without scratches, the following countermeasures are proposed.
2.1 Optimize the Choice of Tool Materials and the Optimization of Cutting Parameters
The type and quality of the cutting tool and the cutting parameters have a great influence on the machining process and the machined surface quality. The cutting tool material should be chosen from the overall performance of the processed material, the cutting environment, the cutting precision and the cost, so as to ensure the durability, economy and efficiency of the cutting tool. The cutting speed, feed, depth of cut, and cutting angle should also be determined according to the cutting performance, the specific material of the workpiece, and the cutting parameters used for clay machining or with similar processing materials.
2.2 Reasonable Tool Sharpening and Selection
The selection and sharpening of the cutting tool is also an important factor in the machining of metal cutting machine tools. For the sharpening of the general cutting tools of good wear resistance, the choice of grinding wheel should be made according to the grinding wheel characteristics and tool characteristics, so as to reduce the grinding distortion and keep the blade sharpness and cutting performance unchanged as much as possible.
2.3 Proper Cutting Fluid Selection
The selection of cutting fluid is an important factor in the processing quality of metal cutting machine tools, and it has important influence on the machining surface state and accuracy. In general, the selection of cutting fluid should be based on the characteristics of the workpiece material and the cutting process, including viscosity index, cooling performance, lubrication performance, environment-friendly performance, etc., so as to reduce the cutting temperature, improve the chip removal performance and protect the tool, and ensure the machining accuracy and surface quality.
3 Summary
In summary, the main cause of scratching on the surface of metal cutting machine tools is the wear of the cutting edge and the abnormal condition in the machining process. The corresponding preventive measures include the optimization of cutting tool materials, the optimization of cutting parameters, the reasonable selection and sharpening of cutting tools, and the proper selection of cutting fluids. Through the combination of all factors, the production efficiency and quality of metal cutting can be improved, and the different requirements of different machining can be achieved.
