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How to improve the surface finish of cnc processing?

Mar 22, 2021

Cause Analysis


1.1 The workpiece is not cleaned and there is no anti-oxidation measures. During the machining process, the parts inevitably come into contact with the coolant, air, and water. Affected by these factors, the surface of the workpiece has white oxidized patches. We use orthogonal experiments to analyze the cooling The influence of three factors of liquid, water and air on the generation of white oxidized plaques is defined as presence and absence respectively. Put the original coolant and water droplets on the surface of the workpiece, and isolate the air by smearing petroleum jelly. The test time is 13 days (the processing cycle of the external dimensions of the part is about 13 days). The results showed that surface oxidation and corrosion occurred under the action of the original coolant and air, which caused the parts to fail to meet the surface treatment requirements. Therefore, uncleaned workpieces and no anti-oxidation measures are one of the reasons for the low qualification rate of parts manufacturing.

1.2 Lack of tooling equipment In order to verify the team’s inference, we trial-produced and processed 3 other products with special polishing equipment during the test, and respectively calculated the scrap rate. Comparing the scrap rate of the test product with the scrap rate of this part, it is found that the scrap rate is nearly 8 times different. Therefore, the lack of polishing equipment is another reason for the high rejection rate of products.

2 improvement measures

The traditional polishing method is to install the workpiece on a rotating equipment, and hold the sandpaper to press the outer circle of the part to polish. The traditional polishing method has the advantages of simple operation and good economy. It is widely used in the machining industry. Its shortcomings are obvious, such as: the polishing force is not constant, the feed is not continuous, and the polishing efficiency of parts is low. We look for tooling design ideas from traditional polishing methods and retain the advantages. The main points of polishing were refined, including: polishing contact surface (hand-held sandpaper), polishing force (generated by arm pressing), feed rate (palm movement), using mechanical structure to achieve the above points, and successfully designed a set of general polishing tooling. After using this tooling, the parts can achieve uniform force during polishing. This tooling can be installed on the tool holder of the polishing equipment, combining the original functions of the equipment to achieve uniform feed. At the same time, in order to avoid the polishing equipment from grinding parts, a softer, tougher, and high-temperature resistant polytetrafluoroethylene material is selected as the material of the polishing head. For polishing sandpaper, we have selected a certain type of polishing sandpaper with softer texture and adhesive backing. 

3 concluding remarks

By optimizing the polishing method of the parts, the machining pass rate of the parts is improved. The design of general polishing tooling is a highlight of this project. This tooling effectively solves the problems of traditional polishing methods such as inconstant polishing force, discontinuous feed, and low polishing efficiency. It provides a basis and reference for processing other precision shaft parts in the future. experience.

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