During the brass parts processing, surface quality control is the key link to ensure the performance and appearance of parts, involving comprehensive management from raw material selection to processing technology, equipment parameters, tool status and other aspects. The characteristics of the brass material itself (such as zinc content, impurity composition) and factors such as force, temperature, lubrication during processing will directly or indirectly affect the roughness, flatness, glossiness and integrity of the surface of the parts. Therefore, targeted measures need to be taken at each link to achieve precise control of the surface quality.
The selection and pretreatment of raw materials are the basis for controlling surface quality. Different grades of brass (such as H62, H68, H90, etc.) have completely different surface performances after processing due to differences in chemical composition and mechanical properties. Brass with a higher zinc content has better plasticity, but it is easy to produce knife sticking during cutting, resulting in increased surface roughness; while brass with a lower zinc content has a higher hardness, and may cause surface scratches due to large cutting forces during processing. Therefore, it is necessary to reasonably select the brass grade according to the use requirements and processing technology of the parts. At the same time, the surface state of the raw materials cannot be ignored. If there are scales, scratches or uneven defects on the surface of the plate or bar, it should be pre-treated by grinding, pickling and other methods before processing to remove surface impurities and defective layers, providing a good foundation for subsequent processing.
Cutting processing is the core link that affects the surface quality of brass parts, and the selection and use of tools are crucial. The material, geometric parameters and wear state of the tool directly determine the cutting force, cutting heat and chip discharge during the cutting process. High-speed steel tools have good toughness but poor wear resistance, which is suitable for low-speed cutting or occasions with low surface quality requirements; carbide tools have high hardness and good wear resistance, and are more suitable for high-speed cutting to obtain a smooth surface. The geometric parameters of the tool, such as the rake angle, back angle and main deflection angle, need to be optimized according to the hardness and plasticity of brass. A larger rake angle can reduce the cutting force and cutting heat, and reduce surface deformation; a suitable back angle can reduce the friction between the back face of the tool and the processed surface, and avoid scratches. In addition, when the tool is worn to a certain extent, the cutting edge becomes blunt, which will increase the cutting force and cause a significant increase in surface roughness. Therefore, it is necessary to regularly check the tool wear and replace or re-grind the tool in time to ensure that the cutting edge always remains sharp.
Reasonable setting of processing parameters is a key factor in controlling surface quality. The matching relationship between cutting speed, feed rate and cutting depth directly affects the stability and surface quality of the cutting process. When cutting brass, if the cutting speed is too high, the brass will be softened locally due to the sharp increase in cutting heat, resulting in sticking and built-up edge, making the surface rough; if the cutting speed is too low, the surface may be uneven due to large fluctuations in cutting force. When the feed rate is too large, the cutting marks left on the workpiece surface by the tool deepen with each rotation, and the surface roughness value increases; if the feed rate is too small, the tool may perform multiple "ploughing" actions without substantial cutting on the processed surface, which may damage the surface quality. The selection of cutting depth should take into account both processing efficiency and surface quality. A larger cutting depth is suitable for rough processing, while a smaller cutting depth should be used for finishing to remove the traces left by rough processing and obtain a delicate surface.
The influence of lubrication and cooling on surface quality in brass parts processing cannot be ignored. Suitable cutting fluid can effectively reduce cutting temperature, reduce friction between tool and workpiece, and help discharge chips, thereby improving surface quality. For brass processing, cutting fluids containing oily additives, such as emulsions or cutting oils, are usually selected to enhance lubrication and prevent sticking and built-up edge. In scenarios where a large amount of cutting heat is easily generated, such as high-speed cutting or deep hole processing, it is necessary to ensure that the cutting fluid is sufficient and the spray direction is accurate, so that the cutting fluid can directly act on the cutting area, take away heat in time and flush away chips, and avoid chips scratching or ironing the processed surface. At the same time, the cleanliness of the cutting fluid is also very important. If impurities or metal debris are mixed in the cutting fluid, it may contact the workpiece surface again with the flow during the processing process, causing secondary scratches.
The accuracy and stability of processing equipment are important prerequisites for ensuring surface quality. The spindle accuracy, guide rail straightness, and transmission accuracy of the feed system of the machine tool will be directly reflected on the machining surface of the part. Insufficient spindle rotation accuracy will cause roundness error or ripples on the machining surface; if the guide rail is not straight or there is a gap in the feed system, the tool will vibrate or crawl during the feeding process, causing the surface roughness to deteriorate. Therefore, it is necessary to regularly maintain and calibrate the processing equipment to ensure that the accuracy of key components such as the spindle, guide rail, and lead screw meets the requirements. During the processing process, attention should also be paid to the vibration control of the equipment to avoid relative displacement between the tool and the workpiece due to external vibration or the vibration of the equipment itself, which affects the surface quality. For the processing of precision brass parts, high-precision CNC machine tools or special processing equipment can be selected to achieve precise control of the processing process through advanced servo systems and stable mechanical structures.
The clamping method of the parts will also affect the surface quality. Unreasonable clamping methods may cause deformation of brass parts during processing, or surface indentations due to excessive clamping force, or vibration due to loose clamping. When clamping brass parts, appropriate clamps should be selected according to the shape and size of the parts, such as flat-nose pliers, three-jaw chucks, special tooling, etc., and the clamping force should be reasonably controlled. For thin-walled or easily deformed brass parts, elastic clamps or auxiliary supports can be used to reduce clamping deformation. At the same time, the clamping surface should be clean and flat to avoid debris or burrs affecting the positioning accuracy and clamping reliability of the parts. During the processing, it is also necessary to pay attention to the clamping status of the parts. If signs of looseness or deformation are found, the machine should be stopped and adjusted in time to ensure the stability of the processing process.
Surface treatment after processing is the last step to improve the surface quality of brass parts. According to the use requirements of the parts, different surface treatment methods can be selected, such as grinding, polishing, electroplating, chemical plating, passivation, etc. Grinding and polishing can further reduce the surface roughness, improve the surface gloss, and make the surface of the parts smoother and more delicate; electroplating and chemical plating can form a layer of metal or alloy plating on the surface of the parts to enhance corrosion resistance and aesthetics; passivation treatment can form a dense oxide film on the surface of brass to prevent surface oxidation and discoloration and maintain good appearance quality. Before surface treatment, it is necessary to ensure that the surface of the parts is clean, free of oil, chips and processing marks, otherwise it will affect the treatment effect. During the surface treatment process, it is also necessary to strictly control the process parameters, such as grinding pressure, polishing time, coating thickness, etc., to obtain uniform and consistent surface quality.
Surface quality control in the process of brass parts processing is a systematic project, which requires refined management of various links from raw materials, tools, processing parameters, equipment, clamping, lubrication and cooling to surface treatment. By reasonably selecting materials and processes, optimizing tools and parameters, ensuring equipment accuracy and stability, adopting appropriate clamping and cooling methods and appropriate surface treatment, the surface quality of brass parts can be effectively improved, so that they can meet functional requirements and have good appearance quality, laying a solid foundation for the wide application of brass parts in machinery, electronics, decoration and other fields.
