What are the details to pay attention to during the polishing process of CNC machining?

Preparation before polishing

Workpiece inspection: Before polishing, carefully inspect the surface condition of the workpiece after CNC machining in Dongguan. Check for obvious machining marks, knife marks, burrs, or dimensional deviations. For existing defects, appropriate repairs or adjustments need to be made first to ensure that the workpiece basically meets the expected shape and size requirements, as serious defects may affect the polishing effect.

Choose appropriate polishing tools and materials: Select polishing tools based on the material (such as metal, plastic, etc.), shape, and size of the workpiece. Common polishing tools include polishing wheels, polishing pads, grinding rods, etc. For example, for metal workpieces with complex surfaces, it may be necessary to use soft wool polishing wheels; For flat plastic workpieces, polyurethane polishing pads may be a good choice. At the same time, matching polishing materials such as polishing paste, abrasives, etc. should be selected, and their particle size and composition should be determined according to the required polishing accuracy.

Cleaning the surface of the workpiece: Ensure that the surface of the workpiece is clean and free of impurities such as oil stains, iron filings, dust, etc. Special cleaning agents or solvents can be used for cleaning, and then dried with clean compressed air or wiped clean with a clean cloth. Because impurities may scratch the surface of the workpiece or cause the polishing material to fail during the polishing process.

Polishing process parameter control

Speed control: The speed of polishing equipment (such as polishing machines) has a significant impact on the polishing effect. Generally speaking, excessive rotational speed may cause the surface temperature of the workpiece to be too high, resulting in thermal deformation, especially for thin-walled or high-precision workpieces. If the speed is too low, it will affect the polishing efficiency. The optimal speed for different workpiece materials and polishing tools varies. For example, when using a wool polishing wheel for metal workpieces, the speed may be controlled between 1500-2500 revolutions per minute, but the specific value needs to be adjusted according to the actual situation.

Polishing pressure control: During the polishing process, it is necessary to reasonably control the pressure between the polishing tool and the surface of the workpiece. Excessive pressure may cause excessive wear on the surface of the workpiece, even leading to deformation, and may also cause the polishing tool to wear out too quickly. If the pressure is too low, the machining marks cannot be effectively removed, and the expected polishing effect cannot be achieved. Pressure can usually be controlled by adjusting the fixture of the polishing equipment or the handheld force of the operator, and it should be flexibly adjusted according to the material and shape of the workpiece.

Polishing time control: The length of polishing time depends on the initial surface quality of the workpiece, polishing target, and polishing process. If the time is too short, it may not be possible to completely eliminate knife marks and defects; Excessive time not only reduces production efficiency, but may also have a negative impact on the surface quality of the workpiece, such as excessive polishing (uneven surface glossiness, pitting, etc.). It is necessary to determine the appropriate polishing time through experiments and experience, and constantly observe the changes on the surface of the workpiece during the polishing process.

Key operating points during polishing process

Polishing path planning: For workpieces with complex shapes, it is necessary to plan the polishing path reasonably. Generally, a gradual approach from coarse to fine is adopted, where the entire workpiece surface is first subjected to preliminary coarse polishing to remove larger machining marks, and then fine polishing is carried out to obtain a better surface finish. During the polishing process, it is important to ensure that the polishing path evenly covers the surface of the workpiece to avoid situations where there is excessive or inadequate polishing in certain areas. For example, for workpieces with curved surfaces, polishing can be carried out along the contour line of the surface, and the polishing direction needs to be constantly changed to make the surface polishing effect more uniform.

Avoid local overheating: During the polishing process, heat is easily generated on the surface of the workpiece due to friction. Be careful to avoid local overheating, as this may cause changes in the microstructure of the workpiece material, affecting its performance and surface quality. Appropriate cooling measures can be taken, such as intermittent polishing, use of coolant, etc. For some temperature sensitive materials such as plastics, cooling measures are particularly important.

Real time inspection of workpiece surface quality: During the polishing process, it is necessary to regularly check the surface quality of the workpiece, observe the removal of machining marks, changes in surface glossiness, and whether new defects (such as scratches, burns, etc.) appear. Inspection can be carried out using tools such as strong light irradiation, magnifying glass, or microscope. Once a problem is discovered, it is necessary to adjust the polishing process parameters or replace the polishing tool in a timely manner.

Processing and inspection after polishing

Cleaning the workpiece: After polishing, the surface of the workpiece should be thoroughly cleaned to remove residual polishing materials, debris, and other impurities. Ultrasonic cleaning machines or organic solvents can be used for cleaning, and then dried with clean compressed air to ensure that the surface of the workpiece is clean and tidy.

Final quality inspection: Conduct a comprehensive quality inspection of the polished workpiece, including surface roughness measurement, dimensional accuracy inspection, appearance inspection, etc. Use a surface roughness meter to measure whether the roughness of the workpiece surface meets the requirements; Check whether the dimensions of the workpiece are within the tolerance range through measuring tools; Conduct a visual inspection to check for scratches, burns, and uneven color defects. Only when all quality indicators of the workpiece meet the requirements can it enter the next process or be delivered as a finished product.