To determine whether the surface burn is caused by the improper selection of grinding parameters, the following aspects can be analyzed:
Observe the Burn Characteristics
Burn Color: In the case of burns caused by improper grinding parameters, the surface of the workpiece usually shows discoloration to varying degrees. For example, a mild burn may appear light yellow, and as the degree of burn worsens, the color will gradually turn brown, purple, or even black. This is because excessive grinding parameters generate a large amount of heat, causing the surface temperature of the workpiece to rise sharply, leading to the oxidation of the metal. Different temperatures correspond to different colors of the oxide layer.
Burn Distribution: Burns caused by improper grinding parameters are generally distributed relatively evenly on the ground surface. Because if the grinding parameters are in an inappropriate state throughout the entire grinding process, the friction and heat generation between the grinding wheel and the workpiece surface are relatively consistent, so the burns will appear relatively uniformly. For example, in surface grinding, if the feed rate is too large, burn marks may appear on the entire ground surface; in cylindrical grinding, the burns may be evenly distributed along the circumferential direction.
Analyze the Processing Parameters
Compare with Conventional Parameters: Compare the current grinding parameters with the conventional recommended parameters for the combination of the workpiece material and the grinding wheel. If it is found that the grinding speed is significantly higher than the recommended value, or the feed rate is too large, it is likely to be the cause of the surface burn. For example, for grinding ordinary carbon steel materials, the normal grinding speed is generally between 30 - 35m/s. If the actual speed used is above 40m/s and surface burn occurs, then an excessively high grinding speed is very likely to be the cause of the burn.
Consider the Influence of Parameter Changes: Analyze the influence of changes in grinding parameters on the grinding force and grinding heat. When the grinding speed increases, the friction between the grinding wheel and the workpiece surface intensifies, and the generated heat will increase significantly; if the feed rate is too large, the amount of material removed per revolution of the grinding wheel will increase, the grinding force will increase, and in turn, the grinding heat will also increase. If surface burn occurs after adjusting these parameters while the previous processing was normal, it can be preliminarily determined that the improper selection of grinding parameters is the cause.
Inspect the Processing Process
Observe the Spark Situation: During the grinding process, observe the sparks generated at the contact area between the grinding wheel and the workpiece. If the sparks are bright and elongated, and there are a large number of them, it indicates that the grinding heat is high, and the grinding parameters may be inappropriate. Under normal circumstances, the sparks should be short and sparse. For example, when the feed rate is too large, more materials will be quickly removed, generating a large number of high-temperature chips. These chips oxidize and burn in the air, forming bright and numerous sparks.
Sense the Machine Tool Vibration: Improper grinding parameters may lead to increased vibration of the machine tool. If there is obvious vibration of the machine tool during the processing, and this vibration changes after adjusting the grinding parameters, and at the same time, the surface of the workpiece is burned, it indicates that the grinding parameters may be the cause of both the burn and the vibration. Because an excessive grinding force will make the machine tool bear a greater load, thus causing vibration, and the vibration will further increase the generation of grinding heat, leading to surface burn.
Exclude Other Factors
Check the Condition of the Grinding Wheel: Ensure that the grinding wheel does not have problems such as passivation, clogging, or imbalance. Because after the grinding wheel is passivated, its cutting ability decreases, which will increase the grinding force and grinding heat, and may also lead to surface burn, but this has nothing to do with the grinding parameters. These factors can be excluded by observing the wear condition of the surface of the grinding wheel, checking the dressing frequency of the grinding wheel, and conducting a grinding wheel balance test.
Confirm the Workpiece Material and Clamping: Check whether the hardness and structure of the workpiece material are uniform, and whether the clamping is firm. Uneven workpiece material or loose clamping may also cause local overheating and burn, but this is not caused by the improper selection of grinding parameters. For example, if there are hard inclusions inside the workpiece material, the grinding wheel will encounter greater resistance when grinding to this part, generating local high temperature; if the workpiece is not firmly clamped and displaces or vibrates during the grinding process, it will also lead to surface burn. These factors can be excluded by inspecting the workpiece material and reclamping the workpiece.
Through the above comprehensive analysis, if the burn characteristics are consistent with the manifestations of improper grinding parameter selection, the processing parameters exceed the conventional range and have a significant impact on the grinding heat and grinding force, corresponding abnormal situations occur during the processing, and other factors that may cause burns are excluded, then it is possible to accurately determine that the surface burn is caused by the improper selection of grinding parameters.
