The dynamic balance of crankshaft is divided into axial balance and rotational balance, and the most important thing in machining is rotational balance. Crankshaft is usually forged, and the precision of the finished product after hot forging is poor. After several kinds of machining, the balance of crankshaft is measured by balance measuring device. Based on this result, in the next process, holes with different depths are drilled in the counterweight to adjust the overall rotational balance. This is a rough adjustment, and then through a more accurate balance measuring machine, and then fine-tune the previous hole. After that, the workpiece will be cleaned under high pressure, dried and measured again. Generally measured at least three times. The whole process is fully automatic, and the balance measuring machine will automatically feed back to the CNC machine tool of the next process to guide the processing. In order to reduce the influence of different tools on drilling accuracy, the aperture size and spacing are generally specified when drilling. All that remains is the number and depth of holes. The accuracy of drilling is micron, and the specific accuracy will be set differently according to the application scope. When measuring the balance, we mainly pay attention to a design index, namely the balance rate (K).
K= eccentric balance weight of rotating part/(total weight of connecting rod and cylinder) First of all, in the internal combustion engine industry, anything involving 5C is a company secret, which is found in ISO (ISO 1940? But this is only a rough technical guide. Each company has its own unique management method to adjust the dynamic balance of crankshaft, and there are many patents on this kind of content. I think there is still a certain distance from everyone. For example, the crankshaft of marine diesel engines is generally 630, and that of automobiles is 40. The manufacturing profit of 5C is relatively high, because most of its processes are unique. Secondly, the hot forgings of crankshaft are more used in internal combustion engines than castings. Because the productivity is relatively low, the cost is indeed relatively high. Some crankshafts in automobile engines are also forgings. Castings have a fatal problem, and the fatigue strength is relatively low. However, at the civil level such as automobiles, castings are indeed used more because of their excellent productivity. Not to mention low pressure and high pressure.