Development of the hottest crankshaft manufacturin

2022-09-23
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The development and evolution of crankshaft processing technology before the 1970s, the machining method used in the rough machining of engine crankshaft was turning crankshaft main journal and connecting rod journal with multi tool lathe. In this way, the machining accuracy is low, the flexibility is poor, the process quality stability is low, and it is easy to produce large internal stress, so it is difficult to achieve a reasonable machining allowance. After rough machining, stress relief tempering treatment is generally required to release stress. Therefore, the rough machining needs to leave a large machining allowance for the subsequent finishing process to remove the bending deformation. Crankshaft finishing adopts ordinary grinding process, which generally adopts mq8260 crankshaft grinder coarse grinding semi fine grinding fine grinding polishing. Usually by manual operation, the processing quality is unstable and the scrap rate is high. From the 1970s to 1980s, the rough machining of crankshaft was carried out by CNC turning and CNC external milling, and the machining condition was improved. Finishing is still based on the grinding process of ordinary grinding machine. In the mid-1980s, CNC internal milling technology appeared again. The machining performance index of CNC internal milling is higher than that of CNC external milling, especially for forged steel crankshaft, internal milling is more conducive to chip breaking. Semi automatic crankshaft grinder is mostly used in the finishing process, and the head frame and tailstock are synchronously driven. The machining accuracy must be improved to ensure that the refrigeration tank is filled with refrigeration materials

Figure 1 double cutter turning turning turning drawing

Figure 2 double cutter high-speed external milling from 1985 to 1990, the crankshaft turning drawing and turning drawing process (Figure 1 shows double cutter turning turning turning drawing) was developed. This process has the advantages of high precision and high efficiency. It is especially suitable for crankshafts that do not need machining on the side of the balance block and have countersunk grooves (including axial countersunk grooves) on the shaft neck. After processing, the crankshaft can be finely ground directly, eliminating the rough grinding process. A few CNC grinding processes have been used for crankshaft finishing, and the dimensional consistency has been improved. In the mid-1990s, CNC high-speed external milling was developed (Figure 2 shows double cutter head high-speed external milling). It has higher production efficiency than CNC turning, CNC internal milling and turning drawing for crankshafts that need to be processed on the side of the balance block of the ball disc friction and wear experimental machine according to the friction pair. In addition, the machining of connecting rod journal by CNC turning drawing process requires two processes, and CNC high-speed external milling can be completed by only one process. It has the following advantages: high cutting speed (up to 350m/min), short cutting time, short process cycle time, small cutting force, low workpiece temperature rise, high tool life, less tool changes, higher machining accuracy, and better flexibility. Therefore, CNC high-speed external milling will be the development direction of rough machining of crankshaft journal and connecting rod journal. CNC grinding machine is used for finishing, and control devices such as static pressure spindle, static pressure guide rail, static pressure feed screw (grinding wheel head frame) and linear grating closed-loop control are used to ensure the dimensional tolerance and form and position tolerance reliably. CNC Abrasive Belt polishing machine is also widely used for superfinishing, and the surface roughness of crankshaft journal after superfinishing is improved by at least one level of accuracy

CBN high speed grinding developed in the 1990s. The crankshaft grinder produced by Landis company in Britain has a grinding speed of up to 120m/s. It takes only a few minutes to clamp it in one time from blank to finish grinding by peeling method. This will lead to a new situation that grinding will replace other rough machining processes. At the end of the 21st century, compound processing technology has entered the crankshaft manufacturing industry. The compound machine tool should have the function of process integration and multiple processing integration. The horizontal turning milling compound machining center (m40g type in Figure 3) produced by Austrian WFL company can "clamp once and process all" before the crankshaft hardens, and the processed crankshaft can be directly transferred to the finishing process; In terms of crankshaft finishing, CBN CNC grinding machines with integrated processes have also emerged, that is, grinding all crankshaft main journals and connecting rod journals at one time (swing tracking grinding)

Figure 3 m40g turning milling composite machining center

from the above evolution, it can be seen that the processing technology of crankshaft is developing towards high speed, high efficiency and composite, which is the motive direction of our investment in thermoplastic materials and silicon-based materials. At present, the more popular rough machining process is that the main journal adopts the turning drawing process and high-speed external milling, and the connecting rod journal adopts high-speed follow-up external milling, all of which adopt dry cutting; The finish machining adopts CNC grinding machine, which has the functions of automatic feeding, automatic correction of grinding wheel, automatic compensation of size and roundness, automatic indexing and electronic synchronous drive at both ends. The main journal and connecting rod journal can be clamped at one time, and all grinding is completed; Ultra precision machining adopts CNC Abrasive Belt polishing machine with size control device. Brief introduction to the performance of typical crankshaft processing advanced equipment

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