Application of CNC internal and external cylindrical grinders in automotive precision shaft parts
The fitting tolerances of automotive axles are getting tighter and tighter. The accuracy level of cylindrical grinding directly determines the transmission efficiency and service life of the entire vehicle. CNC internal and external cylindrical grinders are stuck at this critical node.
Why does the accuracy of shaft parts get stuck the more it gets stuck?
If the roundness deviation of the engine's crankshaft, camshaft, and input shaft and output shaft in the gearbox exceeds 2 microns, vibration will soon occur when running at high speed, and there will also be abnormal noises.
By 2025, the fit tolerances of shafts on new platforms launched by mainstream car manufacturers have been generally compressed to the range of 1 micron to 3 microns, which means that the space left for the finishing process has become extremely narrow.
The three indicators of roundness, cylindricity, and surface roughness Ra are interlocked with each other. If any one of the indicators exceeds the standard, it will cause slippage in the gear mesh or early failure of the bearing. In this way, the actual life of the shaft parts will be cut by more than half.
What are the strengths of CNC grinders?
All parameters such as feed rate, grinding wheel linear speed and grinding stroke are handed over to the CNC system for closed-loop control, so that the grinding accuracy can be stably maintained within the micron level. The purpose of this is to completely get rid of the fluctuation effect caused by different manual feel. As for the accuracy level of inner hole machining, cylindrical machining and step end face processing, cylindrical grinding processing can be done with only one machine. The application of CNC internal and external cylindrical grinders in automotive precision shaft parts does not require repeated clamping and turnover operations.
Compared with traditional ordinary grinders, the scrap rate has been reduced from more than five percent to less than three thousandths. The dimensional consistency of workpieces from the same batch is outstanding. On the mass production line, dimensional drift is almost invisible.
How to smooth the surface in micro grinding
The knife lines left by turning and rough grinding still have residual tensile stress. It is necessary to rely on a CNC grinder to perform 0.01 mm-level micro uniform speed grinding, and then cut these things off. In this way, the surface Ra can be pressed below 0.4, and the coaxiality of the camshaft can be controlled within 3 microns, so that it will not shake when rotating at high speed.
The surface flatness of the parts has been improved, which has resulted in a significant reduction in frictional resistance during operation. The NVH indicator status of the entire vehicle has also been directly and beneficially improved. As long as the user sits in the driving seat and experiences it, they basically cannot hear the abnormal noise in the transmission system.
How to stabilize the rhythm of batch production lines
The equipment program can be saved with one click, and the grinding wheel has an automatic dressing function and an automatic wear compensation mechanism. When changing product varieties and cylindrical grinding processing accuracy levels , the operator does not need to make any manual adjustments to the machine tool. The switching operation can be completed by simply modifying the corresponding parameters.
A transmission shaft manufacturing plant located in a certain location will complete the online work of the system in 2024. After the transformation, the factory's single-shift production capacity has increased from 800 pieces per day to 1,400 pieces today. At the same time, the product yield rate continues to remain stable at a level above 99.5%.
The rigidity of the equipment is very strong, and the vibration during grinding is relatively small. It can process materials such as alloy steel and high-strength steel. By using one clamping method to complete all processes such as outer circles, steps and end faces at the same time, this eliminates the need for turnover between multiple devices and directly reduces the floor space of the production line by one-third.
Grinding ensures longevity and safety
The precision grinding process can reverse the residual tensile stress originally existing on the surface layer and turn it into compressive stress. In this way , the cylindrical grinding accuracy level and the fatigue resistance limit of the shaft can be increased by 15 to 20 percent. After running for 100,000 kilometers, the wear amount of the journal will be reduced by half compared with that of workpieces that have only been rough ground. This change significantly reduces the risk of deformation or breakage.
If the transmission shaft is deformed or broken while running at high speed, the result will be that the power will suddenly stop or the debris will directly injure people. Therefore, the grinding accuracy level is a very important minimum standard to ensure our life safety, and this must not be omitted.
When choosing equipment, don’t just focus on accuracy parameters.
The actual landing situation depends on the frequency of automatic dressing of the grinding wheel, the response speed of the hydraulic system, and the accuracy of the spindle thermal compensation. Because these three indicators determine whether the workpieces in the second half of mass production will slowly drift out of the tolerance zone.
By 2026, the materials used for shafts on mainstream automobile models will shift to high-strength steel and composite coatings. This means that the adaptability of the grinding wheel and the filtration accuracy of the coolant must be upgraded simultaneously. We should not just stare at the few micron numbers displayed on the machine tool nameplate.
In your factory, after completing the grinding process, can the actual measurement value of the roundness of the shaft be stably controlled within a few microns? Everyone is welcome to share and exchange relevant information in the comment area. If you think this content has a certain degree of practical value to everyone, please don't forget to click like and forward it to your friends who are engaged in craft work.
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