Analysis and implementation of crankshaft machinin

Analysis and implementation of crankshaft processing technology optimization

under the influence of the financial crisis, the competition in the automobile market is becoming increasingly fierce, and the automobile and parts enterprises are facing severe challenges. The major main engine manufacturers have increasingly strict requirements for the quality and accuracy of crankshaft. In order to meet the needs of customers, our company puts forward the guideline of "taking technology as the leader", which requires to improve and optimize the crankshaft processing technology, further improve product quality and efficiency and improve customer satisfaction. Through the overall optimization test of the processing technology of forged steel crankshaft, not only good results have been achieved, the product quality of forged steel crankshaft has been improved, but also the production capacity of the production line has been improved, and the problem of the fluctuation of output and quality has been solved

crankshaft processing status

crankshaft is one of the key parts of engine. It has complex structure, large production batch, frequent variety replacement and high precision requirements. The dimensional accuracy of the main shaft connecting rod journal is IT6 ~ it7, the roundness is ≤ 0.005mm, and the surface roughness is Ra0 2～0.4。 Therefore, an advanced crankshaft production line should not only realize flexible production change to meet the market demand, but also meet the process requirements, ensure the machining accuracy, and finally produce qualified products. The forged steel crankshaft production line has the world's top CNC machine tools, advanced processing technology and increasingly perfect management system, which not only greatly improves the processing efficiency of the crankshaft and realizes the flexible and rapid production change capacity, but also the process between them is very troublesome. Moreover, it is the process of users, and they have to pay a certain amount of money to ensure the processing quality of the crankshaft. At present, the quality of crankshaft is mainly guaranteed through the process control of machining and heat treatment. There are roughly three ways:

1 Manual inspection: it refers to the measurement of each process according to the process requirements by professional quality inspectors (or operators' self inspection and mutual inspection), and the timely adjustment of process parameters to avoid the turnover of unqualified products to the next process or batch waste products

2. Equipment control: it refers to ensuring high equipment accuracy. 1. When measuring, first place the oil box on the oil box head seat installed together with the microscope to verify the processing accuracy of the current process. It is an effective way to ensure the dimensional accuracy, shape accuracy and position accuracy. It is also one of the symbols of advanced crankshaft processing production line

3. Process guarantee: process is the "legal" criterion for transforming crankshaft blank into finished product in machining process, the fundamental guarantee of product quality and the premise of improving machining efficiency

for the above three ways to improve product quality, our company has conducted targeted test and demonstration on each production line. Through continuous improvement, we find that it is relatively difficult to detect artificially, but the later improvement effect is not obvious. Controlling the machining accuracy through advanced equipment has been implemented in forged steel production lines and some iron shaft production lines, and the improvement effect is considerable. However, if the whole company popularizes, it needs to invest a lot of money. For the process guarantee, because the processing technology of forged steel crankshaft at home and abroad is similar, and the quality factors such as cutting tool, grinding wheel, cutting fluid, quenching rise, processing parameters and machining allowance involve the characteristics of long improvement cycle, small optimization space and poor popularization, it is undoubtedly the most difficult to greatly improve the product quality through process improvement and optimization

overall analysis of processing technology

after a series of improvement and optimization, the process parameters affecting processing quality and processing efficiency, such as tool material, processing parameters, machining allowance and design accuracy of tooling and fixture, have been basically solidified. When the equipment has quite high processing accuracy, and each equipment is produced in strict accordance with the process, but it can not guarantee that there will be no unqualified products in the processing process, we often think that the problem is that the artificial detection is not in place. Practice has proved that Canadian inspection efforts not only increase the manufacturing cost of crankshaft, but also can not fundamentally eliminate the problem. How to improve product quality requires in-depth research on the current process. Through the data collection and overall analysis of the on-site processing technology, we find that the main factors affecting the processing quality and processing efficiency are concentrated in the process before the fine grinding of the spindle and connecting rod, and the specific problems are reflected in the following four aspects:

1 Due to frequent production changes, there is a problem that the quenching rise of blanks from different manufacturers and different furnace numbers of the same product is inconsistent. Although the rise difference is small, the machining process parameters of the whole production line also need to be adjusted, which affects the production change speed and quality

2. Different processes of the same size do not control the process parameters uniformly, which increases the machining allowance of fine grinding spindle and connecting rod and reduces the machining efficiency of fine grinding

3. Relying on error prevention means such as clip gauge and plug gauge, it has the disadvantages of human factors and large detection error

4. Taking the side of the thrust gear as the positioning benchmark, it changes greatly affected by the wear of the cutting tool and grinding wheel and the quenching rise, resulting in the phenomenon that the side of the journal cannot be finely ground. The processing technology based on the side platform of thrust gear is shown in Figure 1

Figure 1 processing technology based on thrust gear side platform

the above problems seriously affect the further improvement of product quality of forged steel crankshaft production line, which must be completely solved

solution

aiming at the problems of inconsistent quenching rise of different crankshafts, inconsistent control of process parameters and great influence of human factors on detection methods, we tested and demonstrated a new processing technology - gear center distance processing technology. The machining process of gear center distance refers to that the main shaft and connecting rod are always machined to other journals based on the center line of thrust gear in the machining process, and the distance from the reference line of thrust gear to the center line of each journal until the axial dimension after machining, as shown in Figure 2

the gear center distance processing technology is applied to the forged steel crankshaft production line, which has achieved remarkable processing results and fully reflects the unique advantages of the new technology. Compared with the processing technology based on the side of the thrust gear, it has the following characteristics:

1 Ensure that the gear center distance from the Journal of the main shaft and connecting rod to the thrust gear before fine grinding is controlled within the process (D ± 0.05mm), and the axial dimension after fine grinding is controlled within D ± 0.04mm (the axial dimension tolerance of the finished product is d ± 0.15 ~ 0.25mm), meeting the process requirements

2. The problem of inconsistent quenching rise of crankshaft of different manufacturers and heat numbers in the process of production change is completely solved

3. The axial dimension is little affected by the side wear of cutting tool and grinding wheel, the fluctuation of quenching rise and the runout of spindle before and after quenching, which can be ignored

4. In the process of changing production, it is only necessary to accurately verify the gear center distance on the detection platform, which can realize the rapid and successful production change in a short time

5. The phenomenon that CBN fine grinding spindle and connecting rod are easy to cut off after canceling the gear division is avoided, and the grinding quality is significantly improved. Under the condition of unchanged grinding conditions, the fine grinding efficiency is increased by 28% ~ 30%

6. The process of roughing and semi finishing the side of the main shaft and connecting rod is realized

7. Relying on the accuracy of the equipment to ensure the gear center distance avoids the inconsistency of the gear center distance between the front and rear processes caused by the operator's modification of the axial size, and cancels the dependence on the axial caliper

gear center distance makes up for the defects of the traditional machining process based on the side of the thrust gear. After the verification of production change and mass production, it not only greatly improves the product quality, but also effectively reduces the rate of unqualified products. It is suitable to be popularized in the advanced crankshaft production line

implementation of new process and key points for attention

1 Before quenching, the precautions for machining the main shaft and connecting rod mainly include:

(1) for the implementation of the new process, first consider the quenching rise, and determine the shrinkage of the axial dimension of the semi finishing turning main shaft and the finishing milling connecting rod by measuring the absolute rise of each journal

(2) the axial datum of the finish milling connecting rod shall coincide with the center line of the main shaft thrust gear

(3) when compiling the process, take the minimum distance between gear centers as the lower limit of size, and make the through end of caliper gauge according to the lower limit of size

(4) the clamp gauge and plug gauge should be slightly tight, and there is no need to adjust the program parameters if they are too tight

2. After quenching, the precautions for machining the main shaft and connecting rod mainly include:

(1) the main shaft thrust gear datum after finishing quenching coincides with the main shaft thrust gear datum before semi finishing quenching

(2) after finishing turning and quenching, the gear center distance from the main shaft thrust gear reference to each journal of the connecting rod after quenching is equal

(3) ensure that the gear center distance from the thrust gear reference line to each journal is close to the ideal size

(4) ensure that the machining allowance on both sides of the journal is uniform

the implementation of the new process does not mean to replace the original process, but some adjustments have been made to the axial size on the basis of the original process. Therefore, the new processing process is more suitable for on-site use

auxiliary processing process measures

there is a certain gap between the formulation principles and measurement methods of the new processing process and the original processing process. The following auxiliary measures need to be adopted for correction to ensure the smooth implementation of the new process

1. The overall process adopts the principle of tightening before loosening

the principle of tightening before loosening after tightening before loosening refers to determining the machining allowance according to the machining conditions of the whole production line, improving the machining accuracy before quenching and leaving appropriate allowance for subsequent machining. Ensure that the allowance of journal side table is uniform before and after quenching, and ensure the accurate measurement of gear center distance

2. Improve the detection means

the new process should cancel the measurement method of determining the axial size by relying on the caliper, accurately measure the gear center distance of each journal by relying on the detection platform, and input the difference into the machine tool to ensure the accuracy of the gear center distance

the practice shows that the gear center distance processing technology, compared with the processing technology based on the thrust gear side platform, eliminates the problem that the original process is difficult to control the quality by relying on advanced equipment, improves the quality process control, reduces the influence of human factors, has stability and progressiveness, and significantly improves the processing quality and efficiency. Take the new process as the main line, adjust the equipment production efficiency, personnel arrangement and processing parameters of the whole production line, make rational use of various resources, and effectively avoid the backlog of products caused by personnel shortage and equipment overproduction

conclusion

with the deepening of the reform of production mode carried out by our company, the continuous improvement of processing accuracy of imported equipment and the experiment of new technology广州斑秃后长出白发怎样治
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