Seen from the failure of bulldozers

With the continuous improvement of the professional production level of China's construction machinery parts and components, the proportion of accessories and self-manufactured parts purchased by each main engine plant is increasing. The variety and quantity of our company's bulldozers' accessory parts account for about 40% of the whole machine. Therefore, the technical level and quality level of the parts directly affect the performance and quality of the whole machine. The development of the complete machine is inseparable from the supporting parts. The two are complementary and are indispensable.
Judging from the current situation of our company's bulldozers, with the exception of a few products, the technical performance and quality levels of most products are very different from those of similar foreign products, and there are also certain differences from the quality of self-made parts of our company. difference. This disparity caused the quality of the entire machine to be uneven and concentrated in the early stage. The failure rate was high and users were particularly dissatisfied.
The mainframe quality problems that occurred during the early use of the mainframe were described briefly in the following examples: engine, pump, oil, cylinder, and transmission.
Engine: Damaged starter motor, no generator power generation, early wear, water pump leakage, machine cooler failure, cylinder liner corrosion, etc.
Pump: cracked pump, oil seal leakage, large internal leakage, early wear and so on.
Cylinder: oil leakage, large internal leakage, poor seal quality, cracked welds, poor paint quality.
Valve: The valve stem is stuck, the valve body has trachoma, the spring breaks, leaks oil and so on.
Gearbox: There are many internal defects in the casting. There are no gears, oil leaks, early wear of seals, poor gear accuracy, frictional segments, spring breaks, and poor cleanliness during use.
According to our many years of quality tracking and analysis, there are roughly the following reasons for the above quality problems:
1. The manufacturing accuracy of parts and components and the manufacturing accuracy are not stable. According to the quality inspection of parts of some parts, we found that there are clear technical requirements in the drawing, and the control of dimensional tolerances is better, while the control of un-noting dimensional tolerances, sharp corners, burrs, and inverted (round) corners is not strict. Therefore, during the parts manufacturing process, some technical requirements not specified in the drawings, but where common standards require, such as material composition, shape and position tolerances, roughness, heat treatment parameters, internal defects of parts, etc. should be strictly controlled.
2. Poor cleanliness. From our spot checks on some accessories, we found that many of the cleanliness levels did not meet industry standards, and some exceeded the standards. Poor cleanliness is one of the important reasons for the early failure of the host. In particular, hydraulic components, which have poor cleanliness of components, will contaminate the entire system during use, causing the entire hydraulic control system to malfunction or run out of control.
3. Poor assembly quality. The machining accuracy of the part is even better. If there is no good assembly effect, this part will be a defective part. Some supporting manufacturers have some problems in the assembly environment, means, etc., causing oil leakage, bolt looseness, poor clearance adjustment, and interference of moving parts after installation.
4. The test method is incomplete. In the sampling inspection, it is often found that some of the accessories have been factory tested, but the factory test report data is inconsistent with the data of our re-inspection, except for a few individuals who are not responsible for filling, most of them are due to incomplete equipment test equipment, test measurement instruments Unacceptable, some laboratory conditions are inconsistent with factors such as host operating conditions.
5. The use of the product is not clear. From our exchanges with supporting plants for many years, we have found out that the technical staff and quality management personnel of some auxiliary plants are installed on the main engine at what position and function? It is not clear what are the technical requirements for the components of the mainframe.