Auto parts in a variety of conditions applied in the main failure mode fracture, corrosion, wear and deformation, where the greatest danger of fatigue fracture. Even after fatigue fracture fatigue crack initiation, subcritical extended cab factory instability extended three processes, but because no obvious plastic deformation and other obvious signs of pre-fracture, it has a strong burst fracture. Even with a large number of conditions under static tensile plastic deformation of the plastic material cab, under the alternating stress also showed macroscopic brittle fracture characteristics, thus breaking suddenly performed. Cab body size discrepancy led to the settlement of several ideas and solutions: 1, welding precision welding process is the use of spot welding connection individual sheetmetal connection, including the rationalization of welding fixture design, welding fixture failure, welding equipment and other aspects of the order is unreasonable. Welding fixture design is reasonable or not is to ensure that the relative position between the sheet metal parts to maintain the uniqueness of the fundamentals, welding fixture fails, there will be fluctuations in the relative position of the cab shell phenomenon among sheetmetal, but what first spot welding sheet metal parts, sheet metal parts after what spot welding will also affect the entire welding assembly dimensional accuracy. 2, sheet metal parts and operation produced, generally do not go directly to the welding process the cab window, but stored in the library, in particular due to the current sheet metal cover emerged as large-scale, holistic features, so even though it can put an end to produce welding cumulative error, but for stamping die design and manufacturing process design and demanding. Large parts of the cover if stored in a long time, due to internal stress material will produce different degrees of resilience and deformation, while in transit due to improper operation will also bump deformation of sheet metal parts, resulting in welding points assembly deviations. During operation, the welding process, the process will lead to bias unskilled workers produce. Cab shell | Jinan Yiu Cheung (certified) | cab provided by Jinan Yiu Cheung Trading Company. Jinan Yiu Cheung Trading Company (www.jinanyaoxiang.com) Shandong Jinan, engine assembly leader, over the years, the company is implementing the scientific management, innovation and development, the principle of honesty and trustworthiness, and satisfy customer needs. Jinan Yiu Cheung leadership with the staff warmly welcome all inquiries negotiations to create Jinan Yiu Cheung a better future.