Analysis and Solutions to the Problem of Damage to the Working Device of Loaders

Problems that are prone to occur during the assembly and use of working devices

The working device of the loader mainly has the following problems during assembly and use: (1) Difficulty in assembly. If the components cannot be assembled or the hinge does not rotate flexibly after assembly, they need to be disassembled and corrected by flame heating or on the fixture, which is labor-intensive and time-consuming and affects the smooth progress of assembly. Sometimes, although several components can be assembled together, due to uneven assembly clearances, dimensional errors and shape and position tolerances exceeding requirements, local wear and interference phenomena are prone to occur, leaving quality risks. (2) Quality accidents occur after the entire machine has been in use for a period of time after leaving the factory. According to user feedback, the problems that have occurred include: rocker arm bending and breaking, boom deformation, crossbeam welding opening, bucket tilting, tearing, hydraulic cylinder scratching and oil leakage, piston rod bending, etc.

2. Main cause analysis

During the manufacturing process of the working device, due to the welder's assembly accuracy not meeting the requirements, deformation during welding, and non-standard operation during processing, dimensional and positional errors occur, resulting in assembly difficulties and wear and damage caused by complex forces during use. The dimensional and positional errors of the hydraulic cylinder exceeding the specified range are also important factors causing difficulties and damage to the assembly of the working device. By analyzing the problems and quality accidents that occurred during the assembly and operation of the loader one by one, we can draw the conclusion that the main causes of damage to the working device of the loader are concentrated on components such as the front frame, boom and hydraulic cylinder.

2.1 Front frame

The front frame is the basic component of the working device. Other parts are assembled on it and form a certain fit with it. Therefore, its processing error directly affects the assembly and usage effect of the working device. There are hinge holes on the boom, connection holes for the boom hydraulic cylinder and connection holes for the bucket hydraulic cylinder on the front frame. When the coaxiality, verticality errors of these holes and the dimensional deviations at the hinge points exceed the specified requirements, assembly difficulties will occur and there will be mutual interference among the boom, boom hydraulic cylinder, bucket hydraulic system, rocker arm and the front frame. It may even cause scratches, jamming of the hydraulic cylinder and deformation of the piston rod, preventing the loader from performing various normal operations.

2.2 Boom

The boom size is relatively large, resulting in significant shrinkage deformation during welding. For instance, the distance between the two boom plates of the LW42OF loader is 1210mm, and it is reduced by 6mm after welding. The distance between the two boom plates of the LW52OF loader is 1260mm, and it is reduced by 8mm after welding. If the contraction is too large, it will cause difficulties in assembling the boom on the front frame. Secondly, the deformation of the boom plates after welding is also significant, resulting in the two boom plates not being parallel and asymmetrical relative to the centerline. After assembly, this will cause an imbalance in the force on the device, and the bucket will also become skewed, pulling the boom and the connecting rod at an Angle. In addition, the boom has low strength. During operation, due to the impact of turning, jolting and excessive load during work, it is easy for the boom to deform, causing changes in the mutual fit relationship between the boom and other components. As a result, the components of the working device deviate from the correct spatial movement trajectory, leading to wear and damage of each component.

2.3 Hydraulic Cylinder

The main problems with the hydraulic cylinder are as follows: the centerline of the cylinder body is not parallel to the centerline of the piston rod, and the piston is unevenly worn during reciprocating motion, causing leakage or damage to the hydraulic cylinder. The centerlines of the connection holes at both ends of the hydraulic cylinder are not perpendicular to the centerline of the piston rod, and the forces on both ends of the piston rod are not on the same straight line. Therefore, it is easy to cause the piston rod to bend and deform under force. The centerlines of the connection holes at both ends of the hydraulic cylinder are not parallel, which leads to difficulties in assembling the hydraulic cylinder or interference during operation. The stroke of the two hydraulic cylinders varies greatly. It causes deformation or damage to the working device due to unilateral misalignment and asynchronous movement. In addition, incorrect tooling during the welding process of the bucket and connecting rod, welding deformation and deviations during processing will also cause assembly difficulties or interference among the bucket, boom, connecting rod and rocker arm during operation.

Three main solutions

Improvements or new designs have been made to various welding equipment, and strict control has been exercised over the welding and processing of each component to ensure that the quality of the main components meets the requirements. The important dimensions and relevant symmetry of the front frame have been guaranteed to meet the design requirements. Strict inspection and correction are carried out after welding. Reduced deformation during welding and operation. (2) Strictly control the welding and processing quality of each component, and conscientiously abide by all kinds of processes and operating procedures; Strict inspection and control should be carried out on important dimensions. Those that do not meet the requirements of the drawings and processes must not be allowed to enter the assembly process. (3) Add detection tools for hydraulic cylinders. Strict quality control is carried out on the boom hydraulic cylinders, bucket hydraulic cylinders and other components of the outsourced factories to ensure that the parallelism, perpendicularity and stroke between the connection holes, piston rods and cylinder bodies of the hydraulic cylinders are all within the specified range.