Manufacturing link of resistance strain type weighing sensor

1. The metal material of the elastic element plays a key role in the comprehensive performance and long-term stability of the weight sensor. Materials with high strength limit and elastic limit, good elastic modulus time and temperature stability, small elastic hysteresis, and small residual stress caused by processing and heat treatment shall be selected. Some data show that as long as the plasticity of the quenched material is good, the residual stress after processing and heat treatment will be small. Special attention shall be paid to the stability of elastic modulus with time. It is required that the elastic modulus of the material will not change during the service life of the load cell.

2. The working principle and overall structure of the strain type weighing sensor in the manufacturing process determine that some processes in the production process must be manually operated, and the quality of the weighing sensor is greatly affected by human factors. Therefore, it is necessary to formulate scientific, reasonable and repeatable manufacturing processes, increase computer controlled automatic or semi-automatic processes, and minimize the impact of human factors on product quality.

3. The elastic element, shell, diaphragm, upper head and lower pad of the load cell must be designed to ensure that there is no performance fluctuation in the structure after loading, or the performance fluctuation is very small. Therefore, in the design of the load cell, the stress in the strain zone should be as single and uniform as possible; The patch position is preferably flat; The structure shall be able to resist eccentric load and lateral load; The installation force shall be far away from the strain area, and the bearing point displacement shall be avoided during measurement. Although the load cell is an assembled product, it is designed as an integral structure as far as possible to ensure the best technical performance and long-term stability.

4. Processing and heat treatment During the processing of elastic elements, uneven surface deformation will produce large residual stress. The larger the cutting amount is, the greater the residual stress is, and the maximum residual stress is generated by grinding. Therefore, it is necessary to formulate reasonable processing technology and specify appropriate cutting parameters. In the process of heat treatment, due to uneven cooling temperature and phase transformation of metal materials, residual stress in different directions is generated in the core layer and surface layer, tensile stress is generated in the core layer, and compressive stress is generated in the surface layer. The tempering process must be used to generate the stress in the opposite direction to offset the residual stress and reduce the influence of the residual stress.

5. The circuit compensation and adjustment strain type load cell belongs to assembly and manufacturing, and the product is formed after chip assembly and bridging. Due to the inevitable internal defects and the impact of external environmental conditions, some performance indicators of the load cell cannot meet the design requirements, so various circuit compensation and adjustment must be carried out to improve the stability of the load cell itself and the stability of external environmental conditions. Perfect and fine circuit compensation technology is an important link to improve the stability of the weighing sensor.

6. Protection and sealing Protection and sealing are the key processes in the manufacturing process of the weighing sensor, and are the fundamental guarantee for the weighing sensor to withstand the impact of the objective environment and the perceptual environment and to work stably and reliably. If the protective seal is not good, connect it to the elastic element. Both the resistance strain gauge and the strain adhesive layer will absorb the moisture in the air and produce plasticization, resulting in a decrease in the bonding strength and stiffness, leading to zero drift and irregular output changes until the load cell fails. Therefore, effective protection and sealing is the fundamental guarantee for the long-term stable operation of the weighing sensor, otherwise, all technical achievements will be lost. In addition to dealing with the above factors, the most important way to improve the stability of the weighing sensor is to take various technical measures and technological means, simulate the use conditions, conduct effective artificial aging tests, release residual stress as much as possible, and minimize its performance fluctuation.