Development and Innovation of Design and Manufacture Mode of Load Cell

【Summary】The core of "Industry 4.0" is the digitization and intelligence of manufacturing; the essence of "Made in China 2025" is the deep integration of industrialization and informatization, with "innovation driven, structural optimization, quality first, and green development" as the guide for the development of manufacturing policy. This article discusses how load cell companies integrate information technology and manufacturing technology to realize digital, networked, and intelligent design and manufacturing, and discuss the innovation of load cell structure design; innovation in manufacturing process models; and advancement of automation and intelligence in key manufacturing processes Transformation; the establishment of digital weighing sensor technology system and basic process support system and other issues, introduces the basic way of 3D digital design and manufacturing, and provides reference for weighing load cell companies to promote digital and intelligent manufacturing.

[Keywords] weighing load cell; design and manufacturing mode; digitalization; networking; intelligence; three-dimensional digital design and manufacturing

1. Overview When the "Industry 4.0" new round of industrial revolution is approaching, my country has no opportunity to put forward the "Made in China 2025" strategy, which will inject strong development momentum into my country's manufacturing industry and bring unlimited business opportunities to the sensor industry. The core driving force of "Made in China 2025" is to focus on smart manufacturing, which is the fundamental path to solve the problem of China's manufacturing industry from becoming a powerful country. "Made in China 2025" is an upgraded version of Made in China, which embodies: four major changes, one main line and eight major countermeasures. Four major changes: from factor-driven to innovation-driven; from low-cost competitive advantage to quality and efficiency competitive advantage; from extensive manufacturing with high resource consumption and high pollutant emissions to green manufacturing; from production-oriented manufacturing to service-oriented manufacturing .One main line: the main line is digital, networked, and intelligent manufacturing that reflects the deep integration of information technology and manufacturing technology. Eight countermeasures: Promote digital, networked, and intelligent manufacturing; improve product design capabilities; improve manufacturing technology innovation system; strengthen manufacturing foundation; improve product quality; promote green manufacturing; cultivate global competitive corporate groups and advantageous industries; develop Modern manufacturing service industry. How to implement the “Made in China 2025” development strategy for the load cell industry and how to integrate information technology and manufacturing technology to achieve digital, networked, and intelligent design and manufacturing are issues that larger companies in the industry must face.In recent years, three-dimensional digital design and manufacturing capabilities have become the core of competition between domestic and foreign companies, and are the fulcrum and breakthrough point for the transformation of corporate research and development capabilities. This change with the nature of a weather vane should cause load cell companies to attach great importance to it. Although the principle and manufacturing process of the strain gauge load cell determines that it cannot be mass-produced in an automated, intelligent and seamless production line like machine parts, the structural design and manufacturing process of the load cell should also be upgraded with Internet thinking. It is as close as possible to digital, intelligent or partially digital, intelligent production. The Internet is the commonality and foundation, and the management of load cell companies must use information technology and Internet thinking to examine and rebuild the company. Analyze the main elements of an enterprise, one is people and the other is things. The transformation of an enterprise is nothing more than the transformation of people and things. The digital and intelligent transformation of load cell structure design and manufacturing process starts with people and things, that is, from people's design concepts and manufacturing process flow, to achieve structural design and manufacturing process model innovation.

2. Innovation of load cell structure design mode. my country's strain gauge load cell companies currently adopt two design methods. One is the traditional design method, which is the classical calculation method + experience. It is difficult to analyze the boundary influence, supporting stiffness and stress concentration of elastic elements, and it is adopted by some small and medium-sized enterprises. The second is the modern design method, which is an extension of the traditional design theory, the integration of multiple design techniques, theories and methods, that is, the establishment of mathematical models and the use of finite element method for calculation and analysis. Its characteristics are: the design method is precise and computerized, but it still needs physical model installation, physical experiment and test, which is widely adopted by large enterprises.For a long time, domestic and foreign load cell companies have been exploring a scientific, reasonable, cost-effective product design and manufacturing method to support the definition and transmission of data at all stages of the life cycle of product design, manufacturing, testing, and application. The emergence of Modcl Based Dtfinition (MBD) technology provides an effective way to solve this problem. Model definition technology attaches all relevant product design definitions, process descriptions, attributes, and management information to the digital definition method of the product's 3D model, providing a theoretical basis for 3D digital design and manufacturing. The weighing sensor manufacturing company, which is in the position of leader in the international market, started structural design model innovation several years ago, and realized 3D digital design and manufacturing based on model definition technology.Its characteristics are: changing the original load cell design method, starting from the transformation of design tools, and establishing a three-dimensional digital prototype rapid design platform with independent intellectual property rights. Including: the rapid design and calculation of the overall structure of the elastic element; the analysis of the influence of the load and the boundary conditions of the load; the analysis and design of the combined analysis and design subsystem of the indenter of the load, the bottom cushion of the load and the installation platform. Establish a three-dimensional digital prototype of the overall structure of the load cell, replace the physical one with a digital one, realize the "pre-meeting" of the overall structure and accessories, and find and solve the problem of incoordination. From theoretical analysis and calculation, overall structure and accessory design, the performance fluctuation of the load cell is guaranteed to be minimal.

3. Innovation in manufacturing process model of load cell

3.1. Innovation in production mode Break the traditional manufacturing method of load cell and implement innovation in manufacturing process and mass production line of elastic components and accessories. Change the original drawing distribution mode, based on the electronic distribution process, to realize the 3D model from design to manufacture directly to the production line. Compared with the traditional two-dimensional drawing distribution, the work efficiency is improved and the process preparation cycle is shortened. Due to the comprehensive use of structured and three-dimensional visualization methods, it is conducive to the realization of three-dimensional process design and inspection, and ensures that the elastic element has high size, shape and position accuracy and product uniformity.

3.2. Promote automation and intelligent transformation of key manufacturing processes The production process of strain gauge load cells supports the scientific application and integration of processes, basic processes, core processes and special processes. Among them, the core manufacturing process plays a key role in the entire production process of the load cell. The outstanding performance is the pasting, curing and post-curing of the resistance strain gauge; zero temperature and sensitivity temperature compensation; performance testing and verification procedures. Although the principle and manufacturing process of strain gauge load cells determine that it is difficult to seamlessly connect the processes of its production line, today, when Internet thinking has gradually penetrated into various enterprises, the manufacturing process of load cells must also be revolutionary. Otherwise, there is a danger that waves will be eliminated. The experience of load cell manufacturers in the position of leader in the international market is: to promote automation and intelligent transformation of key manufacturing processes, first of all, to automate and intelligentize key manufacturing processes that have a large impact on the quality of load cells. Resistance strain gage pasting process-the pasting quality and positioning error of the resistance strain gage on the elastic element, weight sensing.

3.3.The accuracy and stability of the sensor are very important, so this core process uses robot positioning, brushing glue, and sticking resistance strain gauges, and is equipped with an auxiliary system that automatically installs pressurizing fixtures to ensure that the resistance strain gauge is in the elastic element. The bonding quality of the strain zone and the uniformity of the positioning size. Curing and post-curing process-is a process in which the strained adhesive itself is cross-linked at a specified temperature and within a certain period of time, and adheres to the surface of the elastic element to be firmly bonded. The three elements of the curing process are curing temperature, heating rate, and holding time. The bonding strength increases with the increase of the curing temperature, but it is necessary to prevent the curing temperature from being too high or too low to avoid over-curing: make the adhesive layer brittle, reduce the bonding strength, and reduce the fatigue life; under-cured: make the adhesive layer The polymerization of molecular bonds is not firm, creeping effect occurs, and the creep becomes large.For this reason, the curing and post-curing of resistance strain gauges mostly adopt tunnel-type automation, intelligent heating and temperature control drying tunnel. Tunnel-type heating and temperature control drying tunnel, with high temperature control accuracy, good temperature uniformity in the working section, good uniformity of physical and mechanical properties of the strain adhesive after curing and post-curing, in order to improve the working reliability and long-term stability of the load cell Lay a solid foundation for sex. Zero point temperature and sensitivity temperature compensation process-is the key manufacturing process to ensure that the load cell has excellent temperature performance indicators, and more efficient and intelligent zero point temperature and sensitivity temperature compensation test systems are used. The system hardware is composed of interface unit, large high and low temperature test box and wiring unit in the box, high stability excitation power supply, data acquisition unit, microcomputer system, printer, and powerful weighing sensor zero and sensitivity temperature compensation software. The large high and low temperature box with automatic temperature control has high temperature control accuracy and good temperature uniformity. For multiple types of load cells, different system numbers can be set for archiving and data query. Performance test and verification process-the performance test and verification of the large-scale load cell are carried out on multiple automatic and intelligently controlled superimposed force standard machines that are seamlessly connected. The test data is automatically printed, and the qualification is automatically judged. Shave out substandard products.The performance test and verification of the small-range load cell is carried out in the group control static weight force standard machine system. Generally, 50kg, 500kg, 2000kg group control static weight force standard machine systems are set up on the production line. It is composed of multiple dead-weight force standard machines, high and low temperature test chambers and control systems, and has the functions of tension and compression bidirectional loading. The control system controls the position of the weight and the moving beam through the photoelectric sensor according to the program. The PLC programmable controller and the computer complete the entire control program through the software to realize the independent control of a single static weight force standard machine and multiple static weight The type force standard machine is controlled at the same time. Because this population-controlled static-weight force standard machine has a movable beam, after all the weights are hung, the movable beam can be used for one-time rapid loading or unloading, which meets the requirements of fast three preload tests and creep test loading, and Improve the detection efficiency. After that, each automated and intelligent process with independent operation and control functions is connected to each other through a network and a computer system, and information collection, storage and processing are realized under the management of network software.

The process information is expressed through multiple methods such as multimedia videos, such as real-time display of the production status, quality status, and process status of each process flow (such as resistance strain gage curing, post-curing temperature control; zero temperature, sensitivity temperature compensation success rate; performance testing And verification qualification rate, etc.) in order to control and manage product quality and process operation.

4:Form a digital weighing sensor technology system and basic process support system:The standards for the design and manufacture of strain gauge load cells to form a digital technology system are:

4.1. Unified product development process. In the design of strain gauge load cell structure and process process, it is necessary to absorb the best practice process design at home and abroad, and must have the characteristics of the company.

4.2. Uniform standard specifications Establish the company's weighing sensor digital development standard specifications, covering design, manufacturing, technology, and testing platform construction.

4.3. A unified basic process The elastic components of the load cell use different stresses and structures, and the basic manufacturing process is basically the same. A common, scientific, reasonable, and repeatable production process must be formulated.

4.4 Unified basic database Establish basic common databases such as resistance strain gauge library, standard parts library, raw material library, component library, and general product library, and employ actual data.

4.5. Unified version of software tools All three-dimensional designs adopt the company's unified design tools to improve design efficiency. But it needs to be resolved: (1) Product three-dimensional labeling method; (2) Two-dimensional drawing information to three-dimensional model information conversion technology;

5. Innovation in quality management mode Change the original organization mode and quality management mode of load cell design and manufacture, establish rules and regulations in line with digital design and manufacture, take three-dimensional digital prototypes and products as the core, and integrate design, technology, and inspection , To form a series of quality management ideas and methods under the digital design and manufacturing mode as soon as possible through practice. Through the digital development outline, clarify the overall development requirements of the load cell; through the digital standard specification system, clarify the specific digital work requirements; through the digital design sample acceptance conditions, the requirements for the prototype are equivalent to the requirements of the formal product into the quality management system ; Control the quality of mass-produced products through the networked management of three-dimensional digital design and process platforms and automated and intelligent production processes.

6. Concluding remarks The process of establishing a three-dimensional digital design and manufacturing model for load cells is a process of unifying thinking and changing concepts of business leaders and technicians, a process of reforming and innovating, breaking old work habits, and establishing a new work order. For my country's larger load cell companies, the key factors that play a leading role in this process are leaders and technical leaders. During this period, we must experience the collision of ideas, the running-in of habits, from not knowing to understanding, from disagreement to approval, from some familiarity to skilled application. It is hoped that my country’s larger weighing sensor companies will use the concept of “using all the power, you will be invincible; if you can use all the wisdom, you will not be afraid of the saints” concept, and gather the wisdom and strength of the team to upgrade the main processes of the production line from automation to intelligence To realize the three-dimensional digital design and manufacture of load cells as soon as possible.