Riveting workers are commonly known as "iron tailors". Their task is to connect two or more pieces of metal together, that is, riveting; Electric welding is hot riveting, "riveting and welding are not separated?" Riveting is the commander of metal component construction. After paying-off and blanking according to the drawing, other types of work will be installed.
Main work content
Riveting workers should not only make corresponding metal products according to the requirements, but also have the knowledge of drawing and drawing. Knowledge of common metal materials and heat treatment; Raw materials and general structural parts that can correct large deformation or composite deformation can be made into unfolded drawings with basic shapes, and the length of unfolded materials can be calculated; Able to use and maintain shearing machine, gas cutting, welding machine and other equipment; Be able to read and assemble the drawings of trusses, beams and columns, boxes, boxes and medium and low pressure vessels, conduct all-position positioning welding, riveting and threaded connection, and check the size, shape and position.
Basic knowledge and skills
Mainly know the map; Knowledge of common metal materials and heat treatment; Raw materials and general structural parts that can correct large deformation or composite deformation can be used as the foundation.
The developed figure of the volume, and the length of the developed material is calculated; Able to use and maintain shearing machine, gas cutting, welding machine and other equipment; Be able to read and assemble the drawings of trusses, beams and columns, boxes, boxes and medium and low pressure vessels, conduct all-position positioning welding, riveting and threaded connection, and check the size, shape and position.
Technician training objectives
On the basis of mastering basic knowledge and skills, I can make unfolded drawings of complex structural parts and calculate the length of unfolded materials; Formulate process flow and write process regulations; Be able to make assembly, welding, riveting and calibration process plans according to the technical requirements of drawings, and design fixtures; Familiar with quality management and production management knowledge; Familiar with new technologies, new materials and new processes, as well as the knowledge of related jobs.
main course
The main courses offered by the technician class are: mechanical drawing, mechanical principle and mechanical parts, mechanical manufacturing technology, tolerance and cooperation, engineering mechanics, electrical foundation, metal materials and heat treatment, hydraulic and pneumatic transmission, fixture design, numerical control programming foundation, basic knowledge of welding, basic knowledge of fitter, quality and production management, professional and technical courses, skill training and production practice.
The course content includes many working procedures and various operating skills of riveting workers in the whole riveting structure manufacturing process, from marking materials to processing and molding to assembly. Correct use of tools, fixtures and measuring tools; Practical simple geometric drawing, map recognition and basic expansion methods; Lofting, marking and sample preparation; Introduction, scheduling, installation and correct operation of stamping and cutting materials and gas cutting equipment; Material correction, material bending, calendering, riveting, welding equipment and operating technical performance. Finally, through several typical examples of different types of structural parts assembly, the operation skills of riveting workers are explained in detail. tolerate
Allowable deviation of actual parameter values. Parameters include not only geometric parameters in machining, but also parameters in physics, chemistry, electricity and other disciplines. Therefore, tolerance is a widely used concept. For mechanical manufacturing, the purpose of making tolerance is to determine the geometric parameters of products and make them change within a certain range to meet the requirements of communication or cooperation.
Tolerances of geometric parameters include dimensional tolerance, shape tolerance, position tolerance and so on. ① Dimensional tolerance. Refers to the change of allowable size, which is equal to the absolute value of algebraic difference between the maximum limit size and the minimum limit size. ② Shape tolerance. Refers to the total allowable variation of the shape of a single actual element, including straightness, flatness, roundness, cylindricity, line profile and surface profile. ③ Position tolerance. Refers to the total allowable deviation of the position of the relevant actual elements relative to the benchmark, which defines the mutual positional relationship between two or more points, lines and surfaces of the part, including parallelism, verticality, inclination, coaxiality, symmetry, position, circular jump and total jump. Tolerance indicates the manufacturing accuracy requirements of parts and reflects the processing difficulty.
Tolerance grades are divided into IT0 1, IT0, IT 1, …, IT 18***20 * 20, with decreasing grades and increasing tolerance values. It stands for international tolerance. The basic principle of tolerance grade or tolerance value selection is that the comprehensive economic effect of manufacturing cost and use value of mechanical parts should be the best. Generally, IT5 ~ IT 13 is used for matching dimensions, IT2~IT5 is used for matching particularly precise parts, IT 12 ~ IT 18 is used for non-matching dimensions, and IT8 ~ IT 14 is used for matching raw materials.
cooperate
Relationship between combined holes with the same basic size and shaft tolerance zone. Determine the compactness of the combination. The algebraic difference obtained by subtracting the size of the mating shaft from the size of the hole is positive clearance, negative clearance is interference, and sometimes interference is negative clearance. According to the relationship between the hole and the shaft tolerance zone, that is, the characteristics of clearance, interference and their changes, the fit can be divided into three situations: ① clearance fit. The tolerance zone of the hole is above the tolerance zone of the shaft, and there is clearance fit (including the minimum clearance is equal to zero). The function of clearance is to store lubricating oil and compensate various errors, and its size affects the relative motion between the hole and the shaft. Clearance fit is mainly used for the movable connection between hole and shaft, such as the connection between sliding bearing and shaft. ② Interference fit. The tolerance zone of the hole is lower than that of the shaft, and it is an interference fit (including the minimum interference is equal to zero). In interference fit, because the size of the shaft is larger than the size of the hole, it is necessary to use pressure or thermal expansion and cold contraction to assemble. Interference fit is mainly used for the fastening connection between the hole and the shaft, such as the connection between the gear ring and the hub of a large gear. ③ Transitional cooperation. The tolerance zones of the hole and the shaft overlap each other, and there may be a gap or interference fit (the gap and interference are generally small). Transition fit is mainly used for positioning connection that requires good coaxiality and coaxiality between the hole and the shaft and is easy to disassemble, such as the connection between the inner diameter of the rolling bearing and the shaft.
The allowable deviation of clearance or interference in fit is called fit tolerance. It is equal to the sum of the tolerances of the mutually matched holes and shafts, indicating the allowable variation range of riveting fit tightness; Riveting defect
Allowable deviation of parameter values between tolerances. Parameters include not only geometric parameters in machining, but also parameters in physics, chemistry, electricity and other disciplines. Therefore, tolerance is a widely used concept. For mechanical manufacturing, the purpose of making tolerance is to determine the geometric parameters of products and make them change within a certain range to meet the requirements of communication or cooperation.
Tolerances of geometric parameters include dimensional tolerance, shape tolerance, position tolerance and so on. ① Dimensional tolerance. Refers to the change of allowable size, which is equal to the absolute value of algebraic difference between the maximum limit size and the minimum limit size. ② Shape tolerance. Refers to the total allowable variation of the shape of a single actual element, including straightness, flatness, roundness, cylindricity, line profile and surface profile. ③ Position tolerance. Refers to the total allowable deviation of the position of the relevant actual elements relative to the benchmark, which defines the mutual positional relationship between two or more points, lines and surfaces of the part, including parallelism, verticality, inclination, coaxiality, symmetry, position, circular jump and total jump. Tolerance indicates the manufacturing accuracy requirements of parts and reflects the processing difficulty.
Tolerance grades are divided into IT0 1, IT0, IT 1, …, IT 18***20 * 20, with decreasing grades and increasing tolerance values. It stands for international tolerance. The basic principle of tolerance grade or tolerance value selection is that the comprehensive economic effect of manufacturing cost and use value of mechanical parts should be the best. Generally, IT5 ~ IT 13 is used for matching dimensions, IT2~IT5 is used for matching particularly precise parts, IT 12 ~ IT 18 is used for non-matching dimensions, and IT8 ~ IT 14 is used for matching raw materials.
cooperate
Relationship between combined holes with the same basic size and shaft tolerance zone. Determine the compactness of the combination. The algebraic difference obtained by subtracting the size of the mating shaft from the size of the hole is positive clearance, negative clearance is interference, and sometimes interference is negative clearance. According to the relationship between the hole and the shaft tolerance zone, that is, the characteristics of clearance, interference and their changes, the fit can be divided into three situations: ① clearance fit. The tolerance zone of the hole is above the tolerance zone of the shaft, and there is clearance fit (including the minimum clearance is equal to zero). The function of clearance is to store lubricating oil and compensate various errors, and its size affects the relative motion between the hole and the shaft. Clearance fit is mainly used for the movable connection between hole and shaft, such as the connection between sliding bearing and shaft. ② Interference fit. The tolerance zone of the hole is lower than that of the shaft, and it is an interference fit (including the minimum interference is equal to zero). In interference fit, because the size of the shaft is larger than the size of the hole, it is necessary to use pressure or thermal expansion and cold contraction to assemble. Interference fit is mainly used for the fastening connection between the hole and the shaft, such as the connection between the gear ring and the hub of a large gear. ③ Transitional cooperation. The tolerance zones of the hole and the shaft overlap each other, and there may be a gap or interference fit (the gap and interference are generally small). Transition fit is mainly used for positioning connection that requires good coaxiality and coaxiality between the hole and the shaft and is easy to disassemble, such as the connection between the inner diameter of the rolling bearing and the shaft.
The allowable deviation of clearance or interference in fit is called fit tolerance. It is equal to the sum of the tolerances of the mutually matched holes and shafts, indicating the allowable variation range of riveting fit tightness; Riveting defect
Although riveting is a simple mechanical connection that has been used for a long time, people do not always use enough skills and techniques to complete reliable riveting. The repair of defective riveted products will cause great waste of people, money and materials. This paper only discusses the common riveting defects and their causes as follows:
1 rivet
The diameter of the rivet stem is determined by the actual load borne by the riveted parts. However, as far as the riveting of metal plates (which is also the main form of riveting) is concerned, the diameter of rivet rod is closely related to the thickness of riveted parts. If the rivet and the riveted part are made of the same material, the diameter of the rivet shaft should be 1. 4 times the square root () of the thickness t of the thickest plate. If the diameter of rivet rod is larger than this value, it will cause riveting difficulty, and the strength of riveted parts will be weakened by the increase of nail holes; If the diameter of the rivet stem is too small, the rivet stem may bend during riveting.
When the riveted piece is very thick, as shown in figure 1. An excessively long rivet shaft will bear bending load. In this case, a more reasonable method is to process a counterbore for the rivet head on the riveted part, so that the riveting can be completed with a shorter rivet.
In order to prevent inferior riveting, it is necessary to ensure that the rivet shaft length is appropriate. If the rivet shaft is too long, it will be bent and deformed during riveting. If the rivet shaft is too short, it is impossible to form a complete rivet head.