What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
Most electrical appliance manufacturers only require the size and riveting gap to be tested for riveted contact components. There is no clear requirement for riveting strength. Only a few manufacturers perform torsion testing on riveting strength. The torque detection method is as follows: use a saw blade to open a one-shaped groove on the rivet head of the riveted contact element, and then insert a torque wrench into the one-shaped open groove to rotate, and measure the torque value. Because most of the electrical contacts are made of copper-silver alloy, the strength is low, and it is easy to slip during the test, and when a saw blade is used to open the one-shaped groove, the width and depth cannot be accurately positioned, so the measured value fluctuates greatly. , has always been an unsolvable technical problem in the industry.
Electrical contact element is a kind of low-voltage electrical products and household electrical products widely used in switches, relays, thermostats, circuit breakers, contactors, controllers, timers, etc. There are mainly three types of electrical contact elements. 1. Riveting parts , riveting the rivet on the copper piece; 2. Welding piece, welding the sheet contact on the copper piece; 3. Stamping piece, punching the composite tape into components. Existing rivet contacts on the market at present are usually all made of precious metals, such as a simple metal matrix such as gold or silver. Its electrical contact performance is limited by a single metal material, and its electrical contact performance is poor; and due to certain requirements for metal purity in production, production efficiency is low, and production costs are high, resulting in the production of products that cannot be sold on a large scale in the market. and application.
Usually, the pumped storage unit adjusts the opening of the guide vane through the movable guide vane to control the power generation output and the pumping head of the unit. The torque of the guide vane rotation depends on the relay to act on the control ring, and the torque is transmitted to the guide vane rotating shaft through the connecting rod and the arm. The torque transmission between the crank arm and the rotating shaft all acts on the pin located between them. When the unit is overhauled, it is necessary to remove the pin between the arm and the rotating shaft of the guide vane in advance when it comes to the replacement of the guide vane. However, due to the special position of the pin and the limited inspection space, the conventional method is not only time-consuming and laborious, but also has the risk of damaging the pin. Maintenance work brings inconvenience.
total of 13 domestic automotive fastener companies were interviewed and investigated in this survey, and all the companies under investigation have passed the TS16949 system certification. An average car has about 1500 fasteners, and the total bolt assembly time for each car is about 2.5~3.2h. It can be seen that the variety and quality of fasteners have an important impact on the level of the main engine and the quality of the vehicle. This article analyzes the localization of high-strength threaded fasteners and the management of supply quality from the perspective of the production process of high-strength threaded fasteners. Product flow of high-strength threaded fasteners The production process of high-strength threaded fasteners is raw material transformation → cold heading forming → thread processing (thread rolling or thread rolling) → heat treatment → surface treatment → sorting and packaging, generally used above grade 10.9 Thread rolling process after heat treatment. The steel grades commonly used for high-strength bolts of automotive fastener materials are 35 steel, 45 steel, and ML35 steel for grade 8.8 bolts; 35CrMo for grade 10.9 bolts; 40Cr; 35CrMo, 42CrMo, and SCM435 for grade 12.9 bolts. The raw materials for domestic fasteners are basically in the hot-rolled state, while the steel for fasteners produced in Japan and other countries is basically in the state of direct cold heading. Users do not need pretreatment, which can reduce costs from the link. Common failure modes of fastener failure are assembly elongation, fatigue fracture, and delayed fracture. In addition to the material, the quality of cold heading forming and thread processing (thread rolling or thread rolling, tapping) threaded fasteners, forming equipment and thread processing equipment and molds (production process and equipment) are the key factors to ensure their quality. Especially in the state of large-scale and multi-variety supply, automotive fasteners that require high machining accuracy, how to ensure product consistency and defect prevention is one of the problems faced by fastener production. For the cold heading equipment and thread processing equipment of the investigated companies, domestic equipment accounts for about 40%, Taiwan equipment accounts for 50%, and imported (Europe, America, Japan) equipment accounts for about 10%; Partial folding, thread streamline upsetting, tooth wrinkles and cracks, etc. Domestic fastener factories are limited by capital or other reasons, and most of them use domestic equipment and Taiwan equipment to produce fasteners for automobiles. To ensure the dimensional tolerance and geometric tolerance of large-scale production of high-end fastener products, online monitoring should be increased. Means and mold making level. Eliminate unqualified products in production, so as to ensure the assembly quality of OEMs and OEMs. [1] About 80% of the surveyed fastener enterprises have heat treatment equipment, and most of them use Taiwan heat treatment process lines; the process line equipment is a continuous mesh belt furnace with atmosphere protection, and the atmosphere, temperature and process parameters are controlled by a computer. The high-strength fastener industry is a relatively competitive industry. If we want to have a thorough and objective analysis of the technology and market of the high-strength fastener industry, we need to start from the following aspects: domestic high-strength fasteners Industry and Enterprise Competition Pattern High-strength Fastener Industry Industrial Policy High-strength Fastener Product Technical Standards and Regulations my country's High-strength Fastener Product Technology Competition Pattern Dynamics Regarding these six aspects, many domestic research institutions have conducted in-depth research and research, and many institutions have long been engaged in research and research in this industry.
The above content is uploaded by Yueluo or the Internet. If there is any copyright issue, please contact [email protected].
