What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
In the process of electronic accessories such as mobile phones and computers, especially multi-layer circuit boards, there are generally fixed connections between multi-layer circuit boards or other components. At present, there are two main connection methods. One is to use laser welding. However, the laser welding equipment is expensive and has very high requirements on the position of the weldment. Therefore, during welding, it must be ensured that the final position of the weldment needs to be the same as the laser beam will impact. Solder joint alignment. The other is to use a metal rivet to pass through the positioning hole, and then impact the rivet with a punching needle, so that the open end of the rivet is deformed and opened and pressed on the fixed piece to form a rivet fixed state. However, in actual operation, when the open end of the rivet tube is opened and deformed by the impact, strong cracking often occurs, resulting in a small amount of conductive fracture debris, which falls on the circuit board or other devices to be connected, causing Short circuit, in view of this shortcoming, some manufacturers have changed the metal rivets to plastic materials, but the plastic rivets have poor ductility and often break when impacted with a punching needle, resulting in the failure to achieve the riveting fixing force of the original metal rivets. In addition, the above two fixing methods are complicated in operation and low in installation efficiency.
For a long time, the rivets used in general riveting, especially the ordinary rivets and bolts and other fasteners commonly used in steel structures such as vehicles and bridges, have low connection reliability, especially under alternating load and impact conditions. Looseness is easy to occur, the maintenance cycle is short, and the maintenance cost is high in the later period, which cannot meet the requirements of railway freight.
The spring washer usually includes a washer body and a raised claw head punched and formed on the washer body. The spring washer is often placed between the bolt head of the bolt and the connected parts, wherein the raised claw head is connected to the part to be connected. The surfaces of the connecting parts are in contact, and the plane on the gasket body, opposite to the lifting direction of the raised claw head, is in contact with the bolt head. After the bolt head is tightened, the elastic reaction force generated by the raised claw head after flattening makes the The screwed threads are pressed tightly, and at the same time, the raised claw head is pressed against the bolt head and the supporting surface of the connected parts, which has the effect of preventing loosening. However, the traditional spring washer is a single-claw type. When tightening, the raised claw head will cause great damage to the surface of the connected parts, so it is not suitable for the anti-loosening treatment of parts with small surface hardness.
At present, with the continuous growth of the demand for communication products, higher and higher requirements are put forward for the production capacity of equipment manufacturers, and at the same time, the requirements for the cost, weight and reliability of communication products are also more and more stringent. In order to facilitate the positioning of the equipment, pins are often used to complete the equipment, and a certain cost is incurred for its manufacture and assembly. In the past, such parts have been assembled in the form of threads. In order to ensure that the assembly height is within the specified range and to prevent loosening, bar turning is often used to form threads and positioning steps, and thread pinning glue is used in the assembly, and the cost of machining is relatively high. Large, more material waste. Based on the above drawbacks, in order to better solve this problem, some existing manufacturers use the interference fit riveting method, which solves the problem of material waste and anti-loosening, but the inner diameter of the pin hole and the outer diameter of the pin are matched. The machining accuracy of the machine is relatively high. Once the matching size is out of tolerance, a second matching is required, which wastes working hours and increases the slack time.
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