1, Structural characteristics
Solid or tubular parts with a length greater than three times the diameter are collectively referred to as axle parts, such as the center axle rod, front axle rod, rear axle rod, axle tube, etc. of bicycles. The structural characteristics of these parts are:
(1) The shape is simple, and the processing parts are located at both ends of the shaft, and are basically symmetrical. The unprocessed part in the middle can be used for positioning and clamping, suitable for processing on a dual head machine tool.
(2) The machining surfaces at both ends require good coaxiality and dimensional accuracy.
(3) The roughness requirement is generally below Ra10-2.5um, and there should be no deep cutting marks on the surface. The machining allowance of the parts is relatively small, and they can generally be processed without coarse or fine machining sequence. In response to the structural characteristics of shaft parts, specialized equipment such as double headed lathes, double headed milling machines, double headed grinders, and double headed wire rolling machines have emerged, basically forming a "double headed" machining of shaft parts. Among them, double headed turning is the most widely used and widely used.
2, Blank of parts
The materials for shaft parts are mainly cold drawn round steel and welded pipes, and the length of these profiles is generally 4-9m, so they should be cut according to requirements before mechanical processing. There are several cutting methods suitable for mass production:
(1) When cutting the bar material on the lathe, the cutting blade is fed radially. Due to the small feed rate, the production efficiency is low; And the incision has a certain width, which results in significant metal loss and easy damage to the cutting blade. When cutting round steel, it is required that the cutting edge of the tool be aligned with the axis of the workpiece. If the cutting edge is too high or too low, during the cutting process, when the cutting edge is close to the center of the workpiece, it is easy to squeeze the workpiece and leave a "small tail" on the end face. This method is used to cut small diameter pipes, and the two ends of the cut blank are flat and smooth, with high dimensional accuracy. Generally, end face processing is not required. This method is commonly used for cutting off pipes such as front and rear pull tubes and shaft tubes.
(2) Cut off pipes with larger diameters on the pipe cutting machine. The pipe is clamped by centering, and the tool rotates and performs radial feed cutting. The end face quality and dimensional accuracy are the same as those of the lathe cutting.
(3) Cutting on a punching machine, the quality of the bar section is related to the structure and accuracy of the punching die. When the cutting edge sinks into the metal, the torque generated causes the workpiece to rotate, resulting in a slope on the cross-section. At the same time, the bottom of the bar material is compressed and deformed. Although the occurrence of this defect is limited by the gap between the mold and the tool, it is still inevitable in actual production. Therefore, this method cannot be used to cut high demand blanks. However, the cutting efficiency of punching machines is very high, which has great practical significance for the cutting of large quantities of forged blanks and small diameter shaft blanks, and is therefore widely adopted. The above-mentioned methods are mostly used for cutting the blanks of components such as front axle rods, middle axle rods, and rear axle rods.
(4) A friction saw is a toothless circular saw blade with a wedge-shaped edge that can be made of carbon tool steel or alloy tool steel. The working principle is that the circular saw blade rotates at high speed (with a linear speed of over 5m/s), rubs against the workpiece under a certain pressure, drives the workpiece to rotate, and gradually squeezes the workpiece. The quality of the cross-section cut by friction saw is poor, and there is obvious squeezing phenomenon at the fracture surface, which reduces the diameter of the pipe. The sawing work produces a lot of noise, but the production efficiency is high. Currently, it is widely used for sawing small diameter pipe fittings.
The above is my understanding of bicycle axle parts, hoping to be helpful to everyone. We are Ningbo Shenglu Auto Industry Co., Ltd., a professional factory that produces bicycle accessories. We mainly produce 5 series of products, including bicycle axle covers, discs, center axles, brakes, and bowl sets. Welcome bosses in need to purchase in large quantities. website: https://www.hubs-sf.com
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