Shaft part is one of the most common typical parts. According to the different structural methods of shaft parts, they can be generally divided into three categories: optical axis, stepped axis and special-shaped axis; Or divided into solid shaft, hollow shaft, etc. They are used to support gear, pulley and other transmission parts in the machine to transfer torque or motion.
The machining technology of stepped shaft is typical, which reflects most of the contents and basic rules of shaft parts machining. Next, take the transmission shaft in the gearbox as an example to introduce the processing technology of general step shaft.
The part is the transmission shaft in the reducer. It belongs to stepped shaft parts, which is composed of cylindrical surface, shaft shoulder, thread, thread tail undercut, grinding wheel overtravel and keyway. The shoulder is generally used to determine the axial orientation of the parts on the shaft. The effect of each ring groove is to make the parts have an accurate orientation when they are used in the equipment, and to make it convenient to withdraw the tool when grinding the outer circle or turning the thread; Keyway is used for equipment key to transfer torque; Thread is used for all kinds of lock nuts and adjusting nuts.
According to the working performance and conditions, the typical parts processing technology, the transmission shaft drawing rules the primary journal m, N, excircle P, Q and shaft shoulder g, h, I, has higher standard, orientation accuracy and smaller surface roughness value, and has the need of heat treatment. These technologies need to be guaranteed in processing. Therefore, the key process of the transmission shaft is the processing of journal m, N and outer circle P, Q. The material of the transmission shaft is 45 steel, because it belongs to the general transmission shaft, so the selection of 45 steel can meet its needs. The transmission shaft of typical parts processing technology belongs to medium and small transmission shaft, and there is little difference in the outer circle diameter standard, so ￠ 60mm hot rolled round steel is selected as the blank.
Determine the processing method of the primary surface:
Most of the transmission shafts are rotary surfaces, which are mainly formed by turning and cylindrical grinding. Because the primary surface M, N, P, Q of the transmission shaft has higher service level (IT6) and smaller surface roughness Ra (RA = 0.8 UM), it needs grinding after turning. The processing plan of cylindrical surface (see table A-3) can be as follows: rough turning → semi finish turning → grinding.
Determine positioning datum:
Reasonable selection of positioning datum has a decisive effect on ensuring the standard and orientation accuracy of parts. As several primary cooperative surfaces (Q, P, N, m) and shoulder surfaces (h, g) of the transmission shaft need radial circular runout and end circular runout for the reference axis A-B, and it is also a solid shaft, the center hole at both ends should be selected as the reference, and the double tip clamping method should be selected to ensure the technical requirements of the parts.
The rough datum of typical parts processing technology is the blank outer circle of hot rolled round steel. Three jaw self centering chuck is used to clamp the outer circle of hot rolled round steel blank, turn the end face and drill the center hole. However, it is necessary to pay attention to the fact that it is generally not possible to drill the center hole at both ends by clamping the outer circle of the blank twice. Instead, it is necessary to take the outer circle of the blank as the rough datum, first process an end face, drill the center hole, and turn out the outer circle at one end; Then, take the turned outer circle as the benchmark, clamp it with the three jaw self centering chuck (sometimes set up the center frame at the turned outer circle in the previous step), turn the other end face and drill the center hole. Only in this way can the two center holes be coaxial.
ken. tang@chengcg.com
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