First, the shaft of the workpiece blank and material requirements
(1) the blank required for the workpiece
Shaft class workpiece can be based on application requirements, production process, processing requirements, the required equipment and structure type, the choice of bar, forgings and other rough situation. For the diameter of the outer diameter of the shaft is not the same, usually the main bar to the main; and for the outer diameter of the difference between the steps of the step axis or the important axis, often use forging, which can save material and reduce the mechanical processing of cutting Sales, but also can improve the mechanical function.
According to the different scale of production, rough casting methods are free forging and forging two. Small and medium-sized bulk of the way for free forging, mass production to adopt forging method.
(2) Material requirements for shaft type workpieces
Shaft class workpiece should be based on different working conditions and the use of different materials and use different heat treatment standards (such as quenching and tempering, quenching, etc.) to obtain a certain strength, toughness and wear resistance.
45 steel is a relatively common type of workpiece, it is cheap and after quenched and tempered (or normalizing), you can get better cutting performance, and can get a higher strength and toughness and other comprehensive mechanical function, after quenching Surface hardness of up to 45 ~ 52HRC.
40Cr and other alloy structural steel for medium precision and high speed shaft workpiece, this type of steel after quenching and quenching, will have a better integrated mechanical function.
Bearing steel GCr15 and spring steel 65Mn, quenched and tempered and the outer surface of high-frequency quenching, the outer surface hardness of up to 50 ~ 58HRC, will have a high fatigue resistance and good wear resistance, can produce high precision axis.
Precision machine tool spindle (such as grinder wheel shaft, coordinate boring machine spindle) can choose 38CrMoAIA nitriding steel. This type of steel by quenching and tempering and the outer surface of the nitride, not only can get a high surface hardness, and can guarantee a soft core, so good impact resistance. Compared with carburized steel, it has a small heat treatment deformation, higher hardness characteristics.
Second, the axis of the workpiece function, structural characteristics and technical standards
Shafts are one of the typical workpieces that are often encountered in machinery. It is mainly used to support transmission parts, transmission torque and bear the load. Shaft type workpiece is a rotating body part, its length is greater than the diameter, usually by the concentric shaft of the outer cylindrical surface, conical surface, the hole and thread and the corresponding end of the composition. Select the processing of various types of high-quality shaft parts approved titanium Hao machinery, according to the structure of different shapes, shaft parts can be divided into optical axis, ladder axis, hollow shaft and crankshaft and so on.
A shaft with an aspect ratio of less than 5 is called a minor axis, greater than 20 is called a slender axis, and most of the shaft is between the two.
Shaft bearing support, and bearing the common axis called the journal. The journal is the shaft of the device reference, their accuracy and external surface quality requirements are higher, the technical requirements are usually based on the main function of the shaft and working conditions to develop, mainly the following:
(1) dimensional accuracy
In order to determine the position of the shaft, it is usually required for its dimensional accuracy (IT5 ~ IT7). The accuracy of the journal size of the assembly drive is generally low (IT6 ~ IT9).
(2) geometric shape accuracy
The geometric shape accuracy of the shaft workpiece mainly refers to the roundness, cylindrical degree and so on of the journal, outer cone, Mohs cone, etc., and should be limited to the tolerance range. For high accuracy requirements of the inner and outer circular surface, should be marked on the drawings of the allowable error.
(3) mutual position accuracy
The position accuracy requirements of the shaft workpiece are determined primarily by the position and function of the shaft in the machine. It is usually necessary to ensure that the journal of the assembly of the journal to the journal coaxial degree of the standard requirements, or will affect the transmission parts (gears, etc.) transmission accuracy, and noise. The axis of normal accuracy, the radial runout of the support shaft with respect to the support journal is usually 0.01 to 0.03 mm, and the high precision shaft (e.g., the main shaft) is generally 0.001 to 0.005 mm.
(4) outer surface roughness
The outer surface roughness of the shaft diameter corresponding to the transmission member is Ra2.5 to 0.63 m, and the outer surface roughness of the support shaft diameter cooperating with the bearing is Ra0.63 to 0.16 m.