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How to draw the shaft parts? How to choose the material of shaft parts for different purposes?
Release time: 2023-05-08
The main function of shaft parts is to support the rotation of other rotating parts and transfer torque. At the same time, it is connected with the machine frame through the bearing. It is one of the important parts of the machine.
Shaft parts are rotating parts, the length of which is greater than the diameter. It is usually composed of an outer cylinder, a cone, an inner hole, a thread and the corresponding end face. The shaft often has splines, keyways, transverse holes, grooves, etc. According to the function and structural shape, there are many types of shaft, such as optical shaft, hollow shaft, half shaft, stepped shaft, spline shaft, crankshaft, camshaft, etc., which play the role of support, guidance and isolation.
1. View expression
1) Shaft parts are mainly rotary bodies, generally processed on lathes and grinders, commonly used in a basic view expression, the axis is placed horizontally, and the small head is placed on the right side, easy to see when processing.
2) The single keyway on the shaft is best drawn forward in full shape.
3) For the structure of the hole and keyway on the shaft, it is generally represented by the local section view or section map. The removed section in the profile can not only clearly express the structure shape, but also conveniently mark the dimensional tolerance and shape tolerance of the relevant structure.
4) Small structures such as cutting slot and fillet are expressed in local enlarged drawings.
2. Dimensioning
(1) The main basis of the length direction is the main end face of the installation (shaft shoulder). The two ends of the shaft are generally used as a measurement basis, and the axis is generally used as a radial basis.
② The main dimensions should be noted first, and the rest of the length dimensions should be noted according to the turning processing sequence. Most of the local structures on the shaft are located near the shoulder of the shaft.
(3) In order to make the size of the mark clear and easy to see the picture, it is appropriate to mark the inside and outside size on the section view separately, and mark the size of different processes such as turning, milling and drilling separately.
(4) The chamfering, chamfering, cutting groove, grinding wheel crossing groove, keyway, center hole and other structures on the shaft should be marked after referring to the size of the relevant technical data.
3. Materials of shaft parts
① The commonly used materials for shaft parts are 35, 45, 50 high-quality carbon structural steel, 45 steel is the most widely used, generally conditioned treatment, hardness of 230 ~ 260HBS.
② Less important or small load shaft available Q255, Q275 and other carbon structural steel.
③ The shaft with large force and high strength requirements can be tempered with 40Cr steel with hardness of 230 ~ 240HBS or hardened to 35 ~ 42HRC.
④ If the shaft parts work under the condition of high speed and heavy load, the alloy structural steel such as 20Cr, 20CrMnTi, 20Mn2B or 38CrMoAIA advanced quality alloy structural steel is selected. These steel after carburizing quenching or nitriding treatment, not only the surface hardness is high, and its core strength is also greatly improved, with better wear resistance, impact toughness and fatigue strength.
⑤ Nodular cast iron, high strength cast iron because of good casting performance, and vibration damping performance, often used in the manufacture of shaft shape structure complex. In particular, our rare earth magnesium ductile iron has the advantages of good impact toughness, friction reduction and vibration absorption, and low sensitivity to stress concentration. It has been applied to the important shaft parts of automobiles, tractors and machine tools.
Without the final heat treatment and obtain high hardness of the lead screw, generally available tensile strength is not less than 600MPa 45 and 50 carbon steel. The lead screw of precision machine tools can be made of carbon tool steel T10 and T12. After final heat treatment to obtain high hardness lead screw, CrWMn or CrMn steel manufacturing, the hardness can be guaranteed to reach 50 ~ 56HRC.
4. Technical requirements of shaft parts
① Dimensional accuracy
The diameter and dimension accuracy of the main journal is generally IT6 ~ IT9, and the precision is IT5. For each step length of the step shaft, the tolerance should be given according to the use requirements, or the tolerance should be assigned according to the requirements of the assembly dimension chain.
② Geometric accuracy
The shaft is usually supported on the bearing by two journals, which are the assembly reference of the shaft. The geometric accuracy (roundness, cylindricity) of the support journal should be generally required. For the geometric tolerance of journal with average accuracy, it should be limited to the diameter tolerance range, that is, mark E after the diameter tolerance according to the tolerance requirements. If the requirements are higher, mark the allowable tolerance value (that is, note E after the dimensional tolerance, and add a box to mark the shape tolerance value).
(3) mutual position accuracy
The coaxiality of the matching journal (the journal of the assembling drive) relative to the supporting journal in the shaft parts is the common requirement of the mutual position accuracy. Because of the convenience of measurement, radial circular runout is commonly used. The radial circle runout of the ordinary precision axis for the support journal is generally 0.01 ~ 0.03mm, and the high-precision axis is 0.001 ~ 0.005 mm. In addition, there are axial positioning end face and axis line perpendicularity requirements.
④ Surface roughness
In general, the surface roughness of the supporting journal is Ra0.16 ~ 0.63um, and that of the matching journal is RA0.63-2.5um. For general parts, typical parts, the above generally have the corresponding table and data.
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