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Typical machining time axis for shaft parts

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Update time : 2019-11-19 13:06:23
1. Classification and technical requirements for shaft parts

The shaft is one of the typical parts commonly found in machining. It is mainly used in machinery to support gears such as gears, pulleys, cams and connecting rods to transmit torque. According to different structural forms, the shaft can be divided into stepped shaft, tapered mandrel, optical axis, hollow shaft, crankshaft, camshaft, eccentric shaft, various lead screws, etc. Among them, the stepped drive shaft is widely used, and its processing technology can be comprehensive. The ground reflects the processing law and commonality of the shaft parts.




According to the function and working conditions of the shaft parts, the technical requirements are mainly in the following aspects:

1.1 Dimensional accuracy. The main surfaces of shaft parts are often two types: one is the outer cylindrical journal that fits the inner ring of the bearing, that is, the bearing journal, which is used to determine the position of the shaft and support the shaft. The dimensional accuracy is high, usually IT. 5~IT7; The other type is the journal that cooperates with all kinds of transmission parts, that is, the matching journal, its precision is slightly lower, often IT6~IT9.

1.2 Geometric accuracy. Mainly refers to the roundness and cylindricity of important surfaces such as journal surface, outer conical surface and tapered hole. The error should generally be limited to the dimensional tolerances. For precision shafts, the geometric accuracy of the parts is to be specified separately.

1.3 mutual positional accuracy. Including the inner and outer surfaces, the coaxiality of the important axial plane, the radial runout of the circle, the perpendicularity of the important end face to the axis, and the parallelism between the end faces.

1.4 Surface roughness. The machined surface of the shaft has a roughness requirement, which is generally determined by the possibility of processing and economy. The support journal is usually 0.2~1.6μm, and the transmission part is 0.4~3.2μm.

1.5 Others. Heat treatment, chamfering, chamfering and appearance modification.

2. Materials, blanks and heat treatment of shaft parts

2.1 Materials for shaft parts

2.11 Shaft parts material. Commonly used 45 steel, high precision shaft can choose 40Cr, bearing steel GCr15, spring steel 65Mn, can also choose spheroidal graphite cast iron; for high speed, heavy load shaft, use 20CrMnTi, 20Mn2B, 20Cr and other low carbon alloy steel or 38CrMoAl nitride steel.

2.12 Shaft type blank. Common round bars and forgings; large shafts or complex shafts are cast. After the blank is heated and forged, the internal fiber structure of the metal can be evenly distributed along the surface to obtain high tensile, bending and torsional strength.

2.2 Heat treatment of shaft parts Before forging, the forged blanks must be normalized or annealed to refine the internal grain of the steel, eliminate the forging stress, reduce the hardness of the material and improve the cutting performance.

The quenching and tempering is generally arranged after the roughing and before the semi-finishing to obtain good physical and mechanical properties.

Surface quenching is generally scheduled prior to finishing to correct localized deformation due to quenching.

For shafts with high precision requirements, after local quenching or rough grinding, low temperature aging treatment is also required.

3. How to install shaft parts

There are three main types of installation of shaft parts.

3.1 Using two center hole positioning clips

Generally, the important outer circular surface is used as the rough reference positioning, and the center hole is machined, and then the center hole at both ends of the shaft is used as the positioning precision reference; as far as possible, the reference is unified, the reference is coincident, and the mutual reference is made, and multiple installation and processing are realized. surface. The center hole is a uniform positioning reference and inspection reference for workpiece machining. Its own quality is very important, and its preparation work is also relatively complicated. It is often positioned by the support journal, and the center hole of the car (drill) is centered. Round; outside circle positioning, coarse grinding cone hole; positioning with center hole, fine grinding outer circle; finally positioning the outer circumference of the bearing journal, fine grinding (scraping or grinding) cone hole, making the precision of the cone hole meet the requirements .

3.2 Positioning the clamping with the outer surface

For hollow shafts or short shafts that cannot be positioned with the center hole, the outer circular surface of the shaft can be used to position, clamp and transmit torque. Generally, a universal clamp such as a three-jaw chuck or a four-jaw chuck, or various high-precision automatic centering fixtures, such as a liquid plastic thin-wall centering fixture and a diaphragm chuck, are used.

3.3 Positioning the clamp with various plugs or tie rods

When machining the outer circular surface of a hollow shaft, various plugs or tie rod mandrels with a central hole are often used to mount the workpiece. Plugs are often used for small taper holes; pull rod mandrels with plugs are often used for large taper holes.
https://www.infignos.com/templates/updatelistingnow.cfm?email=ryanlee901213@gmail.comShenzhen Kangda Precision Manufacturing Co.,Ltd.,Machining Manufacturer,Shenzhen,FL