Analysis of typical precision machined parts: sleeve parts

1.What are sleeve parts?

Sleeve parts are divided according to their structural characteristics: various bearing rings and sleeves that support the rotary body, drill sleeves and guide sleeves on the fixture, cylinder sleeves on the internal combustion engine, hydraulic cylinders in the hydraulic system, and electro-hydraulic servo valves. sleeve, cooling sleeve in the electric spindle, etc.

2. Structural characteristics of sleeve parts

The structure and size of sleeve parts vary with different uses, but the structure generally has the following characteristics:
1) The diameter d of the outer circle is generally smaller than its length L, usually L/d<5.
2) The difference between the diameter of the inner hole and the outer circle is small.
3) The coaxiality requirements of the inner and outer circles of rotation are relatively high.
4) The structure is relatively simple.

3. Main technical requirements for sleeve parts processing

The main surfaces of the sleeve parts play different roles in the machine, and their technical requirements are quite different. The main technical requirements are as follows:
(1) Technical requirements for the inner hole. The inner hole is the most important surface of sleeve parts that plays a supporting or guiding role. It usually matches the moving shaft, tool or piston. The diameter tolerance level is generally IT7, and the precision bearing sleeve is IT6; the shape tolerance should generally be controlled within the aperture tolerance, and the more precise sleeve should be controlled within 1/3~1/2 of the aperture tolerance, or even smaller; for long In addition to roundness requirements, the sleeve should also have requirements for the cylindricity of the hole. In order to ensure the use requirements of sleeve parts, the surface roughness of the inner hole is Ra0.16~2.5pm. Some precision sleeve parts have higher requirements, up to Ra0.04um.
(2) Technical requirements for the outer circle: The outer circle surface often uses an interference fit or a transition fit to match the holes in the box or body frame to play a supporting role. Its diameter size tolerance level is IT6~IT7; shape tolerance should be controlled within the outer diameter tolerance; surface roughness is Ra0.63~5m.
(3) Position accuracy between major surfaces
1) Coaxiality between inner and outer circles. If the sleeve is installed into the hole in the machine before final processing, then the coaxiality requirements for the inner and outer circles of the sleeve are lower; if the sleeve is finalized before being installed into the machine, the coaxiality requirements are higher. , the tolerance is generally 0.005~0.02mm.
2) Perpendicularity between the hole axis and the end face. If the sleeve end face is subjected to axial load during work, or is used as a positioning reference and assembly reference, then the end face has a high perpendicularity to the hole axis or the axial circular runout requires a tolerance of generally 0.005~0.02mm.

4. Processing technology of sleeve parts

The main processes for processing sleeve parts are mostly roughing and finishing of the inner hole and outer surface, especially the roughing and finishing of the inner hole is the most important. Commonly used processing methods include drilling, reaming, punching, sharpening, grinding, drawing and grinding. Among them, drilling, reaming, and drilling are generally used as rough machining and semi-finishing of holes, while drilling, grinding, drawing, and grinding are used as finishing.

5. Material selection for sleeve parts machining

The choice of raw materials for sleeve parts mainly depends on the functional requirements, structural characteristics and working conditions of the parts. Set parts are generally made of materials such as steel, cast iron, bronze or brass, and powder metallurgy. Some sleeve parts with special requirements can adopt a double-layer metal structure or use high-quality alloy steel. The double-layer metal structure uses a centrifugal casting method to pour a layer of Babbitt alloy and other bearing alloy materials on the inner wall of the steel or cast iron bushing. Using this Although this manufacturing method adds some man-hours, it can save non-ferrous metals and improve the service life of the bearing.