1.Selection of positioning reference: correct selection of positioning reference of parts in machining, to meet the specific requirements of reliable positioning, high precision, convenient positioning, convenient processing, convenient clamping and simple fixture structure, etc., to ensure the machining allowance of parts .
(1) Selection and determination of rough reference: According to the selection principle of the rough reference, when the parts have different machined surfaces, these unmachined surfaces should be used as the rough reference; if the parts have several unmachined surfaces, they should be The machined surface requires an unmachined surface with a relatively high relative positional accuracy as a rough reference. The surface as a rough reference should be flat and free of burrs, burrs or other surface defects. In the design of the Dechengwang project, the entire surface of the Teflon bushing needs to be machined, and the hole should be processed as the fine reference. Therefore, the outer circle and its end face should be selected as the rough reference.
(2) Selection and determination of fine benchmarks: The selection of fine benchmarks should mainly consider the problem of benchmark coincidence. The design basis, the process reference, and the positioning reference are coincident, which can reduce the error caused by the positioning error and the reference misalignment. The Teflon part hole is the design basis (also the assembly reference and measurement basis), in order to avoid the misalignment due to the reference. For the error generated, the hole should be selected as the positioning reference, that is, the principle of “reference coincidence” should be followed. The inner bore and its end face are selected as the fine reference.
2.Determining the processing plan of each processing surface
The machining surface of the parts has outer circumference, inner hole, end face and thread, and the material is M-18. Refer to [Shenzhen PTFE manufacturer] for relevant information, the processing methods are as follows:
Outer face: Tolerance class is IT6, surface roughness is Ra3.2μm, roughing-semi-finished-finished car is required.
Outer face: Tolerance class is IT7, surface roughness is Ra3.2μm, roughing-semi-finished-finished car is required.
Inner hole: Tolerance class is IT7, surface roughness is Ra3.2μm, rough-semi-precision-fine boring is required.
upper and lower working surface: the surface roughness is Ra3.2μm, and roughing-semi-finishing is required.
Drill-reaming based on tolerance class and surface roughness.
Both ends of the bushing: the end face of the Teflon part is the end face of the rotating body, the dimensional accuracy is not required, and the surface roughness is Ra12.5μm.
Outer circular side of the bushing: roughing-semi-finishing according to the tolerance requirements of the side.
M60×1.5 thread: generally refers to the method of machining thread on workpiece by forming tool or grinding tool, mainly including turning, milling, tapping, threading, grinding, grinding and cyclone cutting, etc. .
3.Formulating the process route
(1) Division of the processing stage: roughing stage, semi-finishing stage, finishing stage.
(2) Heat treatment process: 1 preliminary heat treatment: In order to improve the cutting performance of the workpiece material, the internal stress during the blank manufacturing is eliminated, and the heat treatment is performed before the machining, and the treatment method is annealing and normalizing, and quenching and tempering. In order to eliminate the residual stress inside the bushing, the heat treatment method is normalizing.
2 Final heat treatment: In order to improve the strength, surface hardness and wear resistance of the material, after semi-finishing, heat treatment is carried out before and after grinding. The treatment methods include quenching and tempering, quenching, carburizing and quenching. The final heat treatment selected for the machining of the bearing is quenching.
(3) Arrange the order of machining process: first after the benchmark, first, first and second, first coarse and then fine, first face and back hole, the process is arranged as follows:
Process 1 Forging
Process 2 Heat Treatment: Normalizing
Step 3: Both ends of the rough milling bushing
Step 4 Rough, semi-precision bushing bore 2×45
Process 5 rough, semi-finished car outer circle; rough car, semi-finished car positioning hole upper and lower processing surface
Step 6 Drill, expand to the pattern size 14mm and process 7 thread, and chamfer
Process 8 Heat Treatment: Quenching
Step 9 fine inner sleeve hole and chamfer
Process 10 Finishing the outer circle, finishing the positioning hole and processing the surface, and chamfering
Step 11 Both sides of the roughing and semi-finishing milling bushings
Step 12 Deburring, cleaning
Process 13 inspection and storage
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