The components are made from custom materials, and the quality of each batch varies, leading to inconsistent properties. This instability must be taken into account during the manufacturing process. Due to varying usage requirements and processing constraints, the design has undergone several revisions and is currently in the state shown in Figure 1.
First, Process Planning
1. Part Structure, Size Characteristics, and Requirements
(1) Part Structure and Size Requirements: The parts are nickel-copper alloy rods with a diameter of φ45mm. No surface treatment or heat treatment is required. The structural dimensions are illustrated in Figure 1.
Figure 1
The part’s 1/4 section is annular, with an inner arc radius of R15 mm ± 0.1 mm, a surface roughness of Ra = 1.6 μm, and requires polishing. The outer arc has a radius of R16 mm ± 0.1 mm with the same surface roughness. A central hole on the arc surface has a diameter of φ2.5 +0.02 0 mm. The inner arc has a rounded corner with R = 0.3 mm, and the outer arc interface has a chamfer of C0.2 mm. The positioning dimension for the φ2.5 mm hole is (3.7 ± 0.1) mm, and the angular dimension is 12° ± 2°. Note that when machining, the core material with a diameter of φ15 mm must be removed and cannot be used for part production.
2. Mechanical Processing Technology Analysis
(1) Part Analysis: Based on the design requirements, the following factors need to be considered during process design and manufacturing:
1. The nickel-copper alloy used for the parts is only available as a φ45 mm bar, with an initial hardness of HRC ≥ 38, which is not ideal for cutting operations.
2. The core part of the material with a diameter of φ15 mm cannot be used for part processing, requiring special measures to ensure accuracy.
3. The part structure is relatively simple, forming a rotating body. The maximum material utilization rate needs to be analyzed and calculated carefully under restricted conditions.
4. The part is a rotating body with a thickness ranging from 0.8 to 1.2 mm. Machining a φ2.5 mm hole on the arc surface presents challenges in clamping, and measuring the angular dimension of the positioning hole is also difficult.
5. All R15 mm ± 0.1 mm arcs on the surface require polishing, which necessitates auxiliary methods for proper execution.
(2) Solution: Based on the above analysis and considering existing production resources and processing techniques, the following solutions were proposed:
1. Due to the high hardness of the material, appropriate tools should be selected for processing. Since the material is conductive, methods such as wire cutting or electric discharge machining (EDM) can be used without requiring high hardness.
2. For machining the central φ2.50 +0.02 mm hole on the arc surface, options include general milling, numerical control milling, or fitter machining. As the part is a rotating body, all three methods require tooling. The hole machining requires angular positioning. General milling is inefficient, while numerical control milling involves frequent tool changes, reducing efficiency. Therefore, using a reliable fixture makes fitter machining the most optimal choice.
3. For polishing, there are no strict size or precision requirements. Two methods are available: manual sandpaper polishing by the fitter, or placing the parts and abrasives in a sealed container with a specific ratio to achieve relative motion and polishing.
Second, Tooling Design and Use
Tooling Design
(1) Positioning Analysis and Tooling Requirements: As shown in Figure 1, the central hole φ2.50 +0.02 mm requires high precision. One-time drilling by the fitter may not guarantee the required accuracy, so reaming is necessary.
When machining parts, the selection of the positioning reference directly affects positioning accuracy, which in turn influences processing efficiency and the qualification rate of the parts. According to the principle of positioning reference selection, the reference should be as close as possible to the design basis to reduce or eliminate positioning reference error and thus minimize positioning errors. There are two options for positioning the φ2.5 +0.02 0 mm holes, and the analysis is as follows:
Hot Plate,Electric Hot Plate,Heating Plate,Double Hot Plate
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