Rubber is a non-metallic material known for its unique mechanical properties, such as extreme elasticity, which allows it to return to its original shape even after significant deformation. However, rubber has relatively low strength, making it challenging to work with during machining. Soft and hard rubbers exhibit significantly different mechanical behaviors; for instance, soft rubber is approximately 1,000 times more flexible than hard rubber. In practice, when cutting rubber using conventional tools, issues like sickle-shaped chips, serrated edges, and rough surfaces often occur. However, by employing specialized tool designs and adjusting cutting parameters appropriately, satisfactory results can be achieved.
**1. Process Analysis of Parts**
Figure 1 shows the machining process of a specific aerospace component made from HG1142 rubber. The key characteristics of this material are:
(1) Rubber exhibits high elasticity during processing, leading to large deformations that make size control difficult.
(2) It has poor thermal conductivity and heat resistance. When the cutting temperature exceeds 60–150°C, the material may degrade, melt, or emit an odor.
(3) Although rubber has low strength, it is very tough, requiring extremely sharp cutting edges on the tools.
(4) Industrial rubber often contains impurities, which can cause chipping on the cutting edge.
**2. Tool Design**
Based on the processing characteristics of the part in Figure 1, the geometry of the tool used for rubber differs from that used for metal materials. Due to the special requirements of the rectangular thread on the rubber roller, the groove depth is considerable. To ensure a smooth thread surface, a combined turning tool was designed, as shown in Figure 2.
The tool consists of two cutters: a left cutter with a single straight edge and a right cutter with a 90° edge. When combined, they form a "door" shaped edge, allowing chips to be directed out from the middle, as illustrated in Figure 3. The wedge angle of the tool is kept small (8°–10°), ensuring a sharp cutting edge and light cutting force. The left cutter has an outer slope of 10° and an inner slope of 2°, and it must be tilted to the left, as shown in Figure 4. Similarly, the right cutter has outer and inner slopes of 10° and 2°, respectively, and must be tilted to the right. Its top back angle is 6°, while the inner side is inclined at 25°, as shown in Figure 5.
Both cutters are welded tools, with YG8 carbide inserts and a 45 steel body.
**3. Tool Usage**
After assembling the left and right cutters, a small gap of 0.03–0.05 mm is left between the blades to prevent collision. Since rubber has elastic recovery, the groove width increases by 0.1–0.15 mm after sharpening. To reduce friction and cutting resistance, the tool should be installed slightly below the center of the workpiece. The reduction in height H is calculated as H = 0.707R (where R is the outer radius of the rubber roller). The cutting depth t should be greater than the thread profile depth h, and can be calculated as t = 1.414h.
To manage heat and improve surface finish, compressed air cooling is essential during the cutting process. Before machining, the end of the rubber roller is chamfered at 20°, allowing the tool to gradually cut into the workpiece, ensuring stable guidance.
**4. Conclusion**
By analyzing the properties of rubber and adapting the tool design accordingly, we were able to meet the machining requirements effectively. This approach not only improved the quality of the finished product but also enhanced the efficiency and longevity of the cutting tools.
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