**1. Introduction**
Molds are complex and non-standardized technical products that require a comprehensive process, including creative design, CNC programming, production preparation, machining, assembly, and trial. This entire cycle is lengthy, especially when it comes to machining, which is time-consuming. As a result, improving production efficiency, shortening the development cycle, enhancing the level of mold manufacturing, and reducing costs have always been key challenges for mold manufacturers.
Whether it’s a stamping die or a forging die, the materials used in the cavity are typically high-strength, wear-resistant alloys such as various tool steels and stainless steels. After heat treatment, these materials often reach hardness levels above 50HRC, making them difficult to machine using traditional methods.
For many years, Electrical Discharge Machining (EDM) has been the primary method for processing such hard materials. However, EDM has two major drawbacks: low productivity and inconsistent quality.
The emergence of high-speed cutting technology has introduced a new approach to mold manufacturing. Compared to EDM, high-speed machining offers higher efficiency, better quality, and the ability to process complex shapes, including hard and thin-walled parts. Since the 1990s, many foreign mold industries have started using high-speed cutting for finishing mold cavities.
According to statistics, over 85% of molds in industrialized countries now use high-speed cutting processes. This technique has become a mainstream in international mold manufacturing. In China, research and application of high-speed cutting technology began in the 1990s. The key technologies involved in high-speed cutting include tool technology and machine tool technology. This article explores the related technologies for high-speed milling of hardened molds.
**2. Advantages of High-Speed Milling Hardened Molds**
High-speed milling is the most commonly used method in high-speed machining. Replacing EDM with high-speed milling offers several benefits:
(1) **Superior Machining Quality**: Traditional EDM can damage the surface properties of workpieces due to high-temperature discharge, leading to cracks and poor surface quality. In contrast, high-speed milling operates at much higher speeds, minimizing residual stress and achieving excellent surface finish. The quality after high-speed milling can even rival grinding, eliminating the need for additional polishing.
(2) **Higher Production Efficiency**: EDM is a slow process based on micro-cutting, often requiring time-consuming manual polishing afterward. High-speed milling, on the other hand, is significantly faster and allows for one-clamping machining of both roughing and finishing, reducing overall time. It also eliminates the need for electrodes and manual work, making automation easier.
(3) **Ability to Process Complex and Hard Parts**: High-speed milling reduces cutting forces, making it suitable for machining hardened steel up to 60HRC without coolant—known as dry machining. Its low transverse cutting force is ideal for thin walls and fine ribs in complex molds. However, in cases of deep, narrow cavities, combining high-speed milling with EDM can yield better economic results.
**3. Cutting Tool Technology for High-Speed Milling Hardened Dies**
Tool technology is crucial in high-speed milling, involving material selection, geometry, wear detection, connection methods, and safety.
3.1 **Tool Material and Geometry Selection**
High-speed tools must have good thermal stability, wear resistance, and impact strength. Common materials include PCBN, ceramics, and coated carbides. PCBN is best for materials harder than 55–65HRC, while ceramics suit softer materials. The geometry of the tool, such as rake and relief angles, plays a critical role in performance and life.
3.2 **Tool Wear and Detection**
Wear types include flank wear, crater wear, and exfoliation. Detection methods range from manual checks to real-time monitoring. Accurate detection helps extend tool life and improve efficiency.
3.3 **Tool-Machine Connection Technology**
High-speed cutting requires rigid, balanced, and accurate tool holders. Systems like HSK, KM, and BIG-PLUS provide secure and precise connections, ensuring stability and accuracy at high speeds.
3.4 **Tool Safety**
Safety is vital in high-speed milling. Tools must be tested for deformation and fracture under extreme conditions. Standards like DIN 6589-1 guide safe design and operation, emphasizing balance, structure, and clamping methods.
**4. Conclusion**
By analyzing tool materials, geometry, wear, connection methods, and safety, this article highlights the importance of addressing challenges in high-speed milling. These efforts are essential for advancing the adoption of high-speed cutting in mold manufacturing.
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