The ZHW2950-1Y vacuum chamber assembly is a critical component of the vacuum coating machine (see Figures 1 and 2). It is a typical integral base box structure, designed to support the drive shaft, bearings, gears, and other related parts. The quality of its machining plays a vital role in determining the performance, efficiency, and lifespan of the magnetron plating equipment. High precision in manufacturing is essential to ensure smooth operation and long-term reliability.
Figure 1: Main view of the vacuum chamber assembly
Figure 2: Vacuum chamber component cutaway
**1. Analysis of Mechanical Processing Points**
The box is a steel plate welded structure, with the main machined surfaces consisting of planes and parallel hole systems. Due to the high coaxiality and parallelism requirements of the parallel hole system, the entire hexahedral box is processed separately from the bottom surface. The remaining five surfaces are completed using five different stations, each requiring a programmed origin. The offset values for B0°, B90°, B180°, B270°, and A90° are stored as five coordinate systems (G511–G515), with the X0 values for B0°, B180°, B270°, and A90° being identical.
(1) **Plane Machining Accuracy**: From the processing diagram, only the left and right end faces require a flatness tolerance of 0.08 mm, while the other mating surfaces do not have specific accuracy requirements. Therefore, the primary challenge lies in the parallel hole system rather than plane machining. The large end face (1,888 mm × 1,820 mm) can easily meet the 0.08 mm flatness requirement using standard CNC milling.
(2) **Parallel Hole System Accuracy**: The coaxiality of the two sets of parallel holes (A and G references) is specified at 0.015 mm, while the C reference has a coaxiality of 0.02 mm. All three hole systems meet IT6 or better, with some reaching IT5 level. These tight tolerances make standard boring operations insufficient, requiring multi-station processing with a consistent reference surface and advanced precision techniques.
**2. Selection of Processing Equipment**
(1) Based on the analysis of surface and hole machining, the vacuum chamber assembly requires a floor-type CNC boring and milling machine capable of handling large hole systems and finishing planes. However, gantry-type machines, which excel in plane processing, are not suitable for this task.
(2) **Tool Selection**: As a welded steel structure, the box has lower rigidity compared to castings or forgings. Therefore, face milling cutters with large rake angles and coated carbide tools are recommended for light cutting. Boring tools should include large-diameter double-edged roughing tools and fine-boring tools, combined with tool-setting instruments for precise control.
(3) **Positioning Reference Selection**: The rough reference is set based on the first dashed line, ensuring even machining allowance across key holes. For finish positioning, the design reference and D datum plane are used. To meet high coaxiality requirements, an auxiliary process reference is added, with the top end face of the 5,010 mm size processed higher than the pattern requirement.
**3. Machining Sequence Arrangement**
(1) **Benchmark First Principle**: The bottom surface is machined first and serves as the clamping reference for the remaining surfaces.
(2) **Face and Hole First Principle**: The top and side surfaces are machined sequentially using the bottom surface as a reference, providing accurate positioning for subsequent hole operations.
(3) **Coarse and Fine Machining Principle**: All surfaces and holes are first roughed, then semi-finished and finished to achieve optimal shape and position accuracy.
(4) **Main and Secondary Principle**: Non-critical inner holes are processed after the main parallel hole systems to avoid interference.
**4. List of Main Fixtures and Gauges**
The main fixtures and gauges are detailed in the attached table.
Figure 3: Main fixtures and gauges
**5. Conclusion**
In summary, the TK6916B or TK6920 floor-type CNC boring and milling machine, equipped with a CNC rotary table and vertical milling head, can effectively meet the machining requirements of the vacuum chamber assembly. For high-precision, large box-type components, more advanced equipment such as the DZ-TH6516 planer-style horizontal boring and milling center is recommended. If budget allows, this machine offers the best processing quality and stability, making it ideal for complex and high-tolerance applications.
The silicon powder is used as a raw material, and the desired shape is first formed by a usual molding method, and preliminary nitriding is performed in a nitrogen gas at a high temperature of 1200 ° C, and a part of the silicon powder is reacted with nitrogen to form silicon nitride, and the entire billet is then formed. The body already has a certain strength. Then, a second nitriding is carried out in a high temperature furnace at 1350 ° C to 1450 ° C to form a silicon nitride. A silicon nitride having a theoretical density of 99% can be obtained by a hot press sintering method.
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