Metal processing online covers the actual design process of a large CNC gantry machine's spindle milling head, starting from determining technical parameters, mechanical structure, and transmission methods. This article briefly introduces the design approach and process of the spindle milling head, using a right-angle spindle milling head as an example to discuss and analyze the design procedure. It also provides some guiding ideas and methods for the structural design of large CNC machine tool milling heads.
1. Overall Design of the Spindle Milling Head
First, based on the structural characteristics of the CNC machine tool and the specific forms of the ram and spindle, the overall design and structural form of the spindle milling head are planned, as shown in Figure 1. In this example, the right-angle spindle milling head uses a mechanical transmission structure. The power from the main motor is transmitted through a spline shaft to the main shifting mechanism, then to a bevel gear mechanical transmission system. The bevel gear shaft drives both the tool clamping mechanism and the tool to rotate, completing the machining process. Compared to other types of spindle milling heads, this mechanical transmission type offers unique advantages, meeting both high precision and heavy cutting requirements, fully satisfying the technical parameter needs of the large gantry machining center in this example.
Figure 1 Right angle milling head structure
1. Locating pin 2. Spline shaft 3, 5, 9. Cooling ring groove 4. Pull pin interface
6, 8. Bearing layout 7. Bevel gear transmission 10. Broach mechanism
2. Structure of the Milling Head
Based on the structural form and basic parameters of the machine tool, the key technical parameters such as spindle power, torque, and speed (as shown in Figure 2) are primarily considered to determine the bearing type and layout, gear form, and related calculations. At the same time, positioning accuracy during movement and repeat positioning accuracy are taken into account to determine the accuracy level of bearings and gears. In this example, a double-row Ball Bearing back-to-back layout is used for the horizontal bearing. This layout provides a larger bearing support distance, significantly improving the rigidity of the milling head and offering structural assurance for heavy cutting. The selection of bevel gears makes the 90° power drive conversion simple and practical.
Figure 2 Spindle power torque
3. Structural Optimization of the Spindle Right-Angle Milling Head
Metal processing online notes: In addition to the main technical factors like the overall plan and structural form, the right-angle spindle milling head must fulfill the basic functions of a milling head to ensure high precision, stable, and smooth operation. During the design process, it is also essential to consider the attachment function of the milling head and ram, the clamping method, cooling system, bearing lubrication, and sealing. In this example, the milling head connects reliably with the ram through the hydraulic power of the Latin mechanism, which ensures a reliable and efficient connection. The broach mechanism is tensioned by a spring structure and loosened by hydraulic power. The spline shaft and gear shaft periphery have cooling grooves to dissipate heat from the bearing and gear movement, keeping the milling head at a constant temperature and ensuring geometric and motion accuracy. Bearings are grease-lubricated and sealed within a closed cavity, maintaining optimal working conditions. By comprehensively considering all aspects of the spindle milling head, the structure and functional realization methods are optimized to achieve a reasonable and efficient design. In practice, the milling head’s functionality, geometric precision, motion accuracy, and stability have been verified.
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