Metal processing online provides insights into the actual design process of a large CNC gantry machine's spindle milling head, covering key aspects such as determining technical parameters, mechanical structure, and transmission methods. This article briefly introduces the design approach and process for the spindle milling head, using a right-angle spindle milling head as an example to analyze and discuss the design procedure. It also offers some guiding principles and methods for the structural design of large CNC machine tool milling heads.
1. Overall Design of the Spindle Milling Head
The overall design of the spindle milling head is planned based on the structural characteristics of the CNC machine tool, as well as the specific form of the ram and the spindle. As shown in Figure 1, the design includes the structural layout of the milling head. In this example, the right-angle spindle milling head uses a mechanical transmission system. The power from the main motor is transmitted through a spline shaft to the bevel gear mechanism, which then drives the tool clamping system and the cutting tool to rotate, enabling the machining of the workpiece. Compared to other types of spindle milling heads, this mechanical transmission system offers significant advantages, particularly in terms of high precision and heavy-duty cutting, fully meeting the technical requirements of the large gantry machining center in this case.
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 design focuses primarily on key technical parameters such as spindle power, torque, and speed (see Figure 2). These factors determine the type and layout of the bearings, the form of the gears, and are calculated accordingly. Additionally, it is essential to consider the positioning accuracy and repeated positioning accuracy during the movement of the milling head, which helps determine the accuracy level of the bearings and gears. In this example, a double-row Ball Bearing arranged back-to-back is used for the horizontal bearing. This configuration increases the support distance, significantly improving the rigidity of the milling head and providing structural assurance for heavy cutting. The use of a bevel gear allows for a simple and effective 90° power transmission.
Figure 2: Spindle Power and Torque
3. Structural Optimization of the Spindle Right-Angle Milling Head
Metal processing online emphasizes that in addition to considering the main technical factors like the overall plan and structural form, the spindle right-angle milling head must fulfill its basic functions to ensure high precision, stable, and smooth operation. During the design process, it is also crucial to take into account the attachment function with the ram, the clamping method, cooling system, bearing lubrication, and sealing. In this example, the milling head connects reliably with the ram via a hydraulic mechanism, offering both reliability and efficiency. The broach mechanism is tensioned by a spring structure and loosened hydraulically. The spline shaft and the periphery of the gear shaft are equipped with cooling grooves, effectively dissipating heat generated by the bearings and gears, keeping the milling head at a constant temperature and ensuring its geometric and motion accuracy. Bearings are lubricated with grease, and a sealed cavity prevents contamination, maintaining optimal working conditions. Through comprehensive consideration of all aspects, the structure and functional realization methods of the spindle milling head are optimized, achieving an efficient and reasonable design. In practice, the functionality, geometric accuracy, motion accuracy, and stability of the milling head have been verified.
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