C-Axis Electrospindle Head Layout for Endless Rotation
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Solution Overview
Problem
Current 5-axis machine tools face limitations in dynamic performance due to complex cable management, restricted angular travel, frequent maintenance needs, and lack of endless rotation capability, which hinder high-speed cutting and finishing operations, especially in sectors like aeronautics.
Innovation Solution
The spindle motor is relocated from the ram to the head mounting platform, allowing for improved cable routing without twisting, and a dedicated kinematic chain simplifies assembly and enhances dynamic performance, enabling endless rotation through a slip ring or cable-carrying chain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the spindle motor is fixed to the ram and cables are routed through the C-axis rotation area, then the motor position is stable, but the cables undergo twisting and bending that limits angular travel to +/- 180° and requires frequent maintenance
Solution Approach 1:
The spindle motor is extracted from its fixed position on the ram and relocated to rotate together with the head mounting platform. This separates the motor from the stationary cable routing, allowing cables to rotate with the platform rather than being twisted during rotation, thereby enabling endless angular travel without limiting the rotation range or requiring frequent cable replacement
Solution Approach 2:
The cable routing is moved from a stationary radial path to a rotating axial path through the head mounting platform. By routing cables through the central through-bore of the rotating platform rather than along the stationary ram, the system transforms the cable management from a 2D planar routing to a 3D rotating routing that accommodates continuous rotation without cable twisting
2Ease of operation
If a long transmission shaft is used to connect the spindle motor to the operating head, then the motor can be positioned higher for better accessibility, but the torsional rigidity decreases and limits high-speed finishing operations
Solution Approach 1:
The spindle motor is merged with the head mounting platform as a single rotating assembly. This eliminates the need for a separate transmission shaft between the motor and the operating head, as the motor rotates directly with the platform. The direct-drive configuration provides high torsional rigidity while maintaining motor accessibility through the platform's positioning
Solution Approach 2:
The system is segmented into a rotating assembly (head mounting platform with integrated spindle motor) and a stationary assembly (ram with cable routing). This segmentation allows the motor to be positioned optimally on the rotating platform for both accessibility and rigid connection to the operating head, without requiring a long transmission shaft
3Productivity
If the spindle motor is relocated to the head mounting platform, then cable routing is improved and endless rotation is enabled, but the motor support structure becomes more complex
Solution Approach 1:
The head mounting platform is given multiple functions: it serves as the structural support for the operating head, the mounting base for the spindle motor, and the rotating carrier for the cable routing system. This multi-functionality consolidates what would otherwise require separate support structures, reducing overall system complexity while enabling high dynamic performance and endless rotation
4Ease of operation
If gaskets are placed along the central bore to supply fluid to the rotating platform, then fluid connection is maintained, but friction torques disturb the positioning and machining accuracy
Solution Approach 1:
The mechanical gasket-based fluid connection is replaced with a magnetic coupling system. Magnets embedded in the rotating head mounting platform interact with corresponding magnets in the stationary hydraulic rotary joint, transferring rotational motion and fluid pressure without physical contact. This eliminates friction torques that would otherwise disturb positioning accuracy while maintaining continuous fluid supply to the rotating platform
Data Source
Figure 1~3a
Figure 2
Figure 3
AI summary
A C-axis unit for a machine tool, comprising a bushing (134) adapted to be fixed to a unit support (121) of a machine tool, a head mounting platform (130) adapted to receive an operating head (40), the head mounting platform being supported by the bushing (134) and being rotatable relative to the bushing (134) around a vertical axis, a platform rotation motor (150) supported by the bushing (134) and configured to control the rotation of the head mounting platform (130), and a spindle motor (160) configured to control the rotation of a tool-carrying spindle (45) on the operating head (40) through a driving extension (163) arranged in a through-bore (133) obtained through the head mounting platform (130). The spindle motor (160) is fixed to and is rotationally integral with the head mounting platform (130).