Eccentric Screw Pump Rotor Milling for Precise Restartable Machining
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Solution Overview
Problem
The manufacturing of eccentric screw pump rotors is economically inefficient due to the maintenance-intensive whirling process, which is prone to tool wear and breakage, and requires complex production planning, making it difficult to maintain geometric precision and restart the process in case of interruptions.
Innovation Solution
The use of a milling process instead of whirling, where a milling tool with radially outward cutting edges moves on a convex or planar path, allowing for precise restartability and better tool utilization, and potentially incorporating additive manufacturing for layer-by-layer construction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a whirling process is used to manufacture the rotor, then the eccentric geometry can be produced, but the process is maintenance-intensive and prone to tool wear and breakage
Solution Approach 1:
The patent replaces the whirling process (a specialized mechanical cutting process) with conventional CNC turning and milling processes. This substitution eliminates the need for complex whirling tool coordination and reduces tool wear issues by using standard cutting tools with more reliable cutting edges that can be easily replaced or re sharpened.
Solution Approach 2:
The manufacturing process is divided into separate operations: first turning the basic rotor shape, then milling the helical groove. This segmentation allows each operation to be performed with optimized tools and parameters, improving overall process reliability and reducing the complexity of any single cutting operation.
2Ease of manufacture
If a whirling process is used to manufacture the rotor, then the eccentric geometry can be produced, but complex production planning and control technology are required
Solution Approach 1:
The patent replaces the complex whirling process with conventional CNC turning and milling operations. These standard processes use well-established control systems and programming, eliminating the need for specialized whirling process control and reducing overall system complexity.
Solution Approach 2:
By dividing the manufacturing into separate turning and milling operations, each with its own simplified toolpath and control parameters, the overall control complexity is reduced compared to coordinating multiple cutting edges in a single whirling operation.
3Productivity
If the whirling process is interrupted due to tool breakage, then production must be restarted, but restarting is difficult and geometric precision cannot be maintained
Solution Approach 1:
The manufacturing is divided into separate turning and milling operations. If an interruption occurs, each operation can be independently restarted from the beginning with its own simple, repeatable toolpath, ensuring geometric precision is maintained without the complex coordination requirements of whirling process restarts.
4Adaptability or versatility
If primary forming processes such as casting or forging are used, then shaping freedom is achieved, but post-machining is required to achieve geometric precision
Solution Approach 1:
Instead of starting with a cast or forged blank and then machining it, the patent uses direct CNC turning and milling from a blank stock, eliminating the need for primary forming processes and their associated post-machining requirements.
Data Source
AI summary
A method of manufacturing a metallic rotor of an eccentric screw pump, comprising clamping a workpiece extending along a central longitudinal axis in a workpiece clamping device and removing material from the workpiece by cutting with a cutting tool. The invention further comprises not producing the surface of the rotor in a three-axis whirling process, using the cutting tool to produce the outer surface geometry of the rotor, advancing the cutting tool along an axis of advance that is parallel to the longitudinal axis of the rotor, and rotating the cutting tool about an axis of tool rotation that is parallel to the longitudinal axis of the rotor.