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 and expensive whirling process, which is prone to tool breakage and requires complex coordination, making it difficult to achieve precise geometric tolerances and restart the process without errors.
Innovation Solution
The use of a milling process instead of whirling, allowing for precise restartability and better tool utilization by using different milling tools for roughing and finishing, and enabling the production of complex geometries through controlled movement of the milling tool and rotor, with the option of additive manufacturing for further geometric freedom.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the whirling process is used to manufacture the rotor, then the eccentric screw geometry can be produced, but the process is maintenance-intensive and expensive due to tool breakage and wear
Solution Approach 1:
The patent replaces the mechanical whirling process with a milling process that uses a milling cutter to remove material from a blank workpiece. This substitution eliminates the tool breakage and wear issues inherent in the whirling process, as the milling process allows for more reliable tool usage up to the wear limit without risking geometric errors.
Solution Approach 2:
The invention treats the milling tool as a consumable that can be used up to its wear limit and then replaced, rather than requiring careful preservation and early replacement as in the whirling process. This approach reduces maintenance intensity and costs by allowing full utilization of tool life.
2Manufacturing precision
If the whirling process is used, then the rotor geometry can be produced, but complex coordination of rotary motions is required
Solution Approach 1:
The patent extracts and eliminates the complex coordinated rotary motions from the manufacturing process. Instead of requiring synchronous rotation of the rotor and whirling tool along with axial motion, the invention uses a simpler milling process where the milling cutter rotates and moves axially through the stationary or slowly rotating workpiece, significantly reducing control complexity.
3Productivity
If the whirling process is used, then the rotor can be manufactured, but restarting the process after tool breakage is difficult and time-consuming
Solution Approach 1:
The invention applies preliminary action by using the milling process to remove material in a systematic manner that allows the process to be restarted from any point along the axial length of the rotor. The milling cutter can be repositioned to continue material removal without requiring complex re-synchronization, enabling quick resumption of production after interruptions.
4Adaptability or versatility
If primary forming processes like casting or forging are used, then shaping freedom is achieved, but post-machining is required to achieve geometric precision
Solution Approach 1:
The patent inverts the conventional approach by starting with a blank workpiece and removing material through milling to achieve the final geometry, rather than forming the shape through casting or forging and then machining it. This inversion allows the milling process to directly produce the required geometric precision without extensive post-machining operations.
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.