Stator Inner Wall Machining with Dual Milling Heads
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Solution Overview
Problem
Eccentric screw motors face performance degradation and stator lining destruction due to high pressures, as standard elastomer-lined stators with cylindrical geometry can only withstand pressures up to 24-40 bar, and custom spinning tools are required for each internal geometry, leading to high costs and inefficiencies.
Innovation Solution
A method using two independently controllable milling heads to machine the inner wall of the stator tube, allowing for precise formation of threads with varying pitches and uniform elastomer layer application, enabling efficient production of stators with different internal geometries using a single milling tool and reducing tooling costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a standard elastomer-lined stator with cylindrical geometry is used, then the manufacturing process is simple, but the pressure resistance is limited to 24-40 bar and the elastomer shifts at higher pressures
Solution Approach 1:
The patent applies preliminary action by pre-forming the metallic internal geometry of the stator tube before applying the elastomer layer. This allows the metal structure to provide the necessary mechanical support and pressure resistance, enabling the elastomer to be applied as a thinner, uniform layer that won't shift under high pressure. The pre-formed geometry includes optimized wall thickness distribution with thicker sections at critical locations.
Solution Approach 2:
The patent uses composite materials by combining a pre-formed metallic stator tube structure with an elastomer lining layer. The metal provides structural strength and pressure resistance, while the elastomer provides the necessary friction and sealing properties. This composite approach allows the system to withstand pressures significantly higher than either material could achieve alone.
2Manufacturing precision
If custom spinning tools are made for each different internal geometry, then the manufacturing precision is achieved, but the device complexity and costs increase
Solution Approach 1:
The patent applies universality by designing a single spinning tool that can produce multiple different internal geometries through programmable control. The tool includes a controllable forming element that can be positioned and shaped to create various thread profiles and pitch configurations. This universal tool replaces the need for multiple custom spinning tools, reducing device complexity and tooling costs while maintaining manufacturing precision through controlled deformation of the elastomer layer.
Solution Approach 2:
The patent uses dynamics by implementing a controllable, adjustable spinning tool with programmable motion control. The forming element can be dynamically positioned and the deformation process can be controlled in real-time to achieve different internal geometries. This dynamic approach allows precise control over the elastomer layer deformation to create various thread patterns without requiring physical reconfiguration of the tool.
3Strength
If a thinner uniform elastomer layer is applied on pre-formed metal geometry, then the pressure resistance increases, but the torque transmission capability may be reduced
Solution Approach 1:
The patent applies local quality by creating a non-uniform elastomer layer thickness distribution optimized for specific functional requirements. The elastomer layer is applied thicker in regions where torque transmission is critical (such as at the rotor-stator interface) and thinner in regions where pressure resistance is the primary concern. This localized variation in thickness allows the system to simultaneously achieve high pressure resistance and effective torque transmission.
Solution Approach 2:
The patent uses parameter changes by varying the elastomer layer thickness as a controlled parameter to optimize performance. The thickness distribution is carefully designed and controlled during the application process to balance pressure resistance and torque transmission. By adjusting this parameter locally across different sections of the stator, the system achieves optimal performance for both functions without compromise.
Data Source
AI summary
Disclosed is a method for manufacturing a stator for an eccentric screw motor where at least two milling heads are used for machining the inner wall of the stator tube, wherein, at the start of the machining, one of the milling heads is brought to a predetermined position near the stator with respect to the end of the stator tube, the milling head is fed into the tube interior along its linear axis from this predetermined position, and a thread is machined until the milling head reaches at least the longitudinal center of the stator tube or exceeds a predetermined value, and the second milling head starts its machining of the inner wall surface of the stator tube at this point, wherein the milling head is moved along its linear axis and rotated about its rotary axis until the milling head reaches the centre of the stator tube.