Flexible Power Cable Joint Transfer Moulding for Void Control
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Solution Overview
Problem
The existing methods for manufacturing flexible joints for high voltage cables, such as compression moulding and injection moulding, are labor-intensive, prone to errors, and costly, with challenges in controlling geometry and avoiding voids and thermal degradation.
Innovation Solution
A transfer moulding method is introduced, which involves joining conductors of two cable sections, fitting a mould around the exposed conductor, and forcing a casting material into the mould to form an outer layer, using a single transfer moulding machine for multiple moulding steps with different casting materials and cleaning between steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If compression moulding process is used with pre-extruded tapes, then the joint can be formed with insulation layers, but the process becomes labor-intensive and geometry control becomes difficult
Solution Approach 1:
The patent replaces the manual mechanical tape lapping and compression moulding process with an automated injection moulding system. The injection moulding machine automatically injects molten material into the mould cavity, eliminating the need for manual tape handling and compression moulding operations, thereby improving both ease of manufacture and geometry control
Solution Approach 2:
The patent changes the physical state of the material from solid tapes requiring compression moulding to molten material suitable for injection moulding. This parameter change enables automated processing and precise geometry control through controlled injection parameters such as injection pressure, temperature, and cooling time
2Reliability
If automated tape lapping in nitrogen environment or semi-vacuum is used, then air trapping is reduced, but the process becomes even more labor-intensive
Solution Approach 1:
The patent replaces the complex automated tape lapping system requiring nitrogen environment or semi-vacuum conditions with a simpler injection moulding system. The injection process inherently prevents void formation through proper injection technique and material flow, eliminating the need for specialized atmospheric conditions while maintaining reliability
Solution Approach 2:
The patent segments the manufacturing process into distinct injection moulding steps for each insulation layer (ISC, INS, OSC). This segmentation allows each layer to be formed independently with optimal process parameters, ensuring void-free construction without requiring complex environmental controls
3Productivity
If injection moulding process is used with extruder, then material can be injected in single step, but the equipment becomes more complex and costly
Solution Approach 1:
The patent employs a single injection moulding machine that can perform multiple functions by changing moulds and materials. The same equipment is used to inject different materials (semiconducting and insulating) in sequential steps, eliminating the need for separate extruders and reducing overall equipment complexity while maintaining high productivity
4Manufacturing precision
If multiple extruders and moulds are used for different materials, then each layer can be formed with appropriate material, but the cost and complexity increase
Solution Approach 1:
The patent uses a single injection moulding machine that can be reconfigured for different materials and moulds. The equipment performs multiple functions by injecting different materials in sequential steps, achieving material precision without requiring separate dedicated extruders for each material type
Solution Approach 2:
The patent combines the functions of multiple extruders and moulds into a single injection moulding system. The same machine handles different materials and moulds through sequential operations, merging what would otherwise require separate equipment into one versatile system
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The transfer moulding method offers higher dimensional tolerances, reduced equipment complexity and costs, lower risk of voids, and better handling of geometric variability, making it more efficient and cost-effective compared to traditional methods.
Implementation Method 1
forcing a casting material into the mould by transfer moulding to form an outer layer
Implementation Method 2
forcing a casting material into the mould by transfer moulding
Data Source
AI summary
A method of manufacturing flexible joints (300) in power cables (100, 200) is described, along with a corresponding system (400, 401). The flexible joints are made by joining the conductors (310, 320) of two cable sections to form a joint section (300) with a region of exposed conductor (22); fitting a mould (402) around at least a portion of the region of exposed conductor (22); and forcing a casting material (409) into the mould by transfer moulding to form an outer layer (350) around the region of exposed conductor (22).