Flexible Power Cable Joint Transfer Moulding for Void-Free Geometry
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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
The method involves using transfer moulding to form an outer layer around the exposed conductor of cable sections, which allows for higher dimensional tolerances, reduced equipment complexity, and lower costs compared to traditional methods, while minimizing the risk of voids and improving quality control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If compression moulding is used to form insulation layers from pre-extruded tapes, then the process can create solid void-free material, 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 extruder automatically melts and injects molten material into the mould cavity, eliminating the need for manual tape handling and compression moulding operations while maintaining void-free material formation.
Solution Approach 2:
The patent changes the physical state of the material from solid pre-extruded tapes to molten material that is injected into the mould. This parameter change allows the material to flow and fill the mould cavity automatically, improving geometry control while reducing labor intensity.
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 and complex
Solution Approach 1:
The patent utilizes the phase transition of the thermoplastic material from solid to molten state through heating in the extruder. The molten material naturally flows to fill the mould cavity, automatically displacing air and preventing void formation without requiring nitrogen environments or semi-vacuum conditions.
Solution Approach 2:
The patent replaces the complex mechanical tape lapping system with a simpler injection moulding system where molten material is pumped into the mould. This substitution eliminates the need for complex air evacuation systems while maintaining void prevention.
3Reliability
If injection moulding is used to form layers in a single step, then void formation is prevented, but the equipment becomes more complex and costly with multiple extruders and moulds required
Solution Approach 1:
The patent merges the functions of multiple extruders and moulds into a single injection moulding system. The extruder melts and injects material that forms multiple layers (inner semiconducting layer, insulation layer, outer semiconducting layer) in sequence within a single mould cavity, eliminating the need for separate extrusion and moulding equipment.
Solution Approach 2:
The patent makes the single mould cavity serve multiple functions by forming different insulation layers at different stages. The same mould is used to form the inner semiconducting layer, then the insulation layer, and finally the outer semiconducting layer, making the equipment more versatile and less complex.
4Manufacturing precision
If traditional three-step process for ISC, INS, and OSC is used, then each layer can be controlled separately, but the manufacturing time and cost increase significantly
Solution Approach 1:
The patent combines the three separate manufacturing steps for ISC, INS, and OSC into a single injection moulding operation. The extruder injects material that forms all three layers in sequence within one continuous process, maintaining separate control over each layer while dramatically reducing manufacturing time.
Solution Approach 2:
The patent maintains continuous useful action by keeping the mould cavity in place and continuously injecting material to form different layers without removing or repositioning components between steps. This continuous process maintains layer control while improving productivity.
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
Transfer moulding provides a more efficient and cost-effective process for manufacturing flexible joints, capable of handling variations in joint geometry and volume, with reduced labor intensity and improved electrical and mechanical performance.
Implementation Method 1
forcing a casting material into the mould by transfer moulding to form an outer layer around the region of exposed conductor
Implementation Method 2
a heating system for melting the solid casting material
Data Source
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Figure 3
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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).