Grommet Rib Segmentation for Expansion and Mold Release
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Solution Overview
Problem
Existing grommets face difficulties in expanding to the required size when a wire harness is inserted, and their removal from a metal mold is challenging due to the linkage between the extended tubular portion and the funnel-shaped portion, which affects the gripping force and water sealing functionality.
Innovation Solution
A grommet design featuring a combination of type one and type two ribs, where type one ribs have grooves and type two ribs do not, allows for easy expansion with an expander and facilitates smooth removal from a metal mold by enabling air flow between the center core and the funnel-shaped portion during the molding process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the extended tubular portion and funnel shaped portion are linked by ribs, then the gripping force and water sealing are improved, but the grommet cannot be expanded to the required size
Solution Approach 1:
The ribs are divided into two types: type one ribs with grooves that allow expansion, and type two ribs without grooves that maintain structural linkage. This segmentation enables different regions of the rib structure to serve different functions during expansion
Solution Approach 2:
Different portions of the rib structure have different properties: type one ribs have grooves for flexibility and expansion, while type two ribs are solid for structural support. This local differentiation resolves the contradiction between needing rigidity for gripping and flexibility for expansion
2Reliability
If the extended tubular portion and funnel shaped portion are linked by ribs, then the water sealing function is improved, but the removal from metal mold becomes difficult
Solution Approach 1:
The rib structure is segmented into type one and type two ribs with different characteristics. Type one ribs with grooves facilitate mold removal while type two ribs maintain water sealing, allowing both requirements to be met simultaneously
Solution Approach 2:
The grooves in type one ribs act as intermediaries that allow air to pass through during mold removal, enabling the grommet to be extracted from the mold cavity without damage while maintaining the structural integrity needed for water sealing
3Strength
If the ribs are solid without grooves, then the structural strength is improved, but the expansion with expander becomes difficult
Solution Approach 1:
The rib population is segmented into type one ribs with grooves for expansion and type two ribs without grooves for strength. This segmentation allows the overall structure to achieve both expansion capability and structural strength
Solution Approach 2:
Different ribs have different local qualities: type one ribs have grooves that provide expansion pathways, while type two ribs are solid for strength. This local differentiation allows the grommet to be expanded while maintaining structural integrity
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 grommet effectively expands to accommodate the wire harness without straining and maintains a strong grip on the car body panel while ensuring efficient water sealing and easy removal from the mold, enhancing flexibility and wiring availability.
Implementation Method 1
facilitates smooth removal from a metal mold by enabling air flow between the center core and the funnel-shaped portion during the molding process
Data Source
AI summary
A grommet is formed having a funnel shaped portion and a tubular portion linked to a small diameter end portion of the funnel shaped portion. The grommet is inserted to an aperture of a car body panel after a wire harness is passed through and attached to the funnel shaped portion and the tubular portion, and a body latch groove provided on the external circumferential surface of the funnel shaped portion is latched to the car body panel. An extended tubular portion is provided that projects from the tubular portion, and extends inside the funnel shaped portion. A plurality of ribs is provided on an external circumferential surface of the extended tubular portion. The ribs include type one ribs having grooves on both surfaces of an element linking the rib to the extended tubular portion, and a type two rib having no groove.