Plastic Body Component Rib Layout to Prevent Class A Sink Marks
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Injection molded plastic parts used in vehicle body and trim applications often develop undesirable sink marks on aesthetic surfaces due to internal attachment structures, particularly when hidden fasteners are employed, which can mar the appearance intended for 'Class A' surfaces.
Innovation Solution
A vehicle assembly design featuring a rib integrated into the interior surface of a plastic body component, spaced from the main interior surface, with attachment extensions of reduced thickness to prevent sink marks, and a hidden fastener system that aligns openings between the components to minimize distortion and maintain aesthetics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If hidden fasteners with attachment means (doghouse structure or mounting rib) are used to attach plastic parts, then the fasteners are concealed from view, but sink marks are created on the appearance surface of the plastic part
Solution Approach 1:
The attachment means (mounting rib or doghouse structure) is extracted and relocated to the interior hidden surface of the plastic part, away from the appearance surface. This allows the fastener attachment function to be maintained while eliminating the sink marks on the visible exterior surface.
Solution Approach 2:
A thin-walled extension or intermediary structure is introduced that connects the appearance surface to the interior hidden surface, allowing the attachment means to be positioned on the hidden surface while maintaining structural integrity and avoiding direct contact between the attachment means and the appearance surface.
2Ease of operation
If attachment means are molded or formed on the back or hidden sides of plastic parts, then hidden fastener attachment is achieved, but sink marks are still created on the appearance surface
Solution Approach 1:
The plastic part is segmented into distinct functional zones: the appearance surface maintained as smooth and aesthetic, and the interior hidden surface containing the attachment means. This segmentation allows each zone to optimize its function without compromising the other.
Solution Approach 2:
The attachment means is moved from a two-dimensional planar position on the appearance surface to a three-dimensional position on the interior hidden surface, utilizing the depth dimension to resolve the conflict between attachment functionality and surface aesthetics.
Data Source
AI summary
A vehicle assembly includes a first body component and a second body component. The first body component has an exterior surface and an interior hidden surface, where the exterior surface has in part an aesthetic finish. The first body component defines a first connecting portion having a rib secured by the interior surface. The rib has a first opening formed therethrough. The second body component has an outward extended second connecting portion. A base wall of the second connecting portion has a second opening formed therethrough. The base wall abuts the rib with the second opening aligned with the first opening. A fastener is inserted through the first and second openings from within the second connecting portion.