Offset Rib Locator Pin for Plastic Injection Molding Sink Marks
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Solution Overview
Problem
Cross-shaped locator pins in injection molded plastic components cause sink marks due to local thickening, which existing methods like texturing or thickening around the pin may not fully eliminate, and can be impractical or lead to other issues.
Innovation Solution
A locator pin design featuring a main rib with offset secondary ribs, reducing material accumulation by 15% and minimizing sink marks, comprising a main rib with one secondary rib intersecting at a first offset intersection and another secondary rib intersecting at a second offset intersection, allowing for reduced material retention during the molding process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a cross-shaped locator pin is used, then the components can be located with respect to each other, but a sink mark is formed on the opposite surface due to material accumulation and heat retention
Solution Approach 1:
The patent applies asymmetry by changing the locator pin cross-section from a symmetric cross-shape to an asymmetric configuration with offset secondary ribs. The first and second secondary ribs are positioned at different locations relative to the main rib, creating an asymmetric material distribution that reduces localized heat accumulation and prevents sink mark formation while maintaining the location function
2Object-affected harmful factors
If the smooth surface is textured to camouflage the sink mark, then the appearance is improved, but the manufacturing complexity increases and may not fully eliminate the sink mark
Solution Approach 1:
The patent extracts the sink mark problem at its source by modifying the locator pin geometry itself, rather than applying a secondary solution like texturing to camouflage the defect. This eliminates the need for additional manufacturing steps and directly prevents the harmful effect
3Object-affected harmful factors
If the plastic part is thickened around the locator pin, then the sink mark is reduced, but the material usage increases and may lead to other manufacturing problems
Solution Approach 1:
The patent applies local quality by creating a specific material distribution pattern around the locator pin through the offset secondary ribs. This localized geometric modification optimizes material flow and cooling in the critical region around the pin without requiring overall thickening of the plastic part, thus reducing material usage while still preventing sink marks
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 new locator pin design effectively reduces sink marks by 15% on the surface opposite the pin, providing a more practical solution than existing methods by minimizing material accumulation and heat retention during injection molding.
Implementation Method 1
This increased internal mass retains heat during the injection molding process, maintaining the zone or area in a plastic state so that the material draws inward and contracts as cooling proceeds
Data Source
AI summary
A locator pin is provided for a plastic component. The locator includes a main rib, a first secondary rib intersecting the main rib at a first intersection and a second secondary rib intersecting the main rib at a second intersection. The first and second intersections are offset from each other. A plastic component incorporating the locator pin, a plastic component assembly incorporating that plastic component and a method of reducing sink marks in an injection molded plastic component are also provided.