Heat Stake Flared Section and Dual Taper for Plastic Part Sink Marks
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Solution Overview
Problem
Heat stakes for plastic parts often cause sink marks due to their design, which increases material usage and costs, as the tapered cylindrical sidewall at the proximal end promotes material accumulation during the molding process.
Innovation Solution
A heat stake with a flared section and dual taper at the distal end, featuring a reduced cross-sectional area at the proximal end and radially arrayed slots, allowing for a more robust connection without increasing the hole size, thus minimizing sink marks without requiring additional tooling in injection mold tools.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a tapered cylindrical sidewall is used at the proximal end of the heat stake, then the heat stake can be easily removed from the injection molding tool, but sink marks are promoted in the plastic part surface
Solution Approach 1:
The heat stake is divided into distinct sections: a proximal end with reduced cross-sectional area, a flared section with increased cross-sectional area, and a distal end. This segmentation allows the proximal end to minimize sink marks while the flared section provides structural integrity and ease of removal.
Solution Approach 2:
Different sections of the heat stake have different cross-sectional areas optimized for their specific functions. The proximal end has reduced area to prevent sink marks, while the flared section has increased area to facilitate removal from the mold and provide structural support.
2Strength
If the cross-sectional area at the proximal end is increased to provide more material for melting, then a stronger connection is achieved, but sink marks are promoted in the plastic part
Solution Approach 1:
The solution moves the material accumulation from the proximal end (where it causes surface defects) to the distal end and flared section (where it provides structural strength). The dual taper at the distal end creates additional material in a different spatial location that does not interfere with the plastic part surface.
3Strength
If a dual taper is added at the distal end to provide more material for sonic-staking, then connection strength is improved, but device complexity increases
Solution Approach 1:
The dual taper features (inner lead-in and outer lead-in) are integrated into the single heat stake body along with the flared section and radial slots. This merging of features into one monolithic component achieves the strength improvement without requiring separate parts or assembly steps.
4Ease of manufacture
If radial slots are added to the heat stake body to enable flexing during removal, then ease of removal is improved, but device complexity increases
Solution Approach 1:
The radial slots transform the rigid heat stake body into a dynamic structure that can flex and deform during the removal process. The slots allow the material to bend and accommodate the shape changes needed to extract the heat stake from the molded plastic part without damaging either component.
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 solution effectively reduces sink marks on plastic parts by providing more material for sonic-staking at the distal end while minimizing material at the proximal end, resulting in a stronger connection and reduced material waste without increasing tooling complexity.
Implementation Method 1
The distal end includes a dual taper effectively providing more material to melt during sonic-staking
Data Source
AI summary
A heat stake for a plastic part includes a body having a proximal end, a flared section and a distal end. The proximal end has a first cross-sectional area A1 and the flared section has a second cross-sectional area A2 where A1<A2. The distal end has a dual taper. That plastic part incorporating the heat stake is also disclosed.