Elastomeric Skin Coupling Structure for Natural Motion Attachment
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Solution Overview
Problem
Conventional methods of attaching elastomeric skins to animated devices suffer from material incompatibilities, stress concentration leading to failures, and unnatural motion due to discrete attachment points, requiring expensive tooling and limited size/shape options.
Innovation Solution
A skin attachment system using coupling features made from the same class of material as the skin or shell but with varying properties, such as durometer, to distribute load and mimic natural tissue motion, allowing for more durable and lifelike animations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high-pressure molded polymer actuation points are used with stiffness significantly greater than the skin material, then the actuation points provide structural support and attachment interface, but the abrupt change in stiffness induces failure points at the attachment point and causes adhesion problems
Solution Approach 1:
The coupling feature is designed with spatially varying durometer properties - the distal end has higher stiffness to provide structural support and resistance to bending, while the proximal end has lower stiffness matching the skin material to prevent stress concentration and improve adhesion. This local quality gradient resolves the contradiction between needing structural strength and avoiding stress concentration at the attachment interface.
Solution Approach 2:
The coupling feature functions as a composite structure combining two elastomeric materials with different durometer values in a single integrated component. This composite approach allows the coupling feature to simultaneously provide the structural support of harder material and the stress-compatible interface of softer material, eliminating the need for separate hard actuation points that cause adhesion failures.
2Device complexity
If discrete actuation points with caps are used, then the attachment interface is simplified, but the caps rotate about the posts causing unwanted puckering or dimpling of the skin and wearing out the cap
Solution Approach 1:
The coupling feature is segmented into functional zones with different properties - a distal end for structural support and a proximal end for skin attachment. This segmentation allows each zone to perform its specific function optimally without causing rotation or surface distortion, as the proximal end's reduced stiffness accommodates skin movement while the distal end maintains structural integrity.
Solution Approach 2:
The durometer parameter is varied along the length of the coupling feature, transitioning from higher stiffness at the distal end to lower stiffness at the proximal end. This parameter change prevents cap rotation and skin puckering by allowing the proximal end to flex with skin movement while maintaining secure attachment.
3Device complexity
If high-pressure molded actuation points are used, then the attachment structure is simplified, but expensive customized high-pressure tooling is required resulting in actuation points of limited size and shape
Solution Approach 1:
The high-pressure injection molding process is replaced with conventional molding techniques that do not require expensive customized tooling. The coupling feature is molded as a single piece with integrated varying durometer properties, eliminating the need for complex high-pressure tooling while enabling greater versatility in size and shape configurations.
Solution Approach 2:
The manufacturing approach changes from high-pressure injection molding to conventional molding, allowing for greater flexibility in producing coupling features of various sizes and shapes without requiring expensive customized tooling. This parameter change in the manufacturing process enables broader adaptability while maintaining the integrated varying-durometer design.
4Device complexity
If discrete attachment points are used, then the attachment method is simplified, but the stress is not distributed evenly generating artificial-looking motion and preventing natural-looking control
Solution Approach 1:
The coupling feature is segmented into multiple functional regions along its length, with the proximal end providing flexible skin attachment and the distal end providing structural support. This segmentation allows stress to be distributed more evenly across the attachment interface, enabling natural-looking skin motion while maintaining a relatively simple attachment method.
Data Source
AI summary
An animated device includes a skin. The skin includes a membrane formed of a first elastomeric material and a coupling feature coupled to the membrane. The coupling feature includes an elongated portion, and a second elastomeric material. The animated device includes a shell comprising a complementary elongated portion configured to couple to the elongated portion.