Connection of a support to a molded plastic structure
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Solution Overview
Problem
The blow-molding process is limited in forming complex shapes and configurations due to the requirement of pressurized air and difficulty in controlling outer wall thickness, particularly in creating features like undercuts without material removal or deformation.
Innovation Solution
A method and tooling system that allows the formation of undercuts during the blow-molding process without material removal, using movable tools to create acute angles and overhangs, enabling secure attachment of components without fasteners by integrating undercuts into the molding process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional blow-molding process is used, then hollow plastic structures can be manufactured economically in high volume, but the type and configuration of structures are limited and complex shapes with undercuts cannot be formed
Solution Approach 1:
The mold includes movable undercuts that can shift position during the molding process. These undercuts are not fixed but can move to different locations, allowing the formation of complex shapes and configurations that would be impossible with static mold surfaces. The dynamic movement of undercut elements enables the plastic material to be formed into intricate geometries while maintaining the economic benefits of blow-molding.
2Productivity
If pressurized air is used to stretch plastic into mold faces, then hollow structures are formed quickly, but outer wall thickness becomes difficult to control in larger objects
Solution Approach 1:
The mold incorporates localized undercut features at specific positions where thickness control or shape complexity is needed. These undercuts are strategically placed rather than uniformly distributed, allowing precise control of material flow and wall thickness in critical areas while maintaining rapid production. The local application of undercut geometry enables differentiated control of plastic deformation in different regions of the molded structure.
3Adaptability or versatility
If undercuts are formed during blow-molding, then secure attachment of components is enabled, but the molding process becomes more complex
Solution Approach 1:
The formation of undercuts is merged with the basic blow-molding process itself rather than being a separate subsequent operation. The movable undercut elements are integrated into the mold structure, allowing undercut formation to occur simultaneously with the inflation and shaping of the plastic material. This integration eliminates the need for separate cutting or deformation steps, reducing overall process complexity while maintaining attachment capabilities.
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
Enables the production of blow-molded plastic structures with secure attachment capabilities and reduced manufacturing costs by forming undercuts with sharp edges and acute angles during the molding process, facilitating the connection of frames and other components without the need for fasteners.
Implementation Method 1
The parison, which is disposed within the mold, is inflated with pressured air, which is typically between about 60 psi and about 150 psi. The parison expands into contact with the inner surface of the molds
Implementation Method 2
The air pressure pushes the plastic into the faces of the mold so that the plastic takes the shapes of the mold
Data Source
AI summary
A blow-molded plastic structure, such as a table top, may include an undercut. For example, the table top may include a frame receiving portion and a frame connecting structure with an undercut may be disposed in the frame receiving portion. A first portion of the frame may contact or engage the frame connecting structure when the frame is connected to the table top. In an exemplary embodiment, a first side of the frame receiving portion may include a first frame connecting portion with an undercut and a second side of the frame receiving portion may include a second frame connecting portion with an undercut. The first frame connecting portion with an undercut may be disposed on an opposing surface from the second frame connecting portion with an undercut.