Blow-Molded Plastic Structure with Undercut Frame Connection
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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 the difficulty in controlling outer wall thickness, especially for larger objects, which restricts the variety of hollow plastic structures that can be manufactured and makes it challenging to create features like undercuts without material removal.
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 the production of blow-molded plastic structures with sharp edges and secure attachment features like undercuts that facilitate connection of additional components without fasteners.
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 components (fingers or segments) that can dynamically change position during the molding cycle. These components move to specific positions to form undercuts and complex geometries, then retract to allow part ejection, enabling versatile structure formation while maintaining conventional blow-molding manufacturing
Solution Approach 2:
The mold is divided into multiple independent movable segments or fingers rather than a single rigid structure. Each segment can move independently to form different features of the plastic structure, allowing complex configurations and undercuts to be created while maintaining economic manufacturing through modular tooling
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 especially for larger objects
Solution Approach 1:
The movable mold components can be positioned to apply localized influence on specific regions of the plastic parison during inflation. This allows different areas of the hollow structure to achieve desired wall thicknesses while maintaining overall manufacturing speed through the blow-molding process
3Shape
If undercuts are required in blow-molded structures, then material must be cut away or removed after molding, but this increases manufacturing complexity and cost
Solution Approach 1:
The undercuts are formed during the molding process itself by positioning movable mold components to create the undercut geometry while the plastic is still forming. This preliminary formation of undercuts eliminates the need for subsequent material removal operations, reducing manufacturing complexity and cost
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 creation of blow-molded plastic structures with complex geometries and secure attachment capabilities, reducing manufacturing costs and complexity by forming undercuts and acute angles during the molding process, allowing for secure engagement of components without the need for additional 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 surfaces of the molds
Data Source
AI summary
A blow-molded plastic structure, such as a tabletop, may include an undercut. For example, the tabletop may include a frame receiving portion and a frame connecting structure with an undercut may be disposed in the frame receiving portion. A portion of the frame may contact or engage the frame connecting structure, such as the undercut, when the frame is connected to the tabletop. 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.