Stretch-Blow-Molding Preform With Convex Bottom Setbacks
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Solution Overview
Problem
Existing plastic container production methods in stretch-blow-molding face challenges in achieving a consistent wall thickness, particularly in the container bottom, which can lead to deformation due to internal pressure changes, resulting in increased production costs and potential quality issues.
Innovation Solution
A preform design with a three-dimensionally convex outer and inner surface configuration, featuring set-back areas without undercuts, allows for a continuous increase in distance from the apex to the preform body, enabling a consistent wall thickness in the container body and bottom, thereby reducing material usage and improving strength and barrier properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional preform designs are used in stretch-blow-molding, then production is simpler, but wall thickness consistency deteriorates leading to deformation
Solution Approach 1:
The preform design applies local quality by creating specific geometric features (set-back areas without undercuts, three-dimensionally convex surfaces) in targeted locations of the preform bottom. These localized structural modifications ensure uniform wall thickness in critical areas during stretch-blow-molding, while maintaining simpler designs in non-critical regions. This resolves the contradiction by improving wall thickness consistency only where needed rather than complicating the entire preform structure.
2Loss of substance
If material usage is reduced to lower costs, then production costs decrease, but strength and barrier properties deteriorate
Solution Approach 1:
The invention applies parameter changes by modifying the preform's geometric parameters (three-dimensionally convex outer and inner surfaces, set-back areas) to optimize material distribution. This enables using less total material while maintaining or improving strength and barrier properties through better material placement. The continuous increase in distance from apex to preform body creates optimal wall thickness distribution that reduces overall material usage while concentrating material where it provides maximum structural benefit.
3Strength
If wall thickness is increased to prevent deformation, then container strength improves, but material usage increases leading to higher costs
Solution Approach 1:
The preform design applies preliminary action by pre-configuring the material distribution and geometric structure before the stretch-blow-molding process. The set-back areas without undercuts and three-dimensionally convex surfaces are built into the preform to anticipate and prevent deformation issues during subsequent processing. This preliminary structural preparation ensures uniform wall thickness and adequate strength without requiring excessive material, as the geometry itself prevents deformation rather than relying on material quantity.
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 preform design ensures a largely constant wall thickness in the container body and bottom, enhancing the container's strength and barrier properties while reducing material usage and production costs, and preventing deformation caused by internal pressure changes.
Implementation Method 1
the preform is first heated uniformly
Implementation Method 2
the preform is stretched in the axial direction in addition with an elongated mandrel
Implementation Method 3
inflated by a fluid, usually air, which is introduced with overpressure, expanded in the radial and axial directions
Data Source
AI summary
A preform for a stretch-blow-molded plastic container includes an elongated, tube-like preform body. An outer wall and an inner wall delimit a bottom thickness (b). An outer wall and an inner wall delimit a wall thickness (w). An inner surface and an outer surface (E1) curved in three-dimensionally convex manners are spaced apart such that a distance from their respective apex (S, S′) to the preform body continuously increases. Extensions of the outer wall of the preform bottom along the outer three-dimensionally curved surface (E1), and of the inner wall of the preform bottom along the inner three-dimensionally curved surface (E2) are configured to be interrupted by set-backs area outside of their respective apex (S, S′) thereof.