Offset Parting Line Mold for Blow Molding Stability
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Solution Overview
Problem
The existing blow molding techniques for manufacturing containers result in a burr or bead of material on the base, which compromises the stability and rigidity of flat containers, particularly those with a flattened shape, due to the functional play between the mold and mold bottom, leading to material flow and air evacuation issues.
Innovation Solution
A mold design with a recessed annular peripheral base and a movable mold bottom with a skirt that allows for the formation of a recess to accommodate any burr, ensuring it does not project beyond the standing plane and affecting stability, combined with a method of blow molding that includes moving the mold bottom to a retracted position during the process to prevent material flow into the gap.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a movable mold bottom is used to increase local stretching and mechanical strength of the container bottom, then the structural rigidity is improved, but material flows into the gap between the mold bottom and wall, forming a burr that reduces stability
Solution Approach 1:
The parting line between the mold bottom and wall is offset from the standing plane of the container base, creating a recess that captures the burr in a different spatial dimension. This dimensional offset ensures that while material flows into the gap during molding, the resulting burr is contained within the recess and does not protrude to affect stability.
Solution Approach 2:
The invention converts the harmful effect of material flowing into the gap (which forms a burr) into a beneficial outcome by designing a recess that specifically captures and contains this burr. The burr, instead of being a defect on the standing surface, becomes a feature contained within the recess, thus eliminating its negative impact on stability while maintaining the mechanical strength benefits of increased local stretching.
2Ease of operation
If functional play is provided between mold bottom and wall to enable movement and air evacuation, then the mold operation is facilitated, but material flows into the gap forming a detrimental bead
Solution Approach 1:
The parting line is offset in a radial dimension to create a recess, allowing the mold to maintain functional play for movement and air evacuation while directing material flow into a controlled recess area rather than onto the precision-critical standing plane.
Solution Approach 2:
The harmful burr formation is extracted from the standing plane area and relocated to a dedicated recess zone. This separation allows the standing plane to maintain high manufacturing precision for stability while the recess accommodates the imperfections from material flow.
3Weight of moving object
If the container weight is reduced to use less material, then material consumption is decreased, but structural rigidity becomes inadequate
Solution Approach 1:
The mold design applies increased local stretching specifically to the bottom area through the boxing operation with the movable mold bottom, creating localized reinforcement with arches and ribs. This allows the overall container weight to be reduced while maintaining structural rigidity in critical areas through enhanced material orientation and density at the bottom.
Solution Approach 2:
The heat-setting operation is performed preliminarily during the molding process by maintaining contact with the heated mold wall, which increases the crystallinity rate of the material and pre-establishes the structural rigidity needed to support weight reduction without compromising strength.
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
This solution ensures a correctly formed base with enhanced stability and rigidity, preventing the burr from impacting the container's stability and mechanical strength, while maintaining good blowability and production efficiency.
Implementation Method 1
the structural rigidity of the container can be increased thermally by means of a heat-setting (in English, 'heat set') of the material, consisting in keeping the container in contact with the heated wall of the mold, which increases the crystallinity rate of the material
Implementation Method 2
its structural rigidity can also be increased (or controlled) mechanically by means of an increased local stretching of the material, by means of a mold provided with a stationary wall constituting the impression of the body of the container, and a mold bottom constituting the impression of the bottom of the container
Implementation Method 3
the blow molding of the parison is carried out by injecting therein a fluid (such as air) under high pressure (in general greater than 26 bar)
Data Source
AI summary
A mold (11) for manufacturing a container (2) having a body (4) and a bottom (6), including: an annular peripheral base (8) defining a positioning plane (9); an arch (10) which extends concavely toward the inside of the container (2) from the base (8), the mold (11) including: a wall (12) having an inner surface (13) forming the cavity of the body (4) of the container (2) and having an opening therethrough, the wall (12) having an edge (23) forming the cavity of the positioning plane (9); a mold bottom (14) which is moveably mounted relative to the wall (12), the mold bottom (14) having an upper surface (15) forming the cavity of the arch (10), and a skirt (19) having an outer radial extension that is strictly lower than an inner radial extension of the positioning plane (9).