Blow-Molding Vent Gap Design Using Segmented Parts and Spacers
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Solution Overview
Problem
In blow-molding processes, vent openings in molds are required to efficiently expel air to prevent shape defects, but large sections risk material penetration, leading to surface defects if the vent is too large.
Innovation Solution
A mold design with multiple parts forming a vent gap that spans the entire mold dimension, held apart by spacers to maintain a thin, constant gap, ensuring continuous air evacuation without material intrusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the vent section is made large to efficiently exhaust air, then air evacuation capability is improved, but the risk of softened material penetrating into the vent increases causing surface defects
Solution Approach 1:
The vent is segmented into multiple separate parts (first vent part and second vent part) that are assembled together with spacers. This segmentation allows the vent to have a large total flow section while maintaining a small gap thickness between parts, preventing material penetration while ensuring efficient air evacuation.
Solution Approach 2:
Spacers are introduced as intermediary elements between the vent parts to maintain a precise, small gap thickness. The spacers act as mediators that control the gap dimension, ensuring it remains thin enough to prevent material intrusion while still allowing sufficient air flow through the vent.
2Productivity
If the vent gap thickness is increased to allow better air flow, then air evacuation is improved, but softened material is more likely to penetrate into the vent
Solution Approach 1:
The vent design transitions from controlling air flow solely through gap thickness to controlling it through both gap thickness and gap length (extending over entire mold dimension). This dimensional change allows the gap to be thin (preventing material penetration) while still providing sufficient air flow path area through its extended length.
Solution Approach 2:
The vent is divided into multiple segments assembled with spacers, creating a multi-part structure. This segmentation enables the gap to maintain a thin profile (preventing material penetration) while the cumulative flow section across multiple segments provides adequate air evacuation capability.
3Ease of manufacture
If a single-piece vent structure is used, then manufacturing is simpler, but the vent cannot maintain a thin, constant gap thickness throughout the entire mold dimension
Solution Approach 1:
The vent is segmented into multiple standardizable parts that can be manufactured separately with consistent dimensions and then assembled. This segmentation makes each part easier to manufacture with precise thickness control, and the assembly process maintains uniform gap thickness through the use of spacers throughout the entire mold dimension.
Solution Approach 2:
The multi-part vent structure with spacers serves multiple functions simultaneously: it maintains constant gap thickness, enables easy assembly and disassembly, and ensures uniform vent spacing throughout the mold. This universal design approach improves both manufacturability and precision.
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
Effectively exhausts air during mold closure while minimizing the risk of softened material entering the vent, maintaining article shape integrity.
Implementation Method 1
said or each mold portion comprises a plurality of parts defining a plurality of gaps, each gap having a flow section such that the sum of the flow sections of the gaps is equal to the flow section of the vent
Data Source
AI summary
A mold comprising at least two mold portions, at least one of which includes a vent opening out to the inside of the cavity and to the outside of the mold and presenting a flow section that is predetermined to enable air to be exhausted when the mold is closed. Said mold portion comprises at least two parts that extend over an entire dimension of the mold cavity and that are assembled together, the parts being held apart from each other by at least one spacer so as to define between them a gap that opens out to the inside of the cavity and to the outside of the mold in order to form the vent. A blow-molding machine including such a mold.