Mold Cavity Volume Reduction for High-Pressure Blow Molding
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Solution Overview
Problem
Conventional methods for increasing fluid pressure in blow molding PET containers require costly upgrades in pumps and machinery, limiting the cost-effectiveness of achieving high pressures necessary for forming clear and strong containers with desired crystallinity.
Innovation Solution
The method involves mechanically actuating the mold by reducing its cavity volume during the forming process, increasing the fluid pressure within the container preform without relying solely on pump capacity, allowing for higher pressures to be achieved with less expensive equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If conventional pump-based methods are used to increase fluid pressure, then high pressure can be achieved, but equipment cost increases significantly
Solution Approach 1:
The mold cavity volume is dynamically reduced during the blow molding process to increase fluid pressure. The mold transitions from a larger initial volume to a smaller final volume, creating a pressure increase without requiring additional pumping equipment. This dynamic volume change achieves the desired pressure effect while keeping equipment costs low.
Solution Approach 2:
The invention changes the physical parameter of mold cavity volume during the forming process. By reducing the cavity volume from an initial state to a final state, the system creates pressure through compression rather than through additional pumping. This parameter change allows high pressure to be achieved with existing equipment, resolving the contradiction between pressure and equipment cost.
2Manufacturing precision
If higher fluid pressure is applied during blow molding, then container clarity and strength improve, but equipment investment increases
Solution Approach 1:
The mold cavity dynamically reduces its volume during the blow molding process to generate higher fluid pressure. This dynamic compression of the cavity creates the necessary pressure to achieve excellent container clarity and strength without requiring expensive specialized equipment. The pressure increase is achieved through the mold's own mechanical action rather than external pumping systems.
Solution Approach 2:
The mold cavity serves its own function of generating pressure through its volume reduction. Instead of requiring external pumping equipment to provide high pressure, the mold itself creates the pressure needed for quality container formation. This self-service approach eliminates the need for additional expensive equipment while maintaining high manufacturing precision.
3Strength
If mechanical processing is used to increase PET crystallinity, then container strength improves, but light transmission decreases due to spherulitic morphology
Solution Approach 1:
The invention changes the processing parameters by applying higher fluid pressure during blow molding. This pressure increase promotes biaxial orientation of the PET molecular structure, which enhances both container strength and light transmission. The pressure-driven molecular orientation avoids the formation of spherulitic morphology, resolving the contradiction between strength and light transmission.
Solution Approach 2:
The high fluid pressure is applied locally and temporarily during the critical forming stage of blow molding. This localized pressure application promotes molecular orientation in the specific regions being formed, creating strong containers with good light transmission without requiring extensive mechanical processing that would create spherulites.
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 approach enables the attainment of higher fluid pressures, such as up to 120 psi, while reducing equipment costs and maintaining the quality of the formed containers, with the pressure increase achieved through mechanical volume displacement of the mold cavity.
Implementation Method 1
actuating the mold cavity into a second configuration and a second volume, whereby the second volume is smaller than the first volume, thereby resulting in a second fluid pressure within the plastic preform being greater than the first fluid pressure
Data Source
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AI summary
A method of fluid forming a container comprising positioning a plastic preform into a mold cavity, wherein the mold cavity defines a first configuration and a first volume. The method further includes injecting a fluid within the plastic preform at a first fluid pressure urging the plastic preform into an expanded shape. The method includes actuating the mold cavity into a second configuration and a second volume, whereby the second volume is smaller than the first volume, thereby resulting in a second fluid pressure within the plastic preform being greater than the first fluid pressure.