Pre-stretching Stretch Rod for Blow Molding Contamination
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Hydraulic blow molding faces contamination risks and potential improper molding due to residual product on the stretch rod, which can be at a different temperature than the introduced product, affecting the molding process.
Innovation Solution
A system and method for pre-stretching preforms using a movable stretch rod that is extended within the preform before heating and then retracted before introducing the blowing medium, minimizing contact between the stretch rod and the product, and utilizing a conveyor system with heating zones to optimize the heat profile for molding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the stretch rod remains within the preform during radial expansion in hydraulic blow molding, then the preform can be effectively stretched and molded, but the stretch rod becomes contaminated with residual product and may cause improper molding due to temperature differences
Solution Approach 1:
The stretch rod performs the stretching action on the preform before the blowing medium is introduced. The preform is stretched to the desired shape and dimensions in advance, then the stretch rod is retracted before the hydraulic blow molding process begins, preventing contamination while maintaining molding quality
Solution Approach 2:
The stretch rod is extracted or retracted from the preform before the blowing medium is introduced. This removes the potential source of contamination from the system at the critical moment when the product contacts the preform, while the pre-stretched shape is already established
2Stability of the object's composition
If the stretch rod is located within the preform during hydraulic blow molding, then the preform structure can be maintained, but residual product on the stretch rod may be at a different temperature causing local portions of the preform to be less susceptible to molding
Solution Approach 1:
The stretching operation is completed in advance before the blowing medium is introduced. The preform achieves its final stretched configuration through preliminary mechanical action, eliminating the need for the stretch rod to remain in place during the molding process and ensuring uniform temperature distribution
3Productivity
If hydraulic blow molding is used to eliminate separate filling steps, then productivity is improved, but contamination risks increase due to immediate product introduction into the preform
Solution Approach 1:
The preform is pre-stretched to its final shape and dimensions before the blowing medium is introduced. This preliminary shaping action ensures that when the product is introduced for hydraulic blow molding, the preform is already properly configured, reducing contamination risks while maintaining the productivity benefits of combined molding and filling
Solution Approach 2:
The stretch rod is extracted from the preform before the blowing medium is introduced, removing the contamination source. This allows hydraulic blow molding to proceed with reduced contamination risk while maintaining the integrated molding-filling process efficiency
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 reduces contamination risks and ensures proper molding by pre-stretching the preform before introducing the blowing medium, maintaining the cleanliness of the stretch rod and optimizing the heat profile for effective hydraulic blow molding.
Implementation Method 1
heating the preform to form a heated preform
Implementation Method 2
advancing a stretch rod from a retracted position to an extended position so as to cause elongation of the preform
Implementation Method 3
introducing a blowing medium into the heated preform to form a container
Data Source
Figure 1
Figure 2
Figure 3A~3C
AI summary
A system for pre-stretching a preform utilized in forming a container. The system including an oven, a conveyor system configured for transporting preforms through the oven a blow molding station having at least one mold with interior surfaces defining the shape of the container, and a transfer station configured to transfer a preform from the oven into the blow molding station. The system also includes a stretch rod and an actuator. The stretch rod is movable between retracted and extended positions such that, when in the extended position, the stretch rod is positioned interiorly of the preform and the preform is elongated by the stretch rod to form a pre-stretched preform. The stretch rod is located to form the pre-stretched preform prior to the blowing medium being introduced into the preform in the blow molding station.