Hydroforming Fill Control for Consistent Container Shaping
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Solution Overview
Problem
Existing methods for forming and filling containers using hydroforming face challenges in controlling the pressure peak during the shaping process, leading to inconsistent container shapes and potential damage to the injection device due to uncontrolled hydraulic hammer effects, and are not suitable for reproducible production.
Innovation Solution
A method involving controlled injection steps with a first injection step at full speed, a second step reducing speed before a predetermined switch pressure is reached, and a third step decelerating to stop injection, combined with monitoring pressure and volume to manage the pressure peak, ensuring consistent container formation and filling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a pressure peak is applied to finalize the shaping of the preform into a container, then the shaping precision is improved, but the mechanical stress on the injection device increases and may cause damage or premature wear
Solution Approach 1:
The injection process is divided into multiple phases with varying injection speeds. The injection speed is reduced when a predetermined pressure is approached, creating a periodic pattern of acceleration and deceleration that controls the pressure peak while reducing mechanical stress on the injection device.
Solution Approach 2:
The system monitors the pressure in the liquid injection circuit in real-time and uses this feedback to control the injection speed. When the monitored pressure approaches a predetermined value, the injection speed is automatically reduced, preventing excessive pressure peaks and protecting the injection device from mechanical damage.
2Productivity
If the injection speed is maintained at full speed throughout the injection process, then the productivity is improved, but the manufacturing precision deteriorates due to uncontrolled pressure peak
Solution Approach 1:
The injection speed is made dynamic rather than constant. The system automatically adjusts the injection speed based on the current pressure state, reducing speed when approaching predetermined pressure levels and maintaining higher speed when pressure is lower, thus optimizing both productivity and precision.
Solution Approach 2:
The injection parameters (speed and pressure) are changed dynamically during the injection process. The system transitions between different injection speed regimes based on pressure monitoring, allowing full productivity when conditions permit and high precision when pressure control is critical.
3Manufacturing precision
If the course of the piston is controlled to obtain identical container shapes, then the manufacturing precision is improved, but the reliability deteriorates because air compression in the liquid modifies the piston movement distance
Solution Approach 1:
Instead of controlling the process by piston position (open-loop), the system uses pressure monitoring as feedback to control injection speed (closed-loop). This feedback mechanism compensates for variations in air compression and liquid compressibility, ensuring consistent pressure application and reliable container shaping regardless of piston movement variations.
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 method allows for precise control of the pressure peak, resulting in uniformly shaped containers with reproducible quality and reduces mechanical stress on the injection device, enhancing process reliability and efficiency.
Implementation Method 1
injecting a pressurized liquid in a preform... at a pressure which is adapted to urge the wall of the preform against the wall of the molding cavity such that the preform is deformed
Implementation Method 2
a hydraulic hammer effect can be obtained when the liquid injection is stopped... a second pressure greater than the first pressure, is applied to the preform during a short time in order to create a pressure peak inside the preform
Data Source
AI summary
An injection device for simultaneously forming and filling a container by injecting a pressurized liquid in a preform. The device includes a molding cavity, a pressurized liquid source and an injection nozzle in fluidic communication with the pressurized liquid source. The injection nozzle is arranged to be placed in fluidic communication with a preform in the molding cavity. A liquid injection circuit is defined by the injection nozzle, the pressurized liquid source and the preform. Also provided is a volume measuring feature for measuring the volume of liquid injected in the preform from the pressurized liquid source and a pressure measuring feature for measuring the pressure in the liquid injection circuit.