Stretch Blow-Molding Preform Pressure Feedback Control
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Solution Overview
Problem
In the context of industrial plastic vessel production by stretch-blow moulding, there is a challenge in achieving consistent quality while minimizing material usage and maintaining high production rates, often resulting in substantial scrap rates due to poor material distribution and pressure variations during the pre-blowing process.
Innovation Solution
A method that involves heating a plastic preform to a predetermined temperature, stretching it, and controlling the pre-blowing process by measuring and adjusting parameters such as pre-blowing pressure, flow rate, stretching speed, and heating temperature based on detected pressure peaks to ensure alignment with theoretical pressure peaks, thereby optimizing the distribution of material and reducing scrap rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If vessels are rejected based on pressure curve non-compliance to improve quality, then manufacturing quality is improved, but productivity decreases and material is wasted
Solution Approach 1:
The patent implements real-time feedback by continuously monitoring pressure variations during pre-blowing and using this information to dynamically adjust process parameters. The control unit receives pressure data from sensors, compares it against target values, and automatically modifies parameters such as pre-blowing pressure, flow rate, and timing to ensure consistent vessel quality without rejecting products
Solution Approach 2:
The patent dynamically changes process parameters based on real-time pressure measurements. The control unit adjusts pre-blowing pressure, flow rate, and timing parameters during the pre-blowing phase to optimize material distribution and prevent defects, transforming a static rejection-based quality control into a dynamic optimization approach
2Loss of substance
If material quantity is reduced to save material, then material usage is improved, but manufacturing precision deteriorates due to poor material distribution
Solution Approach 1:
The patent uses pressure sensors to monitor the pre-blowing process in real-time, providing feedback on material distribution. The control unit analyzes pressure variations to detect uneven material flow and automatically adjusts pre-blowing parameters to ensure uniform material distribution even when using reduced material quantities
Solution Approach 2:
The patent performs preliminary pre-blowing actions before the main blowing phase to prepare the preform and ensure proper material distribution. The pre-blowing phase uses controlled pressure and flow to position material uniformly throughout the mold cavity, creating optimal conditions for subsequent blowing and final vessel formation
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 results in higher-quality vessels with improved material distribution and reduced scrap rates, maintaining or increasing production efficiency by ensuring that the pressure peaks align with theoretical standards, leading to more consistent and effective production.
Implementation Method 1
heating the preform to a predetermined heating temperature
Implementation Method 2
the blowing of the preform is carried out by injecting therein a gas (such as air) under high pressure (generally greater than 30 bars)
Implementation Method 3
The stretch blow-moulding technique consists, other than the blowing, in stretching the preform using a sliding rod
Implementation Method 4
a pre-blowing operation is generally provided, during which a gas under reduced pressure (generally between 5 and 16 bars) is injected into the preform
Data Source
AI summary
A method for producing a vessel by stretch blow-molding in a mold from a preform made of plastic material includes heating the preform and introducing the preform in the mold. The preform is stretched by a rod displaced at a predetermined stretching speed. At a pre-blowing cue, the electrovalve is opened for establishing a communication between the inside of the preform and a gas source at a predetermined pre-blowing pressure and a pre-blowing flow rate. Pressure inside the preform is measured and a pressure peak is detected. The moment at which this pressure peak occurs and the corresponding pressure inside the preform is stored and compared with a predetermined moment and pressure for a theoretical pressure peak. Depending on the result, at least one of the following are modified: pre-blowing pressure, pre-blowing flow rate, pre-blowing cue, stretching speed, and heating temperature.