Control Circuit for PET Preform Heating and Blow Molding
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Solution Overview
Problem
Existing control systems for light transmission in PET containers produced by stretch blow molding fail to consider the temperature of preforms leaving the furnace and do not account for non-stationary behavior of light transmission values during transient phases.
Innovation Solution
A control circuit with a higher-level and lower-level control loop that incorporates actual temperature and light transmission measurements to adjust process parameters and heating behavior dynamically, allowing for control before steady state is reached, using a first and second comparator and controller to manage pre-blow time and heating adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If control intervention is performed only after light transmission values reach steady state, then control simplicity is maintained, but production efficiency deteriorates due to delayed control response
Solution Approach 1:
The control system performs preliminary control actions by detecting transient deviations in light transmission values before the process reaches steady state. The controller intervenes during the transient phase rather than waiting for steady state, thereby preventing quality deviations before they manifest in final products. This preliminary action improves production efficiency without requiring fundamentally new control architecture.
Solution Approach 2:
The system implements continuous feedback by monitoring light transmission values in real-time during the transient phase. The controller receives feedback about temperature deviations and light transmission variations, and adjusts heating parameters dynamically. This feedback mechanism enables the system to respond to process variations while maintaining a standard control structure, thus improving productivity without excessive complexity.
2Manufacturing precision
If steady-state control is used, then control stability is ensured, but manufacturing precision deteriorates due to inability to account for transient temperature behaviors
Solution Approach 1:
The control system performs preliminary control actions by detecting transient deviations in light transmission values before the process reaches steady state. The controller intervenes during the transient phase rather than waiting for steady state, thereby preventing quality deviations before they manifest in final products. This preliminary action improves production efficiency without requiring fundamentally new control architecture.
Solution Approach 2:
The system implements continuous feedback by monitoring light transmission values in real-time during the transient phase. The controller receives feedback about temperature deviations and light transmission variations, and adjusts heating parameters dynamically. This feedback mechanism enables the system to respond to process variations while maintaining a standard control structure, thus improving productivity without excessive complexity.
3Manufacturing precision
If control parameters are adjusted dynamically during transient phases, then manufacturing precision improves, but device complexity increases due to additional control loops and sensors
Solution Approach 1:
The control system performs preliminary control actions by detecting transient deviations in light transmission values before the process reaches steady state. The controller intervenes during the transient phase rather than waiting for steady state, thereby preventing quality deviations before they manifest in final products. This preliminary action improves production efficiency without requiring fundamentally new control architecture.
Solution Approach 2:
The system implements continuous feedback by monitoring light transmission values in real-time during the transient phase. The controller receives feedback about temperature deviations and light transmission variations, and adjusts heating parameters dynamically. This feedback mechanism enables the system to respond to process variations while maintaining a standard control structure, thus improving productivity without excessive complexity.
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
Enables precise control of light transmission in PET containers by accounting for temperature gradients and transient behaviors, improving production efficiency and quality by allowing real-time adjustments.
Implementation Method 1
a first measuring device (15) for determining an actual temperature (10) of the heated preforms
Implementation Method 2
a second measuring device (9) for determining an actual light transmission (3) of the containers
Data Source
Figure 1
AI summary
The invention relates to a control loop (1) for a device comprising a heating device for preforms, a blow molding machine for producing containers from preheated preforms, a first measuring device (15) for determining an actual temperature of the heated preforms and a second measuring device (9) for determining an actual light transmission of the containers, wherein the control loop for controlling the light transmission of containers comprises: - A higher-level control loop with a first comparator (4) for determining a first control deviation (5) from a target light transmission (2) and an actual light transmission (3) and with a first controller (6) which, based on the first control deviation as a first input variable for a system (16), outputs a first adjustment (7) of a process parameter of a station of the blow molding machine as a first output variable and controls the process parameter of the station of the blow molding machine according to the first adjustment.The first controller also outputs a target temperature (8) of the heated preform as a second output, based on the first control error as an input. A subordinate control loop includes a second comparator (11) for determining a second control error (12) from the target temperature and the actual temperature, and a second controller (13) which, based on the second control error as a second input for a system (16), outputs a second adjustment (14) of the heating behavior of the heating device as a third output and controls the heating behavior of the furnace according to the second adjustment (14).