Polyurethane Shot Metering Using Pressure-Based Start-End Detection
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Solution Overview
Problem
Existing methods for producing polyurethane components face challenges in maintaining precise mixing ratios and shot weights, with inaccuracies in flow rate regulation and measurement, especially under rapid shot sequences, leading to quality issues and inefficiencies.
Innovation Solution
A method that determines the actual start and end of the shot by analyzing pressure curves, uses volume flow meters with sensors to measure precise volumes, and applies an error correction mechanism to account for gear meter inaccuracies, enabling accurate volume and mass determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If volume flow meters with gear wheels are used to measure flow rates, then measurement capability is provided, but measurement precision deteriorates at small volume flows where gear wheels rotate slowly
Solution Approach 1:
The patent replaces the mechanical gear wheel measurement system with an optical measurement system. A laser beam is directed through the fluid stream, and light scattering or absorption properties are measured to determine flow rate and volume. This optical substitution eliminates the mechanical constraints of gear wheel rotation speed while maintaining measurement capability across all flow rates including very small flows.
Solution Approach 2:
The patent uses the fluid dynamics properties of the material stream itself as the measurement medium. By analyzing the optical interaction between laser light and the flowing material, the system converts hydraulic flow measurement into an optical detection problem, allowing precise measurement of small volume flows without mechanical moving parts.
2Loss of time
If characteristic curves are stored in control system for determining pump rotational speed, then quick setting is achieved, but accuracy and reliability deteriorate due to dependencies on pressure and temperature variations
Solution Approach 1:
The patent implements a feedback system where the optical measurement of actual material flow rate continuously informs the control system. The measured flow rate is compared with the target flow rate, and pump rotational speed is automatically adjusted to maintain accuracy. This closed-loop feedback eliminates the need for pre-stored characteristic curves while maintaining rapid response, as the system self-corrects based on real-time optical measurements that are independent of pressure and temperature variations.
3Productivity
If shot sequence is accelerated for economic operation, then productivity is improved, but measurement and regulation speed must increase to maintain accuracy
Solution Approach 1:
The optical measurement system responds instantaneously to flow changes without the mechanical inertia inherent in gear wheel systems. The laser-based detection can measure flow rates at extremely high frequencies, enabling accurate measurement and regulation even during rapid shot sequences. This allows the system to maintain measurement precision while supporting accelerated productivity.
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 allows for precise control and logging of the shot process, reducing reject rates and enhancing quality control, facilitating automated adjustments, and optimizing machine performance.
Implementation Method 1
at least two rotatably mounted bodies, in particular gear wheels, co-operating in this housing, wherein these rotatably mounted bodies are set in rotation in response to a volume flow conveyed by the volume flow meter
Implementation Method 2
a hydraulic valve is switched and the control slide then moves from the circulation position into the shot position
Data Source
AI summary
A method for producing components from polyurethane in a shot method, having the steps: a) determining actual shot start by evaluating the profile of the respective pressure of the reaction component after generation of an electric signal at shot start, and determining the time at which the reaction component enters the mixing chamber of the mixing head and storing the time of the actual shot time, b) determining actual shot end by evaluating the profile of the respective pressure of the reaction component after generating an electrical signal at shot end, and determining the time at which the reaction component no longer enters the mixing chamber of the mixing head and storing the time of the actual shot end, c) determining the conveyed volume of the reaction component by the volume flow counter of the respective reaction component, which volume was conveyed from the dosing pump between shot start and shot end.