Method for feedback control of the temperature of an ink in inkjet printing
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Solution Overview
Problem
Existing feedback control methods for ink temperature in industrial inkjet printing fail to detect changes in ink viscosity, leading to unimpaired drop formation and potential production halts due to premature ageing or production variations.
Innovation Solution
A method that uses a flow sensor to measure ink flow and convert it into a temperature auxiliary value via a characteristic curve, allowing for feedback control of ink temperature and viscosity adjustment to maintain optimal drop formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If temperature feedback control is performed using only temperature sensors in the ink distributor, then the temperature can be maintained at setpoint, but changes in ink viscosity due to ageing or production variations cannot be detected
Solution Approach 1:
A flow sensor is introduced as an intermediary measurement device to indirectly detect viscosity changes. The flow sensor measures ink flow rate, which serves as a mediator to infer viscosity variations without directly measuring viscosity. This allows the system to detect changes in ink rheological properties that temperature sensors alone cannot detect.
Solution Approach 2:
The patent replaces direct viscosity measurement mechanisms with a flow-based measurement system. Instead of using complex viscometers or direct viscosity sensors, the system uses flow rate measurement combined with temperature data to calculate and monitor viscosity changes, simplifying the measurement system while maintaining detection capability.
2Reliability
If a flow sensor is added to measure ink flow for viscosity detection, then viscosity changes can be detected, but the device complexity increases
Solution Approach 1:
The flow sensor serves multiple functions: it measures ink flow rate for viscosity detection, monitors ink circulation status, and provides data for predictive maintenance. By making the flow sensor multi-functional, the patent reduces the need for additional specialized sensors, thereby limiting the increase in device complexity while maintaining reliability improvements.
Solution Approach 2:
The system implements feedback control by continuously monitoring flow rate and temperature data, calculating viscosity, and adjusting the ink heater accordingly. This closed-loop feedback mechanism allows the system to automatically compensate for viscosity changes, maintaining production reliability without requiring complex manual intervention systems.
3Manufacturing precision
If temperature is increased to compensate for increased viscosity, then drop formation is maintained, but energy consumption increases
Solution Approach 1:
The system dynamically adjusts the ink heater power based on real-time viscosity calculations from flow and temperature measurements. Instead of maintaining a constant high temperature, the heater power is optimized to provide only the necessary heating to maintain target viscosity, reducing energy consumption while preserving drop formation quality.
Solution Approach 2:
The patent changes the control parameter from fixed temperature setpoint to dynamic temperature adjustment based on viscosity requirements. By calculating the actual viscosity and adjusting temperature accordingly, the system maintains manufacturing precision while avoiding unnecessary energy expenditure on overheating.
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 method enables continuous unimpaired production by detecting viscosity changes and adjusting the ink temperature accordingly, preventing production halts and allowing for predictive maintenance.
Implementation Method 1
a flow sensor is operated between the supply line and the return line and in parallel with the print heads and measures the flow of the ink or a measurement signal dependent on the flow is generated
Implementation Method 2
at least one temperature sensor is provided in the ink distributor... to thermally adjust, in particular to heat, the circulating ink fluid during printing operation
Implementation Method 3
an ink circuit... includes an ink distributor (also referred to as a manifold) with a supply line to the heads and a return line to the container as well as at least one pump for delivering the ink through the lines
Data Source
AI summary
A method for feedback control of ink temperature in inkjet printing includes pumping ink through supply and return lines of an ink distributor and between these lines through print heads supplied in parallel with the ink, comparing a temperature actual value with a predefined temperature setpoint value and calculating a manipulated variable for a setpoint value of an ink heater from a setpoint/actual value deviation. A flow sensor is operated between the supply and return lines in parallel with the print heads and measures the flow of the ink or generates a measurement signal dependent on the flow. The flow or the measurement signal is converted by a predefined characteristic curve into a temperature auxiliary value used as the temperature actual value or temperature setpoint value for feedback control. This enables continuous unimpaired production by inkjet printing, particularly upon changes in viscosity of the ink in industrial inkjet printing.