Condensation Control in Inkjet Printers
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Solution Overview
Problem
High-speed thermal inkjet printing is limited by condensation of water vapor on printheads and other structures in the print zone, which increases with faster speeds and higher printhead densities, leading to print defects and reduced ink density.
Innovation Solution
Incorporating a condensation control system that injects hot, dry air into the print zone at a controlled temperature and humidity to lower the dew point, using a shroud assembly with an air injector that discharges pressurized air at a specific angle and velocity to reduce condensation without disturbing ink drops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If printing speed is increased in high-speed thermal inkjet printing, then productivity is improved, but water vapor condensation on printheads increases causing print defects
Solution Approach 1:
The patent changes the physical parameters of air in the print zone by injecting hot dry air at controlled temperature (40-55°C) and low humidity (5% or less relative humidity) to lower the dew point below surface temperatures of printheads, thereby eliminating condensation while maintaining high printing speeds
Solution Approach 2:
The patent introduces dry air as an intermediary substance between the moisture source (condensing water vapor) and the printhead surfaces, where the dry air absorbs moisture and maintains a dew point below the printhead temperature, preventing condensation formation
2Manufacturing precision
If printhead nozzle density is increased to improve print quality, then manufacturing precision is improved, but condensation occurrence increases
Solution Approach 1:
The patent modifies the thermal and humidity parameters of the print zone atmosphere by injecting hot dry air, which lowers the dew point to remain below the printhead surface temperature, thus preventing condensation even at high nozzle densities where more surfaces are exposed
3Object-affected harmful factors
If air is injected into the print zone to reduce condensation, then condensation is reduced, but ink drops may be disturbed
Solution Approach 1:
The patent optimizes the physical parameters of injected air (temperature of 40-55°C, low humidity of 5% or less, velocity of 50 m/s) and injection geometry (45° angle down toward print media) to create conditions that reduce condensation while the moderate temperature and targeted angle prevent disturbance of jetted ink drops
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
Significantly reduces condensation on printheads and other structures, allowing for increased printing speed and ink density without affecting ink drop placement, as demonstrated by injecting 40° C to 55° C air with 5% relative humidity at 45° angle and 50 m/s.
Implementation Method 1
water vapor in the air in the print zone may condense on nearby surfaces
Implementation Method 2
lower the dew point in the print zone below the temperature of nearby surfaces on printheads and other structures
Data Source
AI summary
In one example, a process to control condensation in an inkjet web printer includes injecting hot, dry air into the print zone. In another example, a shroud assembly includes a shroud spanning a full width of the print zone and having openings therein through which printheads are exposed during printing and an air injector attached to or integral with the shroud. The air injector spans a full width of the print zone upstream from all of the openings in the shroud. The air injector is configured to discharge air down and downstream with respect to a print media moving through the print zone during printing.