Our solution allows to identify optimums and instabiltites in large datasets of printing parameters based on dropwatching. We develop our own software to automatically test, record and compare waveforms, inksystem parameters and ambiant conditions. The storage of all the parameters and outcomes in a database guarantes a fully reproducible and transparent workflow.
Our solution can emulate most printing setups for optimizations and analyzes from one common interface. It allows performance comparisons accross different printheads and inks in a fully transparent and reproducible workflow.
Both analog and digital waveforms can be controlled and optimized. All waveform parameters (amplitudes, durations and slew rates) can be swept automatically to measure their effect on the drop properties.
Automatic sweep of printing parameters
The printing parameters to measure are defined in a table that allows the sweeping over one or more parameters automatically. Thousands of dropwatching images can be acquired within a single test session.
All test parameters are stored in a database and can be re-used at any later time to re-run a previous test for comparison.
Drop features extraction and storage
The drop features, such as speed, volume and shape, are automatically extracted from the dropwatching images. These features are then stored in our database together with all the test parameters and sensor inputs (temperatures, misting).
The optimizations steps are tailored to the specific needs of each applications. The most common applications are listed as follows:
- Basic optimization, for relatively low printing frequencies with stable inks.
- High-performance optimization, where the printhead is pushed to its maximal throughput and stability is key.
- Latency optimization, for applications where the drying of the ink in the nozzles is specificially adressed.
- Full printhead optimization, where the performances of every single nozzle will be evaluated over longer durations.
High frequency optimization
Stability over the whole frequency range is critical for applications where the printing speed varies. The stability can be measured by comparing the drop speed at different frequencies. The waveforms are then optimized to minimize the instabilities in the critical regions. In the example below, a critical instability was identified at 27kHz and could be significantly improved through waveform tuning.i
Open-nozzle-time and recovery
The behavior of the drops after non-jetting periods is critical for the stability of the printing process. This is one of the most common issue encountred when printing with solvent, i.e. water-based inks. Our unique workflow allows to evaluate the first drops jetted after idling and compare their recovery in a reproducible manner. This insight is key in optimizing ink formulation, tickling and ink recirculation.
It the attached plot the printhead was jetting at 1kHz after idling for up to 900s. One image was acquired every 50ms once the jetting was re-started. At short idling period, little to no instability in the drop position can be observed. However, idling periods of 60s and higher yield an increased change in the drop position, meaning that the drops are slower at first before recovering. No recovery was observed at 900s, meaning that the maximal open nozzle time was 300s.