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Renner Johannes

Wissenschaftlicher Adjunkt FH

Hauptkompetenzen

Wissenschaftlicher Adjunkt FH

Büro: MIC_10_157

Haute école d'ingénierie et d'architecture de Fribourg
Boulevard de Pérolles 80, 1700 Fribourg, CH

Master of Science in Engineering (MSE) - Bern University of Applied Sciences

2017

Waveform Optimization for Piezo Drop on Demand Inkjet Print Heads by Meniscus Motion Analysis

Wissenschaftlicher Artikel

Renner Johannes, Bircher Fritz

Advances in Print and Media Technology 44 (Iarigai 2017), 2017 , vol. 44, no 1, pp. 15-20

Link zur Publikation

Zusammenfassung:

Waveform optimization is a key to success for piezo drop on demand printing systems. The industry estab-
lished method for waveform analysis and optimization is a drop watching analysis. With a drop watching sys-
tem, usually a large number of droplets has to be jetted for each configuration of the printing system. As inkjet
is increasingly being used in functional printing, an increasing number of fluids with a certain toxicity, limited
stability or very high material cost are jetted. For such applications, there is a need to reduce the amount of
wasted fluid. The aim of this publication is to explore the potential of estimating jetting properties and opti-
mizing waveforms by meniscus motion analysis with a standard drop watching setup. By analyzing the menis-
cus motion at different pulse amplitudes below the drop emission threshold, the voltage necessary to reach a
certain drop speed could be estimated. An estimation of the frequency - velocity variation can be obtained by
analysis of the meniscus motion in the range of actual jetting frequencies.

2014

A direct printed passive RFID sensor for content aware drug bottles

Wissenschaftlicher Artikel

Renner Johannes, Mazza Marco, Pierluigi Civera, Bircher Fritz

Advances in Print and Media Technology 41 (Iarigai 2014), 2014 , vol. 41, no 1, pp. 85-89

Link zur Publikation

Zusammenfassung:

Lack of compliance with regard to medical prescriptions has become a major cause of treatment failure, a problem
particularly faced in the aging population. In order to aid patients in taking their medication properly, various
products for solid drugs like electronic pill organizers have recently appeared on the market whereas there is a lack of
effective solutions for liquid drugs. In this paper, a novel direct printed RF sensor for drug bottles is presented as a
low-cost solution, which can be used for monitoring liquid medication. The fully-printed, single layer metal sensor has
been realized on the top of a polyethylene bottle, acting as a resonant LC tank, which can be read remotely. Resonant
frequency drifts proportionally to the liquid content, since the distributed capacitance value is affected by the per-
mitivity of the liquid.

The demonstrator presented in this article shows an impressive sensitivity up to 316 kHz/mL, resulting in a cost-
efficient and viable solution to detect content variation in the order of sub - milliliters.

2013

Multi Wavelength Imaging for Drop Watching Systems

Buch

Renner Johannes, Karl-Heinz Selbmann

2013, Chemnitz, Germany : Verlag für Wissenschaft und Bildung, 49 p.

Link zur Publikation

Zusammenfassung:

For measurements of drop speeds and trajectory angles, which are independent of a minimum jetting frequency and unaffected by jitter time on the firing of drops, drop watching systems flash twice with a short flash delay between the flashes during the exposure of one image. The drop speeds and trajectory angles can then be calculated with the displacement of the same drops in the image during the flash delay. By overlaying replicate measurements in one image, the variance of the properties can qualitatively be measured for a print system configuration in an efficient way. The main disadvantages limiting the reliability of such measurements, may be errors in the correlation of overlaid objects, a reduction of the contrast or overlapping artifacts. To enable reliable overlaid measurements or increase the performance and reliability of drop watching systems, a solution with a multi wavelength imaging system is introduced in this paper

2011

Simulation aided design of inkjet systems

Wissenschaftlicher Artikel

Renner Johannes, Philip Marmet, Bircher Fritz, Florian Fässler, Philipp Haslebacher

Advances in Print and Media Technology (Iarigai 2011), 2011 , vol. 38, no 1, pp. 69-78

Link zur Publikation

Zusammenfassung:

This paper presents an approach to simulation aided design of inkjet systems by creating an entirely virtual
printing machine. Simulations are used in every domain of inkjet systems, from the single inkjet valves to the
print machine’s structural dynamics and the simulation of the final printout on substrates. All these simulations
are coupled with different interfaces. Therewith the printing machine with its mechanical structure, drive systems
and control algorithms can be optimized as a whole. The impact of vibrations on the final print result can be
achieved with the simulation of the printout.

A deeper understanding of the whole printing process can be achieved due to the ability to simulate the entire
inkjet system. Furthermore it is possible to solve a specific problem by simulating an individual setting, if
necessary simulations can be coupled. A global approach to simulation with well-defined interfaces and
couplings between the different engineering fields increases the interdisciplinary thinking and exchanging of
knowledge. In this way, simulations are an efficient and powerful tool to develop and optimize the complex inkjet
systems for tomorrow’s needs.

Reproducibility of DoD inkjet print-ing systems

Wissenschaftlicher Artikel

Renner Johannes, Bircher Fritz, Gert Schlegel

Advances in Print and Media Technology (Iarigai 2011), 2011 , vol. 38, no 1, pp. 79-85

Link zur Publikation

Zusammenfassung:

For inkjet printing, the maximal possible accuracy of deposition can be reached with the highest reproducibility
of printing and a correction compensating for systematic jetting faults.

In the this article the reproducibility of jetting of a set of industrial print heads in high throw distance and
high print speed operation is investigated. Based on the results, methods for the correction of reproducible jetting
errors are introduced.

2019

Selective inkjet coating of PCBs with paraffin wax

Konferenz

Renner Johannes

TheIJC 2019, 29.11.2019 - 01.11.2021, Düsseldorf (Germany)

Link zur Konferenz

Zusammenfassung:

For protection against moisture and consequent corrosion, printed circuit boards (PCBs) with enhanced environmental protection are, after assembly with electronic components, selectively coated with a protective film, a so called conformal coating. The main current methods for selective electronics coating are spray painting, which has good productivity but very limited resolution, and micro dispensing, which has limited productivity and cannot economically be upscaled. Inkjet technology on the other hand does provide sufficient resolution and the necessary scalability needed in large volume production for selective conformal PCB coatings, but the main drawback is its limitation in throw distance, which is in most applications only a few millimetres against component heights in excess of 10 millimetres on many PCBs. By optimising drop volumes and speeds by means of waveform tuning, reliable throw distances can however greatly increased. In this presentation a solution for selective inkjet-printed conformal PCB coatings with a paraffin based wax at a throw distance of 15 millimetres is presented.

2018

Prediction of open nozzle times for volatile inks by meniscus motion analysis

Konferenz

Renner Johannes

TheIJC 2018, 16.10.2018 - 17.10.2018, Düsseldorf (Germany)

Link zur Konferenz

Zusammenfassung:

Many inkjet printing machines, that are printing volatile inks, are operating in ambient conditions that require nozzle maintenance in certain intervals to ensure reliable operation of the print heads. The maximum time in which ink inside nozzles can be exposed to ambient conditions before they cannot be recovered by jetting is called the open nozzle time. The open nozzle time can be determined empirically by performing repeatedly nozzle maintenance followed by printing after an increasing delay. Determining the open nozzle time empirically is however time consuming, and with certain inks there is a risk to damage the printhead or intense cleaning is required if the ink dried in the nozzles too much. A relatively simple solution to efficiently estimate the open nozzle time without risking damaging the printhead can be a meniscus motion analysis. Thereby the jets are excited with pulses that do not create droplets and the peak excitation of the meniscus, which is the liquid interface at the nozzles, is measured. As, due to drying of the ink, viscosity increases, the peak meniscus excitation is decreasing over time accordingly. By measuring the peak excitation over time, the open nozzle time can be extrapolated without having to wait until the ink is already dried too much for jetting.

Inkjet waveform optimization by meniscus motion analysis

Konferenz

Renner Johannes

TheIJC USA 2018, 12.04.2018 - 13.04.2018, Chicago

Link zur Konferenz

Zusammenfassung:

Waveform optimisation is a key to success for piezo drop on demand printing systems. The industry-established method for waveform analysis and optimisation is a drop watching analysis. With a drop watching system, usually a large number of droplets has to be jetted for each configuration of the printing system. As inkjet is increasingly being used in functional printing, an increasing number of fluids with a certain toxicity, limited stability or very high material cost are jetted. For such applications there is a need to reduce the amount of wasted fluid. One way to accomplish this is the analysis of the meniscus motion. If a waveform is proportionally scaled down to an amplitude that does not generate drops, acoustic timing can be analysed and optimised by analysing the meniscus motion. An estimation of the frequency – velocity variation can be obtained by analysis of the meniscus motion in the range of actual jetting frequencies. By analysing meniscus oscillations at different pulse amplitudes that are below the drop emission threshold, the voltage necessary to reach a certain drop speed could be estimated. As the same setup as for drop watching analysis can be used for the analysis of meniscus motion, implementation of such an analysis in existing systems is expected to be efficient.

2017

3D jet straightness analysis by image analysis in different focal planes

Konferenz

Renner Johannes, Lionel Buzetti

TheIJC 2017, 17.10.2017 - 18.11.2017, Düsseldorf (Germany)

Link zur Konferenz

Zusammenfassung:

One of the most important jetting properties of high quality inkjet printing systems is the jet straightness of the printheads. Dependent on the used printhead the total deviation of printed dots has a systematic error part which can be related mainly to jet straightness errors and a stochastic part that is usually smaller in magnitude. If the average jet straightness errors of a printhead are known, the total printed dot positon errors can be reduced to the level of stochastic errors by software compensation in multiple passes. Current systems to measure the jet straightness in three coordinates (e.g. print direction, cross-print direction and distance from the nozzle plate) need to scan the printhead nozzle by nozzle with two 90° oriented cameras which is in terms of measurement duration impractical for integration in industrial print machines. With a system that analyses droplets of multiple nozzles in different parallel focal planes, the actual positions and velocities in 3D of all seen droplets can be measured simultaneously by either analysing the sharpness function of drops (similar to focus systems in mobile phone cameras) or by measuring the change in magnification with a non-telecentric lens and double flashing. As jet straightness measurements of multiple nozzles can be carried out in parallel the total time to assess a complete printhead can be reduced significantly. As such a system can operate from a single viewpoint, integration in print machines is simplified and by analysing in the printing gap continuous measurement during printing is possible.

Waveform optimization for piezo drop on demand inkjet print heads by meniscus motion analysis

Konferenz ArODES

Johannes Renner, Fritz Bircher

Proceedings of the 44th International IARIGAI Conference, Advances in Printing and Media Technology - From Printing to Manufacturing, 10-13 September 2017, Fribourg , Switzerland

Link zur Konferenz

Zusammenfassung:

Waveform optimization is a key to success for piezo drop on demand printing systems. The industry established method for waveform analysis and optimization is a drop watching analysis. With a drop watching system, usually a large number of droplets has to be jetted for each configuration of the printing system. As inkjet is increasingly being used in functional printing, an increasing number of fluids with a certain toxicity, limited stability or very high material cost are jetted. For such applications, there is a need to reduce the amount of wasted fluid. The aim of this publication is to explore the potential of estimating jetting properties and optimizing waveforms by meniscus motion analysis with a standard drop watching setup. By analyzing the meniscus motion at different pulse amplitudes below the drop emission threshold, the voltage necessary to reach a certain drop speed could be estimated. An estimation of the frequency - velocity variation can be obtained by analysis of the meniscus motion in the range of actual jetting frequencies.

DoD Waveform Optimization by Menicus Motion Analysis

Konferenz

Renner Johannes

TheIJC 2017, 23.08.2017 - 24.10.2017, Düsseldorf (Germany)

Link zur Konferenz

Zusammenfassung:

Waveform optimization is a key to success for piezo drop on demand printing systems. The industry established method for waveform analysis and optimization is a drop watching analysis. With a drop watching system, usually a large number of droplets has to be jetted for each configuration of the printing system. As inkjet is increasingly being used in functional printing, an increasing number of fluids with a certain toxicity, limited stability or very high material cost are jetted. For such applications there is a need to reduce the amount of wasted fluid. The aim of this publication is to explore the potential of estimating jetting properties by meniscus motion analysis with a standard drop watching set?up. By analyzing the meniscus motion at different pulse amplitudes below the drop emission threshold, the voltage necessary to reach a certain drop speed could be estimated. An estimation of the frequency - velocity variation can be obtained by analysis of the meniscus motion in the range of actual jetting frequencies.

2016

Additive manufacturing by solvent jetting on granule beds

Konferenz ArODES

Efrain Carreño-Morelli, Mikel Rodriguez-Arbaizar, Glenn Flückiger, Christian Cachelin, Fritz Bircher, Johannes Renner, Jacques Richard

Proceedings of Powder Metallurgy World Congress, World PM2016 - AM - Powder bed based technologies, 9-13 October 2016, Hamburg, Germany

Link zur Konferenz

Zusammenfassung:

A "Solvent on Granule" 3D-Printing technique has been developed, which consists in the spreading of a powder-polymer granule bed, followed by the selective jetting of a solvent (which softens the polymer contained in the granules), and layer consolidation after solvent evaporation. The granules are prepared by wet blending, drying, milling and sieving. The granule layer thickness can be set between 50 μm and 200 μm, and the volume of the solvent droplets is about 10 pL. A summary of preliminary results obtained with 17-4PH stainless steel parts in a former prototype device is presented. A new concept of table-top machine is developed in this work and its essential components and functions are described.

Increasing Drop Watching Efficency

Konferenz

Renner Johannes

TheIJC 2016, 04.10.2016 - 06.11.2016, Düsseldorf (Germany)

Link zur Konferenz

Zusammenfassung:

Drop watching is a key technology to find suitable operating parameters of inkjet printheads. With a drop watching system, usually a large number of droplets has to be jetted for each configuration of the printing system. As inkjet is increasingly being utilised in functional printing, an increasing number of fluids with a limited stability and potentially very high material cost are jetted. For such applications there is a need for an increased efficiency of the drop watching process. The amount of wasted fluid has to be reduced and the process of finding operational parameters has to be faster. One possibility to achieve these goals is reducing the number of jetted drops per analysis and rapidly changing waveform parameters. By minimising the number of drops per analysed configuration and increasing the frequency in which different waveforms are tested, engaging effects of the printhead and interference with the previously tested waveform are reducing the accuracy of the analysis. In this publication the potential of increasing the efficiency of drop watching by reduction of jetted droplets and faster waveform testing is explored.

2015

Realtime Monitoring of Inkjet Systems with Overlaid Imaging

Konferenz

Renner Johannes

TheIJC 2015, 07.09.2015 - 08.09.2015, Düsseldorf (Germany)

Link zur Konferenz

Zusammenfassung:

One major drawback of using inkjet in functional printing applications is the limited reliability of the inkjet printing process. In order to improve the reliability of the printing process an inline monitoring system is required. Depending on the application, monitoring can be realised by inspection of the printed results on the substrate or by monitoring the printhead itself. To minimise the number of wasted parts and the time of incorrect printing, errors in the printing process need to be detected with a sufficiently small delay. A promising approach enabling real-time monitoring is to use a new drop watching system which allows detecting the presence of all drops in the printing gap. In this paper an approach for inkjet process monitoring based on overlaid imaging is investigated and its potential evaluated by measurements.

2014

Advanced Dropwatching

Konferenz

Renner Johannes

TheIJC 2014, 29.09.2014 - 01.10.2014, Düsseldorf (Germany)

Link zur Konferenz

Zusammenfassung:

In order to optimize the productivity of DoD inkjet printing systems, waveform tuning by means of drop-in-flight analysis (also referred to as drop watching) on dedicated analysis test rigs is used. By using advanced drop watching methods with multi-camera systems or overlaid imaging the reliability and performance of standard drop watching systems can be greatly improved, or drop watching analysis of a printing machine in operation (including analysis of drop landing on the substrate) can be enabled.

Errungenschaften

Suche

Renner Johannes

Wissenschaftlicher Adjunkt FH

Hauptkompetenzen

Mechatronics

Electronic design

Microfluidics

Inkjet

Inkjet printhead

Matlab

Informatique

Wissenschaftlicher Adjunkt FH