Conference Papers

Roll-to-roll (R2R) machines have been extensively used to manufacture a wide variety of consumer products, such as paper, plastics, textile, etc. R2R machines facilitate continuous processing of materials with minimal stoppage time and provide significant improvement in productivity over batch manufacturing. With recent advances in technology it is now possible to manufacture flexible electronics, flexible digital displays, solar films, etc., using R2R processing. R2R processing of flexible electronics requires better understanding of machine and process dynamics to achieve tight tolerances required in their manufacturing. One of the conventional R2R processes that is critical to enable R2R processing of flexible electronics is printing. In this paper, machine and process dynamics for R2R printing are studied in detail. Specifically two control configurations, depending on the type of control input, are analyzed; a compensator based registration control strategy (CRC) typically used with mechanical line shafts (MLS) and a print cylinder angular position based registration control (PARC) strategy used typically with electronic line shafts (ELS), are compared. A comparison of these strategies is given based on a dynamic model for the print section, which includes governing equations for strain in the material, print cylinder velocities, and registration error (a metric that quantifies print quality). An interaction metric is used to analyze interaction of key process variables between print units. Model simulations are conducted for different scenarios to evaluate the strategies. Results of the model simulations are presented and discussed.

A laser based fiber-optic sensor was proposed in our previous work. The sensor developed was based on the principle of scattering of light and the sensitivity directional property of optical fibers. A beam of light is incident on a surface or an edge, the scattered light is received by a linear array of optical fibers. The lateral position of the web edge is determined based on the intensity of light received by each fiber in the fiber array. Static experiments were conducted to show the feasibility of the sensing strategy. In this work, the performance of the sensor is evaluated on an actual web handling platform. The analysis of static and dynamic (with non-zero web transport velocity) experimental data of the sensor under various realistic operating conditions and disturbances is conducted. A direct comparison of the fiber optic sensor and two existing industrial sensors is presented. The experimental data from the sensors are compared using different web materials and under different operating conditions. The new fiber optic sensor is more accurate and the measurements are less noisy. Further, the new sensor overcomes some of the key limitations of existing sensors. The problem of determining the actual position of the web when it is completely outside the sensing window or when it completely covers the sensing windows is resolved; the solution consists of a new configuration. The new configuration also improves the precision of the sensor.

Roll-to-roll (R2R) manufacturing is a type of continuous manufacturing process extensively used to produce a wide variety of consumer products, such as plastics, paper, films, non-wovens, textile, etc. Recent advances in nanotechnology and material science have enabled the possibility of manufacturing electronics on a flexible substrate using R2R printing techniques. Even though the feasibility of printing electronics on flexible substrates has been extensively studied, continuous printing on a moving substrate using R2R techniques has not been adequately investigated. To facilitate progress towards high precision R2R printing, a systematic investigation of the various aspects that affect print quality and ways in which those can be influenced by different control configurations facilitated by choice and location of various components of the print section is necessary.

Existing edge sensors use the concept of blocking/unblocking for measuring web lateral position. The most commonly used sensors employ either ultrasonic or infrared signals to detect the web edge position by measuring the amount of signal attenuation due to blocking/unblocking of the signal. The main drawback of this sensing method is nonuniform signal attenuation due to web material variations and opacity. The research in this paper develops a new sensor which utilizes the phenomena of light scattering from the web edge and the directional sensitivity of optical fibers. A collimated laser beam is incident on the web edge and scattered light is collected by a linear array of fibers spatially positioned above the web edge. The theory of operation and the development of the sensor is described. Experiments are conducted with different web materials to validate the proposed sensing method. A representative sample of the results are presented and discussed.