The performance of a guiding system is a function of several parameters such as the precision and accuracy of the edge sensor, the precision and accuracy of the guide mechanism, and the speed or the dynamics response of the guide mechanism. ARIS, Roll-2-Roll Technologies LLC’s guiding system (Figure 1) is equipped with high performance stepper motor based linear actuator driven by high efficiency constant current chopper drive.
In some applications it may not be possible to guide the web based on the web edge position. For example, in printing applications it is not uncommon to guide the web based on a printed line on the web. In such cases a line guide sensors, that typically employ a camera based system, is used to detect the contrast difference between the line and the background to detect the edge of the line which is used for web guiding. The ARIS I sensor is capable of both edge and contrast detection and in the white paper we show the contrast guiding performance of the ARIS web guiding system.
Experimental Roll to Roll Machine
In order to quantify the guiding performance we test the web guides in an in-house closed-loop roll to roll experimental platform (see Figure 2). The length of web material threaded in the machine is about 20 meters and the web can be transported at a speed of up to 10 meters/sec. The web tension in the machine is maintained using a pneumatic dancer system. Webs with 100 mm and up to 450 mm in width can be transported in the machine which is equipped with two web guides. Two spans with a total length of 1200 mm separate the two web guides. For experimental purposes the upstream guide is used to create disturbances while the downstream guide is used to correct for the disturbances.
Two additional sensors, with a sensing window of 16 mm (see Figure 3), are used to measure the lateral position before and after the downstream web guide. These sensors provide a clear quantification of the magnitude of lateral disturbance entering the web guide and the corrective response of the web guide.
Sinusoidal Disturbance Rejection
Sinusoidal disturbances are common lateral errors seen in industrial converting machines. Hence the performance of the ARIS guiding system is evaluated for sinusoidal disturbances. In the experiments reported in this white paper, sinusoidal lateral disturbances with a magnitude
of 8 mm and frequencies of 0.25 Hz, 0.5 Hz and 1 Hz were introduced with the upstream guide while the downstream guide is used to correct for the disturbances. A composite label with clear carrier film with translucent white labels with a width of 200 mm was transported in the machine with varying speeds up to about 2 m/sec; tension was maintained in the machine using a passive dancer. Figures 4 – 6 show representative sample of results when the web was transported at 1.94 m/sec.
All the plots show the disturbance entering the guide roller (measured using the upstream sensor) and the guiding performance of ARIS (measured in the downstream span using a sensor). A FFT summarizing the performance showing the lateral disturbance and the guiding performance is shown in Figure 7 to further summarize the results.
Additional experiments at a slower speed were also conducted and the summary of results in frequency domain is shown in Fig. 8.
Summary and Conclusions
From the experimental results it is evident that the ARIS guiding system provides exceptional guiding performance in the presence of sinusoidal disturbances. Significant reduction in sinusoidal disturbances and rapid response to disturbances were observed.