Web Guiding In Vacuum PDF
Preview Web Guiding In Vacuum
W eb Guid ing In Vac uum Aravind Seshadri Roll-2-Roll Technologies LLC 2016 AIMCAL Web Coating and Handling Conference W hy d o w e need t o g uid e? Lateral shift at unwind ➔ Non-centered core Imperfect unwind roll ➔ With lateral misalignments Imperfect web ➔ Web gauge variations, camber or bagginess Imperfect machine ➔ Misaligned rollers, out-of-round rollers Imperfect process ➔ Air/ fluid interaction, coating gauge variations, traction issues A typical automatic web guide control system Guid e includes a Mechanism , W eb Posit ion Sensor, Cont rol l er and . W hat ’s d if f erent in vac uum ? Environment Space Limitations ● No air/ gas ● Space is expensive ● Heat dissipation ● Span length constraints ● Outgassing ● Minimum number of rollers Environment Space devoid of gas/ air can affect web position sensors. Pneumatic sensor ➔ By definition need air flow and hence not suitable for vacuum. Ultrasonic sensor ➔ Need air for sound propagation and hence not suitable for vacuum. Infrared sensor ➔ Will work in vacuum but only with non- transparent material. Environment Space devoid of gas/ air also adds constraints such as Heat dissipation ➔ Heat generation from sensor and actuator should be low. Outgassing ➔ Sensor and actuators should not outgas. Id eal sensor t ec hnol og y shoul d p rovid e rel iab l e m easurem ent , shoul d not c reat e exc essive heat Camera Based A camera based system could potentially work, and not out g as. however they are expensive, bulky and may generate heat. Space Limit at ion The second biggest constraint is space: Span lengths ➔ Are typically short Choice of Web Guide ➔ Is limited because of the space constraint Ap p rop riat e c hoic e of W eb Guid e Mec hanism shoul d not t ake up a l ot of sp ac e w hil e p rovid ing t he req uired c orrec t ion. How t o p ic k t he rig ht w eb g uid e f or your ap p l ic at ion?
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