Web Guiding In Vacuum

23 Pages·2016·0.72 MB·English

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?