Authors*: Dr. Dave Lang1
Dr. Calvin Fu2
References: O PAPEL vol. 74, num. 4, pp. 59 – 64 APR 2013
ABSTRACT
It has long been known that the CD profiles from conventional
scanning sensors contain a mixture of MD and CD variations. This
is often referred to as MDaliasing. The reasons for these phenomena
are reviewed.
Simulation studies have shown that scanning a moving web
with a more random velocity pattern can reject much of this MD
aliasing effect. In particular, fast MD variability can be kept from
affecting the CD profile where it would result in erroneous control
actions. Recently, one vendor has introduced a scanner that uses
variable speeds for scanning. CD velocity is changed depending
on direction and the operational situation. The results of a real mill
experiment scanning forward and back and at the edges at different
rates are presented. Variable speed scanning provides more realistic
MD measurements and CD profiles than conventional single speed
scanning. As part of this development, a number of tools have been
built into the quality control system (QCS) to aid mill personnel in
detecting and troubleshooting process variability problems. Real mill
cases are presented where these tools found process issues.
Authors’ references:
1. Metso Automation, Toronto, Canada – E-mail: [email protected]
2. Metso Automation, Toronto, Canada – E-mail: [email protected]
Corresponding author: Dr. Dave Lang – E-mail: [email protected]
Metso Automation Brazilian address: Metso Automation do Brasil Ltda. Avenida Independência, 2500 – 18087-050 – Sorocaba – SP – Brazil
Dr. Calvin Fu2
References: O PAPEL vol. 74, num. 4, pp. 59 – 64 APR 2013
ABSTRACT
It has long been known that the CD profiles from conventional
scanning sensors contain a mixture of MD and CD variations. This
is often referred to as MDaliasing. The reasons for these phenomena
are reviewed.
Simulation studies have shown that scanning a moving web
with a more random velocity pattern can reject much of this MD
aliasing effect. In particular, fast MD variability can be kept from
affecting the CD profile where it would result in erroneous control
actions. Recently, one vendor has introduced a scanner that uses
variable speeds for scanning. CD velocity is changed depending
on direction and the operational situation. The results of a real mill
experiment scanning forward and back and at the edges at different
rates are presented. Variable speed scanning provides more realistic
MD measurements and CD profiles than conventional single speed
scanning. As part of this development, a number of tools have been
built into the quality control system (QCS) to aid mill personnel in
detecting and troubleshooting process variability problems. Real mill
cases are presented where these tools found process issues.
Authors’ references:
1. Metso Automation, Toronto, Canada – E-mail: [email protected]
2. Metso Automation, Toronto, Canada – E-mail: [email protected]
Corresponding author: Dr. Dave Lang – E-mail: [email protected]
Metso Automation Brazilian address: Metso Automation do Brasil Ltda. Avenida Independência, 2500 – 18087-050 – Sorocaba – SP – Brazil
