Rockwell Automation WebPak 3000 DC Drive Application Workbook Version 1.1 - Manual (Page 86)

A-8 WebPak 3000 Drive Application Workbook, Version 1.1
Not all flying splice unwinds will require current memory. On unwinds where the
mechanical sequence isolates the outgoing roll from its tension feedback device,
current memory would be needed. Current memory may also be used to minimize
tension upsets during turret indexing and would be switched into the outgoing roll just
before the start of the index.
A representative splice sequence follows:
• Incoming roll is prepared for splicing with glue pattern or tape.
• Incoming roll diameter is determined and inputted to the appropriate unwind drive
diameter calculator.
• Outgoing roll is indexed to the splice position.
• Incoming roll is started and accelerates to web speed.
• Outgoing roll is sequenced into current memory, if necessary.
• Bump roll and knife assembly engage the incoming roll.
• Knife cuts the web.
• Outgoing roll is stopped and incoming roll is switched from speed regulation to
tension regulation.
• New roll is indexed to unwinding position.
All WebPak 3000 drives have the necessary digital input logic to switch to the required
regulator modes during the splice sequence.
All of the splice sequence logic is done external to the WebPak 3000 drives by a
separate controller. Communication between the devices is by discrete I/O or by logic
commands over a network connection.
A.2.8 Flying Transfer Winders
The exit zone of a web process line, in most designs, duplicates the entry zone
associated with the same line. If the entry zone uses a single-position unwind, the exit
zone will use a single-position winder. A two-position unwind with flying splice
operation will be complemented with a two-position winder with a flying transfer
design.
The individual winder spindle drives have to support the steady operation of winding
the web out of the process under the primary tension control mode in addition to
accurately maintaining tension during the dynamics of flying transfer.
Two basic types of flying transfer mechanical designs are in use. They are identified as
“bump and cut” and “enveloper arm.” The bump and cut type does not contact the
incoming core until just before the knife operates. The enveloper arm design will
isolate the outgoing roll from its feedback device during some part of transfer
sequence, which generates the need for current memory for the outgoing roll regulator
design. In fact, all of the regulator functions provided at unwinds are required at the
winders.