Polychem GP44, Operation And Maintenance Manual, Page: 20 / 105

GP44 Semi-Automatic Strapping Machine
OPERATION - 20-
SEQUENCE OF OPERATION
STRAPPING CYCLE
All strapping machines follow the same basic strapping cycle. They all perform the following functions.
Feed strap
Grip lead end of the strap
Initial retraction/tension
Controlled tension
Release tension, cut and weld. Release strap.
FEED STRAP
With the cam in home position, the strap feed solenoid (sol 4) (PLC output Y27) is engaged which forces the
strap feed roller against the drive wheel and the strap feed motor is engaged in the forward direction. This
sends the strap through the arch until the end of the strap hits the strap end detect switch (M switch) (PLC
input X03) to signal the machine is ready to cycle.
GRIP LEAD END OF STRAP
The package detect photo eye (PLC input X13) is signaled in automatic mode (or the machine is cycled
manually) to start a cycle.
When the cycle starts, the cam shaft motor M1 (PLC output Y01) turns, this causes the first gripper to extend
to the first position with moderate pressure on the strap against the slide plate. Also the slide plate retracts
approx. 3/8” to allow the strap to clear the strap end detect switch area (the switch turns off). The cam shaft
turns until it turns on the cam proximity switch (B switch) (PLC input X05). It then starts a short timer in the
PLC, which then stops the motor by applying a brake. The camshaft should now be in the initial retraction
position (2
nd
detent). NOTE: If the package detect photo eye looses sight of the package during the cycle,
the feed retract motor will stop.
INITIAL RETRACTION/TENSION
When the cam proximity switch (B switch) (PLC input X05) is made, it starts the primary tension motor M2
(PLC output Y02) (in reverse). When the motor starts, it also engages the strap feed solenoid (Sol 4) (PLC
output Y04) to pull initial (soft) tension. This pulls the strap out of the arch. As the strap exits the arch and
tightens on the bundle, it trips the primary tension complete switch (PLC input X06). Initial retraction is now
complete.