Heidelberg's stitcher-gatherers work at a speed of up to 14,000 cycles per hour. If a problem occurs at this speed, unusable copies quickly pile up in the delivery before the operator even notices that something is wrong. Heidelberg has therefore incorporated sensors to monitor thickness, sheet pulling, sheet placement, and binding. Thus any problems are detected immediately and the machine is automati- cally halted if necessary.
Heidelberg equips a series of Stitchmaster stitcher-gatherer
models - from the ST 270 to the ST 400 - with a software-supported
cascade control system to save even more paper. During startup, the
cascade control system delays starting up each feeder until the
first product reaches it in sequence. Afterwards, the
stitcher-gatherer is shut down in exactly the same way in reverse:
the gathering chain does not come to a standstill until the last
product has arrived in the delivery. One after the other, the
feeders stop operating. This approach prevents any incomplete items
from being produced.
The high-end Stitchmaster ST 300 and ST 400 models are additionally equipped with sequential feeder monitoring. This reliably prevents the machine from placing any additional signatures on top of incomplete products turned out by an incorrectly operating feeder.
Another monitoring system from Heidelberg detects wrong sheets: even minimal deviations from the stipulated image cause the machine to be halted.