Warning Light Post: A series of colored lights on a pole, easily visible to operators, that flash when various errors or conditions occur, such as low media condition and "no read" bar codes.

Photo Eye (PE): A sensor that detects the product as it moves down the conveyor and sends a signal for the applicator to print a label. Sometimes, different types of sensors are employed.

Carton Notification Scanner: This is a pre-apply device, usually a fixed mount line or omnidirectional scanner. The scanner reads the appropriate bar code on the container, such as a license plate JD or SKUIUPC number, and relays that to the control software to do the appropriate database look-up and send the data stream to the printer for the next label.

Meter Conveyor: Conveyor upstream from the applicator that provides adequate spacing between containers to be labeled.

Skew Conveyor: Conveyor with skewed rollers that drives the carton to applicator side of the conveyor bed. This provides consistent positioning of the side of the carton to be labeled in relation to the applicator. For batches of fixed width cartons, a guide rail system and belt conveyor may be used instead.

Programmable Logic Controller (PLC): Used to provide conveyor control, such as shutting off the conveyor in the event of a "no read." May also be used to activate warning lights, or to actually send the firing signal to the applicator. More sophisticated controls may be used for controlling induction into the applicator system and post-application sortation to outbound lines.

PC with Applicator Control Software: Can vary from having only a simple label design/printing package with database look-up capabilities, or a more sophisticated software program that accepts downloads from the host, does database look ups, generates printer formats and data streams, and sends data records back to the host or other system.

Verfication Scanner: This is a post-apply device that verifies that a label was applied to the container and that it scans. This information is then usually sent  back to the applicator or conveyor control system to update the carton's status. If a "no read' occurs, the conveyor system usually is stopped so that the problem with that carton can be resolved before it heads to the sorter and ultimately the "reject line."

There are of course many variations to this general system. Often, for example, companies actually deploy two printer-applicators side by side. This enables automatic switch over to the other machine if there is a problem with the first machine, whether mechanical or something as simple as it is out of label stock. This redundant machine approach of course comes in very handy if a printer-applicator has a serious problem that will require repair.

totes Isotoner is one such company that uses the dual machine approach on its print and apply line. Instead of deploying two machines in a line, some companies will instead opt for a "hot spare' approach, in which a back-up applicator can reasonably quickly be installed on the stand if the current machine is in reed of repair.

Another variation occasionally seen is extra equipment to ensure application for difficult to label cartons. For example, for cartons of short height, which cannot take a full six-inch tall shipping label, the label might be applied on the side of the carton for the bottom half of the label, after which a device similar to a whisk broom moves forward to brush down the top half of the label onto the top of the carton (there are many variations on this basic theme.)

With the overview in part 1 of applications and benefits of print and apply in DC operations, and this description of key system components, we'll end this three-part series soon by looking at keys to print-and-apply system deployment success.

What's your take on printer-applicators in the DC? What would you add to our system overview above. Let us know your thoughts at the Feedback button (email) or section (web form) below.