Production challenges will likely arise in the many application stages outlined above, and the key is how products are handled. Inconsistent product handling will make it very difficult to place labels consistently and accurately.
Items must be properly presented to the applicator system for labeling to take place, and for products to be taken away for onward handling. This can be achieved in one of three main ways:
The applicator is mounted over, or onto, an existing production line
The applicator is supplied as an integral unit with its own product handling or conveying system
The applicator is supplied on a pedestal stand or base which can be easily moved from one location to another for either semi- or fully-automatic application.
With the simpler semi-automatic label applicators, the product is manually loaded onto a table or plate at the applicator beak using either a hand-loaded jig fixture, by pushing the product along a short conveyor, or by hand feeding from another operation or a packing table. Product handling is largely manual and does not require sophisticated automation technology.
More sophisticated systems will be required as the line specification moves towards faster speeds, more automation, longer runs, application of two or more labels, the need to place labels in a recess or around corners and to control or orientate the packs. The product handling devices fitted to the labeler then need to become more sophisticated, incorporating conveyors, guide rails, belt assemblies, feed screws, hoppers, elliptical aligners, metering wheels and rotary turntables so the applicator can handle very small or difficult shapes, elliptical and rectangular containers, ampoules or vials, flat or flexible packs.
Verifiers, bar code readers, counters, visual camera/computer recognition, operator alarms, microprocessor-controlled electronics, and ever-more sophisticated operator and system controls may also be incorporated.
The three main methods for bringing the container or product to the applicator are:
Application on the production line. Many applicators can be supplied so that the application head is mounted in position over the customer’s existing production and packaging lines using a wide variety of moveable, static or adjustable brackets and angular devices to control the product and position it for application. Systems are quite flexible and can be built to be mounted above, to one or both sides and even under the production line.
Integral applicator systems. Applicators are frequently supplied as stand-alone systems with integral conveyor, container and product handling devices and with all the necessary interfaces. Both in-line and rotary systems are available.
Pedestal mounted and portable applicators. Flexibility in label application and the rapid deployment from one location to another can be achieved by the use of self-contained, pedestal, bench-operated or portable applicator systems. These can be quickly and easily moved to another production line without the need to be attached to a conveyor.
They may be used in semi-automatic or fully automatic modes.
Figure 5.1. shows a label applicator positioned over an existing conveyor production line to apply labels to the top surface of a product. Portable pedestal applicators can be installed anywhere along a conveyor line as required, depending on the specific application, with adjustable leveling pads fitted as standard.
Figure 5.1 - Top labeling of products traveling along a conveyor line using a pedestal mounted applicator. Illustration courtesy of Herma
We will now review some of the most common product handling devices and controls used with automated label applicators in a wide range of end-use applications.
Conveyor systems. There are various product handling conveyor systems used to present and control the product before, during and after the label application process.
Conveyors are available in different lengths, in single or multi-belt configurations, straight or curved (see Figure 5.2) and in a variety of different fabric types.
Figure 5.2 - Two examples of typical belt and roller conveyors
The most common types of conveyors are:
Of the many types of conveyors, slat (most commonly used with in-line labeling machines. See Figure 5.3), flattop chain and belt conveyors are the ones used for transporting products during pressure-sensitive label application.
Figure 5.3 - A slat conveyor. Photo courtesy of Universal Products
There are also various specialized conveyors available, as well as side alignment or wrap- around belts, top hold down conveyor belts, stabilization belts and rotary spacers.
Conveyor components. Conveyors used for product handling in label application lines will usually be on legs, either fixed or adjustable (casters optional), incorporate chains or belting, side supports and guide rails (see Figure 5.4) and, depending on the application, may also contain star wheels and scrolls.
Figure 5.4 - Use of guide rails on a conveyor line to control the product. Illustration courtesy of Herma
With a simple conveyor, guide rails will control the product reasonably well if the product is round, square, or rectangular. Oval shapes, such as shampoo bottles, cannot be controlled correctly without additional components.
Guide rail options include single or dual rails with adjustable in-and-out as well as up-and-down mounts (see Figure 5.5). They are used to direct the product through the system and ensure alignment at the peel tip for proper placement of the label.
The type of guiderail to be used must be selected after testing with the labels to ensure that there is no scratching or marking.
Figure 5.5 - Guide rails can be adjusted in and out as well as up and down. Photo courtesy of Accraply
A sensor detects the product as it comes down the conveyor and triggers the application of the label at the proper time. Product handling must be tightly controlled to ensure accurate label placement.
Feed screws, also referred to as an In-feed Screw Assembly, enable products to be accurately metered, spaced and/or orientated on the conveyor line in preparation for label application.
Products will be consistently in the same position and at the same rate or speed as the conveyor at the end of the screw.
Single screw models are used for round products (as shown in Figure 5.6 top diagram), while dual screw models (Figure 5.6 bottom diagram) are available to accurately align and meter oval, elliptical, irregular and square products. Product can also be captured by a top hold down belt while they are still in the screws.
Figure 5.6 - Diagram to show the principle of single and double in-feed screws
In-feed screws are mainly used in primary labeling applications, such as consumer products, pharmaceuticals, home products and cosmetics.
Feed screws (Example shown in Figure 5.7), usually custom designed for each product, precisely control pitch and offer maximum product throughput at any given conveyor speed. In some cases, a single screw profile can be designed to accommodate multiple product configurations.
Most applications require multiple screw change parts.
Figure 5.7 - Single in-feed screw metering bottles on an Accraply line
Metering wheels are used to space products along the conveyor line just prior to label application. (This process can be seen in Figure 5.8).
Metering wheels do not provide product orientation and are mainly used on slower to medium-speed application lines.
In general, the higher the application speed, the more unstable the container, hence the need to move on to more accurate orientation and capture using top hold-down belts or a rotary platform (see also Figures 5.9 and 5.10).
Figure 5.8 - Metering of bottles traveling between guide rails on a conveyor line. Illustration courtesy of Universal Products
Figure 5.9 - Shows the principle of a top stabilizer belt
Figure 5.10 - Top stabilization belt on an Accraply machine
Star wheels are another type of handling device that is used for spacing products. They are usually found as a single or double-stacked wheel with a number of pockets cut to the diameter or shape of the container being labeled. The star wheel rotates in unison with the conveyor to space products for labeling.
Different sized wheels can be easily put in place and will only require adjustment of guide rails.
Spacing belt assemblies consist of two opposed timing belts that grip products from the sides and are used to space products at the in-feed end of a system. They are able to provide up to ten times more holding force than a typical metering or spacing wheel. May also be used to transfer products from one conveyor to another.
Top hold down or stabilizer belts, as shown in Figures 5.9 and 5.10, are used to stabilize products after they have been spaced or orientated for the label application process and are an integral component of a product handling assembly. They normally feature a moving belt on an adjustable column above the product conveyor used to hold products stable and maintain orientation while exposing all sides of the product for labeling.
It is vital that the top hold and conveyor speeds match. The top hold must also be parallel to the conveyor. If angled the pressure can increase or decrease, affecting speed and accuracy.
As with guide rails, the top hold down moving stabilizer belt feature can be adjusted vertically to accommodate various height products.
Orientation devices, such as those illustrated in Figure 5.11, are mainly used in slow to medium speed label line applications in which it is necessary to orientate cylindrical-shaped products that may have a handle or seam so that they are positioned in the correct relative position each time prior to accurate label placement.
Elliptical aligners are used to center and orient/align an elliptical, oval or non-cylindrical product on the conveyor top prior to application. Often uses two soft foam belts, with a durable outer skin, to prevent marking the products. The product to be labeled travels between the aligner belts to be positioned.
Figure 5.11 - Shows the use of an orientation device to correctly position products prior to applying labels. Illustration courtesy Universal Products
Wrap belt assembly. Used with some label applicator and product handling systems to rotate or spin cylindrical products (typically a bottle) simultaneously to label application, so completing and finishing label adhesion to the product. The assembly consists of a coated timing belt and an adjustable padded back-up plate. They can also be used with square and rectangular-shaped products.
Foam rollers of different diameters and widths may be used as a secondary application device to ensure complete label adhesion to the product.
Modular options. Modular options include spacing wheels, product in-feed scrolls, in-feed and out-feed rotating tables.
Speed control. With label line integration it becomes important to track the varying speed of a product or web as production speeds ramp up and down. A bespoke speed control system, coupled with the stepper motor technology used in the label dispenser, is designed to ensure accurate labeling across the whole speed range of the production line.
Counting and tab inserting. With some integrated labeling lines it may be a requirement to incorporate a counting and tab inserting machine that counts exactly sheets of cartonboard, paper, plastic, inserting tabs if required.
Figure 5.12 - Examples of foam rollers, courtesy of Accraply
Friction feeding. Integrated labeling lines used for placing labels on many kinds of flat products, such as greeting cards or media products, may need to incorporate a friction feeding system (Figure 5.13), where the lowest product lies on a friction belt, with a braking roller preventing the next product from being pulled through.
The opening between the belt and the braking roller can be set to the appropriate product height to give efficient product changeover.
Figure 5.13 - Diagram shows the principle of friction feeding
Counting can also be incorporated, as well as missing sheet/product detection.
Wrapping. Labeling machines can be incorporated into wrapping lines adding labels to, for example, medical or toiletries products, DIY parts, stationery, cosmetics and greetings cards.
Product handling flexibility. Label applicator product handling systems are highly flexible and can be arranged to label one or both sides, top or bottom, around corners, into recesses, and onto to all types of shapes and products.
Applicators may be stand-alone or rotary systems incorporating all the necessary product handling technology, or can be fitted over, under or into many different points in a customer’s completely conveyorized existing product handling line. Such systems may change direction, go around corners, enable multiple lines to be fed into a main conveyor, have several lines merging onto one conveyor, and may incorporate an in-feed hopper and out-feed accumulation conveyor.