Machines can be supplied as stand-alone units, integrated into existing production lines or installed as fully automated systems incorporating product handling, conveying and finishing units.
Note however, the difference between adding applicators to existing product handling systems and the high level of sophistication and investment in fully integrated labeling machines where the machine supplier takes full control of the customer’s container or package.
In all these cases, the basic principles remain the same. The pressure-sensitive label applicator will unwind and advance the label stock over the beak or stripper plate until a portion of the label dispenses and extends into the path of the oncoming product or package.
As this portion engages the item to be labeled, the label advances at the same speed as the web and is pressed, wiped, tamped or blown onto the product to provide the necessary adhesion. These stages can be seen in Figure 4.1.
Figure 4.1 - The label reel unwinds, a label is dispensed at the beak and pressed onto the product to provide adhesion. Photo courtesy of Accraply
Semi - and fully automatic label applicator systems can be defined as follows:
Semi-automatic labeling machines (see Figure 4.2) speed-up the process of dispensing and manually applying product labels by partially automating the process. An operator is still required to manually place an item onto a conveyor, plate or roller, where the label will be detected and applied automatically.
Figure 4.2 - A pedestal-mounted applicator. Illustration courtesy of Herma
Fully-automatic labeling machines, whether in-line or rotary systems, are used for higher volume and higher speed labeling requirements where the whole label operation needs to be automated. Products travel along a conveyor belt or other handling system and are positioned at the labeling head, where a sensor automatically activates and dispenses the label ready for application.
Fully automatic systems can be configured to suit existing manufacturing or packaging line workflows and integrated with all kinds of manufacturing, overprinting and packaging operations.
Figure 4.3 - Illustration shows an example of a fully automated Accraply labeling machine
LABEL APPLICATOR AUTOMATION
Highly automated systems use a central control module and a range of sensors to control the label dispensing and application process. Sensors are used to detect a product’s orientation and location, as well as the leading edge of the label. The starting and stopping of the labeling head will be determined by a light source and sensor that read the gap between labels.
Product and labeling speeds need to be synchronized; labels and products need to be traced and controlled; missing labels need to be detected; labels or labeled products counted; and in some cases, products automatically orientated.
In addition to these requirements, both semi- and fully-automated label applicators will require a stepping motor, microprocessor controls and usually, some kind of touch-screen control. If there is a printer or coder, the control module will tell it when to operate.
The configuration of an automated applicator will depend upon a range of factors, including type of application, throughput speed, product size, shape or complexity, quality control requirements, product handling needs and the degree of integration with other packaging line operations.
Elements of an automated system will include:
Servo-driven labeling heads
Auto changeover labeling heads for continuous running
Product sensing/tracing (often using code readers with a variety of pre-printed codes)
Label scanning or sensing
Adjustable dispensing speed
Verification system if required
Operator alarms and safety devices
Touch screen control. Touch screen technology is now widely used to control operations previously managed through mechanical dials, buttons and levers. They are also an ideal replacement for the keyboard in industrial environments and are intuitive to use, and with the right choice of touch technology, can be robust, waterproof, and hygienic.
Touch screen installations today are entirely solid state; they use touch panels on a display screen driven by a GUI (Graphical User Interface).
By changing the screen image, the area above it on the touch panel will be visually linked to a different function. This means that, as well as being reconfigurable, the system can coach a user through operations, perhaps on start-up or shut-down, or trouble-shoot when something unusual happens.
Figure 4.4 - Shows an applicator touch screen panel courtesy of Herma
Touch screen interfaces play an increasingly important role in industrial labeling automation, because of their inherently robust nature and ability to cope with the harsh world of manufacturing.
Microcontrollers. Touch screen and touch sensing devices are supported by microcontrollers or microprocessors, together with appropriate touch screen software. Touch screen controller solutions make interfacing the touch panel to the system electronics a simple integration issue.
Micro switches. Micro switches are a key element in today’s electronic automation and are used in a variety of industrial automation applications.
Stepper motor. A stepper motor is an electromagnetic device that divides a full rotation into a number of equal steps – converting digital pulses into mechanical shaft rotation. The position of the motor can be commanded to move and hold position at one of these steps. No feedback sensor is required as long as the motor or servo motors are carefully sized to the application.
The stepping motor automates the label dispensing operation and controls the speed at which labels are dispensed for application, Label and product sensing and control (Figure 4.5). To ensure that labels are applied accurately and consistently, the semi-automatic or fully automatic pressure-sensitive label applicator is fitted with various label sensing or product sensing/tracing control devices.
Figure 4.5 - Illustration of a label applicator label sensing device courtesy of Herma
Sensors range from photocells with reflector mirrors, to transmitter/receivers, proximity switches, spot or color readers or, for certain applications, micro-switches.
Label sensors are usually photoelectric sensors because they are relatively inexpensive. They cannot be used with clear labels, however, in which case capacitive and ultrasonic sensor technologies are used.
Label sensing/tracing devices monitor the gap between the individual die-cut labels and interrupt the web feed at the end of each label. This resets the system to receive the next start signal from the product tracing devices, which include micro-switches, photocells or spot color readers. Other controls on the web may be used to detect end of the reel (Figure 4.6 left diagram), detect missing labels (Figure 4.6 right), or web breaks.
With many applicator systems the product or container trigger the application of the label through the use of product sensing/tracing/control devices. Product position sensors can be optical, optoelectrical (Figure 4.7) or ultrasonic. UV sensors may be used for ‘invisible’ sensing.
Using these various types of sensors, the application system will automatically compensate for erratic or irregular product flow and only dispense a label as required.
Figure 4.6 - End or unwind reel detector (left) and missing label detection (right)
Figure 4.7 - Herma optoelectrical sensor unit
For semi-automatic applications foot switches may be used.
Dancer arm. As the label is threaded through the applicator from the unwind reel it will typically pass around a dancer arm, a self-braking system that is able to slow the unwind reel as demand for the label decreases and so prevent the unwind reel from spinning and unwinding all the labels from the core. When label demand increases the dancer arm again enables the free flow of labels.
Figure 4.8 - An example of a product sensor used on Accraply machines
Very high-speed labeling lines with heavy reels may incorporate powered unwinds to improve tension control of the web feed.
Limit switch/photodetector. A limit switch or photodetector is used to trigger label advancement. It detects the absence or presence of a label to facilitate dispensing. Limit switches are the original method of label detection and can be used for most types of label application.
Photo-detectors use a beam of light broken by the label as it passes between or over the sensors.
Operator alarm system. Operator alarms are common in high-volume and high-speed applicators. There may be visual/optical (flashing lights as shown in Figure 4.9), audio/acoustic (bell, hooter), or a combination of both. They are used as an alert or warning of a web break, missing label, end of the unwind reel, or - with a verifier or scanner - to notify poor bar code readability. Safety guards or optical screens may also be used.
An alarm alerting the operator to the end of the unwind reel can be included. In some cases the alarm system may also trigger a shutdown of the machine or the product handling line.
Figure 4.9 - Operator alarm. Photo courtesy of Accraply
CHOOSING A LABEL APPLICATOR
One of the big challenges for today’s automatic labeling machine manufacturers and users is the increasing variety of packages or products that are expected to run on a single line. This is particularly true in many contract packaging applications which may rapidly change from day to day or even run to run. Many contract packaging facilities may never know quite what items are to be labeled next. They therefore require their application machinery to be highly flexible.
Whether the requirement is for single product labeling or for maximum flexibility, the applicator may need to be custom built with specific product handling, environment, speed or volume requirements in mind. Either way it is likely to be a significant investment.
It is important for the manufacturer to know the environmental conditions around the application machine, such as dust, heat, cold, damp or humidity. Will electrical systems need to be carefully protected? Will the equipment need to be powder-coated?
Figure 5.0 - Operator alarm. Photo courtesy of Accraply
Then what are the volume requirements? Light duty, manual handling application? One, two or more sides to be labeled? A large volume, fully-automated application? High-speed requirements? Integrated into conveyor or product handling lines?
Questions need to be asked about service call-out times, telephone support, and on-line breakdown evaluation. These factors are all vital in assessing what equipment to install.
Ideally, end users should provide samples of the potential products to be labeled before making a final machine purchasing decision.