Barcode Labels:

Pushing the Limits

By Barry Alves

A large number of systems integration projects are requiring bar code labels in harsh environments where they have never been before. New advances in scanning technology, symbologies, and scanning techniques and the need for more information in the barcode are placing additional demands on the bar code labels manufactured today. Barcodes are expected to perform with out failure in more and more demanding applications across the spectrum.

Evaluating and defining the environmental conditions to which a barcode labels will be exposed to, how data collection will be performed, the worst case scenario of testing of the barcode labels and reviewing the proposed data collection procedures will vastly enhance the level of success that you have with your barcode label project. If the barcode label does not work, the link in the data collection process has failed. Then the manual data collection inevitably takes over if the barcode label fails costs time, accuracy, money and not to mention employee morale.

What elements need to be considered?

Heat….. Pressure-sensitive adhesives and the plastics used in barcode label systems are mainly thermoplastic materials. Adhesives will soften with high heats and loose internal strengths. The adhesive will ooze, causing the label to move or flag if it’s applied to a cylindrical surface. When the label sees these high heats it could distort the size and possibly buckle causing a distortion of the barcode image resulting in loss of a good scan.

Direct thermal face stocks are particularly vulnerable to heat and sunlight. Thermal Transfer inks may soften and flow in extreme heat environments. Continuous or extended exposure to heat cycles will stress the label material as opposed to a single or short heat cycle. The maximum heat requirements the label is exposed to and the length of time should always be defined as part of the selection process of materials and the imaging of the harsh environment label.

Cold….. There are two situations to consider. The first is the temperature of the surface on which the label will be applied to and second is when the label is applied to the surface and it either sees extreme heat or cold such as cryogenic environments. A label applied at room temperature applied to a cold surface will loose its heat and cause the adhesive to lose its tack and affect the overall bond with the substrate. Cold or frost will impede or breakdown and destroy the adhesive. Low temperature adhesives (Freezer Grade Adhesives) for use and applied in food –cooler environments can be used where temperatures are at least 10 degrees F above or freezing with the understanding that the strength of the adhesives has been reduced to maintain tack at the lower temperatures.

Bright Light…..Just as a bright reflection of sunlight in the morning can temporarily blind you. A bright light reflecting off the label surface can blind a scanner as well. Matte surfaces on labels can help minimize the reflection. Also, the angle of the scan will help increase scanning.

Turning off or reducing lighting in any room will help reduce and minimize scanning problems. In another case, over hangs and or mezzanines help to shade the scanning surface for labels to be scanned much easier.

Exterior Exposure….. In addition to using outdoor materials made of polyesters and acrylic adhesives with a history of having durable exterior results, over laminating films with UV screening capabilities extends the life of the label as well. Careful planning of label placement minimizing direct sunlight contact will also extend the life of the label.

Abrasions…..In cases of high abrasion, metal labels may be required. There are a variety of different films polyester, polypropylenes, tedlars, teflons, kaptons and laminations polyester, tedlar, teflons, and polyimides which are excellent protectors against your harshest environments.

The best measure of label durability is to place several labels in the actual label environment for at least 90 days and review the test labels periodically for durability and scanning.

Moisture or Wet Environments….. Labels exposed to moisture or wet environments need to be a film with an over lamination to protect against the moisture (humidity). Labels that are in these environments can experience loss in adhesion, delaminating, or distortion of print. Results show that labels properly constructed film labels can be immersed in wet or moist environments for a long period of time. Some adhesives are designed to build strength when immersed in water.

Solvents….. Caution should be taken in testing labels for solvent resistance to observe the edge of the label. The laminated label on the surface may be unaffected by a particular solvent, while the face stock and adhesive may deteriorate by the solvent solution used for cleaning.

Oil, Grime and Grease…..The most common problem that exists in industrial labeling is when a label is applied on an oily surface. The oil is absorbed by the adhesive causing adhesive breakdown and loss of bond to the substrate. A cleaning of the surface being labeled should always be done prior to applying the label to surface of the substrate.

Chemicals….. Cleaning agents are the most common chemicals which come in contact with most labeling surfaces. The alkali and wetting agents in the cleaners will affect the life of the label. Testing labels to all solvents, cleaners, acids or alkalis that they come in contact with is a good practice to follow to eliminate all potential problems.

Surfaces on which the labels come into contact with….. More labels fail because the pressure sensitive adhesive only comes in contact with a small portion of the surface. Textured and uneven surfaces are the bad guys. Heavy mil coat weights of adhesive should be specified (2-5Mils). There must be enough fluid thickness mass to allow it to flow down into the surface and ultimately contact at least 90% of the surface to build a solid bond.

Adhesion failures are also caused by low surface energy plastics. Polyethylene and polypropylene present label challenges. Special adhesives, high tack are required when low surface energy plastics are involved. To assure good label adhesion to plastics, samples need to be tested by your manufacturer for evaluation and let them help you write the specification.

Scanning Parameters….. Make sure you always match the scanner to the barcode. Scanners have near points and far points. Scanners that are designed for long range scanning in a warehouse application (40 Feet) cannot be expected to scan a label from a very short range (12 inches). Measuring scan ability at these angles of view and varying distances from the label determines the scanner’s field of vision relative to the label material.

Symbology….. Symbology may be mandated by the customer requirements or the industry the label is being used in. Fortunately, the newer model scanners are auto discriminating and can read multiple symbologies. Unfortunately there are several number of symbologies listed in the labeling industry, including 2D and RFID that have recently been competing for dominance. By carefully defining your project needs, adhering to industry standards, and taking a conservative symbology approach, mistakes will be avoided.

Bar Code Density and Quiet Zone Space….. A growing number of barcode applications face significant space limitations, especially in the electronics and telecommunications industries. The demand to fit more information into less space grows with the miniaturization.

With new technologies within the hardware industry (scanners), they are able to scan smaller and narrower bar codes giving a new meaning to high density barcodes.

AIM defines barcode density by narrow bar widths: 40 mils and up  are defined as a very low density barcode; low density is in the range of 20-40 mils range, medium density is in the 7-10 mil range, and ultra high density is used for less than 5-mils. In the manufacturing of all barcode must have a proper quiet zone space defined by the ANSI standards which is 10 times the x-dimension. If the proper quiet zones are not with in specifications will cause bad scans or no scans, creating a disastrous project results.

Verification….. When barcodes are used regularly, especially when printed on site, verification is a must. With fines imposed for labels that do not scan at retail, commercial and industrial more than justify the verification equipment as part of the quality control system. Penalties for poor performance are increasingly being imposed in all industries. Specifications defining verifications requirements, including the scanning parameters listed above are very good insurance policies. Regular verification of your bar-coding projects should be part of your label maintenance program.

Training, comfort and skills….. To overlook training, comfort and enthusiastic support from your staff is to create disaster. Training personnel and selling the automation process needs to be among the planning priorities by the implementation team. Supportive employees who have witnessed the benefits of the barcode data collection system can be a great source of ideas on how to improve the program.

By properly qualifying the bar code label you use, by making sure the barcode code and scanner are properly matched, by protecting the label against your harsh environment and by testing the label in worst case scenarios, label project success will be accelerated and problems minimized.