Pre-Printed Bar Code Labels Page
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For years bar code users and would-be users have pondered the solution to a dilemma. To print or not to print - that is the question. Whether it is nobler in the mind to suffer the slings and arrows an on-site, out of spec bar code printer can cause, or to take arms against a sea of labeling troubles by rely on the resources of pre-printed bar code label service companies. The answer depends on your application, and your willingness to expand your company into a new business - bar code label printing.
There are two ways to produce bar code labels. You can purchase bar code printing hardware and software and produce your labels in-house, or you can purchase preprinted bar code labels from companies that specialize in their production.
Preprinted bar code label vendors can supply labels with a variety of information on a multitude of label stocks. For example, rolls of sequentially numbered labels printed on vinyl label stock could be ordered. Opting to use preprinted bar code labels eliminates the need for label printing equipment, the staff to run the equipment, and the management required to assure a quality label. That's because preprinted label vendors have the bar code printing expertise and are accountable for a label that will scan correctly.
If the information to be printed in bar code is fixed and only a few hundred labels per day are needed, buying preprinted bar code labels is more economical than printing them on-site. Likewise, if a large quantity of bar code labels are required for a one-time project -- capital asset inventory for example -- preprinted labels are more cost-effective. The choice of preprinted over on-site printing becomes less clear cut in applications falling between these two extremes. The central question in determining whether preprinted labels will be more cost effective is do you know the data you want to print in advance? In most bar code applications, the symbol is just a license plate. It need only encode a unique serial number, either unique to the individual item or to the product line. The detailed information is then stored in a database under the unique serial number. In such an application, preprinted bar code fits.
In fact, some preprinted label vendors can print bar code labels from variable, customer supplied data. The data can be transmitted by modem or shipped to the vendor on magnetic tape or computer disk.Printing Techniques
Preprinted bar code labels can be produced using any printing process. In fact, some preprinted labels are produced using the same printing systems found in on-site printing systems. However, most preprinted label vendors use one or more of the following preferred printing systems because of their speed and accuracy: Film Master/Printing Plate, Ion-Deposition, or Photocomposition.
The film master/printing plate approach to preprinted labels use a very accurate photographically produced film master of the bar code. This film master is used to produce a printing plate, and the plate is used in a variety of commercial printing presses to produce the preprinted label. Since the data coded in the film master bar code is fixed, This system cannot produce sequences of bar coded serial numbers, or bar coded variable, customer supplied data.
Ion deposition is an electrographic, non-impact imaging process capable of printing bar codes and other information on substrates such as paper, vinyl, polyester, and tag stock at very high speeds. The ion deposition printing station operates similar to a xerographic photocopier, except the image of the bar code is electrostatically placed on a dielectric drum rather than optically imaged on a photosensitive drum. Sequential labels and variable data labels can be printed by ion deposition.
The "best" preprinted bar code symbols are produced by photocomposition. The use of the photographic process to produce consecutively numbered bar code labels has some advantages over other commercial production methods. If the primary considerations are: (1) overall quality of the bar code image; (2) high density messages; or (3) flexibility in label size and construction to meet special application requirements, then the photographic process may be particularly suitable.
Because of the cost and complexity of the technology, photographically produced bar code labels can only be produced by preprinted label companies specializing in this printing process.
Photographically printed bar code symbols are produced by special computer controlled photographic printing machines that produce original images of each bar code symbol, not copies. The hardware and software that make up the photographic process are complex. The actual process of creating the image, however, is relatively straightforward.
A moving beam of intense light "strokes" the bar code image through a lens system onto photosensitive material. This is done in a raster fashion, similar to the way a television image is produced. Instructions for creating the size, shape and placement of each individual bar and character are stored electronically in the computer's memory.
After the image is created, the photosensitive material is processed to develop and "fix" the image, much as photographic film is developed into slides or prints. Next, one of a variety of pressure-sensitive adhesives is applied to the back of the image-bearing material.
After the adhesive with its accompanying release liner is applied, die-cutting is done to create individual labels or label sets of the size and shape required. Die making, previously an inexact art, is now a science, and is being aided by lasers and other computer-controlled processes to produce labels to very exacting tolerances.
In most cases, the photosensitive material that bears the bar code image is photographic paper. But unlike a conventional label where ink rests on the surface of the paper, the photographic process allows the image to be formed within the paper. In this way the bar code image is naturally protected from excessive abrasion, smudging, or smearing. Another important advantage in the photographic process is the nature of the paper and the way the image is developed. This means that it will not fade when exposed to sunlight or ultraviolet radiation, important for bar code labels that depend so heavily on contrast between the background and the bars.
Photographically produced bar code image quality remains constant regardless of the material chosen for the photographic process. Typical resolution is 3,000 lines per inch with a bar dimension tolerance of less than 1 mil X-dimension This extremely high resolution makes very high density bar codes possible using the photographic process.Label Considerations
How well a bar code label has been printed will often determine the success of a bar code system. However, it is a factor which is usually neglected. After all, people can read poorly printed text. Why shouldn't scanners read poorly printed bar code The difference is people can reconstruct lost data from context. Scanning systems can not.
Allowable printing tolerances are a function of the code chosen and the algorithm used by the reader for decoding. Nearly all bar code formats have well defined specifications. These specifications set the maximum total allowable error before reading breaks down. Errors in printing and scanning must not sum to more than the total allowable error for a chosen coding system. Scanners from different manufactures will often use different algorithms for decoding. These different decoding algorithms will produce different amounts of scanning error.
If one knows exactly what scanners will be used to read the labels, one will know the amount of allowable printing error. But most times one will not know what types of scanners will be used.
If labels will be scanned by unknown scanner types, the labels must be printed by processes with low printing error. That's where the choice of preprinted labels over on-site printing can produce significant savings. With preprinted labels, the supplier monitors and certifies the quality of the symbol. However, if the labels are printed on-site, you must establish a quality control plan. That requires bar code verification equipment, and staff to monitor the label print quality as well as perform maintenance to the printing equipment. But print quality is not the only element which favors preprinted bar code labels for producing a readable bar code symbol.Environment
The type of environmental conditions that the label will be subjected to will set the scannable life of the symbol. The type of inks, and label material are the most important factors. Paper labels will soften, discolor, and distort under high humidity. High temperatures, temperature fluctuations, acids, alkalis, solvents, chemical vapors, ultraviolet light, oils, grime, and abrasive materials all can shorten the useful life of a bar code label.
Some preprinted label vendors specialize in producing bar coded metal or plastic tags which are designed to withstand harsh environments.
Even the highest quality bar code printed on material resistant to the environment it encounters is of no use if it falls off the product. The means by which the label is attached, therefore, is also a critical component in a bar code system. Pressure-sensitive adhesives are thermoplastic, and their adhesive properties can change with temperature. An adhesive that works fine for normal indoor temperatures may be useless at the temperatures found on a printed circuit board wave solder line.
The complexity of adhesives and label stock, particularly for labeling application in harsh environments, again make preprinted labels the most cost effective and worry free choice. That's because most preprinted label suppliers have experts that ask the right questions about your application, and design the best match of adhesive, label stock, and printing technique.The Hidden Reason
Beyond the hard dollar costs of equipment, and staffing, there is a hidden advantage to choose preprinted labels over on-site printing. Printing technology and bar code applications are rapidly evolving. Purchasing equipment locks you into a printing technology which may not keep pace with future applications. The two danger areas are density and demand.
The desire to pack more data into smaller labels is a clear trend in bar code applications. High density printing or stacked symbologies such as PDF 417, Datacode and Maxicode are the ways this desire for higher densities are being fulfilled. Preprinted label vendors keep their equipment up to date and often can supply labels in new symbologies before on-site equipment is available.
Nothing succeeds like success, and the same is true with bar code systems. Once a successful system is implemented, it usually expands into all sorts of applications and areas of a company. This expansion often creates demand for bar code labels beyond the capacity of on-site printing systems. Preprinted label vendors can handle virtually any demand requirement, and can usually provide 24 hour turnaround on orders.
Companies that make pre-printed bar code labels.