The different technologies linked to the barcodes :

Individuals new to bar coding often gravitate toward familiar technologies (such as laser printers, dot matrix printers, or ink jet printers) that are already connected to a network and, therefore, deemed suitable for bar code labeling.While these printers can be used for some very simple applications, they have serious limita- tions that make them inadequate for professional labeling. The common limitations among these traditional office technologies include print speed and flexibility, as well as the inability to print labels that are durable enough, or have the longevity or clarity required for all but the most basic bar coding applications.

Dot Matrix Printing

Dot matrix technology uses a hammer or pin to transfer pigment from a ribbon onto the substrate (see Figure 1). Due to the inaccuracy of dot placement and low resolution of the printing technology, these printers are nearly unusable for bar coding.

Advantages:

Dot matrix printers are readily accessible and inexpensive to purchase.
They can print on virtually any type of form, check, or document and can print on wide-web, multi-part (carbon) forms.

Figure 2. Dot Overlap

Limitations:

Dot matrix printers print low- to medium-density bar codes that may not meet certain end user guidelines. The dot size on the matrix printer limits the narrower element size and density of the bar code.
Continuous ribbon re-use on dot matrix printers requires close monitoring of ribbon condition to ensure adequate bar code contrast. Ribbon ink that has become exhausted can also produce an image that is inadequate for scanning, resulting in a low read rate and a high error rate.
Ink saturation can result in paper “bleed,” which can cause image distortion.
A dot matrix-printed label is limited in durability. Dot matrix printers typically cannot produce chemical- or water-resistant labels.
Printing of single labels results in significant waste. The design of the dot matrix printer’s print carriage, sitting far below the media, also does not allow the label space to be maximized.
Dot matrix printing offers no graphics printing capability. Bar code print speed is greatly reduced when best ink coverage for optimal print quality is specified.

Ink Jet Printing

Ink jet printing is used primarily for printing cartons or product packages with bar codes and human-readable data at very high speed. Ink jet printers spray ink onto the label surface in either a continuous stream, covering the entire print width with one spray, or one drop at a time (see Figure 3). However, ink jet printing is not acceptable for most bar coding applications.

Advantages:

Direct ink jet printing requires only one step, while label printing requires two: printing the label and adhering the label to the product.
High-speed ink jet printing is a favorite on high-speed production lines due to its ability to mark “on-the-fly.”

Limitations:

Ink jet printers are often too slow and are unable to reproduce bar codes with acceptable accuracy.
System installation is costly because it is designed for high-volume bar code printing—not for individual or small batch printing.
Ink jet printing requires diligent supervision and maintenance to ensure consistent print quality and prevent ink jet clogging.
Dot placement accuracy and bar code density/resolution are limited due to ink splatter and because the print surfaces are in continual motion.
Most inks used with this technology are water-based and, therefore, streak, run, or blur when they come in contact with water. Non-water-soluble inks are available, but these inks often produce a shine that reflects light back to the scanner, rendering the bar code unscannable.
Bar codes printed on the dark background of corrugated box materials suffer from poor contrast and poor readability.
Scanning devices must be carefully chosen to ensure reliable bar code reading.

Laser Printing:

The laser printer works much like a photocopier; it projects controlled streams of ions onto the surface of a print drum, resulting in a charged image. The charged image then selectively attracts toner particles, transferring the image onto the paper substrate. After the image is transferred to the media, the heat and pressure of the fuser cause the image to adhere to the media (see Figure 4).

Advantages:

Laser printers are good at producing plain-paper documents that require bar codes.
They can print high-quality text and graphics on paper documents and can double as a document printer when not being used to print bar codes.
Bar code density and resolution are also quite high on laser printers, resulting in a scannable code at virtually any wavelength using an infrared scanner.

Limitations:

Laser printers are not well suited for industrial or individual-product labeling operations. They can be wasteful, as they cannot produce single or small labels. A minimum of half a page of media is typically required for the printer to maintain control of the sheet. Unless the label is at least that size or multiple labels are needed at once, the remainder is wasted.
Laser printer label adhesives must be carefully selected to ensure stability under the heat and pressure of the fuser. Otherwise, the adhesive may extrude onto the printer mechanism where it captures stray toner, or may cause the labels to curl at the edges. Because of the pressures used in the laser printer image transfer process, many laminated label materials are not compatible with this technique. Those materials that are compatible may not always be available in the sheet form necessary for laser printing.
Laser printing is susceptible to toner flaking and smudging, making the technology unsuitable for long- term bar coding.
A laser-printed paper label has limited durability. For example, laser printers cannot produce chemical- or water-resistant labels and images.
Toner, drum, and supply costs can skyrocket when printing bar codes instead of typical text on laser printers. While text generally requires only about 5 percent black ink coverage, bar code needs can exceed 30 percent. Toner costs alone could be six times higher when printing bar codes rather than text.

Thermal Technology

The most widely used technologies for dedicated bar coding systems are direct thermal and thermal transfer printing. While both technologies use a heated printhead to create the image on the label, they are suited to different applications. Direct thermal printing utilizes heat-sensitive media that blackens as it passes under the printhead (see Figure 5). Because they print without a ribbon, direct thermal printers are noted for their simplicity. Direct thermal printed labels typically have a considerable shelf life but are not well suited for environments that expose them to heat, long periods of direct sunlight, or abrasion.

Advantages:

Direct thermal printing produces sharp print quality with good scannability.
Direct thermal is ideal for applications requiring only a short shelf life—meaning the label image does not need to last very long. Shipping labels and receipts are ideal applications, for instance, while product labels are not.
Direct thermal printers are simple to operate compared to most other print technologies because there is no ink, toner, or ribbon to monitor or replenish.
With no supplies to replace other than the material to be printed, long-term maintenance costs remain low.
Direct thermal enables batch or single label printing with virtually no waste.
With recyclable materials available, direct thermal printers offer environmental economy.
Direct thermal printers are typically built more durably than dot matrix or laser printers, allowing reliable operation in industrial as well as office applications.

Limitations:

Direct thermal printing is extremely sensitive to environmental conditions such as heat and light (fluorescent and/or direct sunlight).
Direct thermal paper remains chemically active after printing. Because of this, thermal labels, tags, or ticket stock are often top coated to resist UV light exposure, chemicals, and abrasion.