By John Henry, www.changeover.com
Previous articles discussed package coding in general and contact coding in particular. This article discusses non-contact coding.
There are two main types of non-contact coder: Laser and ink jet. Inkjet printers work by depositing ink on the surface of the substrate. Laser coders work by removing ink from or affecting the surface of the substrate. Laser coders do not use ink or toner and should not be confused with desktop laser printers; they are a completely different technology.
There are two types of inkjet — continuous inkjet (CIJ) and drop-on-demand (DOD) — and all inkjets print characters in a dot matrix format. 5x5 dots is a common format, though other matrices are also frequently used. Thermal DOD inkjets print in much higher resolutions, up to 600x600 dots. Although still a dot matrix, the high density gives the appearance of a solid character.
Continuous inkjet pump liquid ink from a reservoir and break it into a continuous stream of tiny droplets charged with static electricity. Charged deflector plates deflect the droplets up or down as needed to form a column of dots in the correct location for the character. The first row of the letter E below consists of five dots. The next row of the letter E consists of three dots. The ink for position two and four in the second column is deflected to return to the reservoir.
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