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Intelligent marking choices are application-driven: a laser system able to provide alphanumeric, 2-D, and logo marking on a variety of metal and plastic surfaces is just one alternative. (ID Marking).

In considering a variety of direct part marking and reading applications, several options are available from Telesis (Circleville, OH):

* Telesis PINSTAMP[R] dot peen marking systems;

* Telesis ProScript[R] laser marking systems; and

* PS-OCR[R]II optical character recognition (OCR) reader systems (PINSTAMP[R], ProScript[R] and PSOCR[R]II are registered trademarks of Telesis Technologies, Inc.)

These systems, as well as hand-held and fixed-station Data Matrix[TM] 2-D code readers marketed by a number of suppliers, can be integrated with production lines for a variety of parts marking and tracking applications.

OCR vs. Data Matrix[TM] 2-0 Code Marking

The 2-D approach normally allows more data to be marked in a much smaller area. For example, using a Telesis PINSTAMP marker, 10 alphanumeric characters can typically be marked in a 0.28" x 0.28" (7.11 x 7.11mm) Data Matrix[TM] code. OCR characters typically need to be about 3/16" (4.8mm) high, requiring a footprint of about 0.187" x 1.87" (4.75 x 47.5mm) to encrypt 10 characters. The smaller footprint of 2-D codes commonly provides a secondary advantage over OCR -- fewer problems with lighting, simply because the light needs to illuminate a smaller area.

OCR characters are also human-readable; obviously, 2-D codes are not. Since human-readability is normally required as a "back-up," this means that a human-readable text string must normally be marked along with every 2-D code. 2-D codes can be read at any angular orientation; OCR reading requires the text string to be oriented with [+ or -]60. This can be a significant advantage for 2-D in automated applications in which the parts come into the read station at various orientations.

The PS-OCRII usually reads more robustly than 2-D code readers in applications with roughcast or seriously flawed marking surfaces. Fixed station 2-D code readers are normally considerably less expensive than a PS-OCRII system that, excluding the cost of camera, light, and integration, is priced at about $15,000. A fixed station 2-D code reader is normally is priced at about $5,000, excluding camera, light, and integration.

There are hand-held 2-D code readers commercially available, but there is no handheld version of the PS-OCRII. Obviously, a hand-held reader can provide many advantages in non-automated applications. Since hand-held 2-D code readers do not typically read as robustly as fixed station 2-D code readers, their applications are limited to certain situations.

Laser vs. Dot Peen Marking Systems

Laser markers, including the Telesis ProScript, normally provide a more precise mark than a Telesis PINSTAMP or any other dot peen marker. Since the precision of the mark is an important factor in machine readability, this results in better readability for laser marking in certain applications.

Dot peen markers cost considerably less than laser markers: typically $8,000 -- $20,000. YAG laser markers are more commonly priced in the $50,000 -- $70,000 range. Telesis PINSTAMP and all other dot peen markers imprint a round dot, where a laser marker is capable of marking a square cell. This adds to the relative readability of laser marks in 2-D applications, since a theoretically perfect 2-D code is based on square cells.

A dot peen marker utilizes much smaller components than a laser marker, making it easier and less costly to integrate.

A laser marker is usually much faster than a Telesis PINSTAMP or any other dot peen marker. For instance, the time to imprint a 10x10 2-D code with a Telesis PINSTAMP marker is normally 1.5-2 seconds; with a laser, it is more on the order of 1/2 second.

Dot peen marks are widely accepted by the aerospace industry for marking critical parts; laser markers are typically not. The cross-section of a Telesis PINSTAMP "crater" (dot) has no sharp corners; only gentle curves, resulting in no significant stress concentration. Laser marking can adversely affect material properties in the heat-affected zone of the mark, which can potentially result in the propagation of cracks in certain materials.

Telesis PINSTAMP marks or marks made by any other dot peen marker are by nature low-contrast marks, which depend solely on illumination techniques to create the contrast required for reading the mark properly. On the other hand, in certain applications, laser marks produce higher contrast, which tends to add to their readability. Telesis Technologies, Inc.

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Publication:Modern Applications News
Geographic Code:1USA
Date:Mar 1, 2002
Words:719
Previous Article:Marking system change eliminates downtime on high-speed production line. (ID Marking).
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