Microscan HawkEye 1500 Series, Руководство по верификации

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Introduction
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v2.4.1, Nov 2008 HawkEye™ 1500 Series Verification Manual 1-3
Care should be taken, however, to use mark quality measurements appropriate
for direct part marking, because using legacy standards can lead to false alarms
or to missing serious marking problems. There are different verification
standards available to meet your needs. Data Matrix codes on labels can be
verified with AIM standard-compliant verifier systems. Directly marked parts,
however, require a type of verification specifically designed for that purpose.
Label Verification
In 1996, the Association for Automatic Identification and Mobility published a
set of criteria, known as the AIM Bar Code Print Quality Guideline, to allow
verification systems to grade a symbol by degree of acceptability (A through F).
Developed for high-contrast paper labels, this type of verification provides a
basic quantitative measure of print quality and allows printed 2-D codes to be
checked against a quality standard. The important note is that the process of
printing a Data Matrix on paper is an optimized process. The paper has been
bleached to be as white as possible and the ink has been dyed to be as black as
possible. Keeping this in mind, the grading thresholds of the AIM specification
are very restrictive because the mark quality is so high. Anything less would not
be appropriate or useful to the printing industry. Typical problems caught by
AIM include:
• Blocked holes
• Too much or too little ink
• Inconsistent inking
Direct Part Mark (DPM) Verification
Unlike the printing process, direct part marks are generally not optimized for
marking. It is more important for the parts to be optimized for their primary
purpose. It is more difficult to make a high contrast laser mark on bare aluminum
than on stainless steel; however, aluminum is specified more on aircraft parts due
to the lighter weight. The weight is more important than the markability. When
verifying the mark on aluminum, AIM generally fails the part due to low
contrast. This is where DPM verification is the appropriate verification method.
The DPM verifier is configurable to verify marks of different marking methods
and different materials. The threshold values for grading are fixed and cannot be
changed. You can configure pass/fail criteria. Then, each mark is measured
against the thresholds and is given a quality grade. Variation in the grade is
usually caused by one of the following: