Critical Component Tracking
For any system to be successful each component must be uniquely identified and permanently marked. This
allows the tracking of the performance of each component and removal of the poor performers from the
Why track components?
Components should be tracked for only one reason; the benefits exceed the cost. Those
benefits can come from several areas sucah as reduced costs, improved yields, improved reliability,
increased life etc. Each situation is different and while benefits can be derived in every
case, the real question is do those benefits exceed the costs.
What are the costs?
The obvious costs are the expense of marking the components, purchasing readers, purchasing computers,
acquiring or developing software and the time or inconvenience to employees (including training and
Who should collect the data?
The personnel directly involved with each step of the process should collect the information. These
are the most effective people and it keeps everyone involved in the process. They will develop
an understanding of how the information is collected, why it is important and the impact it has on production.
When should the data be collected?
Data should be collected at the time the work is being performed. Do not change components
and then try to do the record keeping at a later date. This increases the chance that data may
The Marking process requires three questions to be answered:
- What will be marked?
- What type of mark will be applied?
- How will it be attached to the critical component?
The correct selection is governed by several factors. The environment to which the component will
be exposed (heat, chemicals or wear), cost and the interface to the tracking/analysis system. All
these factors affect the marking decision.
To learn more about the marking process and how Stewart Technologies, Inc. incorporates component marking,
please refer to Direct Mark.
- Paper Tags - Paper is not durable but is it cheap. It should only be used where no
environmental damage is anticipated and very little handling takes place. Such tags can be printed using relatively
- Polyester Tags - Polyester is more durable and slightly more expensive than paper. It offers
more durable and legible print than equivalent paper tags.
- Metal Tags - Metal is very durable but more expensive than either paper or polyester. It is
very resistant to environmental damage. Metal tags must be marked with either a laser or dot
peen machine. Metal tags are more difficult to read than paper or polyester tags.
- RFID Tags - A developing technology using active and passive radio frequency transmitters to identify
components and their location. The current tags are relatively expensive ($30/tag) and this limits their use to
- Direct Mark - Direct Mark is the most durable method of tagging, but also among the most
expensive. It is the most resistant to environmental damage. Direct marks can be applied with either a
laser or dot peen machine. Generally, direct marked parts are more difficult than tags to read.
- Human Readable - The strength of this mark is that each employee can easily recognize and interpret
this mark. The major weakness is the difficulty in electronically reading this mark with a reader; current OCR
software is 90% accurate at this time. It is best to use this mark in conjuction with other types of marks.
- 1-D Bar Code - This is the traditional bar code everybody is familiar with today. It is
easy to print and a wide variety of economical readers are available. The major weakness of this mark is the
amount of space required to display a code.
- PDF-417 - This mark allows more data to be displayed than a traditional bar code. It is
more difficult to read and PDF-417 readers cost more than 1-D readers. It still has a relatively large foot
- 2-D Data Matrix - This mark provides the smallest footprint for data available. It will
display ten times the data in 1/10 the area of a traditional bar code. One concern of this mark is the readers
are more costly than conventional readers.
- RFID - This mark (actually a radio signal) maybe read from a distance without a direct line of
sight. This offers a great degree of flexibility at the read stage. Readers are costly and fixed
readers are more readily available than hand held readers.
- All the tags are available in configurations that allow for self-adhesive, glued, wired or on bags
containing the components.
- Direct marked parts have the code laser etched or dot peened directly into the surface of the component.
- A laser mark provides a surface mark which can be worn or grit blasted off the components.
- The dot peened mark is deeper (~.003 in.) and provides the most durable mask