Barcode basics
The technology improves efficiency and reduces errors
A barcode data collection system consists of barcode labels, printing equipment to produce the labels and barcode reading equipment to scan them. A computer processes and stores the data, sends information to output devices, and communicates with higher-order information systems, such as the CMMS.
Barcode is the preferred choice among recognition system technologies because of its relatively low cost, high speed and accuracy, as well as its flexibility. Barcode scanning has been around long enough to demonstrate its superior reliability.
A disadvantage of barcode systems usually relates to the print quality rather than the reader. Specifically, if a printer produces poorer quality print over time, the barcode may become difficult to read.
Another problem is the print contrast ratio, which refers to the difference in "color" between the code and its background. This is most pronounced with reds, oranges and browns.
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Barcode at work
Common barcode applications include:
Labor reporting: Even the simplest automated time and attendance system requires input information. This can be accomplished using barcoded employee badges and a simple barcode reader. More complex labor reporting systems have input terminals at workstations to record movement to and from each location.
Materials management: Spare parts inventory can be tracked more easily using barcode technology. This includes receipt of parts, capturing the warehouse location, picking a part from stores, capturing parts used, shipping parts for repair and even scanning parts for inventory counts.
Stores personnel scan the barcode and location code of each product received, as well as quantities issued from stores. Some parts may require barcode labels upon receipt, either pre-printed or printed on the spot using high-speed barcode printers. Most CMMS packages can print barcode labels for parts and components, as the code is simply a font option.
Asset management: A barcode-based fixed asset system requires permanent barcode labels affixed to each asset. The CMMS links the equipment history record to each asset number. When a PM routine is conducted, the asset label is scanned with a hand-held barcode reader, and readings are recorded manually or electronically. When the information is uploaded to the CMMS, it can generate reports summarizing the time taken to perform the PM routine, the results of the inspection, and when to begin the next PM routine.
A downtime recording system uses data entry terminals at each machine center. When a machine stops cycling, a sensor on the equipment sends a signal to the CMMS to begin recording downtime. Assuming the default setting is "breakdown," the onus is on the operator to key or scan a code explaining the reason for the downtime. This could be waiting for parts, unscheduled break, set-up, clean up and so on.
Upon arrival, the maintenance worker must key or scan an identification code to begin logging start time. A work order number also can be entered. When the job is completed, the logout is just as easy.
The CMMS can generate reports about total downtime; downtime by equipment or by cause; response time by maintenance technician or by equipment; repair time by work order; machine utilization; and time to begin production following repair completion.
Scanning equipment
Five ways to scan barcodes include:
* Hand-held, contact scanners (wands or light pens).
* Hand-held, non-contact, fixed-beam laser scanners.
* Hand-held, non-contact, moving-beam laser scanners.
* Fixed-location, single-beam scanners.
* Fixed-location, multi-beam scanners.
As well, scanners can be desktop, hand-held, portable or a component of another device, such as a PDA. Finally, scanners can communicate with the CMMS on a batch download/upload basis or online via either a wired or wireless LAN/WAN.
Wands or light pens are the simplest, least expensive barcode scanning devices. Contact with the barcode is required and the abrasion degrades the barcode itself and increases the scan time. Another disadvantage is that scanning is dependent on the operator's and skill level.
Wands are useful in applications involving many barcodes or where barcodes are presented and oriented inconsistently. For example, instead of entering work order data manually or via keyboards, a menu of barcoded information can be scanned. Thus, if a component or job is changed, the appropriate new information can be scanned on the barcoded menu instead of writing or keying the changes.
Of the two types of hand-held, non-contact laser scanners, the moving-beam scanner is most effective and efficient. These devices use moving mirrors that scan the beam across the barcode repeatedly. Fixed-beam lasers require users to move the stationary beam across the barcode, but they weigh less than the moving-beam version and reduce operator fatigue.
Both fixed and moving-beam lasers avoid physical contact. However, the technology is more expensive than the hand-held wands. Fixed-beam lasers vary tremendously in price, but generally cost around $500, whereas moving-beam lasers are slightly more. Another advantage of non-contact scanners over the wands is that poor quality labels are more easily read. Additionally, etched, coated and recessed barcodes, such as those typically used on assets, are more easily discernible.
Fixed-location scanners are faster and more accurate than hand-held devices for a number of reasons. First, they generally use the moving-beam technology. Second, weight is no longer a consideration and third, these systems are usually machine-paced. The fixed-location scanners are ideal for tracking machine uptime and production volumes.
The single-beam technology requires a more exact orientation and presentation of the barcode. In addition, the surface on which the barcode is placed must be fairly flat. Multi-beam technology minimizes the need for flat surfaces and precise orientation because beam motion is a cross-hatched X-pattern. A holographic scanner is a more expensive version of the multi-beam laser, used for reading barcodes in difficult orientations and on variable surfaces.
The cost of fixed-location scanners is greater than the hand-held lasers, depending on scanning technology, degree of ruggedness required, speed of scan, etc.
Another popular device is called a "wedge," and can be purchased for well under $1,000. The wedge allows a user to enter data into a standard computer terminal via a barcode scanner rather than the keyboard.
Contributing Editor David Berger may be reached at david@wmc.on.ca
