Printer basics
Thermal, laser and impact printers are commonly used to print labels and documents in industrial settings.
By Corinne Kator, Associate Editor -- Modern Materials Handling, 10/1/2007
- Thermal printers
- Laser printers
- RFID printers
- Printer-applicators
- Impact printers
- Beyond documents and labels
Printers are a common sight in manufacturing and distribution facilities, especially near the receiving and shipping docks where goods are identified and shipments are documented. When a printer is found in an industrial environment, it's likely performing one of two functions:
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Printing labels, such as picking and shipping labels
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Printing documents, such as packing slips, invoices and bills of lading
Individual labels—particularly labels including bar codes—are usually produced on thermal printers. They are then applied by hand or by automated applicators. Laser printers are sometimes preferred for wide labels or for batches of pre-printed labels.
Documents used in industrial environments can be produced by laser printers or by impact printers, which are capable of printing on multi-part forms.
Thermal printers
Thermal printers can print on virtually any material and can be designed to print on any width of paper. “That's what makes a thermal printer ideal for labels and tags—you can stick anything through it,” says Paul Vogt, industry marketing director for Zebra Technologies. Thermal printers also excel at producing dark black lines, making them the default choice for printing bar code labels in most warehousing and manufacturing environments.
Two types of thermal printing technologies exist: thermal transfer printing and direct thermal printing. The same printer can often be used for both types.
Thermal transfer printing involves pairing a roll of printing media (usually a roll of adhesive labels) with a roll of inked ribbon. When the printer's heated printhead touches the ribbon, it melts the waxy ink and transfers it to the media.
Direct thermal printing doesn't require ink but instead requires heat-sensitive paper. As the paper passes the heated printhead, the paper's heat-sensitive coating turns black, producing an image.
Direct thermal printing is less expensive than thermal transfer printing, but the resulting printout is less durable. Parcel carriers often use direct thermal printing for their overnight shipping labels, says Vogt, because the labels don't have to last very long. By contrast, he says, labels printed on a thermal transfer printer are “virtually bullet-proof.”
To minimize bottlenecks at a central printer, many facilities have begun using mobile thermal printers. Mobile printers need a wireless data connection and a battery to supply power. Small mobile printers can be worn on workers' belts. Larger mobile printers with bigger batteries and the capacity to hold more label stock can be wheeled around a facility on a printer cart.
Laser printers
Laser printing is a newer technology than thermal printing, and while laser printing is less common for producing labels, it does offer some advantages.
Laser printers are often less expensive than comparable thermal printers, and the powdered toner they use costs less and lasts longer than ribbons of thermal transfer ink. Laser printers can print at extremely high resolutions (up to 1200 dots per inch), producing excellent quality bar codes.
But while thermal printers easily produce single labels one at a time with no startup period, laser printers need time to warm up and can't handle small label stock.
These limitations make a laser printer a poor competitor to a thermal printer for printing single labels on-demand. Laser printers are a good option, however, for economically pre-printing large batches of labels onto label stock that contains several labels on a single sheet.
Two styles of laser printers are available: cut sheet printers that feed a single sheet at a time and continuous-feed printers for bulk printing.
The most common printers for producing documents are cut-sheet laser printers. These printers are standard in the back office, and they're increasingly common in the warehouse and on the production floor.
Laser printers produce better quality text and images than impact printers and are less expensive than thermal printers, making them ideal for printing basic documents such as picking and packing lists.
A laser printer can be used at a packing station to simultaneously produce a shipping label and a packing slip. This requires sheets of combination media with a label on top and plain paper on the bottom. This combination media has allowed companies to replace the two printers (a thermal printer and an impact printer) that often sit side-by-side in a packing station with a single laser printer.
Multifunction laser printers—machines that act as printers, copiers, scanners and fax machines—are gaining popularity at the shipping docks as business shifts from a paper environment to a digital one, according to Rick Kallop, senior industry consultant for manufacturing and distribution at Lexmark.
Truck drivers, for example, says Kallop, have traditionally received several carbon copies of a bill of lading and then have physically routed those copies to different offices. Today, he says, a single copy of a bill of lading can be printed on a multifunction laser printer, the truck driver can sign it, and then the driver can use the scanning and faxing capabilities of the printer to route the bill of lading electronically.
RFID printers
Radio frequency identification (RFID) tags are now joining bar codes as a means of identifying goods. Because RFID tags are often embedded in printed labels, RFID encoders are increasingly being added to label printers. As labels pass through the printer and are marked with text and a bar code, the encoder simultaneously writes data to the RFID chip embedded in the label.
While some people refer to these dual machines as printer-encoders, many simply call them “RFID printers.” Nearly all the RFID printers on the market are thermal printers. Earlier this year, Lexmark introduced the first laser RFID printer.
Printer-applicators
Most labels are applied to products by hand, but high-volume materials handling systems often include automated print-and-apply systems. These systems can, for example, automatically apply a shipping label to a unit load of goods that has just been automatically palletized and stretch wrapped.
A standard printer-applicator, says Ann Marie Phaneuf of Weber Marking Systems, includes a thermal print engine (the basic inner workings of a thermal printer), a mechanism for separating the label from its backing, and a mechanism for either wiping or blowing the label onto the product.
Impact printers
Impact printing is the oldest of the print technologies used in industrial environments. Impact printers, such as line printers and dot-matrix printers, are inexpensive and hold up well in harsh environments, but they print at relatively low resolutions—usually too low for reliably printing bar codes.
Impact printing involves striking an inked ribbon with pins or hammers, leaving marks on a page in much the same way a typewriter does. This technology allows impact printers to do something no other printer can: produce carbon copies using multi-part forms.
“Multi-part forms are still very popular for shipping documents,” says Andy Scherz, director of product marketing for Printronix. So even though impact printing is an aging technology, he says, impact printers are still a common sight near the shipping docks of a distribution center.
Beyond documents and labels
In addition to printing documents and labels, some manufacturing and distribution facilities also need to print directly onto cases of products. In these situations, inkjet printing is the technology of choice.
Inkjet printing has improved greatly in recent years, says Graham Podmore of Videojet Technologies. Today's industrial inkjet printers automatically clean their printheads, he says, making these wet-ink printers suitable for dusty environments. Inkjet printing is less expensive than printing and applying labels, he says, making it the most economical choice for marking on secondary packaging.
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