Dymo LabelWriter 450 Duo Label Printer Technical Reference - Page 7

About the LabelWriter 450 Series Printers The LabelWriter 450 series printers (LabelWriter 450, 450 Turbo, 450 Twin Turbo, and 450 Duo) are high-performance, low-cost printers used for printing mailing labels, postage, file folder labels, bar code labels, and more. The printers have a 57 mm wide, 300-dpi print head and a 63 mm wide paper path. The LabelWriter Twin Turbo printer has two side-by-side label printing mechanisms in a single printer. The LabelWriter Duo printer has a label printing mechanism as well as a tape-printing mechanism that can print continuous-length labels in several different widths (6 mm, 9 mm, 12 mm, 19 mm, or 24 mm), using a 128-dot, 180-dpi print head. The 57 mm wide thermal print head uses 672 individually addressable dots to form individual raster lines of data at 300 dots per inch across the print head and either 300 or 600 dots per inch in the travel direction as directed by the print control data. Because they use specially treated, heat-activated paper, the printers require no ink, toner, or other refills. All 450 series printer models connect to a host computer through a standard full-speed USB 2.0-compatible interface. There are no built-in fonts. The host computer is responsible for sending commands and data to the printer to form each individual raster line of data. This is generally performed by printer drivers in the host computer that convert the image of the label into the proper command and data stream required by the printers. The Print Head The print head prints the image onto the label by heating a row of resistive elements; this blackens the thermally sensitive label material. These 672 resistive elements are .085 mm square and are spaced at 300 per inch on the print head. To print a line, the control electronics load the desired data into a serial shift register. This shift register has one register for each print element. A "1" in a register causes the corresponding dot to be printed; a "0" leaves the dot blank. The darkness or density of the image depends upon the amount of heat applied to the label material. The heat depends upon both the temperature of the print head and the amount of energy applied to the resistive elements. The energy applied to the resistive elements depends upon the voltage applied and the length of time that the voltage is applied. In order to maintain a constant density, the control electronics measure the print voltage and the head temperature before each print cycle, and then calculate the required print strobe time. The power supply is designed to handle printing an average of 37% of the total dots per line at full speed. If the voltage drops below 19.3 volts at the print head, printing is suspended until the power supply recovers to 21 volts. In order to protect the print head from excessive heat, the control electronics halt printing if the print head temperature exceeds 70° C. Printing resumes when the print head cools to 56° C. © 2009 Sanford, L.P. Page 7