HP DesignJet

What the HP DesignJet was

The HP DesignJet is a large-format, monochrome thermal inkjet plotter made by Hewlett-Packard for computer-aided design (CAD), architecture, and engineering drafting. Rather than dragging pens across a sheet, it built line drawings and graphics out of ink dots using the same thermal inkjet technology HP had proven in its DeskJet desktop printers. The Hewlett-Packard Journal described the machine as one that "combines the low cost of pen plotters with the speed of electrostatic plotters." The HP Computer Museum records the original unit under the model number C1633B and dates it to 1992, while HP's own product history dates the DesignJet's market introduction to 1991; the plotter's engineering was documented in the December 1992 Hewlett-Packard Journal.

From pen plotters to inkjet

Through the 1970s and 1980s, wide drawings were produced either on pen plotters — slow devices that moved physical ink pens across the page — or on fast but expensive electrostatic plotters. The DesignJet applied HP's thermal inkjet technology to the large format, giving drafting departments plotter-scale output at far lower cost and with greater reliability, because there were no pens to run dry in the middle of a plot. According to HP's own history and the RIBA Journal, the DesignJet arrived in 1991 and went on to become a long-running fixture in architecture, engineering, and design studios, displacing the pen and electrostatic methods that preceded it.

How it printed: thermal inkjet at 300 dpi

The DesignJet printed at 300 dots per inch using a moving thermal inkjet cartridge — the same style of disposable cartridge used in the HP DeskJet 400 and 500 series desktop printers. In a thermal inkjet head, tiny resistors flash-heat the ink to form a vapor bubble that ejects a droplet onto the page. Because one cartridge could lay down many plots before replacement and cost far less than a set of drafting pens, the plotter needed little operator attention. HP later raised resolution to 600 dpi with the DesignJet 600 and added color in subsequent DesignJet models; the original 1991 machine printed in black only.

Media, memory, and interfaces

The plotter handled ordinary drafting media, taking cut sheets from A4 up to A0 and rolls 24 or 36 inches wide and up to 50 metres long, so a D-size or E-size drawing could be produced from a continuous roll. HP's engineering write-up lists 2 MB of DRAM as standard, expandable to 10 MB to hold larger and more complex plots. For connectivity the DesignJet carried an RS-232-C serial port and a Centronics-style parallel port, plus a modular I/O (MIO) slot that accepted add-in interface cards; the Hewlett-Packard Journal notes that HP-IB and Novell Ethernet cards were the options available at introduction.

HP-GL/2 and mixed vector and raster data

Drawings reached the DesignJet in HP-GL/2, Hewlett-Packard's standard vector plotting language, which the CAD packages of the era generated directly. The plotter also understood RTL (Raster Transfer Language), letting an application mix raster image data with vector line work on the same plot — useful for combining shaded fills, scanned images, or rendered views with technical linework. This dual vector-and-raster capability, ultimately resolved to dots by a raster image processor, set it apart from the purely vector pen plotters it replaced.

Place in history

The original DesignJet launched what became one of HP's longest-lived product lines: the DesignJet name has remained in continuous use on large-format printers for more than three decades, expanding into color, photo, and technical-CAD families. The 1991 machine brought HP's thermal inkjet technology to the large format and helped make inkjet — rather than pens or electrostatic processes — the dominant way to produce wide engineering and architectural drawings. Surviving units and documentation are preserved by the HP Computer Museum, and the engineering behind the plotter was published in the Hewlett-Packard Journal.

Reference scope

This page records only specifications that can be traced to authoritative sources — Hewlett-Packard's own product and engineering documentation and the HP Computer Museum. Specifications that could not be verified from those sources, such as physical dimensions, weight, and list price, are omitted rather than estimated. It is not a buying guide and quotes no current pricing or availability.