HPGL Format Guide for Pen Plotters
HPGL (Hewlett-Packard Graphics Language) is the native command language for pen plotters. Invented in 1977, it remains the standard for vintage HP plotters, Roland CAMM-1 cutters, and other professional plotters. Pathhaus exports native HPGL, ready to send directly to your machine.
What HPGL is
HPGL is a simple text-based command language. A typical HPGL file looks like: IN; SP1; PU100,200; PD300,400,500,600; PU; SP0. IN initializes the plotter. SP1 selects pen 1. PU/PD are pen-up and pen-down commands followed by coordinate pairs. The entire language fits on one page. Despite its simplicity, HPGL can represent any 2D vector geometry and is processed directly by the plotter's controller without any conversion.
Pathhaus HPGL export
Pathhaus's HPGL export (Pro feature) converts your font composition directly to HPGL, applying the Travel Optimizer to minimize PU (pen-up) move sequences. The output uses HPGL units (typically 0.025mm per unit for HP machines). You can configure the unit scale and paper size in the export settings. The resulting .plt file can be sent directly to your plotter via serial connection, or opened in HP-GL-compatible software like Inkscape (with the HP plotter driver) or specialized plotter utilities.
Connecting to vintage HP plotters
Vintage HP plotters (7475A, 7550A, DraftPro series) connect via RS-232 serial. To send files from a modern computer, you need a USB-to-serial adapter and terminal software (PuTTY, screen, or CoolTerm). Set baud rate to 9600, 8 data bits, no parity, 1 stop bit (9600 8-N-1). The plotter will begin executing commands immediately as they arrive. For large files, ensure your terminal software supports hardware flow control (RTS/CTS) to prevent buffer overflow.
HPGL vs SVG for plotters
For vintage plotters: always use HPGL — they don't understand SVG. For modern plotters (AxiDraw, Roland modern series): SVG or DXF via the control software is usually easier. For Roland CAMM-1 series: HPGL is native and produces the best results. The key advantage of HPGL is that it eliminates the conversion step — your font composition goes directly from Pathhaus to plotter commands without intermediate software.
Try it in Pathhaus Studio
Free to start — optimize and export your first font file in under 5 minutes.