HP-GL Files
HP-GL is the language of pen plotters, and of the sample-table cutters and vinyl cutters that grew out of them: each layer is drawn (or cut) with a numbered pen. Import a plot file with File › Import › Import…, and write one with File › Export › Export…, choosing HPGL Plot Files or HP-GL/2 Files.
Import
- Everything drawn with the pen down comes in as lines, arcs and curves; a pen put down without moving comes in as a point (a dot, or a hole for a pin plotter or knife cutter).
- Pens become layers. If the file sets its pen colours and a layer in your table already has that colour and line type, the pen goes on it, so a plot file you exported comes back onto the layers it came from. Otherwise each pen gets a layer of its own, in the pen's colour (pen n on layer 200 + n: Pen layers start at in the import options); a pen drawn with several line types gets a layer for each.
- Labels (text in the plotter's own font) come in as text, keeping their size, direction, slant, spacing and alignment. Accented and national characters are read from the plotter's character sets.
- Scaling, rotation and page settings in the file are applied. One plotter unit is 0.025 mm, the HP standard: set Plotter units per millimetre in the import options for a cutter that uses another (39.37, or 1016 to the inch). A file that scales to its page without saying how big it is is read on the Page size you choose (A4 landscape unless you choose another). Files ending .hp2 and .pen are read as HP-GL too.
Export
- Each layer is a pen: the first layer in the layer table is pen 1, the second pen 2, and so on.
- Lines on the Dimension and Tape layers are left out, as they are not cut (unless Leave out dimensions and glue is off).
- Each pen's strokes are drawn together, reordered and turned round so the pen travels as little as possible with the pen up.
- Text is written as the strokes of its letters, or, with Text as plotter labels, as labels in the plotter's own font (TrueType, mirrored and fitted text is always strokes).
- The export options also set the plotter units per millimetre (40), a pen speed, and whether commands are one a line or all on one line.
The two exports differ in what the plotter must understand (each of these can also be switched on or off in the export options):
| HPGL Plot Files | HP-GL/2 Files | |
|---|---|---|
| Lines and arcs | ✓ | ✓ |
| Other curves | as lines and arcs | as Béziers |
| Polylines | as point lists | encoded (much smaller files) |
| Dashed layers | solid | the layer's line type |
| Pen colours | — | the layer colours |
Choose HPGL for older plotters and most vinyl cutters, and HPGL/2 when your machine understands it.
Drag knife
A vinyl cutter's knife (a drag knife) swivels freely, its tip trailing a little behind the axis it turns round, so a
cut sent as drawn has its corners cut off, and a closed cut may not quite meet itself. Set a layer's Overcut and
Blade offset in Production › Tool Options (or an element's own, TOOL OVERCUT=1,BLADE=0.25:
see Element settings), and the export makes up for them:
- Overcut: a closed cut runs on past where it started by this much, so it is cut through where it meets itself and the letter weeds cleanly.
- Blade offset: the path is sent for the knife's axis, kept the offset ahead of the tip along the cut and swung round each corner on an arc, so the trailing tip turns the corner sharply. Use the blade's own offset: about 0.25 mm for a 45° blade and 0.5 mm for a 60° one. Leave it at 0 if the cutter makes up for it itself.
Curves are sent as short lines then. Layers without these settings are written as before.