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Tips to make engravebale HPGL files with Corel Draw
HPGL is the abbreviation for the file format "HEWLETT PACKARD Graphics LANGUAGE". The file extension is PLT. This format was invented for printing of designs on pin plotters. Frontplatten Designer can import HPGL files, which were provided by of other programs. In this way you can use the possibilities of modern plot routines also for the disign of writings and logos on your front plates. Since graphics are engraved on the plates and are not printed, files are to be considered a few characteristics with the production of the HPGL, so that a perfect result is obtained. It showed up, that the function "simulated filling" in some programs (i.e. CorelDraw) results in bed results. Engravings of good quality can be produced however with the outline function. In the following short tutorial we describe the production of a signature as HPGL file by CorelDRAW 8.0. The procedure can feasible accordingly adapted also with other programs.
Tutorial:
1. Resize the grafic to the size it should have on the front plate. Switch to outline mode (menu "View" -> "Outline")
2. Now the graphic should be transformed into the contour for the milling tool. For a good engraving result it is necessary, that the outline lines lie sufficient closely and are sufficiently smooth. In the first step the outer contour must be shifted around half drill width inward, so that an unwanted enlargement of graphics is avoided. In addition you must decide first, with which tools the engraving is to be produced (e.g. engraving burin 0.2 mm for a graphics with fine lines or drill 1 mm for a wide graphics). A possibly existing grouping of elements has to be "ungrouped". Select "Effects" -> "contour" in the menu. Here select the option "inside", for "distance" choose half of the width of the engraving burin and set the "number of steps" to 1.
The outside outline is no longer needed thereafter. Click in the menu "arrange" -> "divide", then the outside outline will be delete.
3.
The further internal outline lines are processed as contour "to center". A possibly existing grouping of elements has to be "ungrouped" also. If several letters are to be worked on at the same time, this could be done by "Arrange" -> "Combine". Choose the distance of the outline lines in such a way, that there are no burrs in the recesses after engraving. For milling using of half the tool width is well proven, but for engraving lower the width a little bit more, because it's tapered. As appoximate values can be considered:
Tool Distance
0,2mm 0,07mm
0,4mm 0,15mm
0,6mm 0,25mm
4. In the next step the graphic should be made bigger for smoother roundings. It's nessesary because graphic programs are showing objects as pologones. The bigger the object the better the results. The original size will be restored after the Frontdesigner import. At first contour lines must be separated, because CorelDraw tries keep the distances between the lines constant. After separation scale up to 500%. Set outline colour to black (or other colour, it's possible to select different tools by colour). Than export to HPGL file. In exportmenu select "Advanced" and set contour resolution to "0".
5. Go to Frontplatten Designer, click on the HPGL icon and import the file. Correct the scaling (here 20%, to restore the original size) and choose the right tool.
6. Click on the looking glass icon and zoom the graphic to full screen. The engraved area should now be displayed fully black and have archs without squares.
(Many thanks to Michael Krusch who translated the german pdf to english language!)
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