Truetype Fonts to DXF

[doug30293]

I've used Desk Engrave several times in the past for engraving with good results. Not so good this time.

We have been provided with a specific Truetype font from which to cut 8 foot letters on a waterjet. I need to create DXF's from the font shapes for additional modifications. We have to cut the letters in sections. The DXF output from Desk Engrave is too rough to be useful.

Can someone recommend a (preferably free) program that converts Truetype to DXF?

[JohnB]

I have been using "Inkscape" to produce the text for my drawings. I normally create my fonts at the proper scale, save them as an "eps" file at the highest resolution available and then use a file converter to produce a dxf.

It's a bit of "screwing around", but it creates nice text. Just make sure you explode it in Inkscape, and don't bother around with the built in dxf export as it's not that clean.

And depending on what you need to do, you might be able to export the native SVG file and import that into SheetCAM

[PK]

I'm curious what is not clean while exporting out of Inkscape. I use Inkscape v.0.48.4 r9939 for some work: Type text, select Path, Object to Path and then Save As Desktop Cutting Plotter (DXF). It seems to work using Draftsight CAD to modify from there, if needed.

Always wanting to learn a better way, though...

Thanks,
Paul

[JohnB]

@PK - Thanks for the input. I guess when I tried dxf output awhile ago, it didn't work that well, hence my work around. I tried your method on some script text, and it looked pretty good in AutoCAD (I assume DraftSight would be the same). Just curious, I noticed a lot of splines. Does that cause any trouble with SheetCAM?

[PK]

You're welcome, JohnB. I don't think splines bother SheetCam. If I remember correctly, SheetCam will convert splines to polylines, but Les can say for sure. I haven't seen a difference that I've noticed.

Inkscape used to output DXF's in R12 format only which ended up being polylines and no splines. I may still have an install of Inkscape doing this. Sometimes Draftsight can't work on splines (fillets, I believe is one) so I save the drawing in R12 format and reopen and all splines will be polylines. There may be a better/quicker way, but I don't know of it.

Paul

[doug30293]

Our waterjet doesn't particularly like small line segments at 300-400 IPM. I found the best approach was to use Desk Engrave to convert the font to DXF, import it to my cad, and overlay arcs and lines to get a smooth profile. Then I delete the original geometry.

It is a lot of work but I only have to do it once. The lines and arcs are now tangent ( or nearly so ) which causes less stress on the machine.

[PK]

I bet - At those speeds especially. Any way to implement path blending or increase a look-ahead buffer on the waterjet's control program in an attempt to 'connect' the lines during a cut?

I know I could see the rough edges of a circle cut at 175 IPM plasma when I missed that the circles were polylines and/or splines making up that circle. Changed the drawing to true circles and the cut edge is much better.

PK

[doug30293]

The control only has one setting that determines what happens at nodes. If the segments more than X degrees off tangent the control goes into exact stop. I currently have this setting at 10 degrees. Once the characters are cleaned up I will turn this down to 5 degrees.

Arcs make a good approximation of the original shape and are easy to get close to tangent simply by tracing over the Desk Engrave files.

I found that some font authors put deliberate flaws in their characters. The font geometry cannot be copyrighted but the electronic compilation can. These microscopic flaws are markers to tell the copyright owner if someone has copied the compilation rather than the geometry.

The markers don't show up when engraving letters on a mill. They make a waterjet go nuts cutting 100 inch tall letters at 300 IPM.

[Les Newell]

In SheetCam go to Options->application options->drawing import and increase the arc fitting tolerance. Set the minimum segments for arc fitting to 4 or 5. These settings only have an effect when you import the drawing. G-code doesn't understand slpines so splines are converted to short line segments or arcs. The arc fitting tolerance specifies how aggressive SheetCam is at matching arcs.

You will have to experiment with the settings a bit. If you go too far you may get odd bulges or other strange shapes.

[doug30293]

Thanks Les;

I did work with the arc fitting tolerance and as you said it can be tricky to get the number right. I found this helps with splines but not with the DXF files from Desk Engrave.

Desk Engrave seems to hunt for the dark/light boundary of a letter and then puts a node at some predetermined approximation. The output is all line segments and they jump back and forth across the font boundary. Sheetcam's arc fitting method doesn't like the sawtooth pattern.

I wrote a data smoothing program to filter piezo noise from diesel PV data years ago. I think I could modify it to pull the noise from the Desk Engrave files. But the method I am using now seems to work very well and doesn't require me to re-learn Fortran. And I only have six letters left to convert.

Doug

[Les Newell]

converted bitmap sawtooth type paths are nasty to convert. I do have an algorithm that I use in Scanything which seems to work reasonably well. At some point I may investigate using that instead of SheetCam's current detail reduction algorithm.

If you are going to do any amount of this you may want to look at Cad-Kas font 2 dxf http://www.cadkas.com/downengcad4font2dxf.php. I have heard some good reports on it. It can also convert fonts to stencil outlines which is pretty neat.

[peter76]

There is Truetype Tracer under Linux which converts TT text to dxf.
See:

http://timeguy.com/cradek/01276453959

Regards, Peter