Older dxf-versions?

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chattermark
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Joined: Sun Oct 12, 2014 8:30 am

Older dxf-versions?

Post by chattermark » Tue Aug 25, 2015 2:03 pm

Recently, I had some problems to import QCAD-generated dxf files into vcarve on a friend's computer. The problem was, as I found out, that vcarve seems to refuse dxf formats that are more recent than R14 (!). No idea about the update status of my friend's setup.

Yes, I know, QCAD can export dxfs as R14 or older, but tells me that all lines will be exported as white etc. Yesterday, I worked with a CorelDraw V15 version. Export to older dxf-formats is possible there too, but the user can choose various parameters like scaling (inch, mm, cm, ...) , pen and fill colors etc. Would that be possible in QCAD too without too much effort?

Cheers,
Chattermark.
Don't try to fix it if it ain't broken.

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hungerburg
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Re: Older dxf-versions?

Post by hungerburg » Wed Aug 26, 2015 10:52 am

Mark, comparing CorelDraw and QCAD is not fair: they have quite different uses: artistic illustrations vs. technical drawings. I am aware, that CD is used a lot with eg. cutting plotters and precision seems to be good enough.

Main difference though: a CAD drawing is not about aesthetics, but conveys meaning instead. Its unscaled 1:1 with respect to some physical object; Colours, stroke widths, dashes etc. signify properties of such object: eg. being hidden, being a wall, belonging to one part or the other, etc. Consequently, when printing to scale, stroke widths remain fixed (they do NOT scale).

That said, CAD drawings can also be used as the basis for CAM, ie. to instruct machines to perform certain actions. A Plotter may use any of line weight, colour, layer name… to tell which tool to use, how deep to cut and so on. There exists no standard mapping. You have to know it and draw accordingly from the start.

PS: only black lines will be exported as white, red lines will stay red

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andrew
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Re: Older dxf-versions?

Post by andrew » Wed Aug 26, 2015 11:07 am

Thanks hungerburg. I only have a few remarks to add to that:

The warning shown when exporting to DXF R15 or older is about DXF format <= R15 restrictions:
- It is not possible to store black entities as black in DXF <= R15. There is simply no color 'black' defined in that DXF format version.
- It is not possible to store entities in full (24bit) color in DXF <= R15. Colors are limited to 256 predefined colors.

These are file format limitations and there is no way around them except using a newer format version. CorelDraw and other applications are equally bound to these restrictions as QCAD. For most CAD uses, these restrictions should not be a real problem though.

The drawing unit of your drawing can be changed under Edit > Drawing Preferences and is stored in your exported DXF file. It would not be practical to ask the user on every save what unit to convert to.

I don't understand your question about pen and fill colors. Pen and fill colors are stored in DXF as defined in the drawing and automatically rounded to the closest available 256 color palette entry when using DXF version <= R15.

chattermark
Junior Member
Posts: 24
Joined: Sun Oct 12, 2014 8:30 am

Re: Older dxf-versions?

Post by chattermark » Wed Aug 26, 2015 12:00 pm

Thanks for your comments - the reason I asked is the task to process some historic cdr files, >15 years old, on a laser cutter. It is not an essential problem to solve, I'll figure out a workaround. Docket closed. ;)

Cheers,

Chattermark.
Don't try to fix it if it ain't broken.

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