KiCAD unit issues with DXF files exported from FreeCAD

[shiftee]

I've no experience in this topic but I came across this in the KiCAD forum.

They are having issues with DXF files exported from FreeCAD.
It seems FreeCAD DXF export does not add $LUNITS and $INSUNITS both of which are needed for correct importing into KiCAD.

https://forum.kicad.info/t/units-once-m ... e/10844/20

Should I create a bug report?

[wandererfan]

https://forum.kicad.info/t/units-once-m ... e/10844/20

I can't tell from this post which Dxf exporter is being used in FC. There are 2 - "legacy" and "new". I know the new one does not have support for units yet. Not sure about the old one.

Any chance we can find out from KiCAD which one was used?
(Note the legacy "importer" also handles exports)

DxfOptionsInFC.png (98.28 KiB) Viewed 2867 times

[easyw-fc]

https://forum.kicad.info/t/units-once-m ... e/10844/20

I can't tell from this post which Dxf exporter is being used in FC. There are 2 - "legacy" and "new". I know the new one does not have support for units yet. Not sure about the old one.

Any chance we can find out from KiCAD which one was used?
(Note the legacy "importer" also handles exports)

I'm not sure if the exporter depends on the 'legacy' setting...
here what I get from the python console:

Code: Select all

import importDXF
importDXF.export(__objs__,u"C:/Temp/step-cadexchanger/internal.dxf")
__objs__.append(FreeCAD.getDocument("Unnamed").getObject("Shape2DView"))
...
import importDXF
importDXF.export(__objs__,u"C:/Temp/step-cadexchanger/legacy.dxf")

If I change the option, I get exactly the same result (I'm using File, Export, 'Save as Type':Autodesk DXF)

legacy.dxf

(1.3 KiB) Downloaded 108 times

internal.dxf

(1.3 KiB) Downloaded 93 times

[wandererfan]

I took a quick look through Draft/importDXF.py and I didn't see anything obvious related to units.

Looks like we need an issue report.

[easyw-fc]

I took a quick look through Draft/importDXF.py and I didn't see anything obvious related to units.

Looks like we need an issue report.

done here:
https://www.freecadweb.org/tracker/view.php?id=3494

[easyw-fc]

I took a quick look through Draft/importDXF.py and I didn't see anything obvious related to units.

Looks like we need an issue report.

following the KiCad forum:

The fun you find while digging into obscure specifications

$INSUNITS was introduced in the “Autocad 2000” specification for DXF.

This means any export methods set to AC1006 = R10, AC1009 = R11 and R12, AC1012 = R13 or AC1014 = R14. Will not have that tag present if the tool is respecting the export option,

Freecads export is for AC1009 / R12, so it will never include that tag so long as they are following the specification, and to include it would involve them remaking the exporter to support whatever the Autocad 2000 version is.

Before this, It was simply that DXF files where unitless, Most tools like solidworks and Autocad assumed this to be in inches if not specified on import,

[ickby]

I had this issue once too. Back than it turned out the DXF version freecad exports does not use units, it is not in this versions standart. You can check the version by the DXF file header, there is a identifier which you can than relate to the spec version.

The conclusion back than was, that the error is on the importing software site: it needs to check the specification version of the DXF and use units only when supportet by it.

Don't know if this is still valid though it if freecad has upgraded the DXF version.

[rawrpenguinzombies]

I am willing to offer a reward to whoever fixes this issue and the related 3594 issue tracker id.

[Kunda1]

2 issues:
issue #5793
issue #5805

[wmayer]

https://github.com/FreeCAD/FreeCAD/pull/6830 adds the unit block to header14.rub file

When I create a sketch and export it as .dxf then e.g. VariCAD viewer no longer prints a warning about the missing units.