AutoCAD DXF file import - wrong scale

Software Carbide Create
1

Hello,

This is my first time using Carbide Create (Build 648, Trial)

I created a simple square (1x1 MM) on Autocad, exported as DXF.
I use MM as units on Carbide Create.
The square gets imported but it’s 25.4mm x 25.4mm, not 1mm x 1mm.

I tried again with AutoCAD, simple square (1x1 unitless), exported as DXF.
MM units on Carbide Create.
Same problem, the square dimensions are 25.4mm x 25.4mm.

Manual scaling by a non-integer factor of 0.039370… can’t preserve the accuracy.
Is it due to CC can’t import metric DXF or I am missing something?

2

I tried this using Inkscape’s DXF export (I don’t have autocad) with mm as the file scaling and imported it into CC v645. It was loaded as 1mm square even if the stock was set to use inches.

Can you upload the file? (actually, this might not be possible given it’s your first post - welcome btw :slight_smile: )

Note that if you change the dimensions of the square or object in CC from 25.4 to 1, it’s going to set it to 1mm. Scaling errors should not be an issue here - I don’t think it will end up being 0.999999982 wide for example (ie: use target size and don’t type in the scale factor manually).

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3

Please send the files in question in to support@carbide3d.com and we will look into this.

My understanding is that DXF doesn’t really have a concept of units:

The usual work-around is to put a box of known dimension around everything before exporting and then resize the box and all its contents.

Another option is to import into LibreCAD and export as MakerCAM SVG.

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4

I think the $MEASUREMENT dxf header specifies imperial (0) or metric (1).

Certainly the Inkscape exporter offers it as a setting.

SVGs don’t have a standard unit specifier for what I remember.

5

SVG files have “abstract user units” apparently (I didn’t dig deep enough for the formal definition of px but it’s buried somewhere in here) called px. Remember the fuss some years back when Inkscape switched from 90 px/inch (ppi) to 96ppi?

Wasn’t svg primarily intended for displays and later adopted (some might say perverted into) a CAD format? Not sure I can remember that far back anymore

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6

It’s a bit odder.

Inkscape currently writes out element heights and widths with a unit suffix, such as width=“210mm”, which get parsed by most other interpreters as “210”, or are ignored completely since it’s supposed to represent the height in ‘the user’s coordinate system’. So Inkscape is breaking the SVG spec in an attempt to move it forwards, perhaps.

It also writes out custom tags like inkscape:document-units=“mm” to give hints to Inkscape about things that are not in the SVG specification.

Personally, I don’t find it a problem. I look at the size of the item in the thing I create it in (for me Affinity Designer), then set it exactly to that size when I import it into wherever I need it.

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For Serif’s Affinity Designer, it works to export as an SVG set to 96 ppi.

8

Thanks for the suggestions! It works.

  • An extra 10x10mm square was created in AutoCAD, encircling all geometries .
  • Imported to CC, their dimensions are all x25.4 times larger.
  • Select all => Scale => Enter manually the “Target Size” to 10x10mm (disregard Scale factor).

Requires two extra steps but this work-around is dead-simple. I hope CC will included this fix in newer build.

Thanks again for the quick answers!

9

A little scary, especially when Inkscape is supposedly the definitive svg editor. I’ve been poking at the svg spec a little lately. I exported a layered file from CC for use in another couple programs and discovered that while there was a proposal for a layer standard around 2016 (iirc) that it never got adopted. Inkscape has it’s own way (groups with inkscape tags), other programs will export each layer as it’s own group, CC does neither. As the saying goes we must love standards, we have so many of them.

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