Splines removed when saving as DXF

[Anonymous]

(Autodesk Fusion 360 v 2.0.1596)

I love the prospect of the 'Save as DXF' feature for sketches - very easy to use. However, I've found that anytime I save as DXF a sketch which contains a spline, the spline doesn't carry over into the DXF file. Lines, arcs, ellipses, etc all save no problem.

For example, here is a sketch with two splines (top and bottom) and two straight lines:

After saving as DXF, I open the new DXF file and only the straight edges are there:

I've tried opening the DXF file in several other programs, so I am confident it is not a problem with the program I am opening it with. Furthermore, I tested a bunch of other shapes and the lack of splines saving was consistent.

I don't know much about the DXF format, so maybe this is intended behaviour? If so, is there another way to get irregular curvature into DXF files?

Thanks!

[jeff_strater]

Thanks for posting.  Can you share one of the designs you are having problems with?  

I just tried a simple case - round trip from Fusion back into Fusion, and it seemed to work OK:

original:

export to DXF and re-upload:

But, of course, there are many variables here.  This was just a simple case.

Jeff Strater (Fusion development)

[Anonymous]

Sure. I just threw together a sample one just now:

Imported the DXF file into inkScape:

Same thing opening the DXF file in eDraw.

Here's a link to the F360 Project - http://a360.co/1F6W0ju.

The DXF file saved from F360 is attached.

[jeff_strater]

I suspect that the problem is in the tools you are importing into.  I was able to do a round trip in Fusion:

source f3d

imported from dxf out of this sketch:

but, imported into inkscape, I get the same results as you do:

I noticed when I did the import into inkscape, that the import menu said DXF R13, which I think is about 20 years old (maybe before there were spline entites in this format).  DXF is just a text file, you can look at it in any text editor, so I went and looked for the spline entity, and it's in there:

I don't know anything about eDraw, but I suspect it has the same problem, it just doesn't recognize this type of entity.

Thanks!

Jeff

[Anonymous]

Thanks Jeff! I didn't know DXFs could be read as text - looked at all the ones I've saved so far from F360 and the splines are all still in there, so yeah it must be the programs I'm loading into.

3 different programs, all can't read splines, what are the odds 😛 I'm especially surprised Inkscape can't do it. Oh well, I will look for another program to do that step of the work on. Glad to know everything is fine on F360's end!

Thanks,
-Mike

[Anonymous · Accepted solution]

Update:

I tried a whole bunch of other programs and found a *lot* of programs have this same issue with loading DXFs that were saved from F360, and it does seem like compatibility with certain DXF versions is the cause.

This workflow fixed it in all the cases I tried:

1. Save DXF in Fusion 360

2. Open the DXF file in QCAD (freeware)

3. Save the design as an R15 DXF Drawing from QCAD

4. Open the R15 file in the program of your choice.

This allowed Inkscape and a bunch of other processes to open the saved design without losing the spline sections. Seems like most programs are compatible with the R15 version.

[yqliu]

Hi Mike,

The reason that Inkscape failed to load the Fusion spline is the spline curves in Fusion are of degree 5. Inkscape and many other tools can only support splines of degree 3. Degree-3 splines are easy to implement but they have less freedom and capability in designing a complex shape. For example, we can constraint the curvature of a Fusion spline, or joint two curves smoothly, while it's not possible to do these with degree-3 splines.

Thanks for posting your finding of using QCAD here. It will help other users with similar issue. I will think if there is any other workaround on this issue too.

Richard

[billdresselhaus]

I have this Fusion T-Spline to DXF to laser cutting problem repeatedly without any resolution and the Forums confirm this as well. I tried this process below and when I tried to convert the QCAD file to R15 it said "not recommended" and it did not work. My honest feeling after trying this with many, many, many tries at remaking the file, remaking the DXF, remaking the Fusion T-Splines, and with multiple laser cutting vendors who all say the Fusion DXF files are always segmented!!! Every Forum "solution" has some stand-on-your-head work-around with using some other program needed or some non-accessible Fusion "plug-in". When some say they went from Fusion to DXF and back again successfully, who cares...so what??? It's the DXF file directly that has to work for laser cutting, not Fusion or some other CAD program. All my Fusion DXF T-Spline files open segmented in QCAD, Illustrator, and VCarve and the Portland State proto lab manager says Fusion 360 DXF files are always segmented no matter the reading program!!! I completely recreated the spline form over my segmented DXF image in Illustrator and sent the eps file to my laser vendor...its perfect!!! And this is old AI CS6. Why can't we just go from Fusion DXF files to laser cutting anywhere in the world without these insane work-arounds...I think this is a grand fail for Fusion and T-Splines as in not an easy-to-use Fusion to laser cutting process. I would love to be wrong...any help???

Thanks.

[menelas09]

Hello all,

This issue is still there.

using QCAD as an intermediate Transfert Tool Seem Saving Files in svg format provide accurates résults ...

Still have to check with the laser machine

Bobe Beverage

[mindabusdrifties]

Almost 10 years later and still no in house solution to this absolutely ridiculous issue.

billdresselhaus has hit the nail on the head. Auto desk Devs should be bloody ashamed.

I feel like i have been scammed paying for this crap when its sole purpose was to be able to use my cnc cutter.

"spline curves in Fusion are of degree 5"

Well how hard is it to convert them to 3 point within fusion so it can be compatible with literally everything else in the world..

What an absolute JOKE...

[mindabusdrifties]

@jeff_strater