Fusion DXF export is a little tricky but sound. What isn’t sound is Ruby’s DXF import. Ideally you create a manufacture model with components laid flat (there’s a tool for this but it’s paywalled), then use the CAM laser cutter tools to generate DXF’s.
DXF is not a unitless format, but dimensions are not accompanied with a unit. The unit should be set in the
$INSUNIT header on a component level. I can’t remember for sure but I think fusion sets this to mm, which is correct.
Ruby uses a proprietary CAD conversion library whose name I have forgotten. I stopped my investigation here, I decompiled Ruby server and found the class that is probably at fault, but without attaching a debugger to a working Ruby instance I wasn’t able to go any further.
You can import DXF’s into Ruby but the unit information is not interpreted properly, so the scaling will be wrong. If you’re going to manually rescale, then you need to be careful as Fusion will have accounted for kerf, so the dimensions might not be what you think they are.
(Q: Does JobControl also import DXF wrong?)
Until I pinpoint the issue with Ruby I’ve been using the glowforge postprocess that produces an SVG.