This was written recently by John Brock and reflects the current state of best practice for sending Rhino files to any type of NC controlled cutter. (cnc, waterjet, laser, etc)
Posting here to make is easier to search for and find than our wiki- Thanks @John_Brock for this, and all the countless other things you do to help this community-
our original wiki post (also written by JB)
https://wiki.mcneel.com/rhino/exporttolaser
And a recent post that may get lost as it’s part of a larger thread… this is the real gold if you are digging for info on this subject…
You’ll need to convert your Degree=3 (and higher), curves in Rhino before exporting them as DXF/DWG.
Your Mill/Router/WaterJet follows G-code instructions. G-code supports three movements:
1 - Straight lines
2 - Clockwise arcs
3 - Anticlockwise arc
It’s your job to make sure you’re only send supported curves to the machine.
Lines, arcs and circles in Rhino are good to go.
Twisty Rhino NURBS curves need to be converted to arc chains. If you don’t convert them, they will be approximated by hundreds of short straight lines.
Since you need more efficient Arc objects in your DXF/DWG file, you’ll need to convert your wiggly Rhino curves to arc segments before exporting.
Use the Rhino Convert command.
Use these command option settings:
Output=Arcs
SimplifyInput=No
DeleteInput=Yes
AngleTolerance=0
Tolerance=0.01mm or 0.002"
MinLength=0
MaxLength=0
OutputLayer=Current
The tolerance controls how far the arcs will pull away from your NURBS curves. Your machining process and project will determine how much is OK. The distance is in current model units.
Then when you Export to DXF, use the “CAM Imperial” export scheme for inches and “CAM Metric” for millimeters. Both of these export simple geometry as lines and circles.
Always check your DXF file by opening it in Rhino before you send it for cutting to make sure it looks good.
Another option is to export using the IGES file format. Nearly all CAM applications support curves through IGES. Choose an appropriate IGES export option configuration for your CAM application.
Cheers