Export to dxf problem


#1

Pretty straight forward problem I need a little help with. Exporting a rhino 5 file to a dxf for a plasma cam application to cut from. I’m sending a file that looks like the first pdf but the CAM operator is seeing what he’s sent back in the second pdf.

I’m exporting with ‘default’ settingsHeat control fans-returned.pdf (14.2 KB)
Heat control fans-source.pdf (79.6 KB)

Any ideas greatly appreciated!


(John Brock) #2

It sounds like you used the “Default” export scheme when exporting to DXF.
Bad move.

The Plasma cutter follows G-code commands. G-code supports three movements:
1 - Straight lines
2 - Clockwise arcs
3 - Anticlockwise arc
It’s your job to make sure you’re only sending supported curves to the cutter.

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.

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.


#3

Thanks @John_Brock. Snappy response with all the information a forum search didn’t provide. Worked great, plasma cutter is eating up dem-der arcs!