NC cut files from Rhino

Just a quick question regarding extracting shapes from Rhino to send to AutoCAD for nc cutting.
For curved (developbable) panels I use the Unrollsrf command, but for flat panels - transverse frames and the like - is it better to do the same, or just use the Make2D command and get the edge curves to define the shape?

 

If you use the make 2D it will be on the c plane when you import into AC. (I think) If you use the curves you may have to rotate and project to c plane.

 

Thanks Gary.
Not sure if that's a problem... I use Make2D, in the appropriate "current view", which puts it on the c-plane in the plan view. When I export as a dwg / dxf it's there ok in autocad. But I was wondering if the resulting lines, typically made up from a stack of little segments etc might send an NC cuttting computer crazy....

 

I don't like the results of the make2D command very much. As you said the resulting lines are kind of messed up.

I guess for flat shapes (frames, bulkheads, etc.) it's easier just do get the surface edge/border with a command like dupborder/dupfaceborder/dupedge etc.

Cheers
Ruy

 

Will sometimes it depends on what flavour DXF you are exporting out in as to whether you get a continuous line or segments or something else, may also help some times to use a different file format for export.

 

I should sit down and write a tut for this just so I can remember it. I used 2000 or older version when exporting .dxf for CNC. If you open it in AC and have segments the export is wrong. It is a matter of selecting the right settings before you export. You are right the little segments will drive the CNC machine nuts as it accelerates and decelerates on each segment. You will also get a bad finish. The machine can compensate for some of this but it is better to have smooth curves to start with. I’ll look at this when I get home tonight.

 

Thanks gents.
I found that when I did Graphite, I had to use R14 in order to get something that that the cutter would talk to! Same as you though Gary - its been so long since I did it...well more than 12 months anyway....that I can't remember all the tricks.... yes a tut would be a great idea!

 

Hi
If you need DXF to NC postprocessor, SoftONE-CNC software can perform this task. Please look to: http://www.onesoft.ro

Ovidiu

 

Hi Guys, I was just doing some testing of this very topic. Glad I found this thread so I can see what your thoughts are.

I don't have Rhino, I use Alias but I think the export is probably very similar into Autocad.

1st I used the R12 DXF export and of course it is many little segments, that I expected. It is the best accepted for the various NC softwares but it never liked any form of bezier or b-spline curve. I do think though that it could be more accurate. In Autocad the curve is a 3D poly. I've never used that command so wondering if the line will be a problem when machining? Has anybody had such curve rejected but the cutter?

2nd I used the 2007 dxf and got splines. Last time I had something cut these were a big no-no and need to be duplicated. Has the machine software gotten better in the last 5 yrs to accept splines? I checked the poly against the spline and there was some small variation but nothing for me to worry about. I really do not want to re-draw with Autocad tools as I know that duplicating all the curves will take forever. Plus lines and arcs may not give me the results I want (such crappy commands).

Finally, how are you finding the final accuracy of Autocad compared the the original NURBS model? I'm sure that it cannot reproduce a nice 5 degree curve. Overall dimensions are good. I just don't want it to wreck my nice curvature plot. I spent so much time making high quality surfs.

Any help would be appreciated.

Thanks, Shaun

 

Some CAM systems still struggle with splines,quite a number have the facility to convert a spline to a series of arcs and you normally need to specify an acceptable deviation from the spline to determine the number of arcs required to approximate the shape of the spline.I know that Mastercam has been able to deal with splines for quite a few years.I don't entirely understand why the original poster needed to translate from Rhino to Autocad given that Rhino can save in .dxf format.

 

WF - my question was more related to the best method within Rhino for extracting the shape... as with all things related to designing with the use of computers, there's a million ways to skin a cat, and quite often sharing methodoly will throw up ideas that can make everybody's life easier.
One tip that I did get is to always export using polylines. Then in Autocad you can make each 'shape' into a region or boundary in order to ensure that you only wind up with a single, closed line / curve for the machine to have to deal with.

 

Cliff has done the work for us and posted it on his site. A very good run down on exporting 2D Rhino to .dxf.
http://www.basline.com/WeeklyTips.shtm
Click export your model to CAD.

 

Fabulous... thanks Gary... and Cliff!

 

i suggest you get squish plug in for rhino and then expand the curved surface .then get boundary curves.