Exporting a file to Alpha cam


#1

I have this pattern of Closed polysurfaces with 2 closed segments that I am exporting to AlphaCam to cut on our CNC.
what is the best practice anyone has found to do this. All the objects are in the same plane. I’m trying import and set my tool paths with the least amout of effort ofcourse.
I have been exporting with a DXF file but keep coming up with different issues making the executable file for the CNC massive. Other times the same size file would be 1k, and the 2 k. Basically, I trying to find some consistency to getting this done.

Thanks in Advance for all your amazing imput.

Bill


(John Brock) #2

Don’t use DXF if you can avoid it.
Try IGES instead.


#3

HI John,

I can do that. Is this the best approach with 3d files as well; I’m usually exporting the as a parasolid,


(John Brock) #4

The problem is you have modeled clean, degree=3 NURBS curves. AutoCAD DXF/DWG does not support NURBS curves so they have to be converted to something else. That usually requires converting the NURBS curves to chains of arcs before exporting and that’s a hassle.
IGES support this smarter NURBS curves and if your CAM application supports IGES, the conversion to G-Code arcs and lines is automatic and tweaked for the machine you’re using so you don’t have to think about it.

DXF should be considered a tool of last resort for Rhino curves intended for CAM.


#5

I export a degree=3 NURBS curve to a DXF file.
Then I read it back the DXF file, and the object is a NURBS curve.
Try:
bla.dxf (162.2 KB)

This is found in the file:
0
SPLINE
5
6F
330
1F
100
AcDbEntity
8
Standard
100
AcDbSpline
210
0.0
220
0.0
230
1.0
70
8
71
3 (degree)
72
8
73
4 (control point count)
etc.

Older DXF ‘slangs’, like R12, don’t support splines at all.
But the current ones do.

-C-H-A-R-L-E-S-


(John Brock) #6

Yes, but I have yet to find a CAM application that will support AutoCAD Spline entities in DXF/DWG files. IGES is still the best option assuming the CAM application support IGES.


#7

That could be an issue; however, a bigger issue is that most 2D CNC even now does not support splines regardless of the file format. The safest thing to do is convert all splines to arcs BEFORE sending the file out so the faithfulness of the conversion is not left to chance or the conversion tolerances on another system. If one is new to the potential issues with spline to arc conversion, the converted arcs should be carefully checked against the original splines.


#8

If a CAM app is able to read IGES, then it is one of the more sophisticated ones.
In this case I would assume that it is also able to read the same data from DXF.

In both cases the spline must be converted to arcs and lines.
G-code is not able to represent splines.

In the 2D world, DXF is still standard from my experience.


#9

Very true.
Rhino is very good in this respect.

Another good point for doing the conversion in Rhino.
A compare is not possible in the receiving software.

In most CAM software that I know one can set tolerances, similar to Rhino.
The results are pretty good, but no chance to really compare.

-C-H-A-R-L-E-S-


(John Brock) #10

Since the original poster was interested in an easy solution, I did not detail using Convert before exporting to DXF.


#11

I’m glad I was able to stimulate such a response. Our biggest concern is not so much simple , since nothing really ever is, more about file size at the end for the G code generated. We are using an older machine with a disk drive and 1.44 in the max on the storage capacity. My assumption could be incorrect, but the simpler the shape the less tool paths are generated; hence a smaller file.

Thanks


#12

Saving as arcs instead of splines can reduce file size significantly.


#13

Hi John, I thought this might be where I could ask about an import question.
I have been sending dxf files to a Stylecad user. This person doesn’t receive all the info. Text and layers are a couple I can think of.
Stylecad doesn’t support iges. I will look on the web as well thanks.—Mark