IGES export settings?

Rhino Rhino for Windows
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1

I do have a quite nasty situation on exporting some curves as IGES using the latest RhinoWIP.

For some reason I can’t get this curves to be as a single SPLINE in Alphacam 2016 excepting one single file exported and I cant find any reason why the other attempts to export the very same curve it is resulting in segmented splines.

How can I find the settings or configuration that was used to export as IGES?

All the IGES files from the ZIP archive are various attempts to export the same geometry without success. Any of them gets imported in Alphacam as exploded spline in different segment parts.

iges_export.3dm (32.0 KB)

iges_export_good.igs (4.1 KB)

iges.zip (18.5 KB)

IGES_import_options

good_1piece
good_1piece1345×746 20.1 KB

bad_6pieces
bad_6pieces1671×743 21.7 KB

2

This is the analysis of your curve:

curve  
  
  ID: ae2970ef-1c3c-432c-ae23-016e58905166 (2)
  Object name: Cut
  Layer name: contour
  Render Material: 
    source = from layer
    index = -1
  
  Geometry:
    Valid curve.
    Open polycurve with 6 curve segments.
      Segment 1:
        Open NURBS curve
          start = (501.99,336.126,-34.1405)
          end = (497.621,197.068,-48.9185)
          degree = 2
          control points: non-rational, count=3
          knots: uniform (delta=139.127), domain = -139.049 to 0.0780947
          clamped at start and end
      Segment 2:
        Elliptical arc
          radii = 12.8117, 12.4
          focal distance = 3.22172
          foci = (488.344,197.359,-46.507), (482.11,197.555,-44.8866)
          center = (485.227,197.457,-45.6968)
          normal = (-0.251343,0.00789689,-0.967866)
          start = (497.621,197.068,-48.9185)
          end = (485.227,185.057,-45.798)
          degree = 2
          control points: rational, count=3
          knots: uniform (delta=19.0884), domain = 0.0780947 to 19.1665
          clamped at start and end
      Segment 3:
        Open NURBS curve
          start = (485.227,185.057,-45.798)
          end = (299.998,185.057,-20.4162)
          degree = 2
          control points: non-rational, count=3
          knots: uniform (delta=213.753), domain = 19.1665 to 232.919
          clamped at start and end
      Segment 4:
        Open NURBS curve
          start = (299.998,185.057,-20.4162)
          end = (114.768,185.057,-45.798)
          degree = 2
          control points: non-rational, count=3
          knots: uniform (delta=213.753), domain = 232.919 to 446.672
          clamped at start and end
      Segment 5:
        Elliptical arc
          radii = 12.8117, 12.4
          focal distance = 3.22172
          foci = (111.652,197.359,-46.507), (117.885,197.555,-44.8866)
          center = (114.768,197.457,-45.6968)
          normal = (-0.251343,-0.00789689,0.967866)
          start = (114.768,185.057,-45.798)
          end = (102.375,197.068,-48.9185)
          degree = 2
          control points: rational, count=3
          knots: uniform (delta=19.0884), domain = 446.672 to 465.76
          clamped at start and end
      Segment 6:
        Open NURBS curve
          start = (102.375,197.068,-48.9185)
          end = (98.0055,336.126,-34.1405)
          degree = 2
          control points: non-rational, count=3
          knots: uniform (delta=139.127), domain = 465.76 to 604.887
          clamped at start and end

So it’s a degree 2 polycurve made up of 6 segments. Then I tested the continuity between the segments and the 4 middle curves are not tangent - by almost 1 degree in the middle and by around 0.3 degrees at the ends. So I guess AlphaCAM might have a problem making it into one continuous curve.

3

But the very SAME geometry I can’t get to be exported-imported again as one spline. The geometry from the example that I provided it is importing perfectly using the first time IGES exported file. After that, no matter what I do I can’t get it to work again as needed!

The geometry from the file ‘iges_export_good.igs’ it is the same with the Rhino file. The picture with the yellow arrow it is shows only one spline. Any other time I do try to export again the very same geometry I can’t get-it to work as needed, I get only six splines instead of one.

4

I re-imported the iges_export_good.igs into the iges_export.3dm Rhino file in the WIP and it still shows as a polycurve composed of 6 segments, not a single spline. As a matter of fact, it selects with SelDup and the original.