Lines don't connect when I export to Autocad

I have to export my projects out of Sketchup Pro 2019 and into Autocad LT in order for our CNC operator to get the drawings ready for the toolpathing in the CAM software. I do a 3D export to a .dwg. When we open the file in Autocad LT, sometimes the lines do not connect by an extremely small amount. As small as .0006. Its very hard to find and causes a lot of frustration with toolpathing. It happens a lot when curves are involved and I am well aware of Sketchups issues with arcs and curves. Does anyone have any advice? Are there tolerance settings in Autocad I can adjust?

Can you share the skp file?

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Here is the .skp file and the .dwg export. The problem area is towards the back where the largest radius is. The framing members that run into the radius touch in Sketchup but not in Autocad?Deck Bench.skp (110.8 KB) Deck Bench.dwg (42.7 KB)

You said you were exporting for cnc? Are you using a 3d export of 2d linework?

In the SKP file the lengths of the members are in fact different.
It would appear you drew them individually.

Draw one and make it a Component.
And then do the Radial array.

I designed the framing members individually and oversized in length. Then I adjusted each one back so at least 1 corner was touching the arc. I believe the small segments in the arc dont allow me to get each corner to touch.
I know the video Aaron has listed above. I am aware that exporting my model as a 3d .dwg will result in a true arc inside of Autocad. Is that the problem? The geometry is to the length of the segment, not to the true arc. I think that is why my parts are slightly different sizes too.

Here is another example of the problem. Simple circle and a line.CIRCLE.skp (2.4 MB) CIRCLE.dwg (20.4 KB)

The circle on the left is showing behaviour that I would expect when exported as a 3d DXF. As the vertices define the edge of the SketchUp segmented circle, when converted into a “true” circle the horizontal edge nevertheless falls short of the boundary in the resulting DXF. If you want the edge to touch the circle boundary then you need to connect the vertices of the circle.

The circle on the right has something strange going on that I think is a tolerance issue. The edge splits the circles’ face and appears to hit a vertex as far as I can see. But in the export the edge does not touch the circle boundary as the edge is actually shorter than the radius of the circle:

My theory is that the vertex of the circle is ever so slightly off the “red axis” that the edge is being drawn along. If I use the rotate tool using a random endpoint of the circle to rotate it back onto the red axis, then redraw the edge, it shows length as 100.000 as expected and exports with the edge touching the boundary of the circle.

In my opinion, it is of no use to have 302 segments in the circle as the “SketchUp circle” will be transformed into a true circle anyway in the export. It also makes inferencing the vertices more difficult as they are closer together/harder to see,48 sides in this case appears to be plenty.

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Therein lies the problem with using that method in SU.

The intersection of the Edge and Arc Segment does not fall on the true arc.
That is, unless the Edge happens to pass through an Arc Segment Vertex.

By definition, the lengths of the radially arrayed members are all the same.
Also, by definition, their length is shorter than the radius of the Arc.

Finding their true length is a bit of a conundrum in SU given the issue of Arc segmentation.
There is a plugin that fills that functionality gap in SU.
It’s free. Simply signup with SketchUcation to download.

SLBaumgartner: Circle Intersect v1.0.0
https://sketchucation.com/pluginstore?pln=draw_angle_dim

The plugin places guide points at the mathematically correct intersections between a circle or arc and another circle, arc, edge, or construction line.


Click through the Scenes in the model.

Deck Bench_001.skp (35.9 KB)

Deck Bench_001.dwg (8.0 KB)

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