Weird, yes I am inspecting each element of the reimported dxf inside the open group. I get tiny line segments on the inside diameter large arc, not the outer or the other arcs but that single one. I tried redrawing the arc but the problem persisted. Gif of my inspection:
All the DXF files posted in this thread looked clean in Autodesk DWG TrueView, no visible exploded arcs. In a DXF/DWG viewer, the number of segments displayed in an arc is determined by the VIEWRES system variable.
What happens to arcs and polyline arc segments when importing to SketchUp might be some kind of dark art. I see no consistent behaviour about arc and circle segments or when an arc is exploded into edges.
Thanks to Mark for providing a lot of information on using SimpleDXF
I’m starting to really cook with SimpleDXF, thanks to @gkernan and @mpoole32 for steering me around the rocks. I’m no longer concerned with the re-imports through simpledxf rarely exploding an arc, it hasn’t been common and anyway all the outputs have been true arcs in dxf so it’s a non issue. Files are cutting just fine and the flipped arcs problem is gone! THANK YOU!!
I did have this file that refused to export, it would go through the motions, allow me to name and push export, but simply failed to write anything to the disk. When I redrew the shapes they exported just fine. Any idea why this file fails to export? Just curious so I can avoid in the future.
Simple DXF Fail 20.skp (86.5 KB)
@endlessfix Your multi circle fail was a great test case. I’d run into the issue before and like you, when I redrew it the export would work. I showed Garry the message SimpleDXF generated in the ruby console and he was able to quickly answer our puzzle of a question. His answer also provides the opportunity to point out an important feature of SimpleDXF for those needing to generate g-code, especially for woodworkers.
For SimpleDXF to do its thing it needs to find at least one Edge. My first comment back to Garry was do you mean, a straight line? His response was one of those simple explanations I wish I’d heard 22 years ago when I first started doing CAD + CNC + Wood.
Garry could probably add some code to his SimpleDXF plug-in and solve this slight issue where he requires an edge. That said it might be better for users to understand what’s going on and use this explanation to get more functionality out of his plug-in.
A circle is a circle and an arc is a part of a circle. An edge could be a straight line or it could be a straight line with a bulge. It’s the straight line with a bulge that I’d never understood.
When you use cad geometry to generate g-code directionality is important for cutting direction. A circle has no directionality, only a center point. A straight line, an arc, and a line with a bulge, each have a starting and ending point. The line with a bulge also helps under the hood to figure out directionality. For me it was super helpful when Garry made the point about how a straight line with a bulge is also an Edge.
I was having a hard time with Garry forcing the issue of requiring an “straight line” edge for SimpleDXF to work because there are items we do that don’t have straight lines. But when I remembered how important directionality is and, how he has provided the means of addressing this issue, it’s probably better if we use the feature he has provided to solve the issue of nothing but circles and arcs and the missing edge.
Click to get into the outermost group and then click on the group that holds that largest circle in you failed test file. With that circle selected but not in edit mode click the Start Marker button.
By doing this on a circle you will get this dialog box. Click yes and this will split that circle into 2 arcs. This gives SimpleDXF the single Edge it’s looking for as a requirement. This feature was added for several reasons and it solves this issue you pointed out with your failed test.
After the marker is added you can see how there are now 2 arcs instead of a circle. I realized that in the past when I redrew items and it seemed to work it was because I was manually breaking the circle and then Simple was finding those arc edges without me using the tool Garry had already provided.
If you have multiple circles as in your example and cutting direction does not matter, you only need to add that marker to 1 circle in the drawing where there are no other straight lines or arcs.
@endlessfix see if this works and then you may want to do one of your quick gifs to show others how this works.
Excellent research and explanation. I’m away from the computer for a few days, I’ll try all this next week. Thanks for responding and thanks to Gary as well.
I have tried splitting a circle to overcome this limitation of Simple DXF, but I do not consistently get the dialogue that asks if I want to split a circle, sometimes it fails to appear? I’m getting many parts that either fail to export or export nothing. It’s taking a lot of redrawing and it’s still a mystery why some parts fail. A little disappointing. Here is another part that I have redrawn twice and still I cannot get to export. @gkernan what could I do better?
@mpoole32 if I can figure out a consistent pathway I will certify make an instructional gif. 
Simple DXF fail.skp (58.5 KB)
Give me a call and we can go over this with Skype
Here is a re-modeled version that exports well. Not sure what the difference is really. I’ll reach out soon to discuss. Thanks!
Turbine Hub 2.3.skp (58.5 KB)
@endlessfix I love seeing little projects like this. It gets old looking at what we woodworkers do all of the time.
I poked around with your failed file for a couple of hours and talked with Garry about it a bit. Get with him on Skype and see if he can shed any light on what’s going on.
I’m curious about how you started off that SU file. Did you start from scratch or did you start with native SU dxf import of that turbine hub?
Thanks. These files start from scratch, a blank SU file, no importing. I had thought at one point that an export fail was due to having mirrored geometry through an extension (curic), so now I am being careful to only use native tools. I was up late last night modifying one file and trying to really understand what geometry triggers the export fail. At one point I would have sworn the extension was sentient and was carefully preventing only the geometry I needed from exporting. I settled into a workflow where I draw one edge then export, see if it works, then draw another edge and export again, by exporting and re-importing at every step I can determine exactly which edges trigger the problem. Even with that process it’s still a mystery to me as sometimes the same geometry will export and sometimes it won’t. Also odd is that the act of exporting sometimes modified the existing geometry. Some grouped circles get exploded in the original after exporting once.
I’m under some production pressure this week as I’m onsite at the machine build, checking on the process but I’ll try to get with Gary asap to better understand.
I have some time to discuss that will possibly speed you up
I will be only supporting clients in September and NOT working on this. So August or October.
Thank you very much, I appreciate your time and attention. I’ll call you this week, and we can schedule a time.
@endlessfix I looked at that blade file you and Garry were testing with and discovered there is something going on with where your drawn entities are seen in Z. After I saw that in the blade file I returned to the turbine file and could see the same thing. The weird part is you can’t see this issue visually.
The only way I could see it was to export both the blade and turbine as you originally created them out of SU 2020 using the native export DXF routine. I used the 3d export with faces only.
When I looked at each entity in Turbocad I could see items off as little as .0001 and as large as 11". Visually you can’t see this in Tcad either. In Turbocad I can grab all entities as a selection set and put them back to Z 0. I also noticed some entities had line thickness so I set those to 0 also.
When I re-import these repaired DXF back into SU using the native SU import routine, then I can edit them or go through the normal procedure required to group individual entities as SimpleDXF requires and then both the blade and turbine export properly. I did not have to recreate any of your original line or arc segments in SU. Only had to correct that Z position value and had to do that in Tcad.
Here’s a PDF with screen grabs from Turbocad that show this issue with items being off z zero.
Z-OffExamples.pdf (145.6 KB)
Maybe @Anssi can look at these dxfs and help us understand why those z position values are off but not visually off. There is an unexploded version in this zip along with one that has been exploded down to the entity level.
Blade cut file SU Export.zip (60.3 KB)
The plot thickens! I did export the blade eventually after re drawing it but I’ll go back to the test file and investigate this. Most of these files start as part of a large complex model of the entire assembly where they are modeled in place. Then I copy paste a given part out of the master model into a fresh file where I clean it up and arrange the proper nesting for export. I’m totally ready to believe there are some ghosts in the machine on this process. That logic makes sense with my experience of tracking down individual arcs and searching out the problem, somehow I’m clearing the bad Z data when I redraw specific nodes. 11” off, but invisible? Weird. Interesting, I’m going to check my process steps again and try to imagine where I might be introducing this.
Thanks for spending your time digging into this. If you’re anything like me an unsolved mysterious problem is kind of irresistible, I just can’t let it go. But I still really appreciate you writing up your findings and explaining it all so well. Gary @gkernan who authored the excellent Simple DXF extension for those following along has also been very responsive and generous with his support and time.
Excellent sleuthing, this is great info. Perhaps the warping is below the SU floating point accuracy tolerance so does not register in SU, but is present in the Arc data. I’ll revisit the creation method for how this could have been introduced. Would your flatten button solve this, or that only rotates the completed plane? I wonder if Eneroths flatten to plane would effect these data points. More to investigate. Thanks!
My flatten button is restricted to x number of decimal points. I was going to look into that
0.00000001
Cool. Did you flatten that using the simple dxf button, or other method?
