Legitimate Sketchup glitch?


I’ve spent allot of time trying to solve this problem and am starting to think there’s no solution.

I’m trying to carve a 1/4 circle out of the long edge of a long rectangular box. I need the 1/4 circle to turn, in place, 90 degrees at either end of the rectangle. Oddly enough Sketchup doesn’t seem to be able to resolve something in the geometry at those turn in place corners. It should work using the follow me tool, but it creates a bit of a mess. When I clean it up manually and get it looking perfect and then go to save, Sketchup asks if I want to fix the problems. When it ‘fixes’ the problems it erases several faces. I’ve tried increasing the number of segments in my arc and changing the scale as well as maxing out the precision of the angles the model will recognize.

I’ve loaded several images and the file to a dropbox location if any of the gurus wants to take a stab at this to see if they can find something I am missing. Thanks in advance for your help!

pictures of the problem and the actual file



Not specifically a glitch. More like just a limitation due to the way the software is written. Part of what I see is that you are butting heads with SketchUp’s tiny face thing. You have edges that are just too short. The edges at the top of the missing area measure 0.00111" long. Considering the coarse precision you have selected for your model, they show at ~0" long.

At the point where the “knees” are there’s 0.00028" between them.

Increasing the number of segments in the arc makes it worse and changing the precision of angles only affects the display of the angle dimensions but doesn’t do anything for you to change this issue.

How much are you scaling up? Most likely, not enough.

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I scaled up by 100 and still have the same problem.



Not enough for this.



There are some shapes that you just can’t scale out of the problem.
The tiny angles are what get you.
You may need to rethink the design.

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Really? But if I scale it up even more, eventually it will let me do this? Would changing the precision of my model help me or just give me more accurate measurements?



It seems like a curve should be able to extrude a 90 degree turn in place. There must be many times when people need to do that. This is where I would use my router on a piece of wood. the 1/4 circle bit follows the inside of a frame to make this cut.



So, I scaled up by 1000 this time and still have the problem. Box must be right. It looks like there is no way to draw this simple shape?!



The precision setting only affects the display.

Scaled 1000x it works just fine. I’m using what someone called “The Dave Method”.



I’m not disagreeing with you, and I haven’t looked at your model. But from the image Dave put up it reminds me of trying to use too many spokes in a wheel, or a fan (the hand type) you just can’t fit all the edges in.

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You must have done something differently than me. I tried scaling up by 1000 and then fixing one face and saving it. When saving it, it just reverted back.



I redid the entire profile using your path and profile shape.

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I think I know what you mean, I will try it now…



Out of curiosity, exactly how would you make this if you were making it in wood?



@DaveR raises a valid point. Most of the time a woodworker would use either a miter or a cope to carry a profile around a corner like that. Any router bit will leave a non-zero radius at the bottom of the corner, so you’d have to resort to hand-carving to get the shape you show.



I’m not sure how familiar you are with wood working tools, but if you use a router that has a bit with the blade shape of the cut I want (the arc plus the vertical segment at the top of the arc) you can easily do it. The router bit spins in a circle and has a wheel at the bottom of it that doesn’t spin but acts as a guide and keeps it exactly where you want it. To get it to turn 90 degrees in place you would have another piece of wood (not shown in my pictures) joining the first at 90 degrees. Essentially you would move the bit all the way around the inside of something like a picture frame to do it.



No offense intended, but I suggest you try what you describe. The router will leave a curve at the bottom of the corner with the radius of the router bit. It simply can’t cut a zero radius.



It could be I’m not understanding you, but I have been making this shape for years as part of a business selling a product online.

a similar bit, though the vertical part of the blade on mine is perpendicular.



The rotational nature of a router means there must be a radius in the corner, unless you join two profile as a mitre.

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Hmm, I am tempted to go open a package I was about to ship to check. It could be that I just haven’t looked that closely at it to notice this. I would think that the blade would cut away precisely the right amount of wood at the corner when it is turning to get the blade close enough to do it. Now I really do have to go check. So far I am unable to recreate whatever DaveR did to make it work on the larger scale.

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