Lines not 100% enclosing an area and still a revolve or extrusion is possible????

edward_omagbemi

This is a really weird question:

So I'm new with Onshape and I watch videos and start sketching on an Ipad.

Everything is fine. I create a simple shape to revolve into a cone.
I create another shape to remove a rectangular section from the cone. Easy. Awesome.

I then see on closer inspection on desktop that the rendering of the rectangular section is not 100%

I zoom in as much as I can and discover that the endpoints of the lines that form the shape do not 100% touch each other.
I rectify the situation by defining constraints for every single line endpoint that reflect design intent.

Now I'm scratching my head and asking myself how on earth a shape can be defined if the enclosing lines do not 100% enclose.

Is there a "Closeness" error - factor implemented in Onshape that I need to know about?
Is it maybe just a mobile bug and I'm better off working on Desktop and using Mobile only for viewing,...

What is the best method to check coincidence while designing? I have not come across any audit tool that checks for possible issues.

NeilCooke

Are you actually having issues or just curious? As long as the profile is shaded, Onshape is happy. What you might be seeing is a limitation of the graphics display rather than the geometry definition. 

edward_omagbemi

NeilCooke said:

Are you actually having issues or just curious?. 

Issues. The face of the cutout wasn’t aligning properly with the cone.

I must add that I transformed the sketch and didn’t think of needing to define the constraints 100%.

I was expecting an auto-constraint feature when selecting multiple instances and doing a transform.

After adding the correct constraints, everything aligned even in maximum zoom.

 I’m more concerned about working on bigger projects where something like this can go unnoticed until you manufacture and assemble.

That’s why I’m picking simple models to learn.

tim_hess427

@edward_omagbemi - If you were able to do something without a closed profile, that would be a bug. But that's such a core part of the app that I think there is likely some other explanation. Perhaps some duplicate geometry or something like that?

Could you share the version of the document where you successfully created profiles without a closed section? 

edward_omagbemi

tim_hess427 said:

@edward_omagbemi - If you were able to do something without a closed profile, that would be a bug. But that's such a core part of the app that I think there is likely some other explanation. Perhaps some duplicate geometry or something like that?

Could you share the version of the document where you successfully created profiles without a closed section? 

I tried to find the point in time where I found the inconsistencies but I had to give up. Too many changes and no versioning. I've just been playing around a lot.

I'll just continue sketching on the IPad and check for these inconsistencies. If I find them again, I'll version the status and post it again.

tim_hess427

Ok - Like I said, I think there's a good chance there was just some duplicate geometry so that there was an open profile on top of a closed profile, either in the same sketch or a different one on the same plane. 

There isn't any "closeness" factor when it comes to coincident points and there shouldn't be any different between mobile/desktop as all of the calculations are done in the cloud. 

The only thing along those lines that you might run into is tessellation quality, where curved lines and surfaces are displayed as a bunch of straight light segments when you zoom in really close, but that's just a rendering thing. You can find more discussion about that here on the forums as well.