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How to add a sharp edge inside of a fill?
fanders
Member Posts: 7 EDU
Hi, I am making a panel for the back of a car and it is a simple fill except for a crease in the middle. This crease is making things really difficult for me since its end is within the fill. Thank you for any help! It is greatly appreciated.
My problem: I need the yellow surface fill to use the two curves within the fill as guides, precisely. This is not working because of two problems.
Some pictures. The reference, pencil drawing shows the piece I am trying to make with the crease.
Note: I will thicken the grey surface to make the panel. The selected lines are where the crease is supposed to go.
My problem: I need the yellow surface fill to use the two curves within the fill as guides, precisely. This is not working because of two problems.
- The surface fill bulges out, back, at the sharp corner, where the selected guides start. This "bulge" is causing the surface fill to be unable to follow the guides precisely. How can I prevent this bulge?
- The surface fill is trying to make round, smooth connections between the edges. This is fine, except for the crease, where it needs to be a sharp edge, not smoothed out. I ran out of ideas for how to fill everything but keep the crease sharp, any suggestions?
Some pictures. The reference, pencil drawing shows the piece I am trying to make with the crease.
Note: I will thicken the grey surface to make the panel. The selected lines are where the crease is supposed to go.
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Best Answer
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fanders
Member Posts: 7 EDU
I got to it earlier than I thought.
https://cad.onshape.com/documents/9acf4342f11a13fb06434825/w/be223a8b05b5be2e883d0dff/e/c8d31120642b45f64ee35ebb
I split the panel into five fills instead of just one. The result is definitely in the right direction and I am okay with it for now, but there is room for improvement:
I cannot get the fills to successfully match curvature continuities (they won't at all) or completely match tangent continuities (they will try and it will look better, but they will not completely match tangent. This is what I did). I do not know if it is just a limitation of Onshape or if there is a better way to make this panel that would result in smooth transitions.
I exported the a .dae to blender and rendered it to make the unwanted transitions between fills more obvious.
0
Answers
I would suggest trying a different approach with this model. Building a complex surface with a single feature can be problematic.
Fill surface bulging:
The curves are meeting at a pinch point and is causing the fill surface to bulge. If the curves were not changing direction so suddenly, the result would be different.
A common method for designing this type of feature would be to construct two or more surfaces, split the surfaces to form the feature and blend the surfaces together afterwards. This would require several surfaces to be constructed.
The fill surface can be controlled by guides to help influence the shape of the surface. For example, a vertex, sketch curve or 3D curve. I don't see guides correcting this particular issue, but it may help you in the future.
Before adding guides
After adding guides
Please take a look at the Advanced Part and Surfacing Design learning pathway in the learning center. This covers several workflows and techniques that may be able to help you.
https://learn.onshape.com/learn/learning-path/advanced-part-and-surfacing-design
Let us know how you make out and good luck!
It seems I have picked one of the hardest shapes to model 😀.
https://cad.onshape.com/documents/9acf4342f11a13fb06434825/w/be223a8b05b5be2e883d0dff/e/c8d31120642b45f64ee35ebb
I split the panel into five fills instead of just one. The result is definitely in the right direction and I am okay with it for now, but there is room for improvement:
I cannot get the fills to successfully match curvature continuities (they won't at all) or completely match tangent continuities (they will try and it will look better, but they will not completely match tangent. This is what I did). I do not know if it is just a limitation of Onshape or if there is a better way to make this panel that would result in smooth transitions.
I exported the a .dae to blender and rendered it to make the unwanted transitions between fills more obvious.
The curves used to construct this wireframe meet at a sharp point and will prevent any type of surface continuity except for G0 or connected. The curves must be properly constrained or the surfaces will fail to match the proper continuity.
The introduction to curves course explains curves and continuity in detail.
https://learn.onshape.com/learn/course/understanding-curves/introduction-to-curves/introduction-to-curves
I will take a look at the course you suggested. Though, all my curves and everything are constrained and , I hope, properly constrained.
@mahir
I'll try rounded the corners a little to test if that helps. I doubt this would ever be manufactured it is simply for concept purposes. The diffuser would be an absolute nightmare to manufacture after all
I tried making the points into small radii instead and it made it too difficult for Onshape to fill, without splitting the panel into more pieces. I didn't want to make more work for something that was good enough, so I left it how I had it above.