Strategy for multiple curves at corner
Strategy for multiple curves at corner
(OP)
Can anyone suggest a strategy for getting good curvature bringing these curves together? Every time I add a hard constraint (such as a guide curve for a loft, or Direction 2 for a boundary), the surfaces become wrinkled.
The whole part is a just a rectilinear box with curved edges and a slightly curved top, and flat bottom, and this model is one corner of it.
The part will be injection molded.
I've put many hours into this, including training (instructor couldn't figure it out), tutorials, books, so I think I have to ask for help now.

The whole part is a just a rectilinear box with curved edges and a slightly curved top, and flat bottom, and this model is one corner of it.
The part will be injection molded.
I've put many hours into this, including training (instructor couldn't figure it out), tutorials, books, so I think I have to ask for help now.







RE: Strategy for multiple curves at corner
Mike Halloran
Pembroke Pines, FL, USA
RE: Strategy for multiple curves at corner
If you mean apply this rule only to particularly troublesome constraining curves, then I have gone much further than that: I've completely omitted them, for example the plan view curve on the split plane. This provides a very comprehensive improvement, but can only be implemented for the first surfaces you make (because later, something else will have to align with those unconstrained edges).
RE: Strategy for multiple curves at corner
Mike Halloran
Pembroke Pines, FL, USA
RE: Strategy for multiple curves at corner
Perhaps somebody's seen this before and can be a more specific, or would like to have a try with the model (not that I want my work done for me, though).
Thanks very much for your thoughts, MH; it's reasssuring to know that I'm generally on the right track.
RE: Strategy for multiple curves at corner
RE: Strategy for multiple curves at corner
RE: Strategy for multiple curves at corner
RE: Strategy for multiple curves at corner
Or, change the Start Constraints to "None".
You are using SW 2014? I have 2015, so can't send it back to you.
Chris, CSWA
SolidWorks '15
SolidWorks Legion
RE: Strategy for multiple curves at corner
RE: Strategy for multiple curves at corner
Another purpose of the tangent is to ensure that the flattening at the 45 plane pushes out toward the more rounded front and side planes. This flattening is very easy to achieve with a file and and epoxy cast, but is the source of the problem. I don't know how to get the flattening effect without pushing the tangents.
So I tried it anyway: tangents to 0.1, apply 'corner plan' sketch as a guide, and I get distortion caused by the change from line to pline in 'corner plan' sketch. Adjusting tangents does not yield an improvement.
RE: Strategy for multiple curves at corner
Scott Baugh, CSWP
FAQ731-376: Eng-Tips.com Forum PoliciesGryphon Environmental
www.2gryphon.com
RE: Strategy for multiple curves at corner
RE: Strategy for multiple curves at corner
RE: Strategy for multiple curves at corner
Also, there is supposed to be a flattish area at 45 degrees around the corner which seems to be not present in your screenshot, as depicted in sketch 'corner top.' Imagine taking a flat file to the corner (which is what I did) and largely flattening the corner, then blending it with the file into the other two edges, which rounded, not flattened.
RE: Strategy for multiple curves at corner
My point is that the corners should probably not be built independently. If the main faces and edges are used to drive the corners, it will require less definition and get a smoother result.
RE: Strategy for multiple curves at corner
RE: Strategy for multiple curves at corner
However, this approach can only work for the first one or two surfaces (because subsequent surfaces will have to be constrained by preceding surfaces).
RE: Strategy for multiple curves at corner
RE: Strategy for multiple curves at corner
RE: Strategy for multiple curves at corner
Scott Baugh, CSWP
FAQ731-376: Eng-Tips.com Forum PoliciesGryphon Environmental
www.2gryphon.com
RE: Strategy for multiple curves at corner
A little clarification just in case: the wonky area is a fill, the final portion left over after doing the main portions of the corner. It is not a constraint. The constraints are defined by the sketches 'cross top', 'long top', 'corner top', and 'corner plan.' It is acceptable to not follow 'corner plan' precisely, but the surfaces must not go outside the corner plan.
I have achieved an excellent top (the wonky area) by sweeping 'long top' along 'cross top' but then it becomes a hard constraint (after trimming it) for the main parts of the corner. This was the approach used in the iphone tutorial, but the iphone has only a simple corner (same profile all the way around the corner).
RE: Strategy for multiple curves at corner
RE: Strategy for multiple curves at corner
Many thanks to all for participating in my puzzle!
RE: Strategy for multiple curves at corner
The profile on the 45 degree plane is meant to flatten the corner. To get that effect, tangency controls are needed there. Loft only offers tangency controls on start and end profiles, so I also modified your steps to make two lofts, with a similar outcome.
A stellar effort, though, and much appreciated!
RE: Strategy for multiple curves at corner
1. Concede that secondary constraints (boundary dir2 and loft guides) sometimes cause wrinkles.
2. In lieu of secondary constraints, use tangency controls.
3. Make two lofts, to get the tangency controls at the 45 degrees sketch.
4. Assume that there may be un-smoothness at the unconstrained edges, and be prepared to trim it. In this case, the lower edges were good, but the upper edges showed some strange curvature within 0.3mm of the edge, which would be fed into the next surface if not trimmed back to a clean portion of the surface.
5. If a secondary constraint is required (for example, the subsequent surfaces), then use the above technique to get the edges close, then add the constraint. SW must then only make minor tweaks to force the alignment.
And voila:
Many sincere thanks to all who read and thought about this.
RE: Strategy for multiple curves at corner
I hope this helps.
Thank you.
Rob Stupplebeen
OptimalDevice.com
My LinkedIn
RE: Strategy for multiple curves at corner