18 Replies Latest reply on Aug 5, 2017 5:21 PM by Joel Rapoport

    cant make a smooth surface

    Joel Rapoport

      hello all,

       

      im working on a machine design which is very curvy.

      im trying to patch an area with a surface in a way that will be completely smooth.

      i have tried all the surfacing methods that i know and i cant seem to get a smooth result.

      here is the area:

      01.jpg

      here i tried to surface fill this area and the problems i get:

      02.jpg

      here is a furface loft and its problems:

      03.jpg

      and lastly, here is a surface boundry and its problems:

      04.jpg

      so you can imagine that i am in a problem here and not sure how to continue.

      maybe the surrounding areas are the problem?

      i know solidworks is very limited in good surfacing solutions but i have been working on solidworks surfaces for years now and was able to always find solutions to such problems.

      i am not looking for a perfect C3 (i think they call it) surface like cars, just a smooth tangent transition that will not show the lines- this is for a high pressure injection molded part that will be mass produced.

      by the way, im working on SW2016.

       

      any help will be great guys,

      thanks in advance,

      joel

        • Re: cant make a smooth surface
          Joel Rapoport

          the weird thing is that with zebra stripes it shown the surfaces to look ok, but they look bad in shaded view

          05.jpg

          • Re: cant make a smooth surface
            Joel Rapoport

            john- these are the profiles and guide curves to the loft and boundary trials:

            06.jpg

             

            J- yes i guess after texturing the mold it will look better, but at that point you have no control of the outcome, and if it will not remove the problem area completely i will be in a problem. anyway i try to give out as perfect a model that i can, and i am not pleased with this result...

             

            joel

              • Re: cant make a smooth surface
                Paul Salvador

                Joel,.. can you share/export just the boundary surfaces?.. (trim away what is not needed and copy/zero offset).. and save the selected offset as a parasolid (native).

                  • Re: cant make a smooth surface
                    Joel Rapoport

                    Paul thats a good idea.

                    im attaching the latest update that i made. it is better then before but still not perfect:

                     

                    link

                     

                    thanks

                    joel

                      • Re: cant make a smooth surface
                        Paul Salvador

                        Hey Joel,... looking at it.. yeah, it's not perfect but the patch is not bad either... I think the surface below the patch is worse if the finish is chrome, imho..

                        ..not sure what material/process/finish will be used but for the most part.. it's not terrible.

                        dx 1.pngdx 2.png

                          • Re: cant make a smooth surface
                            Joel Rapoport

                            the part is just going to be white with a delicate sand texture

                              • Re: cant make a smooth surface
                                Mark Landsaat

                                If the part will have a small texture to it, you should be in great shape. Surface discontinuity is mostly visible on smooth shiny parts. As soon as you ad a texture to the part the light will be so refracted that you will not be able to pick up small imperfections.

                                 

                                Aside from this, the computer exaggerates the discontinuity. Of course we all try to build perfect surfaces, but I believe I read somewhere that the human eye has difficulty picking up tangency errors smaller than 1 degree in real life. One of the checks I use before submitting parts is the deviation analysis tool to check edge tangency errors. As long as I'm below 1 degree, I'm good.

                                 

                                Also, SWX is using a mesh to display parts in shaded mode. If the display mesh is too coarse the model will look bad even if the actual surface quality is good. If you are evaluating surface transitions, make sure to crank up the image quality setting under the document properties. This will produce a more accurate display mesh.

                                Deviation.JPG

                      • Re: cant make a smooth surface
                        Richard Gergely

                        I just wonder if tangency on curves set to certain side faces in loft may give a better out come. This probably has been tried but it's worth still pointing out.

                         

                        Sometimes you need to look a bit further and it may be necessary to remodel the adjoining faces to get a better outcome - leaving cleaner edges and better tangencies. Been down this road many times on automotive stuff it's a pain.

                        • Re: cant make a smooth surface
                          Joel Rapoport

                          MARK- i just tried out the deviation analysis tool (for the first time). i got a max result of 0.12 so i guess i should be fine...?

                          Untitled-1.jpg

                          never tried that tool before. i dont know why there is no tool like it that will give you the deviation on all the surface and not just on the edges (how am i sure that there isn't a small crease in the surface that i cant see?).

                          anyway, as i wrote before, the part will get a gentle "sand" surface (dont have the exact mold-tech number, we use a different catalog over here). my problem is that before you get the texture, in T0-T1, you get a smooth part which is not super glossy but can still show some problems with the surfaces if you have any, and its difficult to be sure sometimes that the texture will remove the problems away. its very difficult in my experience to judge if you really have a problem that will show in the part or not (that also depends on the quality of your manufacturer).

                          by the way, of course my settings in image quality are very high (the most before getting into the red area).

                           

                          RICHARD- yes i have tried all the different options in the loft and boundary features. changing between the profiles and guide curves, and trying out tangent to face and curvature to face on all. also tried to do some adjoining faces from scratch to get better results.

                          luckily for me i dont need to get as good results that are needed in the automotive industry, but still im pretty frustrated from solidworks and how hard it is to get smooth results here (we are not working in 1998, this is 2017, and i dont see any reason why solidworks hasent found a way to get better results in surfacing).

                          for me as an industrial designer, surfacing is my major tool. its the way i model my parts and most of my time i work in surfacing related features. and i havent seen any serious improvements in this area for a long time from SW....

                           

                          anyway, thanks guys for your help....

                          joel

                            • Re: cant make a smooth surface
                              Mark Landsaat

                              Well... I can't make the call for you, at the end of the day it's a judgement call. But there are several tools at your disposal to evaluate surface qualtiy They can all help to make a decision.

                               

                              -Zebra stripes. The stripes should be smooth with good flow. A change in the flow indicates a change in curvature. Unless this is intended, it's usually a minor defect in the surface.

                              -Deviation analysis. This is a somewhat localized tool since it only evaluates the edge condition. But it's a good tool to get some numbers regarding surface transition. It does not give information regarding G2 continuity though.

                              -Face Curves with curvature combs turned on. This one is tedious but it has good information. tools/sketch tools/face curves. in this command create a dense grid of extracted face curves. You can turn on curvature combs for each 3D sketch individually so you can evaluate a small section of the surface. This is great for localized detail. Beware it generates a bunch of 3D sketches that you will have to delete afterwards. But if you are trying to fix a small area I find it can be helpful.

                              -Right Click on the face and select Surface Curvature Combs. If you increase the mesh density it will generate more curvature combs for the surface. This is an automated process of the Face Curves one, but all curvature combs are displayed at the same time and the image can get really busy if the mesh density is high.

                               

                              None of these are perfect, but they can sure help making the judgement call. For my work, if the Zebra stripes behave reasonable well, read smooth. and the edge condition is below a 1 degree tangency error I'm pretty happy in SWX

                               

                              By the way I totally agree that SWX is completely ignoring surfacing tools. Interestingly enough, they use the Parasolid kernel. this is the same kernel as NX, one of the best parametric surfacing packages in the world. Clearly the modeling kernel is not what's holding SWX back. My guess is that DS simply doesn't allow for SWX surfacing to become better because it would become a competitor to Catia.

                              zebra_SWX.JPG

                                • Re: cant make a smooth surface
                                  Joel Rapoport

                                  thanks mark for your help.

                                  i tried out surface curvature combs (didnt know them before...), and they can give some indication.

                                  my problem is that the lines that it uses get skewed in the tangent surfaces.

                                  instead of the lines going on x and y through all the surfaces, they bend with every surface.

                                  in this situation i cant even see if the surfaces are tangent to the others.

                                  do you have any suggestion?

                                   

                                  thanks again,

                                  joel

                                  Untitled-2.jpg

                                    • Re: cant make a smooth surface
                                      Mark Landsaat

                                      Hi Joel,

                                       

                                      This effect is caused due to isocurves of the neighboring surfaces not lining up with each other. Consequently this is most likely also the reason you have some tangency/flow issues in the area. Here's where it gets tricky with Solidworks. We have no direct control over the isocurves and we can't see them. This makes it difficult to judge whether a surface is good or not.

                                       

                                      You can preview the isocurves upon surface creation. If you turn on Mesh Preview it will show you the isocurves for the surface it will create. But this can only be seen in the preview and you cannot run any type of analysis on it. With that said the goal is always to have an orderly structure for the isocurves. The closer you are to a "square" layout the better.

                                       

                                      It is not always possible to have isocurves line-up due to the fact that we work with four sided patches to achieve curved shapes. Anytime we use trimmed surfaces of any sort you are pretty much guaranteed that the isocurves don't match. There are modeling best practices that improve your chances of getting flow across the boundary, but it's very difficult to control this in SWX because, A; we can't control the degree of the output surface and B; we have no control over the controlpoint structure of the surface. In SWX I usually try a variety of tools to see what type of surface is generated and I will pick the one I believe to be best.

                                      mesh preview.JPGUV_CURVES.JPG

                                        • Re: cant make a smooth surface
                                          Joel Rapoport

                                          ok mark... thanks a lot i have learnt a lot from you the past few days.

                                          so what i decided to do in the end because i am still not sure of the surfaces, is to make a bunch of split lines going across the "bad" area.

                                          then i did a deviation analysis for each line (as you suggested before). to each line i got a max deviation of 0.04degrees- so i guess i should be fine.

                                          cant be sure untill the T0 gets here. i dont even think the prototype will have such high quality to show this area as it shown in SW.

                                          but as you said i guess SW does show us thing that might not be there in reality.

                                          here is a photoshop compasite of the deviation analysis i did on the lines:

                                          Untitled-3.jpg

                                            • Re: cant make a smooth surface
                                              Mark Landsaat

                                              Hi Joel,

                                               

                                              The split lines is a great idea and you can take this one step further. Start a 3D sketch and create a fitspline using the splitlines  going across the surface boundaries. Once you have the fitspline you can run curvature combs on this. It will give you the curvature transition between the surfaces. That can be very useful as well.

                                              Curvature_Comb.JPG

                                        • Re: cant make a smooth surface
                                          Mason Morton

                                          About the face curves, if you start a 3D sketch first and then add face curves, they will all be added to a single 3D sketch as opposed to separate sketches for each curve. A lot of good information in this post, Mark!