18 Replies Latest reply on Feb 4, 2011 5:24 PM by Doug Pryor

    Thicken surface with small radii

    Ken Milam
      Hi, I have a surface that has some very small radii.  I'd like to thicken the inside of this surface .25" into the part (towards the inside/backside of the part).   The thickened inside surface is not critical, and the thickened surface does not need to offset the critical shown surface .25" in every location.  Rather, what I'd like to do is create a "best fit" surface that enables a minimum wall thickness of .25" (understanding that the wall thickness will be thicker in some locations on account of various face intersections).  What is the best way to approach this task?  Thanks.ThickenSurfaceExample.jpg
        • Re: Thicken surface with small radii
          Lenny Bucholz
          yes! you pretty much answered your own question, but here is a trick i try first. using surfaces, rmb on one of the faces and select tangency, then try to offset the surface .25, if it works great, cool, if not you may have to make a configuration with less fillets on it, then try it again. then you can either use replace face or delete the faces and trim it together then thicken it.
          • Re: Thicken surface with small radii
            Charles Culp

            Ken,

             

            There are two ways that I attack situations like this.

             

            1. Go back and delete (or more likely, suppress) all the fillets and radii that are too small. Do an offset/thicken/shell. Then add those fillets/radii after the offset/shell/thicken command. This is my preferred method, and if you are designing it with this intent, will end up with better results because you can anticipate the small radii, and just create them appropriately after the thicken command.

             

            2. Often though, this isn't feasable. Either because the small radii are part of more complex curves, or because you can't just "go back" and suppress them. Then, my suggestion is to do an offset surface, with distance 0. Then hide the original surface/solid body. Now you should be left with a new surface body just like the original. Then you can add fillets on top of the old ones, using the "face fillet" command. Face fillet will actually build over existing fillets, just select the two faces on either side, and make a fillet larger than your offset distance (and give yourself some buffer room). If you run into any tricky spots, you can add as many face fillets as you can, then blow away the existing faces with delete face, and add a filled surface with tangent edges on all sides.

             

            Now that you have that, you need to offset it. Hide/delete the modified body (the one you added all the face fillets to). Now you just have to combine this with the original surface. You will probably have to create the "edges" between the two surface bodies now. This is often accomplished by creating a sketch (probably a 3D Sketch) along the outer edge of the new offset surface, and using surface extrude to connect it the distance of the offset. Now use the "knit" feature to knit the original surface with the new copied one, and you will have a solid piece.

            • Re: Thicken surface with small radii
              Jerry Steiger

              Ken,

               

              I'm going to ask a really obvious, probably stupid, question here. Did you try just offsetting your surfaces by .25"? Sometimes SolidWorks is able to offset surfaces which have radii smaller than the offset. It is especially good at it if a given radius surface will completely disappear and especially bad at it if a surface will offset to a surface through part of its length and to an edge through the rest. It looks a number of your fillets do the latter, so I doubt that your surfaces will offset, but it is worth a try.

               

              Jerry Steiger

                • Re: Thicken surface with small radii
                  Ken Milam

                  Charles,

                  Thanks for your answer and detail.  The part file that I received was a Step file (attached), and I am sorry for not specifying this earlier in my original post.  I tried your suggestions, but it seems as though they were intended for a native SW file (I couldn't get the filet function work on my copied surface after I deleted the offending fillets).

                   

                  I've attached my part model for reference.  Again, I need to keep the five surfaces (top, right, bottom, left, and front faces shown in the earlier enclosed pic) and create a wall thickness of .25".

                   

                   

                  Thanks  

                  • Re: Thicken surface with small radii
                    Ken Milam
                    Yeah, Jerry, I gave it a try.  Being somewhat of a newbie to SW, I tried it 7 or 8 times all awhile expecting different results.  No such luck.
                      • Re: Thicken surface with small radii
                        Lenny Bucholz

                        Ken,

                         

                         

                        been messing with it and you have a cluster! i looked at the step file and it came from SW2009 so i'd ask your client for the SW file.

                          • Re: Thicken surface with small radii
                            Ken Milam
                            I think the native file w/ the instructions listed above should get me what I want.  Thanks to everyone for their input.  This was my first foray into the SW discussion group and it's been very helpful.  I'm sure I'll be back again.  
                              • Re: Thicken surface with small radii
                                Jerry Steiger

                                Ken,

                                 

                                Life should be better if you get the SolidWorks original, but if you can't, you can still work with the STEP file. I had a look at your file last night and it is not going to be easy. Almost all of your radii are less than .25", so you will have a lot of radii to remove. You will often find that you can't remove a complete set of fillets in one go. In that case, you can sometimes remove a partial set (having the preview turned on helps to spot such partial sets), then the rest or another partial set. The trickiest part will be the little nubs that stick up above the large notches. In my quick try, I wasn't able to do much with them. I also couldn't remove the center fillet, but I was able to use the Face Fillet that Charles suggested.

                                 

                                A quick way to generate the surfaces that you need is to use the delete face command (with neither fill nor patch set) on the faces you don't need (all the back side faces). That will turn your solid body into a surface body. If you don't want to destroy your solid body, just make a copy of it to run the delete face on.

                                 

                                One approach I have used is to offset all of the surfaces that will offset in sets that will allow you to extend and trim and fillet or face fillet between the sets.

                                 

                                Sometimes you will find that you can't offset a face in a set, even though it seems to have a large enough radius, often times even though a seemingly symmetric face will offset. Try leaving it out of the set and offsetting it by itself, which it may very well do, then knit it to the orginal set. Sometimes it works, sometimes it doesn't. (As I recall, surfaces are fussier than solids when it comes to fillets. Other than face fillets, I think you have to untrim or extend the surfaces till they intersect before you can fillet them.)

                                 

                                Another technique that I have used in the past is to offset the surface as far as possible (probably .175" in your case), trim out the problem areas, then extend and fillet them (or face fillet them without the trim), and then offset the rest of the way.

                                 

                                Jerry Steiger

                        • Re: Thicken surface with small radii
                          Doug Pryor

                          OK, I have a similar problem but a slighly different situation.  I have an imported file that was originally laser scanned from an organic, 3D relief.  I need to thicken the imported surface to make a wall stock model for injection molding.  The backside does not have to follow the original contour exact, but just close.  The laser picked up all of the detail so there are quite a few small radii.  There are over 5,000 faces in the original data so removing the offending surfaces would be a chore, to say the least!  Any recommendations?  Here is a sample section and the same section attached.

                          contour.JPG

                            • Re: Thicken surface with small radii
                              Jerry Steiger

                              Doug,

                               

                              I don't have 2011 loaded so I couldn't look at the actual sample file. I'm also not an expert on importing. Depending on the quality of the imported surfaces, your job will be either incredibly tedious and painful or impossible.

                               

                              If the imported part is good, then you can use the radius of curvature display to spot the surfaces with radii that are too tight for your wall thickness. Offset the rest of the faces. Use Fill Surface to fill in the missing faces. Most likely it won't go that easily. You will discover faces that don't appear to have tight radii that still won't offset, so finding the faces that will offset can become quite a chore. Doing small patches may be the only way forward, followed by lots of knitting and filling.

                               

                              If the imported part is not good, the above becomes almost impossible. Run Check Part on the body. Repair faces if you can. If it has General Faults, you may be out of luck. In that case, it may show you "bad" faces, but once you delete them, new "bad" faces will appear.

                               

                              If the imported part is bad, you might be able to talk the people who gave it to you into generating a better version.

                               

                              Jerry Steiger

                              • Re: Thicken surface with small radii
                                Charles Culp

                                I would do this by offsetting faces by hand. Find the faces that are causing the problems by going to Tools>Check... Then select the option for small edges and minimum radius of curvature.

                                 

                                Then, select all the faces that do NOT have too small a radius of curvature, and use Insert>Surface>Offset, and offset those.  Then you will have to re-create the tight faces manually, how you do that depends on your design intent. A couple options include:

                                Just filling in the gap with the filled surface tool or boundary surface tool (keeping tangency to existing edges)

                                Offsetting that face separately, then fixing up the edges

                                 

                                I will download your part, and if I have time see what I can do.

                                  • Re: Thicken surface with small radii
                                    Charles Culp

                                    Bummer. I checked into your part, and that's going to be a tough one. That is a very irregular surface, and most of the faces are going to cause problems. You really need to have this cleaned up better with the scanning software (higher normalization). You might still have problems, but that depends on the wall thickness you are looking for. What is your nominal wall thickness?

                                     

                                    I will have to think for a while if there is a better way to do this given the existing data, but the best I can come up with involves basically recreating it by hand.

                                     

                                    I converted it to a solid body, and used shell. This gives good Error Diagnostics. I just used split to analyze 1/20 of the model (the whole thing takes way too long), and here is what I got. All the faces with the Isoparams showing (the gray lines) have possible problems:

                                    VeryComplexThicken.png