13 Replies Latest reply on Jan 24, 2012 3:42 PM by Jerry Steiger

    surface offset/cut help

    Mike Young

      Hi guys,

       

      I'm not totally new to solidworks but I never really use many of its advanced features, usually simple sketches and assemblies and I'm hoping you guys can help me out with this one.

       

      What I have is a part from a customer that they modeled in catia, saved in STP and I opened in solidworks and it's all surfaces, no solid modeling that I can see anyways. What I need to do with this part is make a nest for it/remove its profile from a solid block. We had a previous project like this but the customer actually gave me a model of a block with its profile removed and I just built off of that block... this time we do not have that option. From what I could tell it looks like they did some type of surface offset to create a profile and then a surface cut from the solidbody but I cant quite figure it out and feel as though I'm missing a key step or two. If you guys could help me out or point me in the right direction that would be awesome!

        • Re: surface offset/cut help
          Mike Price

          Hi Mike,

           

          Are there a lot of surfaces in the model tree?  Did you run import diagnostics on the part when importing?  Are you wanting the part to be a solid body so that you can perform a combine feature?

           

          This may not be the case, but all CAD packages can have issues with importing geometry that was exported as a solid, as you probably know.

           

          Can you answer the questions and provide a screenshot of a problem area so that we could have more insight?

           

          Thanks,

           

          Mike

            • Re: surface offset/cut help
              Mike Young

              I do not recall there beeing many surfaces in the model tree, I did run import diagnostics, and I'm not sure if I want it to be a solid or not. The part seems to have imported fine and thats not the problem I do not think, I just dont know the steps it takes to use this imported parts face/profile/shape and remove it from a solid body part. Basically a mold... but I dont quite think the mold feature will work with this type of part

               

              and unfortunately I cannot post a screen shot... I do not have access to my work pc from home. I am trying to figure out some options to try when I get back to the office monday

                • Re: surface offset/cut help
                  Mike Price

                  If import diagnostics did not find any faulty faces that is a good start.  Does this have a "watertight" set of surfaces or are there surfaces that are open on the edges that don't line up with other surfaces?

                   

                  You said you don't know whether or not the part is supposed to be a solid or if it a makeup of surfaces.  Can you elaborate why?

                   

                  Without seeing it, what you'll have to do if you want to pocket out a block with this part if you are going to keep it a surface is build a surface that would be knitted with the existing surface(s).  This seemless (no gaps and knitted) surface could be used to cut an extruded block or some other type of solid body.  However, the surface has to extend to/slightly beyond the solid body you want to cut.  For example if you have a 2 x 4 block you have to use a surface to cut through the 2 x 4 face that is at least 2 x 4.  In other words if you are going to cut with a surface, the surface edge cannot terminate within the solid body you'd like to cut.

                   

                  I hope this didn't confuse you.

              • Re: surface offset/cut help
                JOHN GEORGE

                Mike Young,

                 

                Can you please post the original file or some pictures to get a clear idea of what you really looking for.

                  • Re: surface offset/cut help
                    Mike Young

                    cannot post a pic at least until  monday and maybe not even then... this is a customer product and they may not appreciate it being on the net. I dont know how else to describe it other than I have an imported part with lots of curved surfaces (imagine a car interior component ) and I need to more or less make a mold of this piece. I cannot use the mold function for one of two reasons... I am not familiar enough or the part is not a solid body. I need to make a carrier for this piece so that it can be dropped and held in to place as it travels down the line.

                     

                    I am not sure I would classify myself as even an intermiediate solidworks user. Most of my job is doing faily simple rack designs and electrical panel layouts; occasionally I've done some bed of nails fixturing for PCBs.

                     

                    Thanks guys

                      • Re: surface offset/cut help
                        Mike Price

                        Mike,

                         

                        Take a look at this dummy part and pick it apart to get an idea of how you could extrude a solid up to a surface.  If you roll back the part before the knit, you'll see that the surface boundaries are all blue.  This means that you cannot extrude to the surface.  Once you roll beyond the knit, you'll see that you have a surface that is seamless and can be extruded to.

                         

                        If you have to take a suface body and create a mold for that surface body to be able to subtract out its geometry in a cradle, you are going to need to do some work.  If you haven't done anything like that, you are about to have some fun

                         

                        If I'm way off base, get back to the forum on Monday when you can post images for a better explanation and you'll be helped out by many.

                         

                        Mike

                          • Re: surface offset/cut help
                            Mike Young

                            "If you have to take a suface body and create a mold for that surface body to be able to subtract out its geometry in a cradle, you are going to need to do some work.  If you haven't done anything like that, you are about to have some fun "

                             

                            I think this is more along the lines of what I need to do. I dont need to build up to the face, but subtract the face from a solid block. Here are a couple screen shots. I cant show the entire part but I can show a section and the tree, hopefully that helps some. I've also attached an example nest/cradle (white one) along with the base for that the customer supplied. This green base is what I'm trying to replicate with my new part. I think the green block has the steps I need in the tree... but I dont know what I need to do, at all.

                             

                            as a note, I do not need to create a nest for the entire face of the part, in the screen shot you can see it's quite complex. Really I need to get the outer edge of it, maybe about a half inch around the entire edge, and eventually the rest of the block will be cut away.

                             

                            example nest. All other pictures attached so you can see them better. Thanks guys

                            example nest.jpg

                              • Re: surface offset/cut help
                                Mike Price

                                Good morning Mike,

                                 

                                If I understand correctly, you are wanting a cradle that is pretty much a simplified volume boundary shape.

                                 

                                You are going to need to created a simplified surface do do that.  If the part were not complex, say a sphere with an indention in it and you wanted to have a spherical cradle without a positive feature that would go into the indention, depending on the geometry, you could delete/patch faces.  Your geometry looks a bit complex to do that, but I would suggest you try that feature, in case you haven't so you know a little about how it works.

                                 

                                To get a simplified boundary shape for more complex features, you can go about it a multitude of ways.  If you have a face that extends most of the surface you are trying to cradle, you can create a offset surface of that face with 0.00 being your offset dimension.  Then you could try to untrim that surface and see if it gets you anywhere.

                                 

                                Another method is to create a series of planes through your part and then create intersection curves of the surfaces you'd like to cradle on each of your planes.  You can make those curves construction curves and then create curves you need to form a cradle that would be tangent, colinear, etc. with the intersection curves.  Once you have accomplished this, you can create a boundary or lofted surface through each of your sketches and you'll have something.  I say something because this is where you may find that the surface you created is doing some unexpected things as it sweeps through the sketches.  Fixing these issues may prove to be more challenging than creating the surface initially.  Experience with this procedure helps to get you something that looks more of what you want in the shorter term......

                                 

                                Best wishes.

                                 

                                Mike

                                  • Re: surface offset/cut help
                                    Mike Young

                                    I think I may be on the right track, but again I am more or less totally unfamiliar with what I really need to do so maybe I am not...

                                     

                                    I was able to use surface offset and create a boundary, and then did a surface fill followed by a surface knit. To me, I believe this surface/part will work for my mold "functionally"... I say with quotations because this is the shape I need in the real world but I dont know if this is any help for what I need to do in solidworks. Anyways if I AM on the right track what are the steps to take this surface and subtract it from a solid block?

                                     

                                    my apologies on my total lack of knowledge. I've literally never done anything like this before. Most of my time on solidworks is spent packaging and laying things out in racks such as this. A lot of what I use is manufacturer generator models, or basic enough that I can just use the sketch tool to model things up. I have only scratched the surface of solidworks at this point

                                    racks.JPG

                                      • Re: surface offset/cut help
                                        Mike Price

                                        Hi Mike,

                                         

                                        Please lay in your cradle block into this part so I can see how you want it to set in there.

                                         

                                        Also, no apologies necessary.  Every single user of SW had to start from scratch.  Even Deepak and Scott .

                                          • Re: surface offset/cut help
                                            Mike Young

                                            Something like this where nearly all of the part is below the block. What I intend to do eventually is cut away most of the center section of the block so that the nest/cradle only captures 1-2" on the outside edge. We're going to have fingers and probes come up from the bottom and simulate a person pressing buttons. If need be its okay to have the highest edge of the part flush with the block, there will be some cut-outs for your fingers to grab it out eventually anyways. Thanks again for all your help.

                                              • Re: surface offset/cut help
                                                Mike Price

                                                Hi Mike,

                                                 

                                                See where the blue edge of the surface is above the block in some areas and not in others?  You have to get the edge of the surface above the surface of the block, otherwise SW wouldn't know how to cut with a surface.  Also, the surface that isn't shown inside the block has to be totally knitted.  There can't be any gaps or overlaps.  All the surface edges on the "submerged" surface should be black.

                                                 

                                                You don't have to go far so you can try to extend the edges of the surface (experiment with "same surface" and 'linear").

                                                 

                                                Let me know if you have any questions.

                                                 

                                                Mike

                                                • Re: surface offset/cut help
                                                  Jerry Steiger

                                                  Mike,

                                                   

                                                  Try cutting out the center section of the block before making the Cut with Surface that will cut away the rest of the surface. The less cutting you do with the knitted surface, the less possible places for something to go wrong.

                                                   

                                                  If you can get away with it, try recessing the part less in your block, so you don't have to extend any of the edges. Extending surfaces can sometimes get very twitchy.

                                                   

                                                  If you left off some of the faces to get the part that you have recessed into your block, go back and add them in, rather than trying to extend surfaces.

                                                   

                                                  Jerry Steiger