10 Replies Latest reply on Aug 8, 2016 11:55 AM by Damien Long

    Spiral cut tube

    Damien Long

      I'm relatively new to SolidWorks, and was hoping someone could help me with a part I'm trying to model.  It's a long tube with a repeating pattern of cut and uncut sections along a helical/spiral path per JPEG attached.  For example the cut-section might be 45% of a rotation, then an uncut section of 10% of a rotation, and the pattern repeating and repeating. 

      Part.JPG

      I've spent a lot of time at this with no luck and am tearing my hair out.  The closest I got was to wrap a sketch to get the first cut, then using "curved pattern" to get this first cut to repeat along a spiral path.  This worked up to about 100 instances, but any more than that and SW just hung on me, wouldn't solve (see sldprt attached).  Wondering if anyone has any ideas how to do this efficiently, as SW seems to really struggle with the approach I've tried.  Thanks.

        • Re: Spiral cut tube
          John Stoltzfus

          This is what I did in the past....

           

          Make a sheet metal split tube and un-fold it and draw your slits and then re-fold

           

           

            • Re: Spiral cut tube
              Damien Long

              Thanks John S.  Cosmetically this look great, but it leaves a split line along the length of the tube.  I want to use an IGES of the part to laser-cut this pattern into a tube, but part won't function if there's a full-length split line on the tube.  Even if the split is very thin in the solid model, the laser will still try to cut it.  I suppose I could extrude back through the gap, but then some of the slots would be in two parts.  Not ideal, but unless someone knows a better way, I guess I'll have to make this work.  Thanks.

                • Re: Spiral cut tube
                  John Stoltzfus

                  I would set it up in two configurations, one the part development and the other the laser cutting operation.  It is a little more work that way but you'll have good control of the part. 

                   

                  This part looks very similar to a design that I developed in the late 1990's for a variable pitch live bottom feeder, just curious on the application

                    • Re: Spiral cut tube
                      Damien Long

                      I found a way that seems to work well.  I sketched the cut that I want onto a plane tangential to the tube, then I linear patterned the sketch (I had about 1000 instances); then a straightforward deboss wrap onto the tube --> didn't seem to have any problem calculating this way. This avoids the seam issue with sheet-metal function.  Also runs much more efficiently than my previous attempt of wrapping a single cut onto the tube surface and then using a curve driven pattern to get the cut to repeat (kept crashing or giving wonky looking pattern).  Application is for a catheter shaft.

                        • Re: Spiral cut tube
                          Damien Long

                          The only downside I can see is that you can't use equations to drive the linear sketch pattern (not that I can see anyway).  If you want to tweak it, you need to edit the pattern manually (wasn't obvious how to do this either --> right-click any of the patterned sketches, then select "edit linear pattern" from drop-down).

                            • Re: Spiral cut tube
                              Bill Toft

                              Damien,

                              You CAN control the pattern with an equation.

                              Set up a global variable with your equation. Something like: PatternCount = Length / Spacing

                              When you do your linear sketch pattern, make sure "display instance count" is checked. Then double click on the instance count number. In the Modify dialog box make it equal to that global variable PatternCount.

                                • Re: Spiral cut tube
                                  Damien Long

                                  Bill, do you mean double-click on the box circled?  That didn't work for me.  Also, it's not just instances I'd like equation driven, but angle and spacing.  Do you know if that's possible, or is it just instances?

                                   

                                  Image1.jpg

                                    • Re: Spiral cut tube
                                      Bill Toft

                                      Damien,

                                      Here is an example of what I was talking about.

                                      I made a linear pattern of your (Wrap1) Sketch20. See attached screen shot.

                                      1. Check "Display dimension X spacing" and "Display instance count" to get them visible in the sketch.

                                      2. To get the angle visible, I first added a horizontal construction line (yellow highlight), then dimensioned the angle to the construction line (below the 10). Note that 15.63 is 360 - 344.37

                                      3. Now (while you are editing the sketch) you can double click each of the 3 circled numbers and link them to different global variables.

                                      Bill

                                • Re: Spiral cut tube
                                  John Stoltzfus

                                  I'm glad you got it worked out - Driven patterns can create havoc to speed