23 Replies Latest reply on Sep 22, 2010 8:19 AM by Roland Schwarz

    When is coincident the same a concentric?

    Gerald Davis
      My question is, why did SW code the system to add coincident relationships to the centers of arcs /circles instead of concentric ? Is there some deep insight that might simplify my workflow?

      As a specific workflow example, I use the Hole Wizard a lot. I frequently use it to make holes in cover plates. I can then use the resulting feature to create an assembly pattern of hardware (screws, for example).

      While adding points to the positioning sketch for the Hole Wizard, there is a strong temptation to snap the points at the centerpoints that appear when "tickling" other components/features in the assembly.

      If I do that, then the resulting sketch relationship for the new sketch point is "coincident", not "concentric" as one might expect.

      I've encountererd several situations where subsequent model edits cause such automatically created conincident relationships not to rebuild properly. The only solution I've found is to delete the coincident relationships and replace them with concentric relationships.

      My habit now is to drop positioning points to avoid automatic relationships. I then manually add the concentric relationships until the sketch is fully defined. By doing this, I've had fewer rebuild problems down the road.

      It would be much more efficient to be able to trust the automatic sketch relationships.
        • When is coincident the same a concentric?
          Matt Lombard
          Gerald,

          I suspect its because points do not have centers. Arcs have centers. A point to point relationship I think is most appropriately made coincident.

          I've never run into coincidents going south when concentrics work. Do you have an example of that?

          • When is coincident the same a concentric?
            Jason Capriotti
            I can't say that I have ever had a problem with this.

            What is actually happening is you are making the point, line, etc coincident to the "Temp Axis" of the cylindrical face. Pull up "Display/Delete Relations and select that Coincident relation. In the Prop Mgr.....under "Entities", select one of the points and it says "Axis -in- Face of Part1".
            • When is coincident the same a concentric?
              Matt,

              Points do not have arcs either. So why do you add a concentric relation between and arc and a point?
                • When is coincident the same a concentric?
                  Steve Calvert
                  The point has to go somewhere, either it has to lie on the circle or at it's center.

                  Gerald, it would be nice to trust the relations, though...

                  Steve
                  • When is coincident the same a concentric?
                    Matt Lombard
                    Wayne,

                    I think Steve hit it. Coincident between a point and an arc would put the point on the arc. "Concentric" doesn't mean the same thing as "at the center", but it is being treated that way. Plus, a point at the center of an arc requires a word that describes the relationship in a particular direction. All of the other SW sketch relations (except Pierce) describe reciprocal relations - it is the same regardless of direction. So from entity 1 to entity 2 is the same relation as from 2 to 1. With a point and an arc, it would be point "at the center" of the arc. Arc to point would be arc "centered on" point. You could waste a lot of verbal energy trying to make this correct. SW is already guilty of torturing the English language. I can't imagine how bad these things could get when translated into other languages.

                    It would be worse if SW decided to make a separate sketch relation called "at the center" which would only satisfy people who analyze the semantics. I think it says something that this scheme has stood up to years of use.

                    I agree the terminology is not perfect, but it is better than say the Undercut Detection terminology, or if they can find another way to use the word "shortcut" or the new "Layout Sketch" function which has the same name as a technique used by users for years.
                      • When is coincident the same a concentric?
                        Gerald Davis
                        Matt -

                        (off topic - I'm just starting Chapter 9 - so far your Complex Surfacing Book has been an informative and entertaining read! At the very least, it is one of the most comprehensive Enhancement Requests I've ever seen. I've learned a bunch of NURBY stuff, too.)

                        We now resume our regularly scheduled rant...

                        When I CTRL select an arc and a point I can create a concentric relationship. Since the sketch point is on its sketch plane, that concentricity with the circle's axis fully constrains the point.

                        I understand the idea that there is a point in the center of the arc/circle on the circle's plane and that a coincident point-to-point relationship should work. I would prefer it to be a concentric relationship since that will resolve unambiguosly even when the plane of the circle and the plane of the sketch point are not coincident.

                        I've had the automatic point-to-point relationship fail on enough top level modeling editing occasions that I felt compelled start this thread. As with "Failed to Save", it is a challenging workflow to recreate.

                        I can't quickly give you an immediate tutorial on how to experience the problem. Fragile automatic sketch relations are a pain in the mouse, nonetheless.

                        I'd be surprized if I'm the only one who has experienced this!
                          • When is coincident the same a concentric?
                            Matt Lombard

                            Gerald Davis wrote:

                             

                            Matt -



                            (off topic - I'm just starting Chapter 9 - so far your Complex Surfacing Book has been an informative and entertaining read! At the very least, it is one of the most comprehensive Enhancement Requests I've ever seen. I've learned a bunch of NURBY stuff, too.)

                            Ha! 460 page enhancement request! I hadn't thought about it that way, but yes, it is a big workaround for surfacing functionality.
                      • When is coincident the same a concentric?
                        Gerald,

                        Holding down the control key will turn off the automatic sketch relation. As an example if you hold down the control key when placing points in a sketch it will not add the coincident relation if you place it to close to a circle center point.
                          • When is coincident the same a concentric?
                            Gerald Davis

                            Wayne Matus wrote:

                             

                            Holding down the control key will turn off the automatic sketch relation. As an example if you hold down the control key when placing points in a sketch it will not add the coincident relation if you place it to close to a circle center point.

                            Wayne -
                            That's a good technique for avoiding automatic sketch relationships alltogether. However, I want to achieve concentric instead of coincident relationships when I drag a sketch point to what appears to be the center point of an arc or circle.

                            I've tried holding my elbows together while draging points, reversing the orientation of my wedding ring on my finger, and brushing my teeth with the other hand. Still, I'm nonplused that auto generated relationships must be coincident, but human generated relationships are concentric (unless you go through the contrived machinations of showing temporary axis and mating a point to that axis with CTRL-select).

                            Am I proposing that the UI be reprogrammed so that the nature of the sketch entities being related (as a result of dragging) is recognized and suitable relationships are established automatically?

                            My goodness, that would be like expecting the file open dialog filter be set to match the component type when browsing for a replacement component.

                            Or matching the aligned/anti-aligned orientation of components when replacing mates.

                            Or discovering the seed feature in a pattern so I wouldn't have to make sure I drop a toolbox component in the perfect hole for a feature driven pattern.

                            Shoot. While I'm ranting this heresy that the UI should serve the user instead of the other way around, why don't I wish that all Property Manager options were "sticky" from session to session?

                            What would it be like if ToolBox PEM fasteners defaulted to the correct orientation instead of requiring that the flipping TAB key get hammered?

                            I've tried the Enchantment Request route. Apparently my ideas for improvement are so esoteric as to be phantoms of my little opera.
                              • When is coincident the same a concentric?
                                Gearld,

                                I suspect that you could live with Coincident relationship if it would not break on you with model edits. There are inconsistencies in the naming of the different types of relationships. Point and arc concentric, point and point coincident, and end point and end point merge. It does not really matter what they call it as long as all users understand what it does and It does what it is supposed to do, which is to maintain the relationship with model edits.

                                A better workaround until they listen to your enhancement request is to show the location sketchs of the hole wizard holes you are trying to align with. Now when you use the hole wizard holes in your cover, you will automatically capture a coincedent relation to this location point not the center point of the arc. I would think this to be more stable than trying to add a relationship with the hole edge in the other parts.
                                • Re: When is coincident the same a concentric?
                                  Joel Bickel
                                  Or discovering the seed feature in a pattern so I wouldn't have to make sure I drop a toolbox component in the perfect hole for a feature driven pattern.

                                   

                                  Dropping a toolbox component is the perfect hole hasn't been required since SW2008.  Just use the "select seed position" feature.

                              • Re: When is coincident the same a concentric?
                                David Oustifine

                                I feel your pain Gerald....

                                 

                                I often have to line the center of hole wizard holes up on the center of curved or filleted corners and am so tempted to wake up the center point but this always gives you a coincendent relationship and I prefer to use the concentric with round stuff.

                                • Re: When is coincident the same a concentric?
                                  Jeff Mowry

                                  Not only is this a problem with Hole Wizard-related items, but related to that is the dfault mate settings.  If you've got a round/arc surface and mate it to anything else (that's neither an arc or round)--the default mate is Coincident and not Concentric.  Why on earth would I mate something between a round/arc surface and anything else as Coincident by default?  That never takes care of the degree of freedom I'm trying to restrict, so it's daft over 90% of the time!

                                   

                                  This is no big deal most of the time, but with my recent hassles with the roller chain issue I posted about previously, the mates would solve to the undesired/incorrect Coincident condition every time before allowing me to select Concentric!  You should see how this adds up as your mates per assembly approach 100+.  Super slow!  What a waste of time!

                                   

                                  SolidWorks, is there any justification for setting the default mates with round stuff to Coincident rather than Concentric?

                                    • Re: When is coincident the same a concentric?
                                      Josh Brady

                                      Jeff, Jeff, Jeff!  You are an expert SW user!  Why would you ever use SW's idiot-resistant mate dialog for basic mates? :-) Get you some mating macros.  One hotkey and spacebar confirm to add the mate that you know you want.  No waiting on big assemblies for SW to evaluate what are all the possible mate types for the two things you selected.

                                    • Re: When is coincident the same a concentric?
                                      Lenny Bucholz

                                      A point to a point can only be coinicdent, be it a end point, center point, or just a plain old point in the sketch period.

                                      for you to get the concentric it take a combonation of 2 entities to get that solution and the control select allows for more than one option, the automatic relations are set up for the most common solution.....not what you may want for your deisgn intent of the sketch you are doing at the time.....but what 90% of the other people use it for.

                                       

                                      so you are sketching a new line, circle, arc, elipse and you hover your cursor over a arc/circle with automatic relation you have one option coincident to it, so most people want that and most people want a point to be coincident to a point, automatic isn't always going to work the way you want or what I want, sometimes we have to do it the long way the control select way.

                                       

                                      as for enhancement request, I put in for 3d sketches to be able to use 3 point arcs....in SW98 I didn't se it until SW2005 or 06 so I understand it doesn't seem like they listen, it just might be that there are not enough sqeeky wheels out there that have the same issue as you do with the whole is it or is it not the same thing. so if they change the automatic relation from coincident to concentric the others who like it they way it is now start to complain.

                                       

                                      as i taught SW to customer/students and my son, arcs are made up of 4 entities (3 points and a arc) and circles (1 point and a closed arc) are made up of 2.

                                       

                                      JMO

                                      • Re: When is coincident the same a concentric?
                                        David Suelflow

                                        What I would like to see is a way to control which relation(s) will be added.  Many times it will automatically add both a coincident and horizontal/vertical and I only want the coincident, for instance.  It would be nice if you could Tab through the various combinations or have a dialog pop-up to make the selection.