7 Replies Latest reply on Apr 9, 2013 10:58 AM by Roland Schwarz

    use of referance planes while sketching/extruding?

    Kyle Feuchtenberger

      We have a debate within our company about wether to use planes as datum's for the main locating features of the part or to use them to locate the middle of the part at all times. Also using the extrude mid plane command vs extruding with planes as datum's. Is there a benefit to doing this one way or the other? does it really matter what way it is done? I attach an example of each for clarification. I realize this is a very small difference when comparing the example parts but when it comes to more complicated parts that go in large assemblies that need engineering changes or project handoff's the differences make the transition/changes difficult.  Please advise.

       

      Thanks

      Kyle

        • Re: use of referance planes while sketching/extruding?
          John Burrill

          For both reference planes and GD&T, establishing datums is a matter of design intent and trying to say, all of your parts are going to start on the lower-left corner or all of your parts are going to start symetric about a construction plane is to paint yourself into a corner.  I know why you're having this debate, mind you.  At some point, there was an argument because someone expected a plane on a part they had no control over to be somewhere in the middle or on a corner and it wasn't and said person went to the author of said model and said "you should always center your part on the origin and use the midplane extrusion so that when I go to mate the part, I can center it in the assembly more easily."  To which the other party responded, "You should design the part from the lower left corner as if it was sittingo on the machine bed so that you don't have to do math when you key in hole locations."

          Consequentially you're conducting a poll to determine which process on average is going to save the most work and your intention is to implement that system and let the chips fall where they may.

          Might I recommend that instead of going one way or the other, you add a center-plane to the bottom of the part tree to assist matting and name it Cplane or something similar.  Turn it on and turn off the starting plane.

          I do this with PCB's where the ECAD software sets the origin on the lower-left corner.  If the plane is parallel to the front I'll call it XY_cplane (I use coordinate system names for my cardinal planes). I do a lot of top-down modeling so being flexible about my starting point is really important.

          • Re: use of referance planes while sketching/extruding?
            Glenn Schroeder

            Kyle,

             

            Welcome to the forum.  When I'm modeling I definitely prefer your second example, with the planes centered on the part.  Not only does it help with mating, but it's very helpful if you will be using the Mirror function.  With that being said, I don't know that I would try to restrict your CAD people to one method or the other.  As John said, it's easy enough to create a plane at the center of a part if there isn't one there already.

             

            I certainly agree that company standards are needed for drawings, but I don't see much need for restricting modeling practices (with the possible exception of naming features to help with future editing).  However, I'm a one-man show here, so someone else who's in a multi-user environment may certainly disagree, and have points that I haven't thought of.

             

            Since you're a new forum member, here's a discussion with a lot of information that's helpful for new users if you would like to take a look:  https://forum.solidworks.com/thread/39793.

             

            Glenn

              • Re: use of referance planes while sketching/extruding?
                Kyle Feuchtenberger

                Glenn,

                 

                As you stated "I definitely prefer your second example, with the planes centered on the part." I would like more information on Why you like the planes centered on the part.

                 

                We are a company with five SolidWorks users, and are having difficulty with project being passed from one desk to another. with the differences in modeling it makes it difficult for someone to pick up where the other left off. My goal is to better understand how others deal with this and how we can get everyone on the same page to make these transitions easier. I understand that not everyone does everything exactly the same, but the time wasted processing changes and with project handoff needs improvement.

                 

                How do you handle a change that turns a symmetrical part into not being symmetrical. These changes are easier to handle when drawn with the main ref. planes indicating key features of the part. Whereas when drawn mid plane these changes can take allot longer.

                  • Re: use of referance planes while sketching/extruding?
                    Roland Schwarz

                    having difficulty with project being passed from one desk to another. with the differences in modeling it makes it difficult for someone to pick up where the other left off.

                    This is a shortcoming among the user populace.  Making things is easy.  Changing or finishing someone else's work is just inherently more challenging.  No one's work smells quite the same as yours.  Live with it.  Adapt.  More meds.

                     

                    (This, of course, assuming differences are a due to a matter of style, not incompetence.)

                • Re: use of referance planes while sketching/extruding?
                  Chris Michalski

                  By default, yes, I use the origin as the center of most parts, but this is largely because our parts have a certain degree of symmetry.  When the design is best suited to a different reference (i.e. one feature from which everything else is defined) that changes.

                  There have been numerous times that I wish I had used more reference planes instead of mid-plane definitions simply because it can get tricky when editing.

                   

                  But when you get into multi-level top down design and parts that are solely dependent on other geometry it is sometimes simplest if the origin is at the origin of the assembly and is completely meaningless with respect to the part itself.

                   

                  Short answer: when working with someone else's models you have to take a deep breath and realize no 2 people take the same path, at the same step size, at the same tempo in order to get from point A to B.