11 Replies Latest reply on Nov 13, 2008 4:42 PM by Danny Sillett

    Master Sketches

    Brian Hoerner
      I am trying to get a feel for
      1) how many/who uses master sketches in SolidWorks to drive assemblies and other part files,
      2) Pros and Cons
      3) Best practices from those who use them

      I have found in the past with Pro/e "skeleton models" as well as "Master sketches in SW that they can and do cause multiple problems long term. I am wondering if it is just poor planning, or lack thereof, or just not a good understanding of best practices.

      Thanks!
        • Master Sketches
          Roland Schwarz
          Poor results are from poor execution.

          Master sketches work well for most things. Most problems come from mismanagement of in-context dependencies.

          Currently designing hospital beds. Lots of lift mechanisms. Master sketches work very well for this.
            • Master Sketches
              Brian Hoerner
              Roland,

              What do you have as guidelines to control how these layout sketches are used and defined so that you don't end up with mismanaged sketches? Is there one person who controls the project, do you have any documentation guidelines or are they just learn as you go?

              thanks much for your feedback
                • Master Sketches
                  Roland Schwarz
                  I've been letting this subject stew. I am finding I have too much to say on the subject to distill to one post. Forgive and indulge me while I do this in pieces...

                  The biggest problem I see with master sketches or other top-down modelling techniques is that the master sketches are allowed to live beyond their usefulness. Master sketch-based design is great for new development projects. Tying references together at the top can speed up the design process considerably. At later stages of development, master sketches may be less than useful.

                  However, there is a time for a project to graduate from the master sketch mode of design. This is usuall at or near the point where a project is being released for production.

                  When a project is released from development, I find it best for the parts and subassemblies to be able to stand alone. External references should be broken and replaced with internal constraints and dimensions.

                  What of all the development data (including master sketches)? It is still important, and should be appropriately archived. However, it should not be hanging on after a part is released for production.

                  Yes, this is only my opinion.
                  Yes, there are rare exceptions.
                    • Master Sketches
                      Danny Sillett
                      I use them very extensively in my part designs, on a per part basis. I use one for XY, one for YZ, and one for XZ before I even start creating features. I then use the convert entities feature to bring them into new sketches to create my features.

                      Doing it this way allows me to keep the majority of my part dimensions located in one place, and gives me the best idea on how making a change to the geometry affects the rest of the part shape. It also keeps me from having to root through a ton of features to find out what other sketches may depend upon the geometry and figure out exactly why they have changed due to a dimension changing in another sketch. In addition, this also allows me to establish equations within a single sketch without having to cross reference equations from another sketch.

                      My designs are heavily aesthetically based, (I design plastic bottles, sounds basic, but there is a LOT of crazy surfacing involved in it.) Typically most of my designs are 1 part and maybe a few surface bodies. At most I will have two to 3 parts involved in a design.

                      The thing I've noticed though, these master sketches will become very slow once they are built up and driving a completed part if they are overly complex, as there will be a ton of relations & dimensions on the screen, along with a bunch of sketches in features that are dependent upon this controlling sketch. In order to help this, I will roll the model back to the master sketches before I make edits to dimensions. Once complete, I'll exit the sketch, and roll the model forward.
                • Master Sketches
                  Bill Rose
                  We don't use them but we do encounter them in downloaded part & assembly models from vendors (Bimba is one example). Personally speaking, they are a PITA to deal with.

                  Bimba makes pneumatic cylinders and when I want to show an assembly in various positions I either have to decipher the master sketch or break all references to that sketch and insert my own dimensions. It's often easier to ditch the master sketch.

                  I see no pros to their use but I do see cons. If the master sketch were done differently, maybe with some notes or something, I wouldn't see them in such a negative light. I'd like to hear from users that understand the pros to this method.....Bill
                  • Master Sketches
                    Sean Phillips
                    We use them extensively. Currently its the only way to drive part size and geometry from an assembly level. The included driveworks lite doesnt do all we require. I refuse to buy the full driveworks because i refuse to purchase add in software to fix what is advertised as parametric 3d modeling to begin with

                    The drawbacks are some items such as mass properties of parts dont update unless they are individually opened, etc. Also editing a part can sometimes be awkward as you have to teach the operators to edit it from the assembly design table and not the part file itself.

                    • Master Sketches
                      Brian Hoerner
                      How many of you are there to train on using this process? Still seems a bit restrictive/dangerous if not understood by all, down line relations etc. Not sure what you inferred to as not being parametric, care to elaborate your point of view??
                        • Master Sketches
                          Bill Rose
                          Brian,

                          Here's an example of how a master sketch becomes useless down the line. These assemblies are downloaded by customers for use in their own models. The downloaded assembly has moving parts but using this modeling method makes it close to impossible to properly move the parts in the assembly by driving them with the sketch. I find it easier to break the references to the sketch and use mates to allow the parts to be used in a real-world manner. ....Bill
                        • Master Sketches
                          Alan Stoldt
                          Bill,

                          Concerning Bimba and their Solid Models. They are not to be trusted. Period. gross errors throughout. Anything we get from them has to be checked and fixed.

                          I've used Layout Sketches and am using them more often. Used correctly, they work fine.