32 Replies Latest reply on Aug 1, 2018 6:46 PM by Paul Wyndham

    The Design Intent Thread

    S. Casale

      I was requested to begin this thread and am inclined to do so as Design Intent is an important topic to discuss.

       

      I like explain design intent as how a user will design something that others will be able to interpret, review, modify if needed, and use. This is best understand for use between the original design activity and current design activity (ASME terms). Perhaps we can quote SolidWorks' definition, "Design intent is how your model behaves when dimensions are modified."

       

      For the sake of this forum we can discuss the topic in the envelope of SolidWorks.

       

      Every different user has their own special blend, process, or workflow on design creation. Each organization may do it differently. An important part of this is consistency. I'd like the idea that we can consistently design our parts assemblies and drawings in a similar manner every time. This is simply not always so. Each and every part, assembly, and drawing is completely different, which is why they are there own independently.

       

      • When I am designing, my first thought is it's complete application - known as Function.
      • How do these parts work? Fit.
      • The materials, method, of how I should set up each part - known as Form.

       

      In my opinion, here are a few rudimentary examples of bad design intent that I see often:

      1. Deciding that a part is going to be drawn upside down from the XY, when it doesn't need to be.
        • Orienting the part without defining it to the origin (this is done in sketches) - exception referenced modeling.
      2. A circular plate that will have holes and items mounted on it started as an extrusion with all of the holes in the same profile.
        • First of all, we aren't making wedding cakes. Revolve that piece.
        • Second, use the hole wizard for what it is. If you need to make a reference controlling sketch, fine, but define it in the feature tree.
      3. Modeling as if there are no datums that are important. If you dimension your sketch items differently than you do your drawing it ought to be a limitation of the software (as it is some times).

         

        Let's discuss your thoughts on Design Intent.

         

        Update: I in no way consider myself master of anything but the universe.

          • Re: The Design Intent Thread
            Jim Steinmeyer

            The students are starting to assemble.

            • Re: The Design Intent Thread
              Dave Bear

              Watching intently..............

              • Re: The Design Intent Thread
                Dan Pihlaja

                Here is a good article:

                What is this "Design Intent" I keep hearing about? | LinkedIn

                Copy/paste from the link (a portion, but my favorite portion):

                To build a robust, parametric model (that is also easily editable), some design intent in the form of forethought on how the model is to be constructed must be given. After all, designs are conceived to fulfill a purpose. Take for example a 1-inch wide strip of metal. The design mandates a hole to be drilled in the center of the part's width. If you model the design by dimensioning a hole a half-inch from the edge, it is indeed "in the middle of metal strip, but you have ignored the design intent of the hole. If the design changes in the future to a three-inch wide strip, your hole would still be a half-inch away from one side, and no longer in the middle of the part. Had you placed your hole in the mid-plane of the metal strip, no matter what size the width had grown or shrunken to, the hole would have remained in the middle of the strip. The design intent of the hole was maintained, and all it took was a little forethought during the modeling process.

                 

                 

                 

                Also, attached is another good article (PDF).

                  • Re: The Design Intent Thread
                    Dan Pihlaja

                    Also, attached is another good article (PDF).

                    I just wanted to share the conclusion of the paper that is attached.  I think that it has relevance here:

                    Begin Quote:

                     

                    V. Conclusion and Future Work

                     

                    In this paper, we reviewed three formal parametric modeling methodologies specifically designed to emphasize CAD reusability: Delphi’s horizontal modeling, explicit reference modeling, and resilient modeling. We examined the advantages and disadvantages of each strategy and compared their effectiveness when design changes need to be performed. We designed an experiment with a group of CAD users where a series of parts were modeled according to the guidelines of the three methodologies and users were asked to perform a number of model alterations.

                     

                    We observed that horizontal modeling requires the creation of numerous datum planes, even before creating solid bodies, which can be a cumbersome and time-consuming process, particularly when dealing with complex parts. This intricate structure may dissuade designers from adopting this strategy in their regular practices. Although regeneration problems are rare, the logic of the horizontal modeling process may not be intuitive (particularly for novice designers). Additionally, eliminating the parent-child relationships defeats the purpose of parametric modeling (it is difficult to anticipate the evolution of the model geometry if changes are not automatically propagated). From a reusability standpoint, our experiments show that horizontal modeling is prone to modeling errors when users are not entirely familiar with the CAD model and its modeling intent. The fact that no regeneration errors occur when a feature is changed (errors do occur, but many go unnoticed because the application does not return any error messages) may lead designers to falsely believe the part is correct without paying attention to collateral effects. This was by far the most common problem our participants experienced while performing the assigned tasks with the horizontal models.

                     

                    Explicit references modeling provides a method to isolate all solid bodies and features associated with the functional elements of a part that are independent of one another, so that changes on each function can be performed without affecting other functions. However, some of the problems of the horizontal modeling methodology may, to a certain extent, be inherited by the explicit references strategy, as we observed in our experiment. Features that depend on reference geometry may not be automatically updated as expected when functional elements are not clear or certain features overlap. Nevertheless, our results show a significant improvement of this methodology in terms of alteration time over the horizontal strategy.

                     

                    In our study, participants found the resilient modeling strategy easy to use and well structured. Results confirm the participants’ opinions and the effectiveness of this approach, both in terms of final model quality and alteration time and reusability.

                     

                    A relevant factor that could affect the results of the experimental work presented in our study is the participants’ level of CAD knowledge and expertise. Although engineering students can be considered a lower skilled population when compared to design professionals, they also comprise a homogeneous group. More experienced users bring a higher skill level but usually with a more heterogeneous distribution. In this regard, a natural future task requires an experimental study with advanced CAD users in a real industrial setting. It should be noted that conducting an experimental study such as the one proposed in our paper in a real industrial environment is difficult because of the daily workloads and routines of the personnel, inherent risks, and availability. Additional limitations include the sample sizes. In an academic setting, it is difficult to gather a large group of participants with a similar knowledge of a specific parametric modeling tool. It is even more difficult in an industrial setting, where a company with a relatively large design department would be needed. Additional studies are required to further ensure that user actions are not influenced in any way by having prior knowledge of the models and that neither the requested alterations nor the manner the methodologies are implemented (such as using specific naming schemes) in the model influence the outcome.

                     

                    On a broader scope, our results reveal how important the use of formal modeling methodologies can be when targeting CAD reusability. Although the majority of the educational practices related to CAD focus on declarative and specific procedural command knowledge (generic commands, operations, and tools that are typically available within CAD systems), the approach does not provide sufficient strategic knowledge, which is related to the selection of the proper modeling strategies. The concepts of CAD quality, complexity, and reusability are also omitted. In this context, it becomes evident that practical mechanisms to incorporate these methodologies throughout the entire CAD training process are required.

                     

                    The next step of our research on parametric CAD quality will be to determine a method to objectively assess model quality. We are interested in developing complexity metrics that can provide indicators of good modeling practices as well as identify particular aspects of the geometry that may need improvement. This data can provide valuable information to make informed decisions about modeling methodologies, modeling alternatives, and best practices. In particular, we are developing a plugin that can be installed as a module in a parametric modeling package that would allow us to keep track of the specific user actions (such as mouse clicks) involved in performing an alteration to a model. The number of actions could then be used as an additional indicator of complexity. We plan to carry out additional experiments in the near future using this metric.

                     

                    End Quote

                  • Re: The Design Intent Thread
                    Timothy Taby

                    I always like to look at how a part is going to be made and out of what material to determine some of my design intent.  How you plan on making the part is very integral in how you design it.  For instance if your part is small plastic piece coming out of a mold then you know you have to have somewhat uniform wall thicknesses and draft on your outside surfaces.  If your part is machined aluminum then your more free to have straight walls and  larger thicker areas throughout the part. There are things you can do with plastics that you can't do with metals and vise versa, so material can play an important role as well.

                    • Re: The Design Intent Thread
                      Todd Blacksher

                      One of the things that is often overlooked when discussing design intent is:

                      "designing for the tooling/equipment that will be used to make the part."

                       

                      This is one of the examples that I learned about a long, long time ago -

                      Tab & Slot between two pieces.

                      The one on the left looks weird, but the blue part was going to be made on a lathe, and the flats would be milled after turning.

                      (Outside of aesthetics, there really isn't a reason for the extra machining required to make the tab look like the one on the right.)

                      However . . . If you are printing or milling the entire blue part, the one on the right is a little more feasible.

                      todd

                      might not be a great example, but knowing the process for making the part can make all the difference in the world when you are designing.

                      • Re: The Design Intent Thread
                        John Stoltzfus

                        Thanks - S. Casale - one of the toughest things to learn in SW - (I'm still learning)

                         

                        Perhaps we can quote SolidWorks' definition, "Design intent is how your model behaves when dimensions are modified."

                         

                        For the sake of this forum we can discuss the topic in the envelope of SolidWorks.

                         

                        The SW definition is the trump card in this thread - "how your model behaves when dimensions are modified." Surely that quote is important, however I feel there's a lot more prior to moving your model. If you're new or are coming from a bad modeling experience, for starters make a list of the following and answer them before you move on to the next item.

                         

                        1. Knowing the manufacturing process -
                        2. Knowing the Costing Structure -
                        3. Knowing the Design Process required -
                        4. Knowing the Tools of the Trade (here it's about SW) -
                        5. Knowing when to break items into a sub-assembly (this is all based on #1) not file size
                        6. Knowing how to handle Part Numbering Schemes and interchangeable components..
                        7. Designing your Solid Model for easy changes (change a feature or sketch, what's affected)
                        8. Personally I will always say Top Down Modeling is the best approach, however not always required.
                        9. What's more important, designing every component revolving around the Original Point of Axis and the three main planes or (I don't concern myself with that in my Design Intent), do you want to have your components snap into place without mates..
                        10. How your assembly needs to be shown in the (3) views
                        11. All of your templates should be part of the overall picture of your design intent
                        12. oh there's sure to be more....Your Design Intent should include a periodical read of these two posts  https://forum.solidworks.com/thread/204247  https://forum.solidworks.com/message/663599?q=tricks

                         

                         

                        Each of the items in the number list have their own story - which I can't fill out for you, we can only make recommendations for what we see here.

                        • Re: The Design Intent Thread
                          Dave Bear

                          I can see this threads going to get saved as a PDF...........

                           

                          Dave.

                          • Re: The Design Intent Thread
                            Doug Seibel

                            I will add that often, design intent requires that the dimensioning used when sketching/creating the part be completely different than the way the part will be dimensioned/detailed on the print.  I have come across several people who believe that correct "design intent" means that that they must dimension sketches the exact same way that the part will be dimensioned on the print, this is NOT always correct.

                             

                            Classic simple case in point, a square or rectangular plate that has holes near each corner.

                             

                            Now let's say that on the print, we will want to dimension everything from the center of the plate (perhaps this is the way manufacturing prefers to have them dimensioned, since they program the part from the center they want the dimensions on the print to be from center)...so we make the sketch for the holes be dimensioned the same way...

                             

                            Problem...change the size of the plate and we get this...

                            And what we actually wanted was this...

                             

                            So, because the holes were dimensioned to be "just like the print will be", the model requires editing several dimension when the plate size changes...in order to keep the holes positioned in relation to the outside of the plate.

                             

                            BUT...if the build our "design intent" into the sketch...

                            ..by dimensioning the sketch from the edge of the part and using centerlines and symmetric constraints, we are then creating the "design intent" we desire.  Now when the plate size changes, the holes move with the plate.  Of course, when we make the print for this component, it will be dimensioned from the center of the plate.

                              • Re: The Design Intent Thread
                                Jim Steinmeyer

                                Doug,

                                This is very true. Sometimes the distance from the edge is important, and sometimes the plate bolts to a cast ( or any other) part and the hole to hole distance is important. Thus-- design intent is important in dimensioning the sketch.

                                • Re: The Design Intent Thread
                                  Dwight Livingston

                                  Todd

                                   

                                  Good example. In our world, we'd be likely to care far more about the holes than the edge of the plate. To follow design intent, we'd want to dimension the pattern of holes first and dimension the plate perimeter out from the holes. Change the hole pattern, and the perimeter should parametrically change with the holes.

                                   

                                  Trouble is, you can't use Hole Wizard that way. If SW really wanted to follow design intent, one could use hole wizard to make a bunch of holes in empty space and add a plate to them later.

                                   

                                  Dwight

                                    • Re: The Design Intent Thread
                                      Dan Pihlaja

                                      Dwight Livingston wrote:

                                       

                                      Todd

                                       

                                      Good example. In our world, we'd be likely to care far more about the holes than the edge of the plate. To follow design intent, we'd want to dimension the pattern of holes first and dimension the plate perimeter out from the holes. Change the hole pattern, and the perimeter should parametrically change with the holes.

                                       

                                      Trouble is, you can't use Hole Wizard that way. If SW really wanted to follow design intent, one could use hole wizard to make a bunch of holes in empty space and add a plate to them later.

                                       

                                      Dwight

                                       

                                      You are correct.....but you can define your hole spread distance as a global variable, then use it to drive your plate dimensions and your hole dimensions.

                                       

                                      OR, use a skeleton sketch (reference sketch) at the beginning.

                                        • Re: The Design Intent Thread
                                          Craig Schultz

                                          Yep, global variables are an awesome way to drive design.  Lots of fun stuff can be accomplished with the IIF statements too.

                                           

                                          Sketch - you could draw the rectangle (construction lines) for your hole pattern, offset it for your plate --> extrude.  Then use the construction line end points for your HW point locations.

                                      • Re: The Design Intent Thread
                                        Dave Laban

                                        Alternatively, use driving dimensions to locate the holes from the corners, but mark them as not shown on drawing.  Then add driven dimensions from plate centre to holes, but have these set as shown on drawing.

                                         

                                        That way, can be modelled with holes-relative-to-corners position, but when you go to the drawing and Insert Model Items, everything is dimensioned from the centre, and everything moves as intended when the plate size is adjusted.

                                         

                                        This method also works within the Hole Wizard environment.

                                        • Re: The Design Intent Thread
                                          S. Casale

                                          Indeed this is an interesting example.

                                            • Re: The Design Intent Thread
                                              S. Casale

                                              Yeah, I don't really see how that drawing would need to be different than the part. In this case -

                                              - If I need the holes to be a specific distance from the plate outer edge, there isn't a reason I can't control that the same way on a drawing.

                                              - The same can be written for if needing to be controlled by the center of the plate.

                                              - The same can be written if I need to use GD&T.

                                               

                                              The holes and the plate are two different features. Sure it's super nice to have them move with the outer edge, but if that's not how the drawing is going to be navigated, I would do it the other way.

                                               

                                              The choice I see is if we are making a machining drawing then I would dimension it one way or the other. But, for the most part we make engineering drawings because we want the parts to work together, and are inspected as in its application. The point of GDT.

                                               

                                              Again, there is no right way. Just a way that it can be looked at later.

                                                • Re: The Design Intent Thread
                                                  John Stoltzfus

                                                  Yes we can detail the same plate (20) ways, but how we detail the drawing for me is the last thing on my mind when I start a project. Now when the modeling starts, is when the drawing detailing comes into play..

                                                   

                                                  Correct me if I'm wrong, I feel there is a huge difference between a stamping facility and a fabrication shop, while both handle metals or different metals, same goes between light Fabrication like a custom job shop and a heavy Fabrication complex that produces tractors and bulldozers and another comparison in that line the differences between the Automotive industry and the Airline industry...

                                                   

                                                  Within that discussion our Design Intent isn't and can't be the same and if I heard you correctly, you would (rather all of us would), like to see where we start from when getting the Dinner Napkin Sketch and kind of the trail to production, is that right??

                                                   

                                                  My background revolved around Custom Fabrication Job shop/Material Handling Equipment Manufacturer.

                                            • Re: The Design Intent Thread
                                              Rob Edwards

                                              All good stuff!

                                               

                                              When I make a sketch I like to test it to destruction with Instant3D to see how it performs.  It's not a static thing, it should have intelligence.  I'll also include driven dimensions that will end up on the drawing

                                              • Re: The Design Intent Thread
                                                John Stoltzfus

                                                Let's assume your design is a Lawn Mower complete package manufactured by you or your company. Now your Design Intent should revolve around how component assemblies and how replacement parts would get sold.  The engine and hydraulic system would be bought in, however all the fabricated items need to be sorted to which sub-assembly they need to be in and the Design Intent needs to follow that criteria.  Then throw in parametric changes to the individual components, ease of change etc.. Design Intent also needs to include how you show the components in an operators manual... all this requires thought which in reality is "Design Intent"

                                                • Re: The Design Intent Thread
                                                  Steve Calvert
                                                  1. Does the model update as expected when changes are made?
                                                  2. Can someone else update the model and figure out how everything ties together?
                                                  3. Can it be manufactured?

                                                   

                                                  It's easy to sit here and model stuff (and fun, too) but I gauge my designs and those from others as how simple it is to make drastic changes.  I'm not talking about taking a shoe box sheet metal part and turning it into circular deep drawn part in two steps but more along the lines of having that shoe box sheet metal part still maintain its character when the base features change dimension.

                                                   

                                                  I always get these requests from my boss, "Hey Steve, can you fit the components into a quick new design?"  I, of course, can but when he comes back and wants changes, he now understands that doing something fast for a render may not be the best more efficient way to model something for the long run.  I have taught him this...

                                                   

                                                  Reading through all the replys to date, it shows us all here that "Design Intent" is pretty broad

                                                   

                                                  my quick 2 cents...

                                                   

                                                  Steve C

                                                  • Re: The Design Intent Thread
                                                    John Matrishon

                                                    Always good to see this topic, and everyone discussing in a civil way.    This topic has been around since the first Parametric modelers started.   Many of us started on the drawing board, then onto 2D CAD, then 3D Cartesian coordinate based modeling.  Those were the days when everything stayed put, and if you changed one line or hole, nothing else moved unless you wanted it to.  Then parametric modeling starts up, and we all freak out and love it, but it came with a price.   That price is the understanding of how something is Designed.  There are so many ways to accomplish the same ending geometry, it can make life for a group trying to standardize a process very difficult.   Each group should at least come up with a game plan for how their company wants to create, store, edit, and share their CAD data.   If you let all of us model the same geometry, guaranteed we'd all have similar but different ways to do the same thing.  So, the more you can standardize the better the group can function.   Onto to Design intent, I'll agree with Steve, Doug, and others on this one and throw in my thought.  I think the design intent needs to stay in the solid model at this point in time, but the general drawing dimension scheme should follow the solid pretty closely but not exactly.   Remember when you installed SOLIDWORKS long ago and you had to choose if you wanted bi-directional editing from drawing back to model?  Quite a bit has changed since then, but Design Intent is still Design Intent, and each design could have a different intent.   I think the key is to make similar designs all work the same so that you are not seeing every variation under the sun and have to know who did what and how just to perform the same functions.   It's not a black and white line.

                                                     

                                                    JM

                                                    • Re: The Design Intent Thread
                                                      John Stoltzfus

                                                      S. Casale

                                                       

                                                      Found an old informative post that fits right in with the design intent - an awesome response by Mauricio Martinez-Saez

                                                       

                                                      https://forum.solidworks.com/message/52442#comment-52442

                                                      • Re: The Design Intent Thread
                                                        S. Casale

                                                        Just adding this for circular reference:

                                                        Zero, Zero, Zero - 0,0,0

                                                        • Re: The Design Intent Thread
                                                          Paul Wyndham

                                                          Since this thread was revived I will add my 2 cents.

                                                           

                                                          For me design intent is the designing the part/assembly to match the intended use. Like the lawnmower example if I were designing the chassis/blade housing, but purchasing a motor I would need to design the motor mount platform and holes to meet the manufacturers specifications. If I move the motor around on the chassis the mount platform needs to retain all its characteristics and/or dimensions.

                                                           

                                                          I also think that design intent should include consideration for material and manufacturing processes. I should design my plastic injection model draft to coincide with the parting lines of the mold. So, I need to make sure my engine mount platform maintains its characteristics when draft is included.

                                                           

                                                          I don't think design intent has anything to do with the way a part is dimensioned on the drawing.

                                                          In general there are two purposes of a drawing:

                                                          1. Facilitate the manufacturing process
                                                          2. Allow the final product to be verified (CMM) to the required dimensions and tolerances

                                                           

                                                          The manufacturing of the lawnmower chassis might require the engine mounting holes be dimensioned from the corner of the block of aluminum it is machined from. So, on the drawing I might need to show those dimensions (while the design intent is still that the holes are located a certain distance from each other and the crankshaft).

                                                           

                                                          Sometimes while designing a product it might be very important to have features spaced in relation to another part that is not present in manufacturing. For example if I had a crankshaft position sensor mounted to the lawnmower chassis I would need to make sure the sensor was an exact distance from the shaft located long it at the correct spot to align with the activator feature. The drawing would need to detail the part in a way that could be measured when the position sensor was not present. Your part supplier is not going to want to mount an engine and position sensor on every chassis to see if they need to machine a little more off.

                                                           

                                                          To sum it up: design intent is all about making a part or assembly in context with the intended design requirements and has nothing to do with how the drawing or MBD is laid out.