5 Replies Latest reply on May 23, 2016 11:57 AM by Casey Gorman

    How to make a fair comparison between MBD and 2D drawings

    Alessandro Tornincasa

      When you read MBD whitepapers, you always find sentences like this "MBD is a cost-effective tool because it eliminates the time to create and mantain drawings".

       

      It's quite intuitive to understand time savings that are consequent to not creating drawings, but it's not so immediate to understand why you would save time without the need to mantain drawings.

      I found hard to understand this concept because I was keeping on associating MBD to 3D PDF.

      This was my scenario, I was thinking about a part that was produced internally in the company:

      - Normally, when you make changes to a 3d model, the 2D drawing will update automatically and you will have to manage issues by dealing with disconnected dimensions or new dimensions to apply

      - Suppose you created a 3D PDF and you made a substantial change to your model. The process would be:

      1) update DimXpert dimensioning of your manufacturing features (many features will go underdefined or some will require new dimensions)

      2) re-publish 3D PDF

      If you think of it this way it does seem that there's no time saving, but rather more time for the same process.

       

      The big mistake here is the equation MBD = 3D PDF.

      MBD is a process involving the whole company, and this idea should be kept separate by the set of tools that are supplied by the CAD vendor to go drawingless in SOLIDWORKS MBD.

       

      3D PDF is just one of the design deliverables but think about the other design deliverables you can supply (native 3D model with or without PMI, eDrawing, 3D PDF, etc.).

      If we had to make an apple-to apple comparison we would follow this table:

       

      Approaches

      2D drawing approach

      MBD approach

      3D deliverables

      3D models

      3D models + PMI

      2D deliverables

      2D native drawings

      Saved

      2D PDF

      3D PDF

       

      So in my case, since part was produced internally my design deliverable would be in MBD approach "saved": once I fix my dimxpert dimensions I'm making my part available to the whole company in two ways

      1) Native SOLIDWORKS 3D file opened with SOLIDWORKS

      Remember that new in SOLIDWORKS 2016 is the ability to see previously created 3D views in "ready only mode", so even if don't have a SOLIDWORKS MBD license on your machine you can access those 3D views.

       

      Cattura.PNG

      2) Native SOLIDWORKS 3D file opened with eDrawings

      New in SOLIDWORKS 2015 and 2016 is the ability to access 3D views from eDrawings for both parts and assemblies. Anyone in the company (even workshop people who don't have a SOLIDWORKS icense) can access 3D PMI data.

      Here's a demonstration:

      eDrawings and MBD - YouTube

       

      So we have time savings, think about the fact that native drawings update automatically upon 3D model changes, but in reality, things are more complicated due to separate documents adding complexity:

      - Some companies choose to break the link between 3D model and 2D drawings to avoid unintentional drawing changes

      - Some 2D drawings could have lost their original associative 3D models

      - Some 2D drawings may have different access rights from 3D models

       

      There are of course update issues when you change a part: some are applicable to both approaches, while some are unique to 2D drawings such as sheet zoning and view placement.

       

      So:

      1.    It’s unfair to compare 2D native drawings with 3D PDF.

      2.    Native SW MBD files are always the best if collaborators are able to consume.

      3.    3D PDF is just one of the possible design deliverable and it's simply a neutral format more widely acceptable, just like 2D PDF of native drawings.

       

      Alex

        • Re: How to make a fair comparison between MBD and 2D drawings
          Casey Gorman

          Alex,

           

          You left out an approach I have taken in the past (and still use to some degree). That is supplying a STEP file with a 2D PDF. I know there are other companies that do the same. In my opinion, and we are bringing MBD online here, until STEP ap242 is available and others can read the PMI from this, the 3D PDF is a limited step forward.

           

          Casey

            • Re: How to make a fair comparison between MBD and 2D drawings
              Alessandro Tornincasa

              For those who might not know STEP AP 242, I'm attaching an interesting document exaplaining what it is and its advantages.

               

              Alex

              • Re: How to make a fair comparison between MBD and 2D drawings
                Alessandro Tornincasa

                Casey,

                from my experience, sending a 2D PDF plus neutral format file is another aproach with two possibile outcomes:

                - the manufacturer will consider the 3D as the master when the shape is complex and needs to be machined with CAM

                In that case the drawing would carry a note "please refer to the 3D model for machining". Maybe the 2D drawing would only contain te overall dimensions of the part in order to ease the manufacturer in choosing the size of the raw material block or cyclinder

                - the manufacturer will consider the 2D as the master

                In that case complex shapes would not be dimensioned but there would be the note "for undimensioned surfaces please refer to 3d model for machining". For the rest (holes, fillets, and so on) there would be all dimensions on the 2D drawing and those would be the primary reference.

                 

                I can't think of a respective of this approach in MBD, probably it would be the 3D PDF plus the step file in attach as you mentioned. But in this case as well you could just put overall dimensions of the part in the 3D PDF and then put a note in which you're stating that the STEP is the master.

                 

                Alex

                  • Re: How to make a fair comparison between MBD and 2D drawings
                    Casey Gorman

                    Alex,

                     

                    Lucky for us, our suppliers are very happy that we have started attaching STEP files to our legacy 2D PDF. Those suppliers that my department have direct interaction with are informed that we are moving towards complete MBD. With that we also let them know that the STEP is to be where they go if there is a question (model is master). As you know, declaring the Model as the MASTER is the first part of MBD (early level). If you supply a 2D PDF with a STEP and on the PO or 2D PDF declare the Model as Master, your supplier should follow that.

                     

                    Now as far as the PMI that is on the 2D PDF and the 3D PDF's at this point we include all dimensions that need to be inspected (Key Product Characteristics). In some case all the PMI to make the part. This is done to help the transition to MBD.

                     

                    I hope this clarifies my earlier statement.

                    Casey

                  • Re: How to make a fair comparison between MBD and 2D drawings
                    Paul Salvador

                    Hello Casey and Alessandro... which CAD company(s) is/are fully using STEP ap242?

                     

                    btw,.. I meant, to say, "no third party software",.. that is, it is their package integrates the STEP ap242.

                     

                    NX?

                    CATIA?

                    CREO?

                     

                    I personally would love to see this happen (>20yrs ago)... and, I've tried in the past to work with companies... and with NO results or following...

                    The MBD idea is GREAT... and it should be FREE TO ALL (we have PAID FOR THIS over the years),...  but it just seems NOBODY wants it (old users/drafters).. because they are so stuck in the 2D past (job security)...... it's another sad reality of the slow wheels of CHANGE.