How many 3D CAD Programs have you worked with? I started out as a CAD draftsman working for a company that manufactured refuse equipment some 20 plus years ago. Back then everything was done in 2D. We used AutoCAD to create all of our detail drawings for manufacturing. About 3 years after I started there we decided to look into going to 3D modeling. We tested several packages including ProEngineer, SolidWorks, SolidEdge and Mechanical Desktop. We decided on ProEngineer due to its sheetmetal tools and off we went.
One of the big differences for us was that we had to build the models and then create the detail drawings for manufacturing. This was a foreign concept to all of us coming from the 2D world. We would build a model but this was just part of the work. We had a difficult time helping management understand that just because the model was done we weren’t ready to send the design to manufacturing. My boss at the time was the Director of Engineering. I think that he thought that there was a special, “Easy” button that we could press and that the drawing would magically be done for us. In actuality it can take just as long to create the drawing as it does to create the model. It always seemed like we were doing things twice. We would create the dimensions in the model to drive the geometry and then we would have to show the same dimensions on the drawing for manufacturing.
I am sure most have heard the buzzword “paperless.” In a paperless environment everything would be digital. There would be no printing of drawings to send to the shop floor. The digital copy would be the master or single source of truth. People who need access to the data would access the digital copies via their computer using some sort of viewing software. In my mind this is a great idea. The digital data can be controlled better to make sure we are using the correct version of the CAD files and we can provide the correct level of access to the user based on their job role. One of the main problems with the printing of a 2D drawing is that as soon as it is printed it is obsolete. There is no control over it and no way to make sure that manufacturing is working with the latest print. It was very common to take a walk through manufacturing and find quite a few obsolete drawings being used on the shop floor.
So how do we make less work for the engineer/draftsman and make sure that manufacturing has only the correct CAD files. In my mind the answer is “Model-based Definition” (MBD) sometimes also known as “digital product definition.” MDB is the practice of using 3D models and their associated metadata within the 3D CAD software to define individual components and product assemblies. MBD allows the engineer the ability to fully detail the 3D model. This include geometric dimensioning and tolerancing (GD&T), material information, assembly bill of materials, engineering configurations, notes and other data pertinent to design and manufacturing. Using this technique the 3D model becomes the master document and there is no need to create 2D drawings. This way we can avoid have two separate objects that have to be managed, one the model and the other the drawing.
Way back in 2003, ASME published the ASME Y14.41-2003 Digital Product Definition Data Practices, which was revised in 2012 as ASME Y14.41-2012. This standard provides for the use of many aspects of MBD. There are also ISO standards for MBD included in ISO-16792:2006, ISO-1101:2004 and AS9100 documentation. The United States Department of Defense released MIL-STD-31000 Revision A to setup standards for the use of MBD as a requirement for some of their technical data packages (TDP). Today most of your better 3D CAD Programs have tools and process wherein you can create this MBD and follow these ASME and ISO standards.
I know this goes against the traditional way of doing things, but it does allow the model to be the single source of truth and it also allows us to maintain more control over the data to verify that the right people have access to the right data, at the right time and that it has the right information available.
Article Author: Brian Wilson, Sr. Windchill Consultant