| The Death of PMI? |
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If you do not know what PMI is, it will be
explained. First we need a bit of history! For those that have been following me you can skip the history. As a professional draftsman I spent my first 17 years in engineering by creating design layouts and "Drawings". My First 17 Years or "How did we do it without 3D CAD!" In 1982 I was introduced to 3D CAD and never made a drawing again. No I never used AutoCAD which was a "Computer Aided Drawing" system. A drawing is a document made up of independent orthographic views. No you do not create drawings in a 3D CAD system. We are going to use this definition CAD (Computer Aided Design). So what was the form of the documentation I creating? In 3D modeling we generate the documentation in a documentation module. We place different views of the model usually in a border or format. This used to be called a drawing sheet. It looks just like a drawing format. This is where the problem started. The 1980's - 3D CAD - The Beginning In the beginning of 3D CAD this model generated document was printed on vellum or mylar and treated the same as a "drawing". There was no name at the time. We called them drawings, but the Boeing draftsman quickly understood the difference and called them the "flat-file" I get more into this in this article. The Death of the Drawing Around 1988 PC base CNC showed up first using the 3D wireframe model with a bit of 2.5 axis machining. Also Surfacing was introduced and soon there were PC based systems that could use the surfaces for 3 Axis CNC. The 1990's - 3D CAD/CAM Moves to the PC!! We now had the 3D model for use as a pattern and the basis for the "flat-file. We will not go into the other uses in this article but you can see them here. Leverage Your Engineering Data throughout your Organization! Now since the 3D model is a pattern for use with CNC and other manufacturing processes it still needed more information: Material, finish, treatments, tolerance, etc. The flat file took on a different purpose. I coined this the AID (Associated Information Document). I was selling PC based CADKEY to Boeing and all of their suppliers. We were now sending the 3D model as an IGES on a floppy and the AID as a print to the supplier. Yes, we were doing MBE in 1988. At the turn of the century the PDF was introduce and we could print the AID to a PDF and send the 3D model as an IGES or STEP and the AID in an email. The model could be stored in a folder in the native and a neutral format along with the AID. Now at the same time Dassault had released Catia 5 PLM. They quickly found that the 3D model and the AID was becoming very hard to manage. MBE (Model Base Enterprise) was developed and the PMI (Product Manufacturing Information) was created. I find the work product a bit misleading. The only thing you could do with these "parts" was CNC or Sheet metal. The are virtually useless for inseparable assemblies and fabrications. The PMI was a single file in the native CAD system. It had the annotation and dimensions and the model in 3D space. It started fully dimensioned, too cluttered , then just the basic dimensions for GD&T, still too cluttered. The final form was just the mating features defined with GD&T "profile" feature control blocks defining the tolerances of the other features. There are no standards on how these PMI should be prepared. PMI vs AID Now with that under out belt we can go to the topic. The Death of PMI? I saw this posting on Linkedin. |