11 Replies Latest reply on Jan 29, 2010 12:11 PM by Greg Hill

    Dimensioning Principles

      An engineering drawing should be clear, concise, and complete. Can someone here guide me through what I might be missing in my drawing or what I might be doing wrong. I'll attach a sample 3d drawing and its drawing version.

       

      Please mention things like If I have unnecessary dimensions, too many dimensions and especially comment on the title block. One question specifically about that: how do you know if the drawing is in first or third angle of view?

       

       

      Thanks,

      Jaspreet Singh

        • Re: Dimensioning Principles
          Jeff Mirisola

          Your drawing is way under-defined. You have no defined datum point that you're starting your measurments from, no overall length or height. None of the angles are called out. You're also missing tolerance callouts in your title block.

          In all honesty, this drawing needs help.

            • Re: Dimensioning Principles

              OK I made some minor changes. For some reason when I add angular dimensions a message says "Dimension will make sketch overdefined". Anyways, I'm not supposed to go too much into detail for this project. But I'm wondering where would I mention things like how much this part should cost etc. and basically what else can I add to make this part complete or near perfect for anyone to build.

              And how do I add a datum or reference to it.

               

              Does anyone have a good example of what a really good engineering drawing in Solidworks should look like (apparently I can't find much on internet). Thanks.

                • Re: Dimensioning Principles
                  Anna Wood

                  Jaspreet,

                   

                  Good dimensioning practices are a drafting skill.  Doesn't matter how you create the drawing, manually on a drafting board, 2D cad or 3D cad.

                   

                  Get yourself a book or two on Drafting and Mechanical Drawing.

                   

                  http://www.amazon.com/exec/obidos/search-handle-form/ref=dp_srsubj_allbutton

                   

                  For GD&T you want to get the ASME or ISO standards.  If you are in the States get yourself the ASME standard.

                   

                  http://www.amazon.com/s/ref=nb_sb_noss?url=search-alias%3Dstripbooks&field-keywords=ASME+GD%26T

                   

                  http://catalog.asme.org/Codes/PrintBook/Y145_2009_Dimensioning.cfm

                   

                  http://catalog.asme.org/Codes/PrintBook/Y145M_1994_Dimensioning.cfm

                   

                  How much the part eventually costs is a function for your purchasing department when they go out for quotes on your project.  That info is not included on drawings.  You will let the Purchasing Dept know what your price targets are and they will attempt to get a supplier that can meet those cost requirements.

                   

                  It would be a good idea to work with potential suppliers before your design is finalized so you can meet your cost target.  Your design decisions will affect cost.  Best to not have to re-design a project when you find out, after the fact, that you have designed an extremely expensive part from lack of knowledge of manufacturing practices.

                   

                  Are there are no people where you work that can help you with proper drafting and dimensioning practices?

                   

                  Your company should already have established procedures in place for the GD&T standard in use, ASME or ISO.

                   

                  Don't you have people where you work to help you with the established processes for getting parts manufactured?

                   

                  I can't tell if you are working on your own or with an established company.  An established company will have procedures in place for drafting practices, GD&T standards and getting parts manufactured.  All of these practices are independent of the CAD system in use.

                   

                  Cheers,

                   

                  Anna

                    • Re: Dimensioning Principles
                      David Demaria

                      Jaspreet,

                       

                      You need to get yourself enrolled into your local technical college. There you will be in touch with people who deal with this sort of thing for a living. Books are great but will put you on a slow track to progress. As Anna suggested, you need to speak with people who work with technical documents for a living. Using Solidworks is the very least of your problems at present.

                       

                      As a first step, you need to ask yourself... "If someone handed me this piece of paper, do I have all the information I need to fabricate it". Even after years of experience, I still ask myself this question for every drawing I issue.

                        • Re: Dimensioning Principles
                          Glenn Schroeder

                          David,

                          I liked your answer here, especially the part about asking yourself if you have enough info for fabrication.  I try to do that myself, and while I realize it isn't always practical I firmly believe that some hands-on experience building what you will be drafting (or designing) is invaluable.  It's hard to know what information is needed to build it without knowing how to build it.

                            • Re: Dimensioning Principles
                              Greg Hynd

                              amen. i worked in the factory building the stuff i now draw for 6 years. i was always phoning our cad guy up ( he was self employed with no manufacturing experiance) to ask for vital dims, including angles etc. this was one of the reasons we now do our cad inhouse, as it saves so much time.

                              coming from a manufacturing background is invaluable.

                    • Re: Dimensioning Principles
                      Roland Schwarz
                      I wish more young engineers were asking this question.