FreeCAD started out a little shaky, but it has gotten better and better. If you are trying to draw a schematic, it probably isn’t the best way to do it. However, it is a great graphical alternative to OpenSCAD for 3D printing and even incorporates OpenSCAD if you don’t want to choose. However, if you have a 3D part — regardless of how you want to create it in real life — having a proper mechanical drawing is very valuable. FreeCAD’s TechDraw workbench makes this very easy and [Joko] has a tutorial that shows exactly how to do it.
Machinists everywhere are used to looking at these drawings that typically show a top view, a front view, and a side view. The program will automatically project the views you select and then allows you to pick dimensions. It creates them and keeps them up to date if you change them in the model later.
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How does a design go from the computer screen to something you hold in your hand? Not being able to fully answer this question is a huge risk in manufacturing because . One of the important tools engineers use to ensure success is Geometric Dimensioning and Tolerancing (GD&T).
A good technical drawing is essential for communicating your mechanical part designs to a manufacturer. Drafting, as a professional discipline, is all about creating technical drawings that are as unambiguous as possible, and that means defining features explicitly. The most basic implementation of that concept is dimensioning, where you state the distance or angle between features. A proper technical drawing will also include tolerances for those dimensions, and I recently explained how to avoid the pitfall of stacking those tolerances.
Dimensions and tolerances alone, however, don’t tell the complete story. On their own, they don’t specify how closely the geometric form of the manufactured part needs to adhere to your perfect, nominal representation. That’s what we’re going to dig into today with GD&T.
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Mechanical drawings are an excellent way to convey design information, and while sophisticated 3D modeling is slowly taking over, with some companies accepting files over drawings, the mechanical drawing remains the written contract so to speak for complex parts with tolerances and non-modeled features.
But if you didn’t take a technical drawing class (typically Engineering Drawings 101), how do you learn? Well, if you have 15 minutes, this is an excellent video, which speaking from experience, covers the basics from the 101 course.
The lesson covers all the basics, from 2D projection, multi-view drawings, isometric projection, cross sectioning, linear dimensioning, basic tolerancing and alternate views.
Continue reading “An Excellent Primer For Sketching Mechanical Drawings”