I'm not a professional draftsman. I was initially intimidated by FreeCAD, as many people naturally are. I knew when I was glomming parts together using geometric primitives that I wasn't doing *real* CAD, but that inelegant method allowed me to produce simple usable parts. Some complex parts need to be drawn in 2D and lofted or rotated, and that's what I do when I need a complex shape, but if I was drawing Gene's simple part in FreeCAD it's much faster to create two cylinders and subtract one from the other, and it would be much faster and easier for Gene to get the part he wants that way instead of trying to talk him through using Draft mode to draw 2D shapes (which requires selecting working planes, etc.) and then switching to Part mode to extrude the shape into 3D.
I totally agree that restricting ourselves to simple 3D shapes would severely limit our capabilities, but for simple 3D shapes it's easier in FreeCAD to stay in the 3D Part environment and simply create the parametric part I need. The notion of drawing 2D parts and then lofting or rotating them as THE way to work seems to have its origins in the days when AutoCAD was trying to embrace 3D CAD but was barking up the wrong tree because they were adding that capability to their legacy 2D CAD. I assume Fusion360 and Solidworks make it much easier to work in 2D and 3D. It's not terribly difficult in FreeCAD, but I find it cumbersome to switch gears. If I want a rectangular plate with some holes or a disk or tube, it's much easier to use the 3D primitives. It's certainly much easier to talk a newbie through the 3D process than try to convince them to draw 2D parts and then switch to 3D to extrude them, which is similar to telling then to use a 2D CAD program to draw their part and then export that to a DXF and import that into a separate program to loft the part and create the G code. And it IS surprising how complex parts can be when constructed using 3D primitives. Most of us aren't doing a lot of 3D surface machining for injection molds or art objects. Most of us are cranking out simple parts that are readily machinable using 2.5D methods. Gene's part is on the simple side but is a good example. Designing parts from 3D primitives is quite amenable to the types of parts that hobbyists are usually machining. I don't have a five axis machining center in my basement shop, so I had no need for complex 3D CAD until I had a 3D printer that was much less restricted in the part geometry it could create. In fact, for the simple parts I machine on the mill, router and lathes, I prefer to write my own G code from scratch rather than using CAD and CAM. On 9/20/20 6:38 AM, andy pugh wrote: > On Sun, 20 Sep 2020 at 06:52, Bruce Layne <linux...@thinkingdevices.com> > wrote: > >> It's amazing how much can be >> accomplished by using geometric primitives (cube, cone, sphere, >> cylinder, torus) and using Boolean operations to add or subtract these >> components, then using chamfer or fillet on the edges. > I would suggest that this probably isn't the best way to work. > > It is typically rather more flexible to start with a sketch then > extrude it (for milling) or revolve it (for turning). > > The vast majority of lathe parts can be designed from a single > dimensioned sketch revolved about an axis. > _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
