By the way: this is an easy way to create a sketch positioned and oriented to match a face, without having it attached: after detaching, it’s enough to click on “cancel”: the detachment takes place anyway, without reorienting the sketch. I select the menu item “reorient sketch”, which pops up the question “do you want to detach it?”, I click on “yes”. The duplicate is also attached and, of course, sharing the same positioning and orientation parameters. I found, instead, the workaround using the GUI: I duplicated the sketch attached to the face I used for the cut. Studying the 3D geometry math behind the python code of FreeCAD would be a very interesting task, which I keep on the shelf for later, when I will need to code some new features to enhance the tool. The challenge in this case was to find the parameters of the direction perpendicular to this rotated face, to be used for the direction of the extrusion. It is straightforward to do it using the “Pocket” feature of the “Part Design” workbench, but I needed to keep separated the original uncut object (for versions of the train without this window) and the pad like object (created as an extrusion of the shape of the cut) to cut through the window for the versions I need: I wanted to have the final cut as a result of a “cut” boolean operation of the “Part” workbench. The side window is mainly (but not completely) a cut through a face which is rotated with respect to the central part of the back of the coach, where the door is placed (with a window cut along the y axis), perpendicular to the face it is cutting. In these cases, the sketch remains attached to the surface I used as reference, the positioning of the frame extrusions is relative to it. I did similarly for the side window frames. I added a fillet on the spicky front corner. I created a sketch attached on the front face of the cabin, I drew the border of the frame extracting the borders of the cut as external geometry references, then I created an extrusion and I positioned it slightly backward with respect to the front surface. the xy plane, which is not perpendicular to the front face of the cabin). The final object is a solid with a rectangular section, running around the window borders, at some distance from the front surface, lying on the surface of the cut through section plane (i.e. Then I wanted to add a the frame to be placed inside the window cut, representing the rubber seal in the real case, where the modeler can glue the film representing the window glass. I placed the sketch at the origin of the axes, oriented it on the xz plane, created a pad long enough to intersect completely the front slopes of the cabin and cut them out from the cabin shape. The front of the cabin has two main slopes where these cutouts will be made, along the longitudinal axis of the train, which is not perpendicular to the external sloping surface. Starting from the blueprint I created the sketch of half of the front projection of the windscreen and the front lights housing. I already faced some challenging issues related to the positioning and orientation of pads and extrusions, as well as the detachment of sketches from surfaces and their repositioning: the front window of the cabin, the right side window of the back, the side windows of the body. the model of the Mk3 coaches that go together with the locomotive to have and make up the complete train set.Īs the workbenches in FreeCAD are not meant exactly for this approach, the creation of my 3D objects data base was not straightforward: I had to find some tricks and workarounds.the same locomotive with varying level of details for different modeling kits, and.different versions of the locomotive (e.g.My goal was to have a set of reusable single objects that I could plug in a new data base (a so called “project” in FreeCAD) in order to create: I started with the basic full shape, then I added the cuts for the windows, the cuts for the grids, and finally the handrails and roof details. While modelling the Class 43 IC 125 HST locomotive I decided to create an object data base as modular as possible: three basic objects (the cabin, the body, the back end), each of them in multiple, different version. FreeCAD: pad,extrusions and sketches detachment from objects and positioning
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