Drawing a blank credit card is an easy task. 
The fun comes when trying to add the company name and logo: the extrusion of the company name needed just a resizing and positioning, while the gearwheel logo has been more tricky. My idea was to include the core of the gearwheel design in the id badge, keeping it “low relief”. As in the business card the gear appears tilted and turned, I tried to reproduce the same positioning in 3D, I cut out from the badge card the tilted and 
turned extrusion of the full twisted gear and then I inserted in the cutout hole a thin slice, cut symmetrically around the plane where the inside cut changes shape, as well positioned and tilted. After adding a cutout hole for the clip badge holder, I sent it to the printer. For this first print run I choose to engrave the company name (as an alternative of having it also as low relief) and to use white resin.
According to the prototype results, I will add the name of the card holder and have it printed in metal.
The original object is too big to be used directly in the 3d badge. As FreeCAD does not offer so many options to manipulate stl objects (as, for example, Blender does), I decided to generate the same gear using FreeCAD tools (and to consider it for me a challenge to learn more FreeCAD features tipps and tricks, instead of a “not so skilled” way to complicate my life as a designer when a clean and easy way as software developer would be at hand 😉 ). I had available the section of the gear in svg format, easy to be imported inside FreeCAD, but as FreeCAD does not offer yet the possibility to twist a surface while extruding it, I had to find a different way to build the twisted gear.
I created an “ortho” array of “lofts” elements connecting two copies of the same “polar” array of the single “tooth” of the gear. This is really building a whole from the single element 😀 . (Yes, I’m aware of the one code line with OpenSCAD, but where would be the 3d designer fun? I would have been the same proud as a coder, had I written myself that one code line…). No need to enter details about the inside cavity: a cylinder and a cube used as cutout tool for a Boolean “difference” with the gear.
Then the idea came to my mind to design a 3d corporate badge, to gain more company visibility when we are at the FabLab workshop, printing our prototypes, or we take part to workshops, sharing ideas with other professionals. Wanting to keep the same appearance of the business cards, I asked 
ame shapes in 3D with 
wrong node in the agglomeration is kept in the import. This made a lot easier to h
ave all the letters as surfaces and extract the internal cutout surfaces (for letters like “P” or “D”) to create by boolean difference the exact text-shape to be extruded. 
basically to downgrade the intersection object into lower level objects: first from a surface to a wire, then a wire into single edges. Once the edges are available, a wire closing the internal profile must be drawn, to be selected together with the the edges making the internal profile to be joined together again into a new “wire”object which will then be upgraded to a surface.
This is the outer surface to be then extruded and cut through for housing the engine and letting the bogies to be connected (the whole object being mirrored to have it complete).
The first geometrical challenge puzzling my mind was how to combine together two ore more knot patterns, oriented at special angles one respect to the other, making it look like a continuous pattern, with no weird crossings or overlaps. As my 
The next step is to design the angular connecting block, joining the threads of both patterns, in way that geometrically could represent a 3D physically possible continuity (my goal is to create 3D printable objects, not 2D “impossible” paintings). To be noticed that the angular block must match the geometry of the crossovers and the width of the threads: threads with longer or shorter elements, of the same width can use the same angular block.
As an alternative, the horizontal thread can be moved up an left, to match it’s upper left diagonal side with the lower right diagonal side of the vertical thread, shrinking the angular part as in the picture. This is more compact but optically more tricky to imagine the vertical ribbon bending with a 45 deg angle and such a spiky external corner. It could be easier imagined as sheet of paper either folded as an origami or with the shapes cutout and then interwoven by hand.
I’ve seen my nine years old son drawing this geometry on a squared notebook. He saw my interest and simply told me “mummy, I can show you how to draw it” and repeated the sequence of segments just for me. I started being captured by the sequence, the 2D geometry, the symmetry and I imagined it as a 2D projection of an “8” shaped spiky knot. I have always been fascinated by knots, especially as patterns, like the celtic motifs. This triggered me now as a 2D/3D designer and I came up with decomposing the shape in simple repeated elements to be reproduced as an array (copied, mirrored, turned).
Then, mirroring the left array symmetrically on the other side of the “S” shaped one ,
I could easily reproduce a sequence of “two crossing ribbons”, without closing the ends as in the initial “8” knot.
