Freecad tutorial – U-joint – Product design #102

Hello! In this tutorial, we’ll be making a U-joint. We’ll start by creating a body, and sketch. Choose XZ base plane, to start with. And, we are in sketch mode. Start with Polyline. Each click starts the new segment, RMB will end the operation. Now, line needs some constraints. Add horizontal distance to bottom line, and enter 50. Since we need this line to be symmetrical, select two end points and vertical axis, and add symmetry constraint. Horizontal constraint, will appear as redundant. Select it, and delete it. Line will jump to correct position. Next, select same line, and center dot, and make line fixed on center. Vertical lines need to be solved as well. Select one of them, and apply vertical distance, enter 3.5. Now, to make things simple, select both vertical lines, and make them equal. Next add an Arc, from the dropdown menu, choose “Center and end points”. Now, with mouse over the axis, and “fix” icon appears, click to start the arc center. And define both end points. Add angle constraint, and enter 180 degrees. Add radius as well, and enter 15. Select arc center, and apply vertical distance. Enter 40. To make both ends on the same line, we’ll use construction line. To do that, add line. we’ll use construction line. And make both ends coincident. As shown. Now, while line is selected. Change the mode to construction. Add two more arcs, “two point” arc might be easier to draw. Make all points tangent. One more constraint will complete the sketch. Add horizontal distance to lower arc. And enter 12. Add two more arcs, on the opposite side. And make them tangent as previous are. Select two bottom arcs, and make them equal. This will make the sketch complete. Close the sketch. Next, move the sketch. Make the Origin datum planes visible. Select and press “Space”. Will be easier to tell if sketch is moving. Select sketch again, within position, enter -25 for Z direction. While sketch is selected, apply “Pad”. And enter 50. Next, select bottom face, And create sketch. To clear the view, select the Origin again, and press Space to make planes hidden. Now, choose circle, and with the mouse over center, and small dot visible, click to start the circle. Click again to complete. And add radius constraint. Enter 22. Extrude this sketch also, using Pad. Enter 20. In general, this would be a Base shape. Now, we’ll add fillet. Select any line from both sides. And apply fillet, enter 2. Change shading to wireframe, it is required for the following operation. Now, with nothing selected, select sketch. and choose XZ plane. And to make things easier, we’ll link one of the arcs, to the shape we already have. We can see arc created as a reference. This reference will be used to create a circle. Choose circle, and start the shape by clicking on the arc center. And complete the circle by selecting one of the arc endpoints. Notice that sketch is fully constrained. Close the sketch. Extrude the sketch. But now, select symmetric to plane. Enter 55, or, use mouse wheel to adjust the length. use mouse wheel to adjust the length. Change back to normal shading. The reason we had to add the fillet, is these curves. other methods would only brake the geometry! Select one arc on both sides. And apply fillet. Enter 2. Now we have the working fillets, and shape required. Next, with nothing selected, create the sketch. And choose YZ plane. Switch back to wireframe shading. And add rectangle. First, make bottom vertices symmetric to the vertical axis. And add rectangle. Delete redundant (horizontal) constraint. Select one of the bottom vertices, and apply vertical distance. Enter 8. For the bottom line, add horizontal distance. Enter 35. And for the vertical lines, select one of them, and apply vertical distance. Enter 55. Switch back to normal shading. And close the sketch. Apply pocket feature to this sketch. Select Symmetric to plane, and from the dropdown menu, Through all. Next, select one of the inner vertical faces, and create sketch. Use external arc, as a reference. and create sketch. Next, create a circle. Use arc center to start the circle, and complete the command within the shape. Add radius constraint. And enter 12. Close the sketch. Make extrusion with 2mm. While pad is selected, apply mirror. Select XZ plane. Click OK. Select right side circle, any circle could work in this case, and start new sketch. Use external arc again. and create circle. Start with mouse over the ref. center, and complete circle within the shape. Add radius constraint, and enter 10. Close the sketch, and apply Pocket feature. From the drop down menu choose Through all. Apply Fillet again, to the circles as shown. Enter 1.5. Select bottom lines, and apply fillet. Enter 7. Next, select line, as shown, since it’s a continuous line, can be used any. Apply Fillet, and keep the current 1. Same for the bottom one, apply Fillet, and enter 1,5. One more, select bottom circle, as shown. and enter 7. Next, while nothing is selected, create sketch. and select XZ plane. Change shading to wireframe, so we could see inside. Choose circle, and make sure center is constrained to vertical axis. Apply radius of 4mm. Select the center, and apply vertical axis of 12mm. Close the sketch, and apply Pocket feature. Make it symmetric, and Through all. We’ll have a hole connecting both sides. Select one side, and apply Chamfer. Change shading to normal, to better see what’s happening. Enter 3. Next, select bottom face, and create sketch. Choose circle, and make sure it is constrained to the center. Than,select again circle, and apply radius constraint. Enter 17. Next, close the sketch, and apply Pocket here, as well. Enter 17. For the next step, we could use only sketch, but we’ll use datum plane here. Choose datum plane, If nothing is selected, you’ll get notification “invalid selection”. Click OK. Tool will stay active, and to solve the issue, notice, that tool waits for the reference. Select side face, as shown. We can see now, plane is used as a reference. Click OK. Change shading to wireframe. While datum plane is selected, create the sketch. Use the hole line as a reference. While tool is active, you can freely select datum plane, and make it hidden, by pressing Space. By using this method, we won’t get circle center. But we could add construction line, to help us. Select line, and make sure it is constrained to spline vertex. Keep it horizontally constrained, and fixed to the vertical axis. Select line, and change the mode to construction. Next create the circle. Make sure it is constrained to the center. Click one more time to complete the circle. Select the circle, and apply radius constraint. Enter 6. Close the sketch and apply pocket feature. Change shading back to normal. And for the pocket length, enter 7. And click OK. And we can use Texture mapping in the end, to have better preview of the curved surfaces. Thanks for watching!