The past posting described how to get the horizontal disk to rotate as per the position of the servo. Now it’s time to add the second servo as well as a nice box to house the electronics, and a little multipurpose battery box for such times as the Arduino cannot be powered via USB.
Let’s go ahead and see how the horizontal cradle is going to be inserted into a frame, which will contain the servo for the vertical axis. The two ends of the frame have small parallelogram-shaped projections which will fit into the middle bar. That way you can assemble the cradle and the frame ends to fit.
The hole in the cradle axle is printed to be 6.3mm in diameter, which is the axle size of any regular servo. You may have to use a little sandpaper or a file to make sure the servo fits, but don’t make it too loose – then you need something to keep it attached.
The servo cradle has been provided for you with a breach in the perimeter so you can fit the servo wires through it, as well as holes for M3 thread screw for fixing the servo to the cradle. The vertical movement servo can be attached to the vertical slots in the frame ends with long M3 screws too, and its top is kept in place by the cradle axle.
The box that keeps the Arduino looks like this. It is 6cm tall to accommodate the Arduino in comfort and to allow the potentiometers to have space below them and not touch the Arduino. In this context it might be a good idea to tell you how to make the slits for the pots.
The holes have been designed after measuring the potentiometers. The length of the slit is 73mm, the width is 3mm, and at the ends, exactly 80mm apart, are two 3mm holes.
This is easy to achieve thus: when you have the lid, a flat cube essentially, you give it three edge loops. The one in the middle runs exactly down the centerline, and the other two are in the centerline of each half. Then you create two narrow cubes to act as drills when you use a Boolean operation on them.
The key to this whole operation is snapping. There is a tool in Blender, called the 3D Cursor, which is one of the most intuitive tools ever, as soon as you get the point of its operation. In this example, you can see it in use. When the three loop cuts have been put in place, they are available for snapping. Just select one,
then press Shift S, and from the quick menu, select ”3D Cursor to Selected”.
This places the cursor on the edge, in the center of it. When you now Tab out of edit mode, the 3D cursor stays in place nevertheless. Now just select the cube to snap on the cursor, and press Shift S again. Instead of selecting Cursor to Selected, select Selected to 3D Cursor.
Now you can see the narrow cube going through the lid cube at exactly the center of the right half of the lid. Before using the Boolean operator, it’s good to create a copy of this cube, and join them together. This way you can get away with just one Boolean operator.
As you now go into the Modifiers tab of the Properties panel on the right, you can see a modifier called Boolean.
Those operators, Difference, Intersection, and Union, can be used to manipulate two meshes so that you either get one subtracted from the other (Difference), join them together (Union) or get the piece that is common to these two (Intersection).
Since we have to get holes, it’s Difference. Merely select the main mes, then select Difference, then pick the piece to remove from the main mesh, and press Apply.
After that, the lid has two neat holes in it, perfect for the slider of the potentiometers. The pots are attached to the lid with two 3mm screws, so it’s just a question of creating two cylinders of 3mm diameter, and placing them at exactly 80 mm apart.
The easiest way to do this is of course to create an edge of 80mm length, by creating a square plane and deleting the two unnecessary vertices. Snap the cursor to one vertex of the edge, then snap the first cylinder to it.
When you snap the second cylinder to the other vertex, you have the proper distance. Join the objects, and remember to use Object – Apply Location, Rotation and Scale, to make sure the boolean operation will work.
And this is what the final, printed, piece will look like the two images here. The pots fit exactly, and the lid then fits the box that houses the Arduino, as you can see in this video.