This time I thought I’d write up a little device I have put together with Arduino and printed parts so that I can point a webcam in two directions. (That’s the first use I thought of, after getting the idea of trying something with two 180° servos). To achieve this, I bought two potentiometers (adjustable resistors) and set up two servos to rotate the stand.
Now that the scanning works, it’s time to explain the design of the tool. The size of the finished system of course makes it impossible to print it with any current 3D printer available to me, but even with MiniFactory’s 15 x 15 cm build table, it is doable. I wanted to have a 30 cm diameter turntable, and a 60 cm diameter frame base so as to have space to shoot objects bigger than 15 x 15 x 15 cm. The turntable is printed in 12 parts, assembled with screws, just like the arcs. I didn’t want to use glue, even if ABS is easy to build with glue. There are a couple of other parts too, like the cup below the turntable on which it revolves, and the three vertical arc mounts. There is a small triangular part at the top to assist in fixing the top arcs together, and that is done with a bundle strap. It’s easier than using screws and works just as well.
I modeled all parts in Blender, exported to STL and printed on my three Minifactories. I wanted to keep the design as simple as possible, and recycle parts so as not to have to change the printing setup every time a part was finished. Therefore the base arc and the three vertical arcs are of the same parts, and as ABS flexes a little, the whole setup can be put together and held in position by a single bundle strap at the top of the arcs. Let’s see the parts in detail.
Now that the frame is complete and ready to print, as seen in Part 2, it’s time to do the moving parts. This is a very good place to show you the Blender 3D Cursor in operation, because I will not be designing with exact dimensions, but rather with exact locations and approximate dimensions.
The 3D cursor is the thing that moves around the screen, when you click the left mouse button. You can place it with nice precision, when you use the views that are flat, ie. Top, Left, or Right, because then the cursor moves in only two dimensions. Placing the cursor in the User Perspective view is really hard, unless you snap the cursor onto something – most of the time it is not even possible. I’ll show you what I mean.
I will now try to take you through the design of the trebuchet which has been shown in Part I of this post. This description that follows is actually aimed at showing you how in Blender all design is based on very simple starting points. The trebuchet frame is based on a single circle, the hole in which the main axis will eventually be placed, with a diameter of one Blender unit. Around this circle I based an octagon with the same center, but with a diameter of three.
For some time now, I have been thinking of printing a trebuchet. On Youtube you see massive trebuchets capable of hurling a flaming piano (!) to a distance of 200 meters, or trailer-based versions used in pumpkin-throwing contests. This sort of machinery is clearly beyond my MiniFactories and even the Print-Rite model I was handed the other week, but a small one should be within reason.
As always I first tried an unstable one before hitting on the right design. The first version seemed fine in Blender, and I was thinking of creating a system with many separate parts to maximize size. The first version looks like this in Blender:
So, my son scavenged two 320GB drives from two laptops that were not very functional. He had space inside his own cavernous computer for them, and even a drive cage where he could fix the 2.5″ drives side by side. He screwed the drives onto the cage and it looked solid enough, but surely it’d look even better if there was something holding the tops of the drives. It was also a question of having space for the connectors, because this is not a standard layout, but would enable him to install both at one go. Continue reading Quick but not dirty printing→