We all have things in our everyday environment that consist of small things, which you don’t notice even, until they break. Then you look into it and find that replacement parts are not readily available, at which stage you are faced with a simple choice: Buy a new one, or create some sort of hack with duct tape and parts from other broken-down household items.
That may work but it is annoying to see something and remember it’s broken. Luckily today it is very easy to print the parts you need to fix something, and if you have access to a variety of print colors, the result may be so good as to be indistinguishable from the real thing.
I’ll give you an example. There’s a Finnish manufacturer of housekeeping items, such as cleaning tools and laundry management systems. They make a fine rack for drying clothes, which can be extended across the bathroom and pinned against the walls. The clotheslines are plastic, and they also can be adjusted for different room widths. The crucial item in this system is a tiny piece of plastic with two holes in it, and sometimes, it breaks.
As you can see in the image, this object is an elongated cylinder through which there are two holes. It is about 23 mm wide, 15 mm across, and 2.8mm thick. To model something like this, it’s easy to grab a picture of the object, place it in the background, and then create the mesh on top of the image. It’s also a good idea to just do the shape properly and not to worry about the size at all, since in the digital 3D world, you can rescale the object even at the printing machine to get it to the proper size.
So first, add a circle. Scale it so that it matches the curve of the broken object. Then, tab into Edit mode. Select the vertices on the right side, and then press G and drag the vertices out to make the other end of the object. This gives you the basic shape.
Select all vertices and press F. This places a face between all the edges. The face is called an N-gon, because it’s a polygon with multiple vertices. Select the face and move into side view by pressing 1 or 3 on the NumPad. With the face selected, press E for Extrude, and move the mouse up a little to give the object its thickness. It doesn’t matter how thick you make it now – all that matters is that it has some thickness.
Now we can drill the two holes using a modifier named Boolean. Booleans are a set of operations to join pieces, remove one piece from another, and see the intersection of two objects. This image is from the Blender manual, showing the union, intersection, and difference of a sphere and a cube:
Before attempting to use any Boolean operation, you must “normalize” both meshes by applying their location, rotation and scale. When you move, rotate, or scale any object, Blender remembers the modified values, and the Boolean operation may or may not work. When you apply those values by pressing Ctrl+A, Blender resets, location, rotation, and scale to 1. This I have found to b very important for the Booleans to work.
Now, go back to the Top view (7 on the keypad) and hit 5 there to go to Ortho view. Now the photograph of the object is visible again. Press Shift+A to create a cylinder and scale it until it matches the hole in the photo. Scale it on the Z axis so that it is thicker than the piece you are making. Duplicate the cylinder, and move it along the X axis so that it matches the image. Then select both cylinders and join them with the Ctrl+J command. This way, you can drill two holes with just one Boolean. Do the Apply location, rotation, and scale for the cylinder object too.
Now select the piece you are going to print, and then go to the Modifiers tab. Select Boolean, then Difference, and then the Cylinder object in the Object list. When you press Apply, Blender removes the volume of the cylinders from the object you want to print. This makes the printed object perfect as to shape, but not as to dimensions.
On the Scene tab, in the Length dropdown, see that you are using Metric as dimensions. Now the object gets to be a certain size. Press S for Scale, then drag the mouse, until the length of the piece is 23 millimeters. Then use the Z spinners to make the thickness of the piece to be 3mm. Now the piece is perfect in size and shape, and ready for printing, except for one thing: I have found that I need to rescale things by a factor of 10 in the RepetierHost printing software, due to a mismatch between the two systems. I therefore now scale it up by 10, merely by pressing S and 10 and Enter.
Then all you have to do is to check for manifold, using the 3D Print tab on the left, and export to STL. When the piece is on the RepetierHost software virtual print table, you can check to see the size, and then slice it into printable slices. I used a layer thickness of 0.1mm this time, just to make sure it will be a solid piece, as well as an infill value of 40%. A small piece like this becomes almost solid with these settings.
The design time for this item was around 5 minutes. The print time for such a tiny piece is only 12 minutes, and when printed in ABS, it’s as good as the original (which probably is made of extruded ABS too).
I hope this shows you how easy it is to make things when you still have the original piece or its copy available, although you can do very nicely with just a photo and good dimensions.
I recorded a short video on how to do this, if you’d like to see the process.