There is a variety of 3D printer designs out there, but for the one I built, it makes sense to work on the DIY 3D printer Y-axis first.
If we are going to talk about 3D printing, it would be good to explain what it means to print in 3D or “3 dimensions”. Three-dimensional objects have a width, depth, and height. Each of those measurements tells us how much space the object takes up in each of the three dimensions. In school we talk about the X, Y, or Z axis to describe where something was in one of the dimensions. (Here is the Wikipedia article on three-dimensional space.) With 3D printing, we also use the terms X, Y, and Z axes. Looking at the front of the printer, we use points along the X axis to describe the width, Y for depth, and Z for height.
X, Y and Z all start at one point, and in 3D printing, that is usually the front-left corner of the print surface. Using that one point we can define any point in our print area as a distance to the right of (X-axis), behind (Y-axis), and above (Z-axis) that first point. A 3D printer needs to move along all three axes in order to place plastic where we want it to go.
DIY 3D Printer Y-Axis
The first axis that we need to work on is the Y-axis. On my printer, the print surface moves toward the front or back to get the plastic in the right position along the Y-axis. This means that instead of moving the extruder (the nozzle where the hot plastic comes out), the print surface and the printed plastic moves under the extruder.
The Y-axis on this printer starts with two hardened steel rods that run from front to back. On these rods, there are four small assemblies designed with roller bearings so that the move smoothly along the rods. These assemblies are connected together with some 3mm plywood cut into the shape you see in the picture above. The design for the plywood took a little extra time. I had to modify what I saw that others had done because I made the printer wider and a little deeper so that I could use a larger print bed.
Once the bearings, plastic assemblies, and plywood were fastened together and the steel rods were inserted into the assemblies, the whole thing was placed loosely on the frame. The rods needed to be lined up so that the bearings roll smoothly all the way from front to back and then the rods were tightened down on the frame. After that a larger piece of plywood was fastened to the four plastic assemblies. On top of the plywood there is a piece of cork and the heated print bed. The cork provides some insulation below the print bed so that it heats up faster. There are also springs between the plywood and the corners of the print bed along with screws in the corners so that the height of each corner can be adjusted. This way the bed can be made level.
The one thing left for the DIY 3D printer Y-axis is the stepper motor that will be mounted in the back and a belt connecting the motor to the bed. With this in place the printer will be able to move the print bed to any spot along the Y-axis that is in the print area.