Custom FDM 3D Printer

I wanted to make sure the Z-axis was as rigid and precise as possible, so I used a 25mm wide linear guide mounted to a solid aluminum square bar and a 1204 ballscrew to control the printer bed. The bed itself is made of 3/8" ground aluminum MIC6 plate that I ordered online and was surprisingly cost effective, though did require some machining to smooth the edges. The entire bed assembly rests on a cantilevered steel frame that bolts to the linear guide. By using a single large linear guide and strong steel frame, I could avoid the complexity of trying to align multiple smaller guides mounted to different parts of the frame.

The printer bed has three L-shaped mounts that bolt to the bed and have various profiles machined into them. The mounts rest on three threaded studs that can adjust in height to form a fully constrained, leveling kinematic mount. With this design, I'm able to lift the bed off its mounts and place it back down, and the bed settles back into the exact same position and remains level.

Here is the back side of the frame, as well as the Z-axis and bed assembly fully assembled:

The extruder moves along the X-axis on two 9mm linear guides mounted to a machined aluminum frame. A NEMA 17 stepper motor, mounted to the back of the aluminum frame, controls the X-axis.

This frame moves in the Y-direction using two linear bearings (shown in the above image) that ride along two 16mm steel rods bolted to the frame. The Y-axis is controlled by a single stepper motor that rotates a rod with GT2 timing pulleys on each end. These pulleys control belts mounted on each side of the X-axis assembly and move in unison to prevent "racking" of the X-axis. I was able to house this pulley system within the tube frame, narrowly avoiding the Z-axis ball-screw.

Here is the X-axis assembled after machining all of the individual components. All of the large holes are meant to lighten the frame, though it still turned out to be quite heavy. On the far right is a belt tensioner I designed to make tensioning the X-axis as easy as possible.

Here is the X, Y, and Z axis mounted to the printer frame:

Here is the printer after I added the stepper motors, cable chains, extruder, fans, bed heater, power supply, controller, and all of the wiring. This is how it looked for a long time while I was putting it together: the wires are quite messy and none of the electronics are covered, but at least everything is plugged in where it needs to be.

Here is a close up on the controller board, solid-state relay for the bed heater, and power supply. I used a Duet wifi controller to control the 3D printer.

Here are some of my first test prints. The first was a benchy, which showed that I did not have enough cooling on the part. I added a fan to blow air at the extruder location and it seemed to help print quality. The second part is a test cube that I used to make sure the frame was square and the scale of each axis was correct.

Additional photos of the fabrication process: