reprap 3d printer

If you’ve been following along with Part 1 of this tutorial, you now have a mechanical shell of a printer. The shell of the printer should include the makings of your X, Y, and Z axes. In Part 2, we’ll put together electronic components to create a functional 3D printer. We’ll be assembling RAMPS, connecting stepper motors and hot ends to the boards, and adding a power source.

Final printer specs:

        Desktop Footprint: 11in x 13in x 13in

        Maximum Build Space: 105mm x 130mm x 80mm


  • 3D Printer shell from Part 1 of this tutorial
  • Arduino Mega
  • Ramps 1.4
  • SD card of any size
  • 5 x A4988 Stepper Motor Driver with Heatsink
  • 6 x mechanical end stops
  • 20 x male to female wires
  • Smart Full Graphic Display from Discount RepRap
  • Power Supply (12V 30A, OEM)
  • Three prong wall cord and connector (see Figure X)
  • 6 x ¼” ring crimp connectors
  • Large gauge wire
  • Logic wire
  • Electrical tape
  • Tape, Velcro, or other cable management solutions


  • Arduino IDE
  • Marlin 3D printer Firmware
  • Cura 3D Printing Slicing Software


  • Soldering iron
  • Solder
  • Wire strippers
  • Crimpers


  1. Gather Supplies
  2. Assemble RAMPS
  3. Connect Stepper Motors
  4. Connect Hot End
  5. Connect Power Supply


After the mechanical build of Part 1, we must now move to the electrical design. The first step is to define your power requirements. Find the datasheets for all your arts and add up their current draw. This is your absolute minimum power requirement. For a factor of safety, add 30 percent to this number. Keep in mind, though, that as you add components, you’ll have to get larger power supplies if you cut too close to the maximum draw. As such, I decided to use a 12V 30A power supply, since that would continue to serve the printer even with the addition of multiple new parts, such as another extruder or heated bed. Much of the rest of the electrical design is heavily dictated by RAMPS. There are labeled pins on the board for every component that is used in this tutorial. Therefore, the RAMPS board is probably the most important part of the electronics and we will begin there.

Step 1: Assemble RAMPS board

Prepare RAMPS 1.4 board. Some models of the board come assembled, while others require you to solder some connectors. If the second option applies to you, solder the components to your board until it resembles Figure 1.

reprap 3d printer

Figure 1: RAMPS board fully assembled / ©RepRap Wiki

The RAMPS board can also be used for other application, so we’re going to configure the board for 3D printing. Your RAMPS board should have come with a bag of header jumpers. Insert 3 jumpers into each of the teal boxes shown in Figure 2 to connect the vertical headers. Stepper motors move in steps, allowing them to be highly accurate. These headers allow all of the steppers to move in 1/16th steps, increasing the accuracy.

reprap 3d printer

Figure 2: Ramps component placement / ©Rob’s 3D printer

Now, carefully guide the bottom male headers of the RAMPS board into the female headers of the Arduino. Make sure the USB of the Arduino is below the pin labeled D10 and then press them together.

reprap 3d printer

Figure 3: RAMPS board pressed into Arduino board

Step 2: Connect Stepper Motors

reprap 3d printer

Figure 4: Stepper motor wire diagram / ©RepRap Wiki

Insert the five motor drivers into the female headers above where you put the jumpers earlier. Make sure the current limiting potentiometers are faced away from the blue D8 to D10 pins. If you do not set the orientation this way, it could damage the stepper motors. Please refer to below Figure 5 for the correct orientation.

reprap 3d printer

Figure 5: Correct motor driver orientation

For ease of construction, you’ll need to partially disassemble the printer shell that was assembled in the last step. Start by removing the top section of the printer with the pulleys, motors, and extruder. Separate out the wires from the motors. They’ll be needed to connect to RAMPS later. Also, remove the print bed support plate, which was put on the z-axis motors.

reprap 3d printer

Figure 6: Disassembled Printer

Once those preliminary steps are accomplished, it’s time to start soldering. Most stepper motors will come with bare wire ends. These can either be crimped or, as in the case with this tutorial, soldered with another wire to facilitate the connection these motors to RAMPS. I soldered the male end of a wire to the bare wire and used the female end to connect to the header on RAMPS.

reprap 3d printer

Figure 7: Soldered connection between wires

Finally, connect the stepper motors to RAMPS via the pins labeled x, y, and z. In the case of our belt configuration, the two motors on the top plates should be connected to the X and Y headers. It doesn’t matter which of the top motors is attached to which axis due to the configuration used. That will be discussed further in the belt configuration step later. The two Z axis motors should be attached to the headers labeled Z. Check the documentation for your stepper motors for in which order the wires are connected to the board. For the NEMA 14 steppers used in this tutorial, the connection order goes black, green, blue, red, with the black wire at the 2B pin. You may need to flip this polarity if you have set up your z-axis to run in two different directions. Figure 8 below shows the complete set up for all the motors.

reprap 3d printer

Figure 8: Final setup of stepper motor drivers

Step 3: Connect Hot End

reprap 3d printer

Figure 9: Hot End wiring Diagram / ©RepRap Wiki

The hot end and extruder for your printer should have four sets of wires: the extruder fan, the extruder motor, the heater, and the thermistor. Figure 11 will show the final connection of all these components.

The extruder fan should be connected to its dedicated power pins as shown in Figure 10. Your printer may use other fans whose wirings are also shown below. You will need to solder this connection and trim the wires afterward.

reprap 3d printer

Figure 10: Fan placement in RAMPS / ©RepRap Wiki

The extruder motor should be connected to the pins labeled E0. RAMPS has an extra header for a second extruder if you wish to use it in the future.

reprap 3d printer

Figure 11: Extruder connection

The heater will have bare wires that will need to be stripped and crimped. The heater then should be connected to the D10 pin. If you would like to connect a second extruder heater, it would then be connected to the D9 pin. If you would like a heated printer bed, the heater for this would be plugged into D8.

The hot end thermistor should be connected to pin T0. T1 would connect to a heated bed thermistor. T2 would connect to a second extruder thermistor.

reprap 3d printer

Figure 12: Thermistor and heater connection

reprap 3d printer

Figure 13: RAMPS with hot end components connected

Step 4: Connect Power Supply

Take out your power supply. For this tutorial, I used an OEM power supply as shown below, so this tutorial will focus on how to connect that power supply type.

reprap 3d printer

Figure 14: OEM power Supply

Take out your three-pronged cable, shown in Figure 15.

reprap 3d printer

Figure 15: Three-Pronged Cable

Cut off the end, keeping the female plug end. There should be three wires inside colored green, blue, and brown. Crimp these wires and connect them to the power supply. The green wire connects to ground on the power supply. The blue wire connects to L on the power supply. The brown wire connects to N or neutral on the power supply.

reprap 3d printer

Figure 16: Crimped connection of 3 prong plug

If these are not the colors of your wires, either find the datasheet or use a multimeter to test the plug.

Take four large gauge wires of sufficient length. Strip and crimp on the connectors on one end of the wire. Screw the crimped end of the wires into the power supply at the four -V and +V terminals. On the other end, plug these into RAMPS at the green connection pin.

reprap 3d printer

Figure 17: crimped wires for power connection

reprap 3d printer

Figure 18: Final Picture of Power Supply

You can now start reassembling the printer. Put the power supply on the floor of the milk crate and strap it down with Velcro or zip ties. Make sure all the wires are out of the way, then thread the build plate back onto the thread screws. Place the top piece over the top again, making sure all of the wires can reach RAMPS, which will be placed on the outside of the crate. Strap the control board to the outside and your printer should look like below.

reprap 3d printer

Figure 19: Printer Reassembled

We’re almost there! We’re just a few steps away from this wired “framebed” to a fully functional 3D printer. In Part 3, we will continue to configure some of its mechanical parts (e.g., belts and end stops), as well as program codes to test the printer.