A $2000 open-source metal 3-D printer which is controlled with an open-source micro-controller and is a combination of a low-cost commercial gas-metal arc welder (GMAW) and a deltabot RepRap 3d printer.

It runs on free software, has free and open hardware designs, requires no specialized training in welding and existing self-replicating rapid prototypers can print the primary custom components necessary for its fabrication.

Control is provided by an Arduino-based microcontroller board designed for RepRap 3-D printers and requires a host computer to operate.

Customized functional mechanical parts from standard STL files can be 3D-printed.

Specifications

• Miller Spoolmate 100 weld gun supplies the feedstock material.
• Millermatic 190 gas metal arc welders (GMAW) melts the feedstock material.
• Utilizes open source Raspbery Pi and Arduino based electronics.

Design

The metal 3D printer shown in Fig 1 consists of two units, an automated 3-axis stage, which is controlled with the open-source microcontroller and a low-cost commercial gasmetal arc welder (GMAW). The stage is a derivative of the Rostock, a deltabot RepRap. The design of the system adheres to the standards of the RepRap class of 3D printers, so that it runs on free software, has free and open hardware designs, requires no specialized training in welding and existing self-replicating rapid prototypers can print the primary custom components necessary for its fabrication.

Figure 1: Open-source metal 3-D printer during deposition.

The electrical schematic is shown in Fig. 2 and the custom printed mechanical components are shown in Table 2. After acquiring the BOM shown in Table 1, the stage is relatively straight forward to assemble. It consists of three identical axes that are connected together by aluminum stock to form a right equilateral triangular prism.

The three identical axes consist of six printed components (motor end, idler end, pulley, carriage and a pair of belt terminators), two guide rods, stepper motor, limit switch, timing belt, linear and rotary bearings and various fasteners. A single pillar is built by attaching the motor, limit switch, idler and the two smooth rods. Two LM8UU bearings are inserted into the slots in the plastic carriage and slide onto each rod and the two 608zz bearings are fastened into the center holes in the top plastic idler.

Figure 2: Electrical schematic of the open-source metal 3-D printer

The T5 belt is looped around the pulley and idler, fastened together with a pair of belt terminators and then one terminator is fastened to the carriage. The end effector is also a printed component and is attached to the frame by six tie rods. The tie rods are constructed from carbon fiber rods and miniature tie rod ends used in remote controlled models. The plastic end effector is protected from the heat of welding by a 1.5" thick piece of calcium silicate. The stepper motors, power supply and limit switches are wired to corresponding terminals on the microcontroller board as shown in Fig. 2, which is connected to a computer running Linux with a USB cable.

Control is provided by an Arduino-based microcontroller board designed for RepRap 3- D printers and requires a host computer to operate. The welder is setup for the wire to be used for printing by manually running beads and assuring that it is functioning correctly. Shielding gas (75% Ar/25% CO2) is employed at a rate of 20 CFH. The stage is placed under a fixture designed to hold the welding gun perpendicular to the build surface. After leveling the stage, the distance between the build surface and nozzle is set to about 6mm by adjusting the welding gun fixture.

Upon receiving a print job, the printer controller moves the stage into its initial position and starts the welder feeding wire. The arc is initiated automatically and the stage moves at a relatively constant speed laying bead in the pattern dictated by G-code. The model is built in the z-direction essentially by padding one bead atop another until the entire depth of the model is created. The model can be hollow or partially to fully infilled. Upon conclusion of printing, the stage moves the piece away from the welding gun and terminates wire feed and welder current. Prints approaching an hour in length have been performed without hitting the duty cycle of the consumer-grade welder employed in this initial investigation; print duration is of course a function of the size and complexity of the model being printed.