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RepRap 3D Printer

Author: Rodolfo Antonio Salido Benítez​

Completion Date: Summer, 2015

Software: Simplify 3D, Arduino, Printrun

Place of Creation: Califronia Institute for Biomedical Research. (Calibr)


Techniques: Computer aided design & manufacturing, additive manufacturing, and micro controller programming.

Materials: Bill of Materials

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A RepRap 3D printer is a self-replicating rapid prototyping device utilizing Fused Filament Fabrication (FFF) methodologies to produce 3D models from thermoplastic materials. These machines are meticulously designed to replicate themselves by manufacturing their own components, which can then be assembled into additional RepRap units. Parts that the machine cannot fabricate are designed to be easily sourced and highly standardized.

Founded by Adrian Bowyer, the RepRap project is frequently cited as a significant catalyst for the popularization of desktop 3D printers. The conceptualized RepRap machine was envisioned as a self-replicating autonomous robot with a mutualistic relationship with humans, where the latter would assist in the assembly of parts in exchange for additive manufacturing services. Bowyer posited that to maximize the machine's "fecundity," its source should be freely available, enabling users to own and replicate the machine. Consequently, the RepRap project was licensed under the GNU General Public License.

Mini Kossel

A modified Mini Kossel, a variant of the RepRap, was constructed by 3D printing necessary plastic components in Polylactic Acid (PLA) using a Robo R1+ commercial desktop 3D printer. Non-printable components were independently sourced from online retailers such as Robotdigg, Amazon, McMaster Carr, and e3D-online.

The electronic components of the machine include the widely adopted RepRap Arduino Mega Pololu Shield (RAMPS 1.4) and the open hardware Arduino Mega microcontroller. Motion is driven by NEMA 17 motors coupled with Pololu stepper driver boards. The machine features an e3D v6 hot-end with a Bowden extruder fed by a geared NEMA motor. Due to the highly modular design of the RAMPS 1.4 shield, the Mini Kossel was later equipped with an LCD screen and SD card reader for interfacing. The machine operates on Rich Cattel's Marlin firmware, which allows for automatic calibration of an uneven printing bed and correction of imperfect frame geometry.

The personally manufactured Mini Kossel is capable of printing PLA with a resolution of 200 microns in the Z dimension and 35 microns in the XY dimension, based on empirical testing. It features a cylindrical printing volume of 160 mm in diameter by 210 mm in height.

I opted to build a delta 3D printer rather than a Cartesian printer due to my fascination with the kinematics underlying the former's design. While a Cartesian printer operates in the XYZ coordinate system by assigning X, Y, and Z motion commands to motors that drive independent translational movements in their respective planes, a delta printer achieves movement in the XYZ coordinate system by orchestrating the coordinated movements of three interdependent motors.

In simplified terms, disregarding various constant offsets, three motors move carriages along vertical towers to mechanically form three right triangles, with one corner of each triangle converging at a common effector head. These triangles have fixed hypotenuse lengths but variable side lengths, which can be precisely adjusted to position the effector head accurately within the XYZ coordinate system. Thus, to execute 3D printing instructions, a delta printer must perform inverse kinematic calculations to translate XYZ displacement into coordinated vertical tower movements. For instance, a Cartesian printer effecting a 10 mm movement in the Y direction requires only the use of a single motor dedicated to the Y plane, whereas a delta printer must orchestrate the movement of all three motors to achieve the same displacement.

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Diagram of one mechanical triangle illustrated with variables and constants used to calculate inverse kinematics. Image from Delta Robot Kinematics by   Johann C. Rocholl

delta printer looping layer composition.

The 3D printed projects presented in this portfolio, with the exception of those described on the Device Prototyping page, were manufactured using this 3D printer. This demonstrates that a personally manufactured, self-replicating machine can be employed to materialize a wide variety of ideas, with applications ranging from simple ergonomic workstations to complex mechanical devices that interface with the human body.

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