Building a CNC machine

SketchUp 3D drawing of the CNC machine model provided by

Most computer aided manufacturing systems have a common structure: a multiple axis control system. This allow for accessing a specific point in space to either remove material (laser cutter, milling machine, CNC router) or add material (3D printing). The number of axes depends on the type of machine and the flexibility needed. It can vary from two axes for a laser or plasma cutters up to five axes for the most complex milling machines. The most common tools can be controlled in three directions for the tool to reach any point in the 3D space.

After a first taste of computer aided manufacturing using a 3D printer, I realized that the mechanical part of such a system remains relatively simple. For each direction, one motor provides the motion of the tool. The most common system involves a stepper motor combined with a mechanism that converts the rotation of the motor into a translation. This can be achieved by belts or lead screws. Added to that, one or several rails are used to limit the friction forces during the motion of the tool.

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A 3D printed arm for Aristide

Model of The RIT Arm v2

Few month ago, I was told the story of Aristide. Due to a congenital disease, Aristide is born without arms nor legs. He is now 9 years old. He lives in Senegal where it is difficult to get help with such a complicated pathology. It is already hard to have access to simple leg prosthesis so thinking about a patient specific bionic arm was completely out of the question. Fortunately, the rising of 3D printing methods allow for the realization of relatively simple custom prosthesis. Several examples can be found ranging from the simple shape to futuristic bionic arms a la Star Wars.

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