With a team of 4 others, I helped design and construct a 3-axis CNC router as a project for the class Principles of Integrated Engineering. The class tasked us with an open-ended project: over a couple of months, we were to create anything that integrated both mechanical and electrical engineering along with some aspect of programming. We were assigned groups of 4-5 people with different disciplines of interest and experience. My group decided to build a desktop CNC router inspired by our school's Shopbot Router.
Over this project, I worked primarily on designing, manufacturing, and assembling the mechanical systems within the router, focusing on the gantry system and how to make it rigid enough to handle cutting loads. For a more in-depth explanation of this and the other systems please look at our team website linked below.
The "Shopnot" CNC Router is able to produce a reasonable quality cut with reasonably low tolerances. The first test piece it cut can be seen to the right, a pi symbol token. G-code for simple shapes like this can be easily generated and sent to the router for it to cut in its software. For more complex shapes, dxf files can be uploaded along with fusion CAM.
To get such a high degree of accuracy, rigidity was one of the main concerns in the mechanical system. Hence, the entire frame is metal, manufactured with high precision with a mill and water-jet cutter in order to ensure the motion of the gantry system is steady.
The main movement of the x and y axes of the gantry is carried out by two NEMA 23 stepper motors with lead screws coupled to them. For each axis, there is a lead screw nut mounted to the body that moves (the spoil board for x and the spindle head for y and z). We opted to move the spoil board itself for one of the axes as it reduced the complexity of the gantry and overall improved the rigidity of the entire system. Pictured to the right is the x-axis of the gantry on which the spoil board moves. On this axis and all others, two linear rods provide stability to the motion.
The (z-axis) spindle moves with the same method as the other two axes; however, it uses a much smaller motor as it has far less to move. A high-speed DC motor was used for the tool head. Any standardized ER 11 collet and tools can be placed in the head and should be usable for the router.
