Roughly one year ago I was taking “Design and Manufacture Lab” — a requirement for access to the university’s mills and lathes. The only other student in my section not studying mechanical engineering was a friend studying chemistry. The two of us had decide the semester prior to build a CNC — or computer numerically controlled machine, more specifically a machine with three dimensional control of a cutting tool. The lab included a lecture emphasizing the precision of modern manufacturing and the calculations of cutting speeds and feed-rates that allow us to safely work with aluminum. We began our project with medium-density fiberboard and ultimately found our way to 80/20 slotted aluminum extrusion.
The aluminum can be easily cut using a hand- or band-saw, although most suppliers can accommodate orders with specified lengths. In the image two extrusions have been joined using a cheap machine screw. Ideally the hole is drilled on a drill press and the end is tapped on a vise. No tapping fluid is required as long as you remember to discard piled up chips frequently!
While constructing our machine, my colleague and I were lucky enough to gain access to a commercial CNC that was housed in Broun Hall of Auburn University. By using this machine to make simple cuts into plastic (HDPE and PLEXIGLASS) the lessons learned in the Design and Manufacture Lab were translated into g-code.
By the end of the semester our machine began to move. After some trials with plastic the machine was put to the test cutting wood. Given a different spindle this CNC could easily mill aluminum. A much quieter — and IMHO also more interesting alternative would be a plastic printer. Rather than cutting away material the tool would deposit plastic much like a hot glue gun. Luckily the RepRap has inspired many people along with myself and kits have become readily available.
As of March 2011 motor controller issues have been the biggest hang-up. Once the current parallel port based interface is replaced with a more modern USB unit the process of mounting the extruder will begin. Due to the current requirements of the stepper motors used on this CNC the MakerBot electronics will not work out of the box. Being an open source project all schematics and BOMs are readily available, and the lack of progress on this project lies mainly with me!
The plastic extruder heater and nozzle.
Tags: 8020, aluminum, Auburn Alabama, Auburn University, Broun Hall, CAD, CAM, CNC, Design and Manufacture Lab, DIY, gcode, HDPE, machine, MakerBot, making, RepRap, RepStrap
