In this video Bill explains some of the engineering principles underlying the design of a DLP (digital light processing) 3D Printer. The printer featured is an Ember printer, manufactured originally by Autodesk, but now an open source project. Learn more about ember: http://ember.autodesk.com.
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Videos linked to in at the end of the video:
Micromirrors
Ember Details
Overview of 3D Printing
Element 14 video: