Week 14 - Apr 18th 2012 - Mechanical Design
Weekly Assignment - Begin the class machine project
Over the next three weeks, the class is required to develop and fabricate a machine - whether this is the MTM Snap milling machine, another project that has been made available, or something entirely of our own creation. As a group, we decided to try and make something of ongoing use to the Manchester FabLab and soon decided to put together a 3D scanner, given the current lack of 3D scanning capabilities. There are many such projects published online, and after trawling through many of them we decided to base our machine on the FabScan project, developed by Francis Engelmann.
For the initial week, we split into groups to make initial assessments of the mechanical and electronic requirements. I worked on the mechanics, which for this project require a camera mount, stepper motor-mounted laser mount, and stepper motor-rotated turntable to be enclosed within a case. The project documentation provides files for laser cutting these parts from 5mm MDF, however as our build is intended to be a long-standing item of lab equipment we decided to beef up the specs a little, so will make the case from 12mm MDF and the inner structure from 6mm MDF. This means we will need to use the shopbot rather than the laser cutter to fabricate these components. Also, the original case uses screw slots to hold the components together while we felt slot-and-tab fittings would be just as good provided they could be made tightly enough. I therefore began making new files using Sketchup based on the internal measurements in the original plans, but modified for 6mm/12mm MDF with tab fittings.
Below, a test run for one of the internal components to ensure 6mm MDF would be strong enough:
6mm MDF was deemed fine, so the entire structure was built in Sketchup (by me and David C) then fabricated on the shopbot.
Using nominal tabs and slots strong joints were achieved, so the case is ready for the addition of hardware in the following weeks.