Week 16 - May 2nd 2012 - Machine Design
Weekly Assignment - Fabricate the class machine project machine control components
As outlined in Week 14 we have decided to build the FabScan 3D scanner. We re-designed the mechanical components and fabricated them on the ShopBot. We now have to design and manufacture the electronics that will control the scanner and interface with the hots computer.
The FabScan project uses two A4988 Stepper Motor Driver Carrier boards to interface with the stepper motors. In the FabLab Inventory we carry the A4985 stepper driver; this is an equivalent chip to the A4988 except the current rating is 1A vs 2A, and the package is different. I designed equivalent driver boards (based on the typical application circuit shown here) in Eagle which will need to be fabricated. The Eagle schematic and layout for these boards is shown below (Allegro Eagle library here).
These boards will interface directly with a fabduino which will connect to the host computer via an FTDI cable and allow the existing software to control our updated fabscanner.
We also 3d printed two components that are required for the FabScan; a part to hold the laser, and a part to mount the turntable on. Designs for both parts were available with the FabScan documentation, however the dimensions were not correct as our laser size and also stepper motor spindle diameters were not exactly the same as those used in the original project. Luckily the CAD files were supplied as OpenSCAD format, meaning the dimensions could quickly be altered within the code, and appropriate .stl files exported that would fit our components precisely.
