Add links to 3D enclosure designs

hardware/README.md

@@ -44,7 +44,7 @@ An older version can be found
 ![Slightly simplified WALT Schematic](WALT_schematic_simplified.png)
 
 
-### Notes ###
+### More electronics notes ###
 
  * If using Teensy 3.1 instead of LC, it won’t be able to directly read
    the screen photodiodes - a buffer opamp will be needed. The screen photodiodes
@@ -56,3 +56,11 @@ An older version can be found
  * Note the different setup of the laser and screen photodiode. The laser one
    uses internal pullup resistor (about 20k), enabled by pinMode(PD_LASER_PIN,
    INPUT_PULLUP);
+
+## Mechanical ##
+
+Enclosure must be made from a non conductive and non transparent material.
+
+* The enclosure used for r0.7 production run is available in this repo as [STL](enclosure/WALT_recessed_enclosure.stl) and [STEP](enclosure/WALT_recessed_enclosure.step) files. It also used four M3x6 screws (McMaster-Carr PN 92000A116) and M3 hex nuts (McMaster-Carr PN 91828A211)
+* A slightly simpler enclosure suitable for printing on a desktop 3D printer is available as a [public OnShape project](https://cad.onshape.com/documents/6410a1ac7964cb29c4a5ba41/v/32bc78539f48ab7f514eeb31/e/fa513fcc84a825e97020c8b3) and [STL](enclosure/WALT_3DP_enclosure_v7.stl) file
+* A minimal enclosure suitable for 2D cutting from any 5 to 8 mm thick substrate is available as a [public OnShape project](https://cad.onshape.com/documents/5d7f21c8877ea8961bc499ef/v/84a66f3baf5f4a8f41be3bd7/e/e2a23559efbeb63be3916123)