Portable External Monitor version 2.0 (PEM2) explored a different construction technique from PEM1. Instead of building a box by assembling its six side pieces (top, bottom, left, right, front back) the box is built up by stacking sheets of acrylic.
With this construction technique, it is much quicker to place components in arbitrary locations in 3D space. Control along the X/Y laser cutting axis are trivial. Control in the Z axis takes a little more effort. The components can be aligned to the thickness of the sheet of acrylic, but if that’s not enough, it is possible to use engraving operations to precisely locate the component in Z.
In contrast, when we want to locate components inside a box at a specific coordinate, we’ll have to design additional pieces – supports and brackets – to mount the item at the appropriate location in the box.
It is also very easy to assure alignment between the parts of the box. Cut a few fastener holes at the same location across all the sheets. After they are stacked up, inserting the fasteners to align all the sheets.
The downside of this approach is that it is very wasteful of material. Each layer will consume an acrylic sheet of the overall X and Y dimensions. And if we only cut away the parts we need for the components, there is potential for a lot of unnecessary acrylic in the final assembly. They add weight without usefully contributing to the structure. Putting in the design time to cut away those parts reduces the time savings of this technique, as it starts approaching the work needed to design supports and brackets in an empty box.
If there’s an upside to the wasted material, it is the fact that this glue-less technique can be easily disassembled. When we’re done evaluating this prototype, every sheet of acrylic can be reused as material for future (necessarily smaller) projects.
Lesson learned: This “stacking plates” construction technique offer a trade off of reducing design time and effort at a cost of reduced material usage efficiency.