the images above show the final CAD model of the unit. Over all dimensions are 198mm [7.8″] wide, 275mm [10.8″] deep and 287mm [11.3″] high. The walls of the chamber are made of a single piece of 0.5mm PS sheet that I had leftover from another project. The sheet is held in place by being fit in the slots in the base (light Teal) and top frame (Dark Teal). All internal surfaces will be lined with aluminum foil to help reflect the light all around. The design uses only a few screws with the rest of the parts nesting or being press fit into each other. You can see the user control panel with its green & red LEDs and black button, at the top of the unit near the opening lid (light red). The height and diameter of the chamber were sized to accommodate the four N95 masks that I modeled, while still getting the masks as close to the UV-C bulb as possible. It should also be possible to fit many other disposable N95 masks types in here as well.
The above image shows the cross section view of the unit. You can see how the UV-C lamp and the vertical channel (light yellow) are captured between the top frame and base. The vertical channel has a hollow opening inside of it to run the wires for the daughter control board and the safety limit switch down to the main control breadboard (green) in the base. The light purple part is the big internal tooth gear that is pressed onto the U-shaped rotating part shaft (light teal, center). I added flats to any shafts that have gears pressed on them so there is no chance of anything slipping. The gray TT motor in the bottom right has a small pinion gear on its top shaft which mates to in the internal gear teeth. Again all joints and rotating parts use small 1060 bearings.
In the above image I made a number of the parts transparent for clarity. You can see the elliptical reflector shape around the UV-C lamp which helps to try and reflect some of the extra light on the bulb backside around directly to the mask. On the bottom back side of the unit, you can see the two DC barrel jack plugs and the trinket usb micro connector port. As the unit will be fairly light, the large Lid has hard stops (as shown) to prevent shifting the center of gravity and tipping the unit over, while still providing access to the mask.