Smily Mask (Antex style) Proof of concept

####Update 20200220_1903
SmilyMask(Antex)_Param.f3d Now can customize with how big you want it to be.
Changelog: Offset using midpoint, so most time will work. Do not change parameters drastically, change one mm by one mm (Less likely will break)
Still known problem: Changing JawDepth,JawHeight and JawClerance will make the Loft Object randomly decide to Twist/Add a seam that result in broken extrusion of the links, but you can go back to the yellow/red step and fix it ( Fairly easy )
Experimental: SmilyMaskParamFixSupport.f3d, need to allow single extrusion wall when slicing.

####Background
As the new Novel Corona Virus outbreak happened in Wuhan, despite WHO/CDC experts opinion that there is no evidence that suggest that surgical mask and N95 mask can prevent healthy people from infection ( because of lack of traning and fitting test ), people have anxiety when they see someone without a facemask.
As we do not live in an isolated society, I beileve we also should understand people's anxiety. Also any mask can reduce the risk of droplet transmission if the one wearing it is a carrier of the virus.
This remind me of a kind of transparent Polycarbonate sheet mask that they wear in food service industry that exactly does this: prevent most droplets and does not make breathing harder, and the mask can be cleaned with alcohol to prevent microbe from building up.
I did a bit of research online and I don't know who originally designed it, but most result comes from a company http://www.antexmask.com/. So I decide to replicate the design and share it (fair use principle).
Other than the print, you'll need:

• Some elastic straps
• A polycarbonate sheet (0.5mm in the design, but I'll share the source file for you to change it)
  After printing, you'll need to cut the sheet to the length to the slit(approximate, no need to be precise) and slide it into the slit.

Known problem / future improvement:

• Although when doing the engineering drawing, I used a parametric method for various size, becaused I used a lot of tangents and offset when sketching, the computation will result in error if the parameter is changed too much.
• May need to redraw the model using less chained constrain for better calculation (Also might switch to OpenSCAD/JSCAD)
• The center of the Chin-rest needs support which makes it uncomfortable if not sanded.