Prefacing this post with a disclaimer that this may not necessarily be the best solution to making visors but it is the process I've come up with that'll work on nearly any shape of visor and is relatively quick, dirty and can be done with commonly available materials since the printed parts and the resins are just nice to haves. Visibility isn't crystal clear but it's much better than my previous attempt and is much cleaner than using the tint film on the complex curves.
To start the visor process I modeled the exact form that I needed to match the helmet by creating a Patch surface leading from the internal edges where the visor would be mounted. This zero thickness patch was then manipulated to add the curvature required, was thickened and prepared for printing. Before cleanup begun I did a test fit to make sure that there was no warping or deforming in the printing process, everything checked out and I moved onto a quick 80 grit cleanup with the mouse sander. From there I mixed up a small batch of XTC3D for gap filling and to create a hard glossy surface that would create a cleaner vacuum pull. If you don't have access to a 3D printer you could sculpt or carve out a vacuum buck as well, it'd just take a different skill set to pull off and I'm super not great at sculpting.
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For the vacuum former effectively all you need is heat source, a vacuum and some sort of nozzle for the vacuum to heat and shape a sheet of
1/32" PETG. For the heat source I used a toaster oven that was left in the local free stuff pile that appears at the end of the month when people are moving. The vacuum was my trusty ShopVac. For a nozzle I built a quick box using 1/4" MDF, hardboard and pegboard the same size as the maximum area of the toaster oven. To hold the PETG sheet in place in the oven I built a quick frame using hardboard and a system of bulldog clips since both would be safe heated to the temperatures in the oven.
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Since I was being cheap with filament I only printed the visor buck 2mm thick and filled in the back of the buck using scrap
XPS foam carved to a rough shape. The chunks were glued together with
Spray Super 77 clamped together with a standard weight toolbox and left to cure. Once the spray adhesive was set the backing shape was cut using a hot wire foam cutter. Gaps were then plugged with air-dry clay to help reduce the volume the vacuum had to pull which will result in a closer fit to the buck.
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I got plenty of practice vacuum forming for this project, all said and done I pulled six different visors. Plenty of different combinations of heat, time and surface coatings. The one lesson to pass on for this is to treat it like a BBQ, low and slow. Get to the transition temperature of the plastic and let it sit there for a bit and watch for the droop.
I've tried a few different surface coatings and as I prefaced the post with, this is the easiest by far I've tried. The following 12 images are the test application of
Krylon Looking Glass Silver, there is also apparently a gold version which could work well for Mister Chief but I had this in a local store and thought it was worth a shot. Light coats one minute apart and then fully set within ten minutes is what the label says, this was sprayed on in 32°C temperature so times were slightly reduced. The first image in each pass set is the interior as sprayed, the second is held up with a background ~20ft away set as the camera focus and the third is a side on shot to check opacity with a darker background which is more illuminated than the normal interior of a helmet. Three passes on the test piece seemed like the magic number for visibility through and selectivity of the outside surface.
First Pass
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Second Pass
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Third Pass
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Fourth Pass
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I'm a sucker for yellows and oranges so I used a
Tamiya TS73 Clear Orange Spray Lacquer in three light coats and let cure for 24 hours and then added three coats of the Looking Glass Silver. The overall colour is more consistent with less grain to it and the visibility is much better. It's not great in the picture here because the visor isn't yet fitted but in the dark of a helmet to the light of the outside, everything is awesome. The last image is what I was dealing with for the test fitting looking at the same wall with the assistance of contrast from inside the helmet darkness.
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I'll likely be looking for better procedures to improve on the build but this will work for the next couple of conventions.
