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Christ · 07-11-2009, 11:43 PM

You need something that's already the shape that you want, to use as a mold, of sorts.

For plastic convexes, you just use the oven, and #1 or #2 plastic (check the recycling logo, or just know what you're working with.) Set your mold in a pan (in case you melt the plastic too much) and preheat the oven to about 240*. Place the plastic disc (not trimmed out yet) on top of your mold and walk away for about 5-7 mins. Once it's in the proper shape, shut off the oven and let it cool without opening the door. (The sudden cool-down might warp it if you open the door.)

For metal: Use a soft metal, such as galvanized or aluminum sheeting. Find something that approximates the shape and size of the object you want to make. Center punch/drill your metal's center, fasten it to your shaping object, securely. Set up so that your shaping object can spin at a relatively low speed (~100RPM, give or take). Get a 6" steel caster wheel (smaller works, but will take longer, obviously) or a steel ball that fits in a socket that allows it to spin freely in all directions (this is better, casters are easier to come by). While your metal is spinning, starting from the center, apply mild pressure (you'll feel it bend a bit) and start working your way to the outside. NEVER go from the outside in, as this will wrinkle your metal. Work from the center out as many times as it takes to get the desired cone-shape and pitch.

What happens (in the metal one) is that you're actually stretcing the metal over the mold, the same way you would with leather or fabrics. The thing is that as you "work" the metal with the wheel, it heats up ever so slightly (it should get warm to the touch, but not hot) this makes the metal more malleable, and it loses it's "memory". Once you're done working it, give it a few mins to cool and calm down before you remove it from the mold, and it will "memorize" the new shape. You'll need to work the metal from inside to outside several times, though. This process is not fast. It's pretty intensive.

For wheel skirts, I'd stick with denser plastics in the oven, personally.

07-11-2009, 11:43 PM	#10 (permalink)
Christ Moderate your Moderation. Join Date: Nov 2008 Location: Troy, Pa. Posts: 8,919 Pasta - '96 Volkswagen Passat TDi 90 day: 45.22 mpg (US) Thanks: 1,369 Thanked 430 Times in 353 Posts	You need something that's already the shape that you want, to use as a mold, of sorts. For plastic convexes, you just use the oven, and #1 or #2 plastic (check the recycling logo, or just know what you're working with.) Set your mold in a pan (in case you melt the plastic too much) and preheat the oven to about 240*. Place the plastic disc (not trimmed out yet) on top of your mold and walk away for about 5-7 mins. Once it's in the proper shape, shut off the oven and let it cool without opening the door. (The sudden cool-down might warp it if you open the door.) For metal: Use a soft metal, such as galvanized or aluminum sheeting. Find something that approximates the shape and size of the object you want to make. Center punch/drill your metal's center, fasten it to your shaping object, securely. Set up so that your shaping object can spin at a relatively low speed (~100RPM, give or take). Get a 6" steel caster wheel (smaller works, but will take longer, obviously) or a steel ball that fits in a socket that allows it to spin freely in all directions (this is better, casters are easier to come by). While your metal is spinning, starting from the center, apply mild pressure (you'll feel it bend a bit) and start working your way to the outside. NEVER go from the outside in, as this will wrinkle your metal. Work from the center out as many times as it takes to get the desired cone-shape and pitch. What happens (in the metal one) is that you're actually stretcing the metal over the mold, the same way you would with leather or fabrics. The thing is that as you "work" the metal with the wheel, it heats up ever so slightly (it should get warm to the touch, but not hot) this makes the metal more malleable, and it loses it's "memory". Once you're done working it, give it a few mins to cool and calm down before you remove it from the mold, and it will "memorize" the new shape. You'll need to work the metal from inside to outside several times, though. This process is not fast. It's pretty intensive. For wheel skirts, I'd stick with denser plastics in the oven, personally. __________________ "¿ʞɐǝɹɟ ɐ ǝɹ,noʎ uǝɥʍ 'ʇı ʇ,usı 'ʎlǝuol s,ʇı"