Instructables
Picture of How to make a big suspension lampshade
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We had to improvise a sery of lamps for the annual design school exhibition of 2010. We came up with an idea of a very big dôme shiny blue inside and mate black outside. But how to produce over 20 giant lamps in only 2 weeks? Here is the solution we found :








 
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Step 1: Trash can

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First, we found a big trash can. A kind of big cardboard sonotube. This seemed perfect to create a vacuum chamber.

Step 2: Hole

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We inserted a tube inside the sonotube and sealed it with silicone. The tupe was was the good dimension for our shopvac. We attached them together with black tape. 

Step 3: Thermoform

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We heated up a 1/8 clear sheet of Polyethylene clamped in a steel frame. Of course... you need a really big oven (wich we had). The sheet was 2'X2'.
Once the sheet is just above it's melting point (the surface starts to curve), put it on the trash can. Start the vacuum and wait until the dome is formed. Make a T shape ruller to know the radius of the dome while forming. 
Stop the vacuum and let it solidify.

Step 4: Hole

Picture of Hole
To create the hole on top of the lamp shade, we heated an aluminum tube with a torch during 30 seconds. Once reached the good temperature, we used it to melt a circle on top of the dome. We used IKEA suspension kits so the hole had to be 1 1/4 inch wide. 

Step 5: Cut extra plastic

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We clamped a Dremel to a table and used the flat surface to cut a regular edge. You will probably have to remove some extra plastic with grid 120 sandpaper. 

Step 6: First layer

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The first layer on the clear surface has to be the color you choosed. Use a paint that has very good covering capacity.

Step 7: Second layer

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The second layer has to be while paint. This will give the glow to the color inside and patch the light holes. 

Step 8: Third layer

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The last layer we chose was mate black paint (or black board paint). It gives a nice contrast with the colorful and shiny inside. 

Step 9: Bulb

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Chose your bulb. Don't go over 60 watts. Make some tests! 

These are great!

knoakes4 months ago

very nice! Good job!

zappenfusen2 years ago
Sam,
Do you have any idea what the Melting point is? I've been searching for this method for awhile.

thanks,
Zapp
Samuel Bernier (author)  zappenfusen2 years ago
Sincerely, the figure out the melting point with my eyes. When the sheets gets about 3 cm under the frame, it is time to start the vacuum. PET is easy to work this way. Unlike other plastics.