Are We Not Men? We are Geo.
Posted on February 24, 2008 in Behind The Scenes
This year’s Advertising Federation awards party (ADDYs) had an 80’s retro theme. For us, there were few 80’s icons that were cooler than the great New Wave band, Devo. Our idea was to come dressed as the band with a slight change in name from Devo to Geo. And though creating a costume would be relatively simple, it would need to include the band’s signature red “Energy Dome” hat. Unfortunately finding these unique hats became a problem. Either they were very expensive to purchase or out of stock from online costume retailers. The solution…make them ourselves. Animation director and engineer-hobbyist extraordinaire, Troy Davis, took on challenge to recreate the plastic multi-tier hats. Here’s how he did it:
How to make a Devo Energy Dome
To construct the hats, I needed to start with a single pattern that could be used for multiple castings. This was made with 2 thicknesses of multiple density fiberboard (MDF) to create the varied heights of the different layers. The bottom two layers are 1-3/4 inches tall, the third level is 1-1/4 inches and the top layer is ¾ inches thick. The pieces for each layer were cut out and the same size pieces glued together to make a solid block for each layer. The layers will remain separate from each other until they’re milled into the proper shape.
The discs that make up each layer have a slight taper of about 15 degrees leaning toward the center of the hat. To cut this shape I decided to use a rotary table and my Harbor Freight Mini-Mill. Holes were drilled so the wood could be securely attached to the rotary table. The column of the mill is rotated 15 degrees off its vertical center to make the tapered cut.
The wood is bolted to the turntable and the head of the mill is slowly lowered as the table is rotated. I’ve only used this machine to cut metal, so when the MDF began to cut it was hardly noticeable (except for the unbelievable amount of sawdust that went everywhere). The wood is soft and easy to cut, but I still made a lot of rotations and lowered the mill head a little bit each time around.
The rotary table has a handle that spins 72 times for each revolution of the table, so by the time the bit finally made it thru the bottom of the wood, I’d had a pretty good workout. I had to constantly use the ShopVac to try to contain the sawdust.
Finally the layer is complete, with a fairly smooth and angled surface. It can now be removed from the machine and flipped over to form the base. The next layer goes thru the same process…after three more the mold is beginning to take shape. Finally the separate layers are glued together and sanded.
The vacuum process that will form the plastic hats will transfer any imperfection from the mold to the casting so the mold has to be as smooth as possible. I used multiple coats of Bondo to smooth the wooden mold and sanded between coats. The Bondo turns extremely hard as it dries and I eventually just used plaster to make the smoothing process a little easier. The photo here shows the mold right after the 1st layer of Bondo was added.
I built a simple vacuum forming table based on the online tutorial found here.
It’s basically a piece of MDF with a hole in the center sitting on a small riser. An insulated border around the hole helps to crate a seal when the hot plastic entirely covers the mold.
Underneath an ordinary vacuum hose is securely attached to the table. Silicon sealant was used between the metal and the MDF to prevent air from leaking into the system. I found an extra sprinkler head part in the garage and it made an air-tight link between the vacuum hose and the threaded pipe connector. The vacuum I used was a 1400 watt household vacuum with a hose attachment.
Aluminum framing designed for window screens is used to make the frames for holding the hot molding plastic. The base diameter of the DEVO hat is just under 10 inches so I made 14 inch square frames to allow for a little extra room all the way around the mold. Giant paper clamps are used to keep the two frame pieces held together. One of the most difficult aspects of this project was trying to find metal corner brackets to keep the aluminum frames connected. The stores in my area sell plastic corner pieces that aren’t designed for the high oven temperatures these will be undergoing, so I ended up milling these from a piece of ½” 6061 aluminum bar. They had to be thinned to slide into the openings, but they fit snug and work well to keep the frames together.
I found a local plastic supplier and purchased two 8’x4’ sheets of .080” high impact polystyrene (HIPS) to use as the material for hats. The material is easily cut by scoring one side with a utility knife and bending the other until it pops cleanly from the sheet. I probably could have used a thinner plastic, but I like the sturdy thicker weight of the .080”.
The 14 inch squares of plastic are placed between the two frames and these large paper binder clamps are used to keep them firmly pressed together. I’ll put one or two on each edge of the frame and remove the wire handles from the clamps before they’re heated.
I taped the foam border sheet to the table and checked to make sure the seal of the insulation perfectly matches with the aluminum frame. It’s important that the vacuum be as tight as possible to closely capture the shape of the mold.
When the hot plastic is ready to be formed, I’ll have to move quickly to transfer the plastic’s frame from the oven to the mold. To help line-up the frame to the insulation border below, I’ve added two support frames to the vacuum table that will easily identify the corner above the mold so I can bring the frame straight down onto the mold. The smooth (however unattractive) mold is placed onto the table and we’re ready to start melting plastic…we’ll almost.
The mold can’t completely block the vacuum hole, but it can’t be too high either otherwise the molding material will to try to form under the mold. I attached these rubber feet to the mold, it seems to create the right height so the molding plastic just makes an edge at the bottom of the mold without tucking under its edge.
I heated the oven to 400 degrees and placed some coffee cups as risers at the corners of the oven rack. These are used to separate the frame from the wire rack below. As the plastic gets hot, it will begin to bulge and I didn’t want the hot plastic to touch anything in the oven. After a couple of minutes the plastic is ready to go. With gloves now, I quickly grab it out of the oven and rush it to the waiting vacuum table just 3 feet away. The vacuum is already running and I rush to align the edge of the frame with the alignment guides I installed earlier.
The frame is brought straight down over the mold and because the plastic is hot, there is almost no resistance. The vacuum takes just a few seconds to remove all the air from under the soft plastic. It quickly begins to take the shape of the model underneath. Both of these photos here show the moment the aluminum frame has just contacted the foam insulation and created the vacuum seal. The plastic is curving into shape but the ridges and steps haven’t been formed. The final shape is formed in just a few seconds, and after 5-10 seconds all the detail is clearly defined. I kept the vacuum going for about a minute to allow the plastic to cool. I also used a heat gun for a few seconds blowing high heat onto the top two rings of the hat to keep the plastic there soft a little longer. This helped to add definition in an area that the vacuum was stressed to empty.
After the plastic has cooled, it is taken off the vacuum table and the mold is removed. I thought the conical shape of the hat would allow the mold to be extracted easily, but it’s captured inside the plastic extremely tightly and took a lot of pressure to get it to release. I ended up pulling the edges of the plastic sheet while pushing down on the top of the hat plastic to free the mold. After that I used a utility knife to trim the hat from the excess plastic, then used a file to even the edge and finally touched up with sandpaper to smooth the sharp rim.
There were a lot of hats to paint, so I constructed a small spray booth from a plastic storage container and an illuminated ventilation fan. The fan is the kind normally used in a bathroom and I attached a hose to vent the fumes outside. Filter material was taped to the fan inlets to reduce the amount of actual paint moving through the fan. A turntable was used to easily rotate the hat during the spray painting producing a smoother and more consistent finish. I picked a red spray paint designed for use on plastic to prevent the paint from chipping or flaking from the semi-flexible hat. Two coats inside and three coats outside and the hats were beautifully painted.
To keep the hat firmly held onto the head I thought a foam ring would be a good way to go. I found a local foam supplier and had them cut 1 ½” thick foam into 9” discs. This is the kind of foam that is used for camera cases with cutouts to hold custom shaped parts. The foam cut OK with the serrated bread knife technique that was recommended by the foam dealer, but since the bread knife left a bit of a ragged edge, I ended up using an electric carving knife to cut the inner ring. I clamped the knife’s handle into the jaws of my bench vise with the blade penetrating an open hole in a strategically placed table saw platform. I was able to guide the foam smoothly around the powered blades to cleanly cut out the shape for the head. The exposed bottom side of the foam was painted black, leaving the original foam unpainted where it will be contacting the skin.
To secure the foam ring to the interior of the hat, contact cement was painted onto both surfaces and when nearly dry they were pressed together. Once the two sides of the contact cement touch each other they’re connected for good so I used wax paper to separate the pieces during alignment and then removed the paper.
Finally, completed hats! Actually, the hats turned out better than expected. The surface is smooth and reflective and the construction is lightweight, sturdy and comfortable. Now we’re ready to suit up and head to the awards. Check it out.