Tuesday, January 31, 2012

Vacuum forming on the cheap

Vacuum formed cars. They sucked.

For a long time now I've been planning a small tutorial on how to build and use a inexpensive vacuum former. You can make a lot of things with a former, but I'm going to show you how to copy cars to use as terrain. This idea was the inspiration for my project.

The Materials

1/2 " MDF board, about 24 in square
A high suction vacuum with the hose( I used a Shark I got from goodwill. Don't laugh, its got some power!)
PVC elbow that fits your flange and your vacuum hose
3/4 " weatherstripping
plastic or acetate
3/4 to 1-1/2 wood for your frames
screws, glue, wingnuts
4 sturdy plastic cups or blocks to use as risers
metal window screen
shelf brackets
Plastic for sale signs or other thin polystyrene

There is a lot of info on how to build a vacuum former and the concept of its uses available on the Internet. I strongly suggest you reference other materials besides my amature how-to. Our end goal is to build this:

Please note: Your end results may vary. I'm not responsible for your project not turning out, your house burning down or any bodily harm you might cause on yourself or others. Use your brain, be safe, and don't try this if your unsure of any aspect of it.

So lets get Started!

Making the board
This is the board, topside.  I partially drilled a hole larger than my flange size in the top of it. Then I completely  drilled a hole exactly the flange size through the board. I sanded the edges some, the idea is to create a black hole effect increasing the suction velocity as it narrows.

The boards bottom side. I glued and screwed my flange on the bottom, lined up with the hole. I used apoxy, but you can use silicone if you prefer. The main point is to make sure its sealed completely. My PVC elbow is threaded into the flange with thread seal tape. I also glued on plastic cups to give it some lift so its more like a table and everythings not balancing on the elbow. (ignore the grid, it was from another project)

This is why i used that elbow size, it fits the hose. adjust yours accordingly.

Building The Frame
Frames are going to have different size variables based on several things: the size of your board, the size of your mold material, and the size of the object your copying. Instead of giving you exact measurements and the like, I'm going to lay down some hard fast rules you need to follow when you make it.
1. The frame set must be smaller than your mold material. if there are any gaps, you will not get a a seal and the process wont work.
2. The bottom frame must have all the corners sealed with caulk or glue.
3. For every frame set you have of a different size, you will need a matching weatherstrip pad. (more on that in a bit)
So In my design i used two matching frames. The bottom frame is sealed and is where all the action happens. The top frame is there to just hold the plastic in place while its all hot and melty. I lined these up with a bolt and a wing nut.

I used signs as my mold material. they're pretty cheap and come in a variety of thicknesses.

The weatherstrip pad (cause I can't think of what else it should be called)

On my board, I put down a sheet of acetate that was bigger than my frame with the center cut out of it. You can just cut enough so its not obstructing the hole, if you prefer. I glued down my 3/4 weatherstrip to the acetate the exact size of my frame. I again sealed any joints or corners with silicone caulk.

Onto this I laid out a single layer of window screen. This acts as a diffuser for the suction.
I then taped down the acetate edges, just to make sure there were no leaks.

The Process

I used clamped-on shelf brackets as a guide to line up my prepped frame. Speed is key to a sucessful form, so this will help you align your hot plastic and frame quickly.

Center your object or objects so there is space from the sides of the frame and from each other if doing multiple projects. A word of caution, multi projects can cause the plastic to "string" from one object to the other, kinda like a wet bedsheet. After everything is set up, turn on your vacuum and  place your prepped frame in a pre heated oven. (about 350 degrees) I put mine on a wire frame that keeps the plastic off the racks and the oven bottom. This process will take only seconds so dont go anywhere. I dont even close the oven door all the way so I can keep an eye on it.
 * safety note* You are about to melt a sizeable chunk of plastic in your oven. Besides needing to be extra cautious so you dont have your body parts shrink wrapped, You need ventilation. Run your exhaust fan. Open your windows. Run a fan. Wear a respirator if you have one.  
Your plastic will start to ripple, then it will smooth out, and then start to sag. When it sags its time to move! Take it out quickly yet gingerly, line it up with your shelf brackets, and drop it down on your project. Let the suction pull for a while. If, when you gently tap the plastic, its ridgid again, you can turn off the vacuum. Thats it! Remove the item you copied and cut off any excess sheet and finish it as you would like.

For these cars, I cut them out and gently heated them with a heat gun. Then I carefully smashed them down in appropriate places. I expirimented with cutting along hood and door lines prior to heating on some with some good results.

This site was really helpful and is where I got most of my ideas from.

Have Fun,
Papa Spanky

1 comment:

  1. That's really cool, but I'm super afraid of heat, so I might just make a plaster mold and try to do something similar because a pile of cars seems awesome.