NOTE--This article was originally posted at SheekGeek. This is my first tutorial or instructable.
Plastic vacuum formers are an important part of prototyping. If you need a nice plastic robot body, or custom case for a project you are doing, get your tools, 'cause this one's easy to build and fun to play with.
The vacuum former uses a simple concept. They use the power of a vacuum to suck gooey plastic sheets very tightly around an object you place in them, making a 3D copy of pretty much what ever you want.
Plastic vacuum formers are usually big, expensive machines; however we don't always need to make huge pieces for our projects, so these machines would be pointless to have, or at least that's what I tell myself so I won't want one ;)
Our molder will have a good size for most projects that you probably deal with. If you get confused or just want to see what I am talking about, watch this short clip showing the video of a vacuum form I made.
Step 1: Gather the Pieces
The main parts to this machine are:
-A top; which is the place that the object to be copied is put and the magic happens. This has holes drilled in it so the suction is about the same over the whole surface.
-A hollow cavity, like a strong, airtight box. This is to get the same approximate suction on all parts of the top
-A vacuum cleaner (shop vacs are a pretty good choice because they have a lot of suction, but a normal vacuum cleaner will work too.) This is the source of the suction.
-Two frames to hold sheets of plastic. This can be two picture frames, or something made of Popsicle sticks.
The first plastic molder I made was a test run of what I wanted, but it worked so great, that I usually use it for all the small parts I make. I will first tell you how to make one of these, you don't have to build it, but it will show the concepts of how and why the machine works. The bigger machine is described later in this article.
Parts list for very small plastic molder:
1 - Plastic peanut butter jar or similar. (Don't use glass, you'll need to cut it some.)
1 -2 liter coke bottle or similar.
1 - Home vacuum cleaner, or similar.
A few sheets of saran wrap.
Some good tape, like electrical tape or duct tape.
-- A good sharp cutting knife or razor (be careful don't cut yourself!)
--An electric drill with a small drill bit, a Dremel works nice with the standard 1/8 inch drill bit.
Ok, got it all? Let's start.
Step 2: Start Building
First, drill a bunch of little holes in the lid of the jar, spaced about 1/4 of an inch apart. Try to evenly space them in a grid pattern. This will become our "workspace."
Step 3: Prepare the Jar
Second, cut a hole in the side of the peanut butter jar just large enough that little more than the tip of the 2 liter bottle top will fit through it.
Step 4: Adding the "port"
Then use the knife to cut the top off of the coke bottle, Put the top of the bottle through the hole in the jar from the inside like this:
Step 5: Make It Air Tight
Now saran wrap and tape the whole assembly. (Make sure to get saran wrap in the threads of the screw top of the jar.)
Step 6: Put a Lid on It!
Put the lid back on the jar. The whole thing should be air tight except for the holes in the top. For plastic, I use the sides of one-gallon water jugs or milk jugs. Cut off the sides of the jugs and clamp them (or hold them somehow) between the two frames.
Step 7: Use It
Select what ever object you want to copy. Some tips on selecting objects:
-- Make sure that the object is not tapered on the bottom. This will make it impossible to get out of the plastic shell we are making.
-- Make sure that the entire object fits on the workspace leaving plenty of holes around the edges.
--Make sure the object can stand the pressure and heat of the process, otherwise they will deform or melt.
--Make sure the object is not too tall, if it is too tall, the plastic will be stretched too much, and become too thin to work with.
--Make sure there isn't too much detail on the object.
I chose the body of a tiny RC car.
Now place the selected object onto the workspace and put a spacer under the object so that the final product will look better. Use the vacuum cleaner's attachment hose to connect the vacuum cleaner to the 2 liter bottle top on the vacuum former. Heat up the plastic between the frames with a heat gun or hold the plastic over the burner of an electric oven until the plastic starts to get gooey and sag in the middle. HDPE plastic will turn from white to clear when its warm, this is normal. DO NOT use a gas burner; it will catch the plastic on fire which is not good.
Step 8: Stetch It Over the Part
Once the plastic is good and saggy, slowly place it over the object. The plastic will stretch over the object. Try to get a good seal all around the object, it should be air tight to get maximum suction. Once the airtight seal is formed, turn on the vacuum. Don't keep it on, just hit it with a good second-long burst.
Step 9: Done With Molding
The plastic will suck tight to the object and the workspace. If when you turn off the vacuum cleaner, the plastic is still gooey enough to try to come up slightly, hit it again with another burst from the vacuum cleaner. It should be done by that point. Hold it steady as the plastic totally hardens. When it is done, leave it alone for a little while so the plastic can cool off.
Once the plastic is cooled, take the frames off the plastic. It should look something like this:
Step 10: Clean Up the Edges
Cut the extra off and put it in the recycling bin and you are done!
Step 11: Building Bigger...
Get some more practice with it; see what you can do and how it all works.
If you would like to make a bigger vacuum forming machine, you will need the following:
--One 5 gallon plastic trash can with an approximately 8x12 inch rectangular top.
--One 8x12 inch metal baking pan
--One or two tubes of silicon caulk.
--One 20 ounce coke bottle or similar.
--Two picture frames about 8x10 inches.
Do basically the same thing as above on a larger scale. Drill a grid pattern of small holes in the baking sheet. Cut the bottom off the 20 ounce coke bottle. Cut a hole just large enough for the 20 ounce bottle near the bottom of the trash can. (Now here's where I have had a bit of a problem, you may need to reinforce or brace the inside of the trash can and/or the bottle with some wood or something before you go on, otherwise, it'll collapse under the vacuum some. It hasn't caused too many problems for me, but it could for you.)
Put the 20 ounce bottle in the hole in the trash can and caulk the seal between them pretty strongly to make sure that it is air tight. Then turn the baking sheet up side down and caulk it to the trash can. Let dry, and you are done.
Step 12: Closing Thoughts
Large plastic sheets are available online from many suppliers. Check out the United States Plastic Corp. for material, or be creative and use things around the house. If you find anything good to use that's freely available, please add a comment for others to use in their projects.
When you are finished with the plastic mold, you can fill it with either fiberglass resin or Alumilite to get an exact copy of your original object.