Instructables

Step 8: The First Test

Picture of The First Test
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Now is its time to test. I got a sheet of .020in. thick Polystyrene from a hobby store. This is a little on the thin side for vacuum forming, but it all depends what you are making. A normal thickness would be between .040 and .080. A thinner material can be formed with more detail but needs to be watched closely while heating. This is the problem I had with my first test. I turned of the oven and let it preheat for a little bit. I cut out another piece of hardibacker to be a cover for the oven while it was heating. Then I put the plastic in the frame placed it over the oven and put the cover on top. When the plastic starts to heat up it will start to warp, then it will start to sag. Usually you can determine when to form the plastic by the amount of sag there is in it. But this learning has to come from experience, your first couple of times might not turn out so well. Due to my lack of experience the first time I used the machine the plastic heated up a lot quicker than I expected, saged to low, touched the coils and caught on fire. As you can see from the pictures it melted all over the oven. This ruined the oven but I can be cleaned up and used again. I don't the time to do it though. I'm living away from home for the summer and won't be able to work on it for a couple of months.

So at least for now I learned a lot about how a vacuum forming machine works and how it could be put together. I might try to change some parts of the machine to make it a little more solid and heat the plastic more evenly. If there is one thing I can tell you about build a vacuum forming machine here it is, when you are testing for the first couple of times have a fire extinguisher ready to go.
 
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kewrw282 years ago
Practice will make perfect. Dont give up now!
hmmm.... you should try using a heat gun for your heat source. its a bit slower but no flames
With a heating gun you won't be able to get even enough heat for the whole sheet. The easiest and best way is actually to have your heater placed directly abouve the table upside downso that the sheet gets heated from above and away from the coils not closer to the coils. You're gonna have to mount your sheet frame on rails, but it's a much safer approach to vacuum forming.
ss30004 years ago
Good job and nice build. I worked for a company that made items by vacum forming (Sailing Specialties Inc) a few years ago working in the CNC department. First suggestion, stop using styrene, styrene is a light weight plastic that is not very good for heating amd forming. If possible try to PVC, ABS, or even lexan. They are much better suited to heating and forming. Number two, instead of the hinged tray that flips make a tray that slides like a drawer. Which takes me to the third. Instead of the heating elements on the bottom, place them on top, or better yet elements top and bottom with metal plated for heat spreaders (they would also cover the elements and should prevent fire and make clean up easier.
mikesnyd4 years ago
Like you said. it sags and then touch's the element. An easy solution to a even and uniform heat is to have say a hotplate with lid that covers all you have. Thus heating from the top down to your styrene. So it is basically a box where your styrene is the bottom and small venting around its perimeter. I have seen a few guys using the top element in the oven. And you can notice when the plastic(styrene) is ready due to the mat finish it receives from heat. If you have at least a 1000W vacuum it will help pull a bit better if it happens to be to the cooler side of readiness. Man vacuum forming is fun. i feel like i am running a sweat shop some days.
jiganto4 years ago
I think some sort of heat spreader mounted over the heaters would give you more even heating and prevent melting plastic from falling onto the heaters and catching fire. Maybe a sheet of aluminum or thin steel.
EGSMachine4 years ago
you get a x10 in XP for the humble pie you just ate. thanks for sharing!
Quite agree! "There are no experimental failures - there's just more data..." If I might suggest: Masonite for the platen/vacuum manifold - hard and smoooooth surface, can be had in both solid and perfboard, tolerates heat pretty well, less work, greater hole-pattern precision at, probably, slightly greater expense... Also, some kind of heat-resistant "honeycomb" separator atop the elements would keep the sheet from sagging into the "free-fire-zone" when it goes too floppy, too fast like that.
sturmey4 years ago
Very cool idea. I like how you hinged the material holder to make the switch from heater to vacuum plate easy. I may borrow this idea for some of my projects.

Also, congratulations on a successful test of your fire suppression system. I hope your next test goes better.
jegner24 years ago
vist www.tk560.com/vactable4.html there you will see something similar, based on Thurston James' machine.
vernonstien5 years ago
OOOPS, Awsome, I thnk yoou did a good job for your first time!