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Discussion Starter #1 (Edited)
This is going to be rather lengthy, so if you like I'll wait while you go get yourself a cool, refreshing beverage.

Are you ready now?

Now, I’m not saying this is the only way to vacu-form, or even the best way. I’m saying this is how I do it and have been doing it for more than 20 years. I started doing my own sprinters in 1986 and have now expanded to eight body types. I haven’t been keeping close track, but I’d say I’ve made close to 750 to 1000 bodies like this over that amount of time. Not all of them came out perfect but that’s just how it goes sometimes. Also, and I say this with the utmost seriousness…don’t rip off anyone else’s designs to sell. Either make your own molds or if you do a die cast mold please change the design significantly enough to make it an original concept. Don’t steal someone else work and call it your own and try selling them.



All of my cars start as a 9” X 12” sheet of PETG. K&S makes my plastic and I get it from Tower Hobbies for $3.49 for a pack of 3 sheets. Each sheet is quartered, cut into 6” X 4 ½” sheets to fit my rack for my vacuformer. My rack is basically a rectangle with the middle cut out, the dimensions fit the top of my airbox. The racking part is about an inch and a half wide. I can actually do two molds at once but I sometimes get thin spots so I don't do that very often. The PETG I use is 0.010 thick although they also make thicker stuff.

The process begins by preheating my toaster oven to about 400 degrees. It’s critical to make sure that there is enough heat to cause the plastic to begin melting but not catch fire. Fire = Bad. If you set your toaster oven on fire you did something wrong. As such, neither the administration of this forum nor myself accept any responsibility if you happen to burn your house down trying this. YOU DO SO AT YOUR OWN RESPONSIBILITY. After the heat source is preheated I begin by clamping a piece of the PETG into my rack. This is done by ATCO clamps and over the years I’ve found it works best to get all four corners and along the sides like shown. Make sure you have at least ¼” of the plastic under the clamps because it will try to shrink as it’s heated. Select the mold you will be using and place it on the airbox, turn the vacuum source on and you’re almost ready.



Once the plastic is racked it’s placed in the toaster oven. Heating only takes a few seconds, initially you’ll see the plastic do what I call reaching “altered states” where it quickly warps then straightens out again. About 15 seconds later the center begins to sag, and watching the glare reflection off the heating element (you can see it in the oven pic) when the sag reaches a certain level I pull the rack our and push the whole rack straight down over the airbox and mold. The reason you go straight down is because if you drop at an angle you can create creases, thin spots or knock the mold off the airbox. I always flip my rack upside down from its heated position, this places the sagging plastic directly in contact with the surface of the airbox and gives a very crisp seal.





As the vacuum is still going, drawing cool air across the PETG and the rack I begin unclamping it, this causes the hot plastic to cool and cure around the mold, and also cools the hot clamps and rack. After about 10 seconds the plastic is cool enough to touch, and the mold takes only a little encouragement to remove from the plastic. I set the finished body aside and begin racking up for the next car. The whole process from racking to popping out the mold takes less than a minute. If I’m doing several molds at a time and switching them out to allow cooling I can do 2 bodies a minute if I hurry. Usually hurrying also affects quality so I just take my time.







Essentially all you would need to duplicate this process is an airbox and rack with clamps, an old vacuum and a heat source. Like I said, using a toaster oven for me gives me the best control of equal heating. PETG is a hard plastic to deal with and it cools very fast. But it has proven to be very durable and accepts most paints, so it’s my choice. Those of you who have run my stuff know that it can take the punishment.

I published this so that those of you who are legitimately interested in vacu-forming can see how I do it. Like I said, this isn't the only way but this has worked for me over and over for a lot of years. The only thing that has changed over the years is the plastic I use, and for the last 5 years PETG has been my choice. Each car would cost me 30 cents each to make if they all came out. I have about a 3 to 5 percent spoil rate for various things like not enough heat, too much heat and not dropping the rack just right. It still comes out to under 40 cents each for materials, the real cost comes in building the molds and the equipment. My airbox that I use was built in 1986, it's one of two I own and is made from 1/4" lexan. It has survived multiple moves, and I can even stand on it (or used to be able to), so it's virtually indestructible.

Anyway, that’s a tour of the secret backroom at AMG Racing.
 

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Model Murdering
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I'll have a toasted PETG on an onion bagel, please.....

Hey Pete! Thanks for taking the time to share your craft. I'm always excited to learn something new.

It only adds to my appreciation for your modeling skills to see another step of your process that was previously unseen.

Howz yer hobble?

Bill
 

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Duke Dave of Sealand
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Thanks for sharing Pete, that was very interesting. But next time could you get some hot super model to pose in the pics? lol


Dave
 

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Discussion Starter #10
T-Jet, made it myself, the airbox is lexan and the rack is a polymer plexiglas that can handle the repeated exposure to heat without warping. I recently replaced the rack with the black one you see here. I have a red one too, and I'm working on a better way to clamp it.

Bill, the hobble is what it is, I'm supposed to be non-weight bearing for 3 weeks. I have a nice rolling desk chair I've been using in the shop since it has a concrete floor.

Coach, my Super Hot Model (the wife) was the one taking the pictures...
 
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