HippyTreeHuggerGarage presents: Vac-U-Formed Glass

This is a tutorial on basic Vac-U-Forming. 

It is my intent to take the mystery out of this useful process, be it forming glass, small parts or even slot car bodies. In general, The process is the same for all I have mentioned.

Vacuforming is simply the the process of forming parts from heated plastic sheet by stretching the plastic over a form or "buck" with the aid of vacuum and allowing it to cool. The stretched plastic retains the shape of  what it was formed around or over.

There are several different ways vacuforming is accomplished.  Some years ago, I was fortunate enough to find a Mattel Vac-U-Form machine (1965) in good shape on the Ebay  though very good results can be achieved from home-built formers.  There are many How-to's to be found with a simple search of the net and they can be built rather inexpensively.  The Focus at this time, however, is not the machine itself, but the process of the forming.  The subject here is forming "glass" for the Pantom39 custom truck.

I started by cutting the roof of the testshot Phantom39 (pic1)  neatly away from the lower body, then cleaned the window openings with my little files.  Once I was satisfied with how the roof sat, (plumb and square) I taped over the outside of all the window openings, making sure that all of the edges were sealed.

Next, I mixed very small amounts of JB-Weld (A&B) with a small pick and filled the window openings (pic2) from the inside of the roof, taking care to smooth the JB and remove any errant smears with the pick.  I allowed it to cure some five minutes before moving on to the next one, mixing more and  making sure that each section I worked on stayed level until it had cured enough to move on.

Once all of the windows were filled and cured, I removed the tape and  moved on to forming the buck(s)  that I will mold the actual "glass" over.  I like to use a product called Sculpy III. It is a polymer clay that can be bake-hardened in the home oven. (pic3)  In this instance, I used marble sized chunks of the clay , rolling and warming it in my palms until it was quite soft.  I pressed the clay into the roof and cut it level with a #2 x-acto blade before digging the (sticky) clay out and setting it aside. I repeated this three more times, forming four bucks in all, that I will make the "glass" with, all at one time.

 Each bit of clay was rolled around again in my palms, taking care that there were no breaks in the clay surface. The goal here is a completely smooth surface.  Next, I treated each of the four clay balls to a light dusting of flour (pic4)  to prevent sticking to the inside of the roof again.  This time I set the floured clay ball on my smooth surface and pressed the roof form down on top of it.  The flour does a good job of preventing the clay from sticking.  After all four were formed up again I  baked them at 275 for fifteen minutes. (Sculpy recommends 15 minutes time for each 1/4 inch thickness)  Once cooled, I filed the four faces of each until smooth,(pic5)  taking care to not change the overall shape of the bucks. This also allows room for the plastic inside the roof as the buck, when first formed is the exact size that I need the "glass" to be.

The four bucks were placed on the vacuum plate (pic6)  of the preheated former and a sheet of clear plastic was inserted into the clamp/frame. After a couple of minutes, the plastic was soft enough and it was ready to go.  A quick flip of the frame trapped the bucks under the plastic (pic 7) while I operated the vacuum lever, drawing the clear plastic tightly over the window bucks.  A few seconds to cool and I have four window sets all ready to cut out and glue in place! (pic8)

As always, I am happy to answer any questions.

Thanks for the read, there is more to come!