I have a full vacuform machine that can vacuform sheets of acetate up to 19″X 28″. I am doing some R&D on making leaves (see previous blog entries) and I didn’t want to make up full sheets of leaves, at least not yet, until I can get a good system developed. So I took my individual mold, drilled air holes around the leaf and up the stem. I then drilled a 1 1/4″ diameter hole about 1/2″ deep into the mold from behind. The hose of my vacuum cleaner fits snuggly into this. I used a cutoff disk on my Foredom tool to join each of the drilled air holes to the larger hole.
I lay the sheet of acetate on the surface of the mold, turn the vacuum cleaner on, and using an industrial heater, I melt the acetate, which gets sucked down onto the mold. In this case, I have to switch the vacuum in the middle of the process to a second hole to get the whole leaf. This works well to get one leaf and can be done cheaply without having to buy an expensive vacuform machine.
UPDATE N0vember 25, 2013:
I have found that the above system for vacuforming doesn’t work as well as making a small box with a hole drilled in the bottom to the diameter of the vacuum hose. The individual leaf mold is laid into the box, acetate laid over that, and heated while the vacuum is on. I made the box 6 1/2″ x 7 1/4″ (ID) and as long as the PETG acetate covers the entire surface while heated/melted down, the suction is strong and I am able to get better vacuform casts. here is a photo: