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Build Log

Fig. 1

This is a build log about how the maker space I belong to, Inventor Forge, built the vacuformer machine shown above. Vacuformers are machines that form partially melted sheet plastic around a mold using a vacuum system. After looking at the many DIY shop-vac type machines out there that have varying success rates, it was decided to build a more substantial machine that accommodates a 2x4 maximum sheet size. It is built from plans by Workshop Publishing as Proto-Form, their name for the machine. It is quite similar to the 2x3 foot machine that Adam Savage acquired and modified, whose video gives a good demonstration of it in operation. Another good demonstration of the machine is here.

This design can form plastic up to 1/4 inch thick, and has 8 heating elements that are 1200 watts each, for a total of 9600 watts, which will certainly require a 220v connection. The kinds of plastic it will form is just about anything that is thermoplastic in nature, like ABS, styrene, PVC, Polycarbonate, Acrylic, Butyrate, Polyethylene, Polypropylene, and PET-G. Conventional wisdom is that ABS is cheap, strong, and widely available, but not the best choice for fine detail. Styrene, however is widely available, cheap, and does provide excellent detail at the expense of strength. Also, the heater will be divided into two zones so that less heat can be used for smaller sheet sizes.

It is important to note that the machine is not meant for continuous duty. For reasons of both safety and economy, the oven should be on only for the time necessary to melt the plastic, then turned off. Therefore, a timer switch will be used to control the oven. If many sheets need to be processed, time between the operation needs to allow the machine to cool off a bit, but this is somewhat enforced by the time it takes the vacuum system to pump down between operations anyway.

The machine can be considered in three parts - the oven, the forming frame, and the cart. We'll start with the oven.

Fig. 2

The frame for the oven is sheet metal and the design calls for a couple of steel wall studs to be shaped as shown above using tin snips. Also, suspended ceiling parts are used to hold the tile elements in place, forming an inflammable tile rack.

Fig. 3

It was decided to buy a kit of parts for the heating elements from Desktop Engineering, mostly due to the difficulty of finding the right insulation tile material upon which the heating elements are mounted. The kit consists of the tiles, the nichrome coiled wire, nuts, bolts, bus strips, and wire and connectors.

The tiles are first drilled to accommodate holes for the bolts and pins. The nichrome wire is then stretched on a jig, the corners marked, and the wire ends are bolted onto the tile. Then, the wire is mounted by inserting small stainless steel cotter pins over the wire through the tiles and bent. This is easily the most tedious part of the build. Above shows two tiles, front and back.

Fig. 4

Here the tiles are mounted in the tile rack, and the tile rack is riveted to the stud frame. The bolts holding the ends of the nichrome wires have copper tinned bus straps to connect the tiles for each zone. The center four tiles are one zone, and the other four tiles make up the other zone. These will be wired so that two wires come off of the oven for each zone, and each zone will be connected to a relay.

Fig. 5

Here is the oven shown in figure 4 turned over so that you can see the heating elements. Four blocks of 2x4 wood, hidden inside the stud flanges, is screwed onto the frame ends to provide a place to mount the outer oven cover.

We'll come back to the outer cover later as it was decided to make that after the oven is mounted to the forming frame in order to ensure a good fit.

Fig. 6

The forming frame holds the sheet plastic in place, and once the plastic droops from being melted, it moves the sheet from the oven down over the forming mold. It is made from welded steel tubing and angles. To help spread the work and also to acknowledge my poor welding skills, fellow Inventor Forge member and friend Bryce Graeser volunteered to do this portion of the build. Above shows some of the frame pieces he cut to prepare to weld.

Fig. 7

Here, Bryce has tack welded some of the frame in place. The trick is to ensure that the frame is kept square and dimensionally correct during the welding.

Fig. 8

Here the lifting frame is nearing completion, needing only the lifting handlebar to be added.

Fig. 9

Here the lifting bar is in the upper position, showing the frame up near where the oven will be. As the bar is lowered, the frame will lowered down to the platen, or forming surface. Next up, we will cover the cart.

Fig. 10

The cart consists of some 2x4s and two 2x4 ft pieces of 1/2 inch plywood. On top of the pile shown above are the four legs, followed by the two shelves, followed by the cart top. The 2x4 are joined using lag bolts and washers.

Fig. 11

With a little encouragement, the cart pieces formed themselves into the cart above. Four casters, ones that can lock both the wheel rotation as well as swivel, were added to the bottom. The bottom shelf is for storage of sheet plastic blanks, and the middle shelf will hold the vacuum system. The steel lifting frame, seen above in the background, will be mounted by simply centering it on the top of the cart and four blocks will be bolted into the frame and the cart.

Fig. 12

The cart and the middle shelf were sanded, given a sealer coat of shellac, and then enameled with the color of the maker space logo.

Fig. 13

Here the middle shelf has the three air tanks and the vacuum pump mounted on it. The tanks are from Harbor Freight and each one had a manifold sticking out of the tank for a hose, gauge, and pressure relief valve. That manifold was cut off and a steel flange (#12555K55 at McMaster Carr) with a 1 inch NPT thread was welded over the hole.

Fig. 14

Here you can see the welded flanges, as well as a 1 inch hose plumbed to each. The blue hose fitting on the far right goes to the vacuum valve, and from there to the forming platen. The smaller 3/8 hose barb, shown above just to the left of the pump, goes to the pump through a check valve with a vacuum gauge looking on.

Fig. 15

Here a box made of oak, which had some CNC work done on it, has been bolted to the top of the frame. The oven shown in Fig. 5 is laying on the lift platform, where it will be lifted up into the box and mounted. Then, a finish will be applied to the oak and then the electric panels can be mounted on the back.

The vacuum valve has been mounted under the upper cart frame, just above the tanks.

Fig. 16
Fig. 17

Figure 16 shows the electrical boxes mounted on the rear of the upper oak frame, with the wiring of the breakers on the left, and the wiring of the relays on the right. The top of the relays have heat resistant wires that go to the oven coils, and the wires exiting the breaker panel go to the 220 volt appliance plug and the control panel. A piece of conduit drops down to a box where the plug is connected, shown in Figure 17. Thanks to Bryce for the neat wiring job.

Fig. 18

Above, I've added the lower box, and both the upper and lower boxes got a rub of gel stain and wipe-on poly. I've also added a control panel that is sloped a bit to make seeing the vacuum gauge (just behind the round hole in the panel, not yet mounted) easier. The left-hand switch turns on/off the vacuum pump, the middle two switches turn on/off the outer and inner ovens, and they go into a timer that limits the time the oven can be on. When an oven is on, a red light is also on to make it easy to tell if the oven is turned on or off. I added some aluminum angles on both sides the panel to dress it a bit and make the edges durable.

Next, we need to mount the gauge, finish the panel wiring, and install the particle board table top, which is shown leaning against the red brake on the right.

Fig. 19

I've installed the particle board table top with a few mods. The plans do not really address how to easily swap out platens - in fact, the plans for the 2x4 model do not really allow it since the table top has three holes in it and assumes some way to easily disconnect the hose. The hose has to be heated with a heat gun to get it onto the fittings, so that won't work. I decided to use a PVC union, but the three holes need to be made into a slot, and a part widened to allow the union to pass through.

This picture also shows the control panel. On the left is the vacuum gauge, measuring how well evacuated the tanks are. The left-hand switch turns on/off the vacuum pump, the middle two switches turn on/off the outer and inner ovens, and they go into a timer that limits the time the oven can be on. When an oven is on, a red light is also on to make it easy to tell if the oven is turned on or off. I added some aluminum angles on both sides the panel to dress it a bit and make the edges durable.

Now to build the platen.

Fig. 20

Fig. 21

Fig. 22

Fig. 23

The four layers of the platen. The top figure is the 3/4 inch particle board base, with two holes drilled for the PVC pipe fitting to be glued into from the bottom. The next layer (Figure 20) is a sheet of 6061 I had that is cut the same size as the base, just 1/4 inch less around all sides, and fixed with contact cement onto the base. The next is a layer of 1/2 inch "hardware cloth" or wire mesh to provide support between the layers as well as provide a place for the air to flow out of when the vacuum is applied. The next layer is a sheet of softer aluminum that will be formed over the edge of the base all around the perimeter, and drilled with 1/16 inch holes, at one inch intervals both horizontally and vertically. The three upper layers will be silicone sealed around the edge.

One note - you only get one chance at getting a good seal between the layers shown above, so it is important that attention is paid to this. The silicone tube says that it takes 24 to cure, but that is with one side of the silicone exposed to the air, like in a bathroom caulk around a tiled corner. When the silicone is confined like this, it takes much longer. Also, make sure you've applied a tall bead around the perimeter when clamping the layers together to cure.

Fig. 24

Here is the completed platen, upside down. The PVC fittings were epoxied onto the board with hose fittings, and 1 inch hose is routed to a tee then into one half of the union fitting. The other half of the fitting is under the table on a length of hose that is fixed to the vacuum valve.

Fig. 25

Here is the finished platen showing the edges that were formed over the board and the 880 holes drilled and countersunk into the top layer of aluminum. A 2x4 foot piece of plastic is lifted up to the oven and melted in the carrier frame to the point of sagging, and then brought down over this surface where the vacuum in the tanks will suction almost all of the air out through these tiny holes. This makes the plastic conform tightly to whatever pattern is placed on the platen.

Fig. 26

Above is the finished machine, with a cardboard insert to protect the platen. We've decided that a smaller platen, say 12x24 inches, would be a good idea. In the near future, I hope to show some of the pieces made from this.

Comments may be directed to gary at liming daught org.

Thanks for viewing this build log!