www.TK560.com: Vacuform Table IV

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Build Your Own Vacuum Form Machine
Make your own vac-u-form machine in your garage from simple hardware store items, here's how

Vacuum Forming Machine Project: Thurston James' Design

Thurston James's Vacuform machine from The Prop Builder's Molding and Casting Handbook, page 175.

The OriginaI design:

This is the Thurston James' vacuum forming machine from his book The Prop Builder's Molding and Casting Handbook, page 175. This is a great book and I have most of Thurston James' books. Get them at Amazon.com today, if you don't have it already. His design is discussed in detail, but not to the extent that I could just sit down with the book and build his table. Its not a building guide. There is enough concept and general information to get started, however, and with a little time and effort, reverse-engineering and researching, this project has finally taken off. There are no plans, or building diagrams in his book, except for a wiring diagram for the oven. The rest of this project has to be "re-imagined".

A lot of vacuformers will tell you to just use pegboard, and a shop vac. This does work pretty well. The only downsize is the pegboard has to be supported, and does have a tendency to sag under the weight of a large mold. The shop vac can deliver surprising results with thinner materials. But for a detailed pull on a larger machine, I wanted to follow as close as possible to what Thurston James describes. Besides this is a re-examined "practical" and cheap replica of his famous table. The following is my documentary on the production of this table.

Click on the image for a larger view.
Still a work in progress, but it does work!

Note, vacuum forming, accustom,'vac-u-form', vac-forming and thermoform are interchangeable terms.

This project consists of several "modules" that should be built in sequence. Here is an outline:

Module 1 - Forming surface: this is the section that will get the most "wear and tear" and is the easiest to build with common tools and materials. DONE

Module 2 - Holding Frames: 3/4" steel tubing MiG welded. Hinges and clamping assembly are added. Alternate materials could also be used, including aluminum square-tubing, or even 1x1 pine. DONE

Module 3 - Forming Cart: This is made of 2x4's and a 24" square sheet of MDF. I added caster to the side so it will be easy to move this around the shop. DONE Considering how much space this machine takes up, I'm considering making my machine a "table-top" version; no cart!

Module 4 - The Oven: made from a 3'x5' sheet of 1/2" Hardibacker 500* concrete backer board, a length of precoilled Nichrome wire #22, and some 60 ceramic posts. External shielding is made from the Hardibacker 500, an angle iron 1" base is also made to hold the whole thing together. An electrical box with wire and a switch. The oven works! DONE

Module 5 - Oven Cart: Like the forming cart, this is made of 2x4's and a 24" square sheet of MDF. DONE Again, I need more space in my shop, so its off to design a table-top box for my machine.

Module 6 - Vacuum System: UPDATE: My first successfully pull using the machine was done with a 3hp shop vac. It works pretty well. I'm thinking of using a sump pump check valve rigged with a self closing spring, and a tank with a fair amount of vacuum. The two vac sources working together should give me the most practical and useable approach. Another option for more vacuum could be to use 2 shop-vacs in sequence to generate more inches of Hg. I think one of these two solutions will solve most of the vacuum issues, and eliminate the need for the more complicated tank and pump and plumbing system. We'll see.

The pump/tank option uses a GAST 1065 pump, and a 30gallon slim hot water tank, two one quarter turn 3/4 inch valves, and some 3/4 inch pipe fittings. IN PROGRESS

The availability of the parts is what determines the construction sequence for me. I went with the forming surface, then the holding frames, then the forming cart, then the oven, oven cart, then the vacuum system.

*It has come to my attention that, over time, the high heat from the nichrome wires will cause the Hardibacker 500 to fatigue, and eventually crack. This could pose a potential fire hazard. Currently a replacement calcium silicate fiberboard is being researched. I got 3 years of regular use from my machine build with the Hardibacker 500, but anyone considering this material should understand it's limits. Consider it a less than ideal substitute.

MODULE 1 - The building process begins: Vacuform Machine Forming side


Here a look at the innards of the forming surface. Note, I used 3/4" MDF for the top and bottom and scrap 1/8" plywood for the "sandwich". I then silicone caulked the whole thing together. Make the MDF 21.5" square.	Here I am centering the floor flange. I used a 1" floor flange so that I could hook up my shop-vac right to it. For the hi-vac parts, most of the plumbing will be 3/4".	This is a shot of the sandwich screwed together. I have positioned my aluminum sheet metal evenly under the forming sandwich.

Here is a view of the sandwich. Its clamped to the work bench, and I just use my hands to bend the aluminum sheet metal to the sides. A snip at the corners and some light tapping with a mallet and I'm done. Its ready to seal with adhesive-backed aluminum tape. I used a 1/2" brads to mount the sheet metal to the MDF.	Starting from the center I drew a 1" square grid pattern. Then using the block of wood as a depth guide, I drilled the 1/8" holes. Lots of holes... 484 or there abouts. I could have used a box made of 1x4s and pegboard, like my other tables. But...	Forming surface finished! Now, onto the holding frame. I already know the scale of the frame, I'm just avoiding having to break out the welding machine. Normally, the holding frame would have been made first. I found this relatively easy, skill level II.
MODULE 2 - The holding frames

Laying out the Holding Frame: Using 3/4" square metal tubing, I wanted the outside edge of the frame to be 24". Measure and cut the metal tubes. I made the bottom one with 5" extensions. Two at 24", two at 29", and four at 22.5". Try to be precise and make clean cuts. Grind down any extra metal and be sure the corners where the edges meet are plumb and flush.	MiG weld that baby together. I used a magnetic welders guide to get the frame square. I worked on the floor mainly because I don't have a fire proof work surface. Please don't laugh at my poor welding technique. Its been 20 years since I last welded something! I really like MiG welding, and if done properly it should hold up fine. Just be sure to get a good "bead". and, yes that my welders helmet.	Here is a shot of the welders guide and the final weld.This process took more time to cut the tubes than to weld together. MiG welding is pretty easy, once you get the hang of it. Practice welding on some scrap first. This could have been pop-rivited together with pieces of metal straps, or brazed or stick welded. Heck, I could have made these from sturdy 1x1s and L brackets or aluminum tubes.

If you did all the work correctly, there should be a 1/2" or so space between the forming surface and the inside of the metal frame. It would look something like this. Make sure the corners of the forming surface has no sharp edges. Otherwise, it might tear the hot plastic and loose vacuum.	I found in my parts bin a bunch of these metal brackets. So I used them for the frame mount. The bolt is a 1/4" with a wing nut. I think these came from one of those toilet tank repair kits. I cut the bolt down to be just longer than the wing nut.	Here is some scrap "piano" hinge I cut down, and pop riveted it to the frame. I then MiG welded it to the frame. That chrome plating on the hinge sucks, so does my welding...

More of those little metal brackets I used earlier for the holding frame hinge, now I'm using them to make some handles .A wooden dowel rod screwed into the holding handle. I need to make three. One on each end of the frame.	The clamping fixture is a wing nut, a long eye bolt and 4 'L' brackets mounted as shown. The receiving end gets the corners ground down a bit to make it easy to tighten down. The originals bent bolts just did not hold up. UPDATE: Jan. 2007	Here is another view of the clamping fixture. Works like a charm! These are pop riveted and tack welded in place. Each part is easy to replace if there is an issue. UPDATE: Jan. 2007

I then cut a sheet of MDF to the proper dimensions and bolted the frame assembly and forming surface down. Underneath, I cut a hole for the floor flange to poke through. This is all there is to the forming side of the vac-machine. If I scrap the complex vac-system, this becomes pretty portable.	Inside the frame I used some of that non skid surface tape. 3M makes the stuff for ladders and steps, and its self adhesive. I'll see if it can take the heat. If not, I'll epoxy some sand on it! the first test pull seems to indicate this will hold up fine. But over time, I don't know.	Here is a view of the forming surface with the frame in the open position for removal and installation of Styrene sheets. Really easy way to do this step. Much better than my old machines.
MODULE 3 - The forming cart

Test fitting some of the stormtrooper armor parts. If I can pull this much at at time, that would be nice! The frame will be painted to prevent rust and to look pretty. Now its off to building the cart.	Thurston James made his from square metal tubing, but said a 2x4 fir would work just as well. I wanted to keep the vacuform machine small enough to move around, so instead of making it on one big "cart" I'm putting the forming surface on one small cart, and the oven on another. We'll see how this works. If I ditch the complex hi-vac system, I can scrap the carts all together, and build it as a table top unit.	The forming cart will attach to the oven cart to make one large vacuum table. I made the cart from 2"x4" studs. The inside dimensions are 24"x24". Height is 30" to the base. The same height as my Workmate. I put casters on the side so I can tip it over and roll it around the shop. At this point the forming side is complete. All that is left to do here is solve the vacuum issues.
MODULE 4 - The Vacuform Machine's Oven

Here is a shot of the Hardibacker 500 cementbaord material I'm using as the oven walls and floor. Basically cut a 28" square of the stuff, and then make four 28x 4.5" strips. To get the taper sides, you just measure from the center out to 24" and mark. The sides are then cut at an angle and you have the trapezoid.	This is a detail of how I attached the sides. Its a strip of aluminum with holes drilled and short screws holding it all together. Cut two of the sides 1" shorter, this allows for the thickness of the Hardibacker material. Finally to hold the sides together, I too some scrap aluminum sheet metal, and folded, trimmed it to fit, and screwed it to the sides.	The oven is sitting on the forming surface. The scale worked out fine from the book. I'll add a reinforcing walls, and a metal base soon. The walls will be made from the roof flashing material and painted black. Skill level II, but you will need a power saw to cut the concrete board.

After welding a 1" angle iron material to form a sturdy base frame, I began drilling the holes for the post mounting screws. Off set all but the tapping posts 1/2 inch from the wire guide lines. use a masonry bit that is slightly larger than the #10 screw.	Here are the ceramic posts and mounting screws. I used 2" #10-24TPI for the terminal posts and a top mounted wing nut...	Some test fitting.. Regular ceramic post and terminal post [the one with the wing nut]

Starting from the center... Mount the screws. The underside of the backerboard might need some scraping, as the holes drilled through are rough on the underside.	And this is what mine looked like after drilling and mounting all the ceramic posts and terminal posts. Note the metal frame, and the cart!	Here is a detail shot of the way I mounted the oven frame to the cart. I'm thinking of reworking the carts to convert this to a table top machine. Storing this contraption is getting hard!

Now for the wiring. I started with the high voltage first. Using 10-2G wire, some real big wire nuts, a 20AMP switch, an electrical box and cover, and a plug, I'm ready to begin. CLICK HERE for some details.	I cut three, 3 foot segment of wire, and stripped off the orange outer cover. Then removed the black, white and bare wires. Then I stripped the ends off the black and white wires like so These wires will be wrapped around a 2" bolt, so don't strip too much wire!	This is test fitting of my terminal post. Starting from the bottom, its a 2-inch #10-2 bolt, #10 washer, Wire bent to form around the bolt, another washer, a #10-24 nut, tightened up, another washer, the ceramic spacer, two washers on top and finally a #10-24 wing nut.

Here is an underneath shot of the black and white wires, with the terminal posts already mounted. There are only 5 to do. Check the section on this page about oven wiring for details.	Here is what the underside of the terminal post looks like. Also, note the ceramic post mounts, and the distance they stick out. The 1-1/2" bolts get the job done.	Up next is the on/off switch, and mounting the switch box.

Wire pulled to the switch box. All that is left to do is wire these to the switch, add a power cord, and I'm ready to add the heater coils. Wiring a light switch basically means take all the black wires and tie them together with a 4" pigtail using a wire nut. The wire all the white wires, but this time include the white wire from the power cord. The switch has the black wires connected only. The black wire from the power cord, and the black wire from the pigtail.	I got excited and forgot to photograph the wire stretching, so all I have photo-wise is a shot of the small wires I used to tie off the heater coils. This process was easy, but my biggest concern was where to start. The instructions in the book, call to start from the center of the segment, and start from post D. The wires have a lot of slack in them, and I'm not sure if that's good or bad.	And the finished oven coils all tied down and ready to test. kind of saggy coils, but that's ok. After a few test, the last thing to do is add some head reflectors on the walls to better control the heat flow. The corners are going to be the cold spots.
	I have been asked to take a Ohms reading. Here are the results: each segment draws about 5 ohms. The resistance varies from 4.9 to 5.1 ohms. I assume this is pretty good considering the home-made nature of the oven. Total of 20.1 ohms across the whole oven coil.	OVEN WIRE COILS: From John H. regarding the wire you get from www.infraredheaters.com. [the precoiled type vs. the instructions found in Thurston James' book] "Well, correct me if I'm wrong, but the book says to wrap the wire around a 1/4" rod. Infraredheaters.com pre-coiled wire has an approximate inside diameter of 1/4" so, I think it's the right size as far as that is concerned. So basically to calculate how much pre-coiled wire I would need, I first figured out how many turns per inch the 22 gauge wire gave me by taking the outside diameter subtracting the inside diameter and dividing that by 2 (.30 - .25)/2 = .025 wire thickness. I then took 1" and divided that by .025 and got 40 turns per inch. Then I took 88' converted it into inches (8812) then divided it by 40 (26.4) then converted it back into inches (26.4/12) and came up with 2.2 feet of coiled wire to do the entire job. If you look at the pic on page 184 it shows the guy holding 1/2 of the wire required for the entire job and it looks to be about a foot or so. So I think this calculation is correct. With that said, we should both be able to split the cost of the 10' precoiled wire and still have plenty left over. " And for the info regarding how much to stretch:* First I cut a 2' 1/4" [24.25 inches] length from the 5 feet of coiled wire, then cut it in half to make two 1' 1/8" [12.125 inches] lengths. I then marked the center of each length of wire at 6 1/16" with a Sharpie Marker. After that was done, I put the marked center on a nail, grabbed both ends and stretched the wire to 95 1/2". WARNING: Use a pair of pliers to hold the ends! I made the mistake of stretching one of the pieces with my bare fingers and wound up with a nice puncture wound under my finger nail... ouch! Thanks John!
Here is the finished oven sans the lid and frame. The next challenge will be to test the rig without blowing a fuse or breaker! I also want to try to convert this to a table top machine and ditch the carts. skill level III, mainly because the oven parts are hard to get, and the safety concerns regarding the proper wiring.
The first test...

Here is my vac-table rig. Note, the shop vac, and the air tank [not used] Look how much shop space this thing covers.It would be nice to set the rig on a counter and when its not in use, stack the oven on the forming surface.	This is my first pull using the new table. Some things to note: the oven takes some time to heat up. I will need to make a lid for it. And the loose coils might need to be adjusted to concentrate the heat in the corners. Also, I don't like the exposed heating elements, so I need to track down some metal grating material to add as a protector.	Pretty decent detail from a sheet of clear acrylic storm window covering! That stuff was all I had on hand to test with. Its a .125 thick material, and as I expected, the corners did not get as hot as It needed to. Since my vacuum source was a 3hp Shop-Vac, I did not expect it to pull as well as it did.

Yes, its clear, and the beast needs a little fine tuning. The flash s seemed to exaggerate the dust on the surface, and no, its not that opaque. Again, the corners need to be reworked, to heater more evenly, but overall, I'm blown away.	This is a shot of the acrylic thickness. Its about 1/8th inch or .125. Much thicker than I plan to use.
Making some test pulls & learning how to use the machine

After getting some .080 thick HIS sheet and cutting it down to 24x24 inch squares, I mounted it on the frame, and began trying to melt it. The oven was not hot enough, and the corners did not get warm so the pull was poor. No vacuum seal.	I continued heating the oven, and installing the lid, I was able to get a better pull. This one had an issue; there was such a deep draw between two pieces, the styrene had a hole pop in between the forearm and the shoulder. This caused a loss of vacuum and loss of detail.	So, I decided to try a wider spacing approach. This seemed to work, and revealed the webbing issues, and the need for risers. Careful attention to arrangement of the molds on the forming platen will minimise the webbing issue.

The oven had been running for 20 mins. by the time I pulled this, and I found that if I wear gloves, I can massage the hot plastic to conform to the mold better. Note, the belt and the shoulder bell are on risers. The drop boxes, and other small parts are not.	I had one error, I overheated the pastic, and it melted onto the coils. It was a lost cause. But after reloading the machine, and using the latest mold, the upper back, I had a good pull. It too needs a riser to reduce the flare that happens where the mold sits on the forming surface.	Here is a detail shot of the popped plastic. I was really hoping for a lot of parts that could be pulled at one time with this machine. I will need to carefully cosider the mold placement to best minimize these issues.

Take a look at some of the webbing. Note, that a better arrangement of the plastic on the forms will reduce the webbing issues.	Another detail shot of the last test pull. Pretty decent detail. These parts are on risers and will trim out nicely.	A few more pulls were made over the weekend. I finished the upper chest and now all the "armor shirt" parts are done. Time to work on the abdomen and lower back sections.

Each mold that has a hard deep end to it, like the biceps and the shoulder bell, are going to need to be reworked with tapers to aid in the release of the mold from the pulled plastic.	I am hopefull, if the tapers work, that I will be able to make some plaster casts from a good pull of the shoulder bell, biceps and forearms. That way I can pull a complete set in one pull instead of having to pull the same mold twice. [and save me from making another mold from scratch!]	The collars need to be reworked with an arch built in. The flat straps just do not bend well. Also, the knee boxes and belt seem to pull poorly using the thicker .080 material. I need to use .060 on these parts. Above are some of the molds.

I'm pretty happy with the chest mold. It was a challenge to get the proper shape to the pecks, and I think it worked pout pretty well. This mold was used before I top coated it with the spot filler primer. It looks ugly, but it pulls fine.	As I make a mold, I learn something new. Bondo is a wonder material! It helps contour and shape the rough blocks that I make, transforming them from MDF to vac-molds! A sealer coat also helps hide imperfections. MDF has a tendancy to fuzz a little on the surface. It needs a coat of spot putt to smooth things out. This is th eupper back, and it need some fine tuning, but its mostly there.	I'm working on the scale drawing of the thighs. Once the upper body is finished, I can see the light at the end of the mold making tunnel. Once the upper body is made, all that is left to do are the: inner and outer calves, the inner and outer right thigh and inner and outer left thigh. Some sort of fabricated thermal detonator and its off to the helmet molds!

Additional Information

Forming Surface & Frame
The cost has been a sheet of MDF, and some 3/4" metal tubing. I had on hand the 2x4's and the casters, hinges, and other materials. Say $40.00, and if you already have some of this on hand, your ahead of the game.

Oven Materials
(Calcium silicate is expensive!) A temporary working substitute for the oven is James Hardi's Hardibacker 500*. Available from home improvement centers. Look in the floor tile or bathroom shower sections of the store. A 3'x 5' x 1/2" sheet is $10. They are basically a concrete board 60% calcium silicate. I've talked with a chemical engineer about the plausible use of this and he seems to think it will work, but I need to use a 1/2" inch thick sheet instead of the 3/8". It will get hotter and might not insulate the heat as well. Also, the engineer suggested lining the interior of the oven with sheet metal to help support the material. The first test of the oven has been successful, and the Hardibacker 500 seems to work fine. Including the angle bracket and screws, the $60 for the ceramic posts, and another $10 for the NiChrome wire, and factor in another $15 for the electrical, the cost of the oven is around $95.00.

Vacuum system
I've given up on the 30gal. tank and Gast 1065 vacuum pump for now. The proper tank to use is a $144 narrow hot water heater tank from the home improvement center. For my budget, its just too expensive. I did purchased a small 4.3 CFM air-vacuum pump and an el cheap-o vacuum gauge from Harbor Freight. Total cost was less than $25. My test pull was done with a 3hp Shop-Vac, and it seemed to work fine. Cost = $0.00 since I've had the shop-vac for 10 years!

There are two alternate ways to imporve the vacuum. One will be to use a second shop-vac. I can use two shop-vacs in sequence and get more in/Hg instead of the 3-4 in/hg from a single unit. Also, a check valve might be a good idea, to help hold the vacuum once it's pulled. I've also purchased a sump pump check valve, that can be modified to use a spring loaded check valve, and a hi-vac low volume source. I'm considering my options here. Here is an example from the book "Do It Yourself Vacuum Forming for the Hobbyiest" by Douglas E. Walsh.

I've not completely given up on the tank/pump idea, but thats gowning to have to wait until I can figure a cheap way to plumb it, or I find a cheap Gast 1023 or 1065 vac pump.

For the pump/tank vac system, Gast sells different models and the one Thurston James suggests is Model 1065. Its actually a 8.5 CFM unit that requires a motor. Gast Model 1023 is a 10 CFM unit with a built in motor. The plumbing is going to be a nightmare! Here is a list of plumbing gear I need:

Vacuum Pump with motor
Check valve [so the system dos not back-draw any air through the vacuum pump]
air Filter [so there are not particles to destroy the pump]
Tank [30 gallon, 15 is too small; not enough volume]
Pressure switch [to keep from imploding the tank]
Vacuum gauge [so you can see the amount of vacuum and the vacuum rate]
Valves [to close off parts of the system and to open the table valve to start the pull]
Plumbing fittings [lots of these, nipples and elbows, flanges, couplings,etc.]

Conclusion:
Whoa! It worked! It really worked. I'm just blown away. Why commercial vacuform/thermoform machines are so expensive is beyond me. The hardest part by far to make is the oven, and only because of the exotic nichrome wire and the ceramic posts. If there are hardware store substitutes for these items, please let me know. Every hobbyist should make a vacuform machine. If your into model railroad, RC car and airplanes, scale models, arts and crafts, prop replicas, costumes, or any other hobby, get to work on your vacuform machine NOW! Its that easy. Total cost for the test pull: Less than $150.00. The molds are more work, but once you make a good hearty mold, you can pull as many copies as you want.

Forming Supplies:

I almost gave up looking for polystyrene. Locally, no one seemed to know what the stuff is. After some research I came to the conclusion that Polystyrene is a chemical name, High-Impact Styrene Sheets is what you want to search for. Sometimes called HIPs [High-Impact Polystyrene Sheet] I've had the best luck searching for HIS [High-Impact Styrene Sheet] Below are some suggested sources. Be sure to get 48"x96" sheets not the 40"x72" sheets. For trooper armor you will need between .060 and .080 white. No texture. This material will have to be gloss coated to get that shiny appearance. A harder to form material called ABS is used by some to create a really glossy trooper. Finding that glossy color is difficult. I'm mainly looking for styrene.

ProfessionalPlastics.com [good customer service. Thanks Lydia!]

Indplastic.com

USplastic.com [claims they sell the .080 in 48x96 inch sheets, but I can't find it in their catalog. Only the smaller 40x72 inch sheets.]

Basic Math:

Some basic conversions: .125 is 1/8th inch thick, .062 is 1/16th inch thick, and .083 is 1/12th inch. .090 is 1/11th.

Ohms:

I have been asked to take a Ohms reading. Here are the results: each segment draws about 5 ohms. The resistance varies from 4.9 to 5.1 ohms. I assume this is pretty good considering the home-made nature of the oven. Total of 20.1 ohms across the whole oven coil.

Misc. Comments:

Here are some helpful tips I've received from the RPF and other fine folks who have helped me out. Thanks guys!

Click here or here for ExoRay's multi-tank vacuum diagram.
Click here for John H.'s information on how to wire the oven.
Click here for a gas powered version of the oven. Thanks Prop_Master Paul!
Click here, here, here and here for some of Charlie M.'s [TI-386] oven and frame diagrams for a 24"x32" vacumform machine. Thanks Charlie for sharing these cool blueprints!
A special thanks to Phil G., aka Blaxmyth for his encouragement, and for getting me off by duff, and to build a vacuform machine. I just wish I had his mold making talents. His MDF molds are great!

Second pull, and some fine tuning:

Update: I managed to make several pulls using my new contraption. Here is what I learned:

Make a lid. I used the leftover Hardi-backer 500 material that I had from the oven construction, and it makes a nice lid. I made a handle from some angle brackets and a piece of dowel rod and some large washers. Works great. It speeds the oven heating, and plastic melt time. But watch out! you can over heat the plastic! I did! Man, what a mess, and smell!
I added a second handle to the frame. This gives extra pressure to hold the frame to the molds and forming surface. You will need the extra downward pressure to get a good vac seal.
The oven needs time to heat up. You can start pulling hot plastic in say 5 mins. But the longer time the oven has to heat up, the better the quality of pull you get. With the oven hot, the corners even get nice and soft! Thats convection heating working for you. Don't rush the oven preheat.
Keep the lid on at all times. Even when you are heating the plastic. It sits right on the frame and helps hold the heat in. set it aside only when you are pulling the hot plastic. Have an assistant replace the lid on the oven as soon as possible to hold all that hot air in.
Wear leather gloves. When you start to pull a mold, you can massage the hot plastic to get into the stubborn areas. Also, it keeps you from burning your hands!
I used HIS [High Impact styrene sheet] in a .080 thickness. It works great, but to be honest, on small parts, you really don't need that thick of a piece of plastic. It does however work great for the larger [deeper pulls] pieces.
The molds all need risers. Period. Otherwise you get a curved bottom, and that means poor fitting parts. Also, the molds need to be fine tuned for easy release from the melted plastic. A slight taper, grooves, or something to help the parts slip out from the vac-ed plastic. Each mold had to be pounded out! I even broke a mold trying to release it. The slightest undercut can cause this.
The imperfections on my molds even show up on the .080 thick material. I thought it would not be noticable. I was wrong. Time to break out the Bondo and sanding paper!
Forming time is pretty short, say 15 8-10 seconds, with another 5 seconds that you can massage the plastic with. After that, the plastic is so still it won't bend anymore. It takes a good 30 seconds to cool to touch enough to remove the plastic from the frames. if the molds will release better, the production could go pretty fast. Right now, I have to pound the molds from the plastic.
Overall I pulled seven panels in about one hour. 2 were good enough to give away to a friend who wanted the parts, one was a boo-boo, total melt-down, and one was not hot enough to form. One was OK and I trimmed out the parts, and one was decent, but not good enough to use any of the parts. It does make an interesting wall art decoration though!

What's next:

Take oven thermometer and check the temperature. It gets plenty hot, I'm just curious how hot it gets.
Add a metal grating above the coils to hopefully keep the overmelted plastic from ruining my heater coils.
Rework the vac system. The 3 HP shop-vac is ok, but a better option might be a combination of technologies, a cut-off valve, and a low volume, high vacuum secondary system for stronger pulls. Click here for a diagram.

UPDATE 10-15-09

It has come to my attention that, over time, the high heat from the nichrome wires will cause the Hardibacker 500 to fatigue, and eventually crack. This could pose a potential fire hazard. Currently a replacement calcium silicate fiberboard is being researched. I got 3 years of regular use from my machine build with the Hardibacker 500, but anyone considering this material should understand it's limits. Consider it a less than ideal substitute.

UPDATE 6-25-05

I've been running the machine for some time, and have pulled a total of 9 suits. [one suit averages 16 trips through the machine, for a total of 144 pulls] Some things I have learned; the Hardibacker 500 will crack after prolonged use. Not sure why, or how bad it will get, but I intend to keep using it until the oven falls apart. Another option would be to make a box for the frame, and line the box with insulation material and shield it with aluminum. I'll do that when the oven falls apart, but until then I'll keep using the current system.

The 3M non-skid material I was using for the holding frame to 'grip' the plastic, has started to come unglued. I lost several pulls due to this, so I reworked the holding frame's grip material this time using JB-Weld, and play sand. I mixed the JBWeld, a 2 part engine epoxy according to the instructions, and smeared it on the inside of the holding frames where the 3M material was.Then sprinkled it with a good dose of play sand that I had sifted to remove the really big pieces. Then let it dry over night. The results appear good, and the JB weld is suppose to resist temps up to 300 degrees C! That is way more than I'll need. Also, I can always add more JB-Weld to the frames if I need to.

Also, I have upgraded the vacuum system to use a 6.5 HP shop vac and my old 3.0HP shop vac as a booster. To be honest, I really can't tell much differece between the pulls the 6.5 make vs. the 3.0. I was hoping for a big boost, but thats just not the case. I've tried running them in parallel, and can on occassion get a tighter pull, but this is not consistent. I need to add the cut-off valve, and a high vac secondary system.

Finally, I tried some .062 ABS. One side glossy, the other side a 'haircell' texture. With my current oven setup it heats fine. No orange peel or other heat issues. My problem pulling ABS is with the vacuum side. The ABS has more rubber in it, and it is much slower to cool down compared to HIPs. My vacuum system can't seem to stay up with the needed vacuum to hold the shape before the plastic cools back off. For now, I will stick with HIPs.

I've added a discussion board for questions and feedback from other vac-formers. Check it out!

You can help support this site by purchasing a book version, with additional how-to information. Just click on the button below:

Older News
[Update 28-January-2007]
Just a short update:

The new holding frame clamps on the vacuum form machine worked great. Here is a peek at the new clamps:

The History of my Vacuum form Machines
Follow along as I tried to make a practical vac-table on a shoe-string budget.

	Vacuform machine #1 prototype This is the Mark I desing based ona website I found. Simple and quick to construct but had some issues. Mostly heat relate. Click here for more info on this design.
	Vacuform machine #2 The Mark II used parts from the original Mark I but incorporated an Over/under design. Worked much better but still had some heating problems. Click here to learn more about this design.
	Vacuform machine #3 The Mark III "oven scale" design is much improved but again, still plagued with heat and a size forming table large enough to accomidate the larger Stormtrooper armor. Click here form more info.
	Vacuform machine #4 Thurston James type T he final table design, based on Thurston James' design from his book. This has a 24"by 24" holding frame, and will use a vacuum pump/vacuum tank for the vacuum process. Also, a custom made 28" by 28" electric heating oven will be made. Click here for more information.

Supplies:

Below is a running list of parts and materials I used to make the vacuum forming machine.

BASIC SUPPLIES
QTY.	Name	Size	Source
1 Sheet	MDF [Medium Density Fiberboard]	3/4" by 4' by 8'	Lowes or Home Depot
3 tubes	square metal tubing	3/4" by 3/4" by 6'	Lowes or Home Depot
6	#2 2x4 pine or fir	stud length	Lowes or Home Depot
1	3/4" Floor flange or 1" floor flange	3/4" or 1"	Lowes or Home Depot
1 sheet	Sheet metal [aluminum]	24" by 24"	Lowes or Home Depot
1 tube	silicone caulk		Lowes or Home Depot
2	piano hinge hardware	3/4" x 4"	Lowes or Home Depot
2	bolts for clamping hardware		Lowes or Home Depot
2	wingnuts		Lowes or Home Depot
1	dowel rod	3/8" dia.by 5"	Lowes or Home Depot
1 sheet	Hardibacker 500 backer board **	1/2" x3'x5'	Lowes or Hoime Depot
1 roll	nichrome wire	#22, 81 Feet	Infraredheaters.com
56	ceramic posts	item # PI-B-1-S	Infraredheaters.com
1	Vacuum Pump 10 CFM Gast model 1065, 1022 or substitute *	10 CFM	Gast, Ebay
3	3/4" ball type valves *	3/4" threaded	Lowes or Home Depot
1	hot water tank, pressure tanks, air tank or propane tank *	30 gallon "slim" hot water heater	junkyard, RV center, Lowes, or Home depot.
1-2	3hp or better Shop-Vac	3hp or better	Lowes or Home Depot
1	Sump Pump check valve	1-1/4 to 3/4"	Lowes or Home Depot
1	10-2-G electrical wire	25'	Lowes or Home Depot
1	20am light switch [gray]	20amp with ground	Lowes or Home Depot
2	large wire nuts	#10 - 4 wires	Lowes or Home Depot
1	Light switch box with cover	std	Lowes or Home Depot
1	3 prong electrical plug with ground	20amp	Lowes or Home Depot
1 box	1-1/2 inch screws with nuts [50]	#10-24	Lowes or Home Depot
1 bag	2 inch screws [5]	#10-24	Lowes or Home Depot
1 bag	flat washers [25]	#10	Lowes or Home Depot
1 bag	wing nuts	#10	Lowes or Home Depot
	* not used so far in this project **It has come to my attention that, over time, the high heat from the nichrome wires will cause the Hardibacker 500 to fatigue, and eventually crack. This could pose a potential fire hazard. Currently an replacement calcium silicate fiberboard is being researched. I got 3 years of regular use from my machine build with the Hardibacker 500, but anyone considering this material should understand it's limits. Consider it a less than ideal substitute.

This project was last update on October 15, 2009.