Tag Archives: Vacuum Forming

Dryer Box

How to build a heating Dryer Box

Plastic absorbs water. Moisture absorption (also known as water absorption) is the capacity of a material to absorb moisture from its environment. Type of plastic, temperature, humidity, how stored are all factors to how much is absorbed and how fast. When heating and then trying to mold plastic this a bad thing. Heated water turns to steam, expands 100 times it size and generally just makes a mess of the pull. So, how to get the water out of a sheet of plastic before molding?

Easy, you dry it. Yes, dry it. Heat the sheet plastic to a warm but not mold able state and bake the water out. Then mold, the now dry plastic with no problems. Polycarbonates are partiality sensitive to absorption.  So all you car body makers out there, need a Dryer Box.

A Dryer Box is easy to make. Think Easy Bake Over scaled up. Using heating duck board, a few 40-100 watt light bulbs, and temperature controller you can build a box with a few shelves that will hold your plastic the 4-24 hours it needs to dry before use. Times very based on temp, water absorbed, type of plastic, square area exposed excreta. Search for your plastic type, the recommended drying temperature and time. 

Simple materials to come by. I got mine at Granger.  Cuts easily with a box knife and yard stick.  Goes back together with the aluminum tape. Folds nicely with V groves. You can even use the tape for door hinges. It is important to put in a vent. You want the water to escape so add a 2″ vert hole in the top. Note the step cut in the door edge above. this makes a good seal. Worries about making a box, watch some HVAC videos that cover it all for you and you will be a pro.

I mold 2’x4′ sheets so mine is bigger than 2’x’4 on the inside. Works great. holds several sheets at a time.  Is a good way to dry paints, wet molds, cure epoxy, bond solvent type glues and all manner of other uses.

This a quick build in a few evening. Wear gloves and protective gears as the board is fiberglass and will be exposed until you get it all taped up. 

The simplest way is to use a grill temperature probe from the Grill department from your big box store (about $10)  and swap out light bulbs until you find the combination that keeps the box at temperature you want. I fine 2- 60 watts and a 40 keeps the box at a nice 125-130F.   The other way is to build a  STC-100 controller. There are several videos, here is one   How to build a Temp Controller with a STC-1000

Vacuum Form Machine Enhancements -Cheaper Heaters

Building Cheaper Heaters

One of the biggest costs to building a Vacuum Form Machine is the Heaters. Right? Well maybe not.

So kits are the simple way to go. As seen in the related article you can just order kits. They come with all the stuff you need. Spend an evening or two drilling holes and forming wire and poof, you have heaters. See Kits Here. For my first 2×2 that’s what I did. It was quick, no muss, no fuss and you wire them in. Not cheap mind you easy and quick.

What if it’s not as costly as we think?

When you look at the kits you get to thinking. At a rough cost of $60+ per 6 in x 24 inch panel you start to wonder what if one breaks? Yes, folks they do break, they are like light bulbs in that respect. They are good until they’re not and then you need new wire.

here. The key information is getting the right amount on each 6″x24″ board. The magic number is 42 ohms.  For the 220 v systems you need each panel to meter out at 42 ohms. They need to be balanced to heat evenly.

So boards. The suggested material is ceramic fiber board. What is ceramic fiber board and why do we want it? Well it turns out that ceramic fiber board is used as shelves in pottery kilns. It’s cool stuff designed to get very hot (up 1500 F), be somewhat easy to cut, used a few times and when to much glaze gets on it, and it is thrown away. Yes, tossed. If you have a pottery firing place near you, you might find it there. If not you might try what I did.

So what else gets fired in a kiln and takes high heat?  Well, the ceramic & porcelain, right? What are floor tile made from? Ceramic & porcelain. Now, I can’t find any information as to what heat a floor tile is rated for but if it can be fired in a kiln a few times to put glaze on (at 1500 F or so ) then it should work for us. And it does nicely. Cheap 12 in x 24 in white floor tile from your local home supply store is much better than any Hardi-backer.

Cut it with a wet tile saw into 6 in x 24 in (or a little under so it fits nicely in the ceiling grids). Lay out the hole pattern and mark it. Drill very carefully with tile bits and water. Lots of water and very slowly. The bits won’t last, so you will need several. Drill the corners first with fresh bits! As you can see in my photos, old bits and corners don’t mix and you get a break.

One tile makes two boards so you only need 2 or 4 at $2 a sq foot. With the wire, which has been spun, measured, and stretched on the kit frame. Affix with cotter pins “loosely”. Bolt the ends down and through to the heavy gauge 220 v wire on the back and light them up. Mine sit side by side with the kit ones and have been going for a year.

Building a MSE-6 Droid

Making a MSE-6 Droid R/C Car body

The goal of this project was to build a MSE-6 mouse droid in time to take to the con.
Ok, Plan B: will be to turn a mold in to a shell and then the shell in to an R/C droid for next years con.

Droid Mold  Droid top and bottom shell   What your finish droid should look like.

Steps

  • Join the yahoo group for MSE-6 mouse droids. Ask around for where to get, buy or order MSE-6 shell. Get no response.
  • Spend seven months building a home vacuum form machine (See how here)
  • Use the pdf plans from yahoo group to build form to build wooden mold. See nice photo gallery below. Invent new math to make the angels work out because plans are not complete or correct.  The mold is about 19 inches. 10.5 inch wheel base for standard R/C car components. NOTE: These are scaled! Not full size.  About 86%. If there is demand for Full 1 to 1 scale then I might build a second set of molds.
  • Use new home Vacuum Forming machine to make MSE6 shell on the molds you just built. See cool vacuum pull videos below.
  • Looking for Greeblies and Side panels!

Vacuum Form Build part Fourteen

Operation

Here we are at step 14 and Operation.

To make it possible to plug in the vacuum form machine, I needed to install a very large Over/Dry size outlet.  For me this meant running 35 feet of #6 copper, wiring into new outlet, and adding the largest breaker in the house power panel I have ever seen.  Not at all a little scary. That done, I now have the power I need to operate the vacuum form.  We used an oven plug rated at 55 amps. It won’t run the whole 2 x 4 but it should handle the a 2 x 2 or 2 x 3. It will in fact take two different circuits to power both zones of the 2 x 4. Each zone needs about 30 amps. Remember this is like running two kitchen ovens at once.    

With the house wiring done, the build is over and now begins the testing and operation. For this we now need a mold and a huge sheet of plastic. It’s been almost 6 months since the start of this build. It’s time to find out if the effort we have put in will pay off or burn the house down. This is always a good time to double check everything. Have that buddy come over and double check your work or stand by with the fire extinguisher.

First test: The goal will be to use the Vacuum Form machine to turn these new sheets of 4 x 8 plastic, a new mold (see Building a MSE-6 Droid) into an R/C car body. Here’s the plan.
Does:
4’x8′ sheets of ABS   + Droid R/C car body mold  + Vacuum Form Machine  = MSE-6 Mouse Droid?

+ + = ?The Droid you want

We will see.

Vacuum Form Build part Thirteen

The Holding Frame

I wanted the flexibility to use the vacuum form machine in whatever size configuration best fit the job I was working on, 2 x 2, 2 x 3 or 2 x 4.  So, my lift frame is a simple 2 x 4 angle iron design with some added easily moved cross braces. Two screws and I can quickly adjust the lifting frame size to match any of the three Platens. Then just swap the Platen and you are off. To do this I will also need top frames in each of the 3 sizes. This set of photos shows the 2 x 2 setup with the top frame clamping to the lifting frame. The top frame is oak with neatly screwed corners and a very tight fit. The side slots allow for large size paper clips/clamps to hold the plastic sheet in place. You might think this would not be enough to hold the plastic, but the clamps do a great job and are easily replaced for a few bucks a box should they get tired.

Vacuum Form Build part Twelve

Top Cover

The heater box is covered with a vented cover. The cover is important. It is over lots of hot 220v wire and the heat from the back of the heat tiles must escape. It’s also important that things ( spiders, cats, mice, etc.) and dust don’t accumulate on the back of the heating panels. This could cause a dangerous fire hazard.  If I let the machine set for anytime at all I remove this cover and blow all the dust off both sides with the air compressor.

I revised the design a little adding support and for efferent use of materials. My design is made of 4 pieces allowing the top cover to be made from two 2′ x 4′ sheets of ply instead of requiring a full 4′ x 8′ sheet. The end to end size is 52″, just over the 48″ width of a sheet. I couldn’t see buying a whole sheet for just 4″ so I added a 1×6 seam down the middle with from some scrap from one of the earlier steps. This makes the top stronger and saves half a sheet of 1/4 ply. My hope is the added strength will prevent sagging. Since the cover is over lots of hot wire and exposed to heat be sure to seal the wood on both sides and use Hi Temp paint on the vents. 

Vacuum Form Build part Eleven

The Plumbing

In this step we show how the Vacuum lines get hooked up when using the Two Stage systems with two tanks, two gauges, a selector valve and a main vacuum valve. These photos don’t show the check valve but there is one, right on the pump line.

Again this is a step that I thought shouldn’t take long. But it does. Working out what connects to what, how long that hose is and which fittings are needed where is all on you. There’s no parts list of what to buy and what size pipe thread fits where. This took several trips to several plumbing departments to find all the right fittings. And no I didn’t guess right the first time and yes I have a few parts left over. 

I start here with the pump and tanks I used and deciding where to place them. There is lots of room to work with. I moved the the tanks to under the valve to try to keep the hose lengths as short as possible since longer hose means less vacuum.

Vacuum Form Build part Ten

Switch Mount

In building my own Lift Arms and not welding them, it left me with coming up with a way to mount the safety switch for the heating elements. I’m all for safety and not wanting to simply leave this switch out. I needed a new place and way to mount it. The goal of the switch is to only have the heat on when the frame that holds the plastic is in place at the top and ready to be heated. So I decided to mount the switch under the deck and trigger it off the frame guides. It’s a funky little block of wood that holds the switch and a hinge and mounts to the side of the lower frame. It all makes more sense if you see the pictures.

It works like a charm. As soon as you lift the bar to slide the plastic up the heat starts coming on. As soon as you come down with the plastic the heaters cut off.

Vacuum Form Build part Nine

Front Control Panel and back Power Box

The power box and front control panel are two of the more challenging parts to build.

The rear power box because, IT IS the POWER BOX. It has 100 amps @ 220v running through it. Making an error here can mean shock, fire, a burn up or any number of bad things. There are lots of wires here and getting just one crossed or using the wrong gauge can be the end of our little project. So we test and retest and go over the wiring diagram again and again. Also a good time to have a buddy double check your work.

The front panel was a challenge because again we had no instructions to follow. Opting for the more advanced Two Stage Vacuum System design we needed a “two way selector valve” to switch the vacuum from the tanks to the pump vacuum during operation. This required two vacuum gauges on the panel, the selector valve the pump switch and main vacuum valve to all be within easy reach during operation. Having no plan to follow I decided the front panel needed some tilt so the gauges could be more easily read and chose 1/4″ Plexiglas (non conductive).

The results are quite nice. It presents a very smooth and finished looking front panel with everything easy to read and get to.

Vacuum Form Build part Eight

Fast heat Heating Panels kit build.

Fast heat Heating Panels kit build. The kits are great. Everything you need is in the box (except tools) and you don’t have to know how many feet of wire at what wrap gives you the right resistance to make each one 1200 watts. And then how far to stretch it to make it fit and still keep the edges warm so there are no hot spots. All those calculations are worked out for you. That said they are still kits and have to be very carefully assembled so as not to break the ceramic fiber board or kink the wire. There are many hours in this project and this step is one that takes longer than it looks.

One note about the heating panels. This is the heart of the machine. If this doesn’t work well you do not get good performance out of you vacuum former. The TK560 forum goes on and on about this topic.  It all comes down to this. A vacuum form machine is an oven. A big oven. In fact by the time I have both zones of mine working it is twice as much power (in amps and watts) as a kitchen oven.  A very good source said (see link below) that you need to heat the plastic from room temperature to forming temperature (about 350-400 F) in about one minute to keep the plastic pliable. Heat too slow and you change the plastic elasticity. This is like baking 15 minute rolls in one minute.  It takes a lot of heat. This my second try to build a machine. The first I abandoned for lack of heating power.  110v is just not enough to do the job. The kits are not cheap but the price is fair for the work and research that has gone in.  Heating is king in this game and Doug has it worked out.

For more, read down around page 16 of the document linked here from one of the commercial heating element suppliers which talks about Estimating Power Requirements. It works out to just under 11 watt/in2. That’s watts per square inch. So, if you have a 2′ x 2′ machine that’s 24 x 24 x 11 or 6336 watts a minute needed.