At this point I want to introduce you to the world of plastics. Depending what type of plastic you use, it can be easier to work with than wood, and doesn’t necessarily cost more. Plastics usually don’t require a coat of paint or polyurethane when the job is done, and they can enable creative designs that would be difficult or impossible with other materials.

I’m going to begin with ABS, because it’s versatile and affordable. You may not have heard of it, but everyone comes into contact with it at some time or other. Lego blocks and other children’s toys are made of ABS. Many 3D printers work with ABS. I am fairly sure that the wheeled trash can outside my house is molded from ABS, and so far as I can tell, even the little computer speakers that I have on my desk are in ABS enclosures.

There are so many things you can make very simply by bending plastic, I’m going to include four mini-projects here that only entail cutting and bending. Gluing and screwing parts together will be dealt with in the next two chapters, and transparency and colors in the two chapters after that.

Getting Acquainted With ABS

ABS is an acronym acrylonitrile-butadiene-styrene. The “acrylo” part of its name tells you that chemically speaking, ABS has some family ties to acrylic plastics that go by brand names such as Lucite, Plexiglas, or Perspex.

It looks and feels quite different, though. Acrylics are transparent, brittle, and relatively hard. ABS is most often sold in opaque black and white sheets. It can be bent or curved at a relatively low and safe temperature, doesn’t crack or split unless severely abused, and while being soft enough to be shaped easily, it is tough enough to take substantial loads.

You can buy sheets online in sizes from 12" x 12" upward. (Just check eBay.) If you live in a city, you can probably find a retail source for sheets that are 48" x 96". Thicknesses include ¹/₁₆", ¹/₈", ³/₁₆", and ¼".

Preparation

Your first step with a new piece of ABS is to clean it. This will be much easier than after you have cut it into pieces. Wipe both sides with a damp, nonabrasive rag or sponge, adding a trace of dishwashing liquid if necessary.

When handling ABS, always remember that you probably won’t be painting or otherwise improving its finish. It scratches easily, so treat it gently. Avoid laying tools on it, and when you place it flat on a work surface, make sure there are no sharp objects such as nails or screws underneath it.

Most ABS is textured on one side and smooth on the other. The textured side is slightly tougher and doesn’t show scratches so easily, and I think it looks nicer. I’m assuming this will be the outside surface for your project.

To draw a pattern on the smooth side of ABS, you can make pencil lines, but they will be very faint. Personally I like to use a fine-point water-based roller-ball pen. This makes cutting easier because the lines are so visible—assuming you are not using black ABS, of course. If you’re wondering how to mark that, stretching pieces of masking tape is an option.

You should be able to wipe away water-based ink without any difficulty, but don’t use a permanent marker. The most effective solvents for removing marker ink also dissolve ABS.

Cutting ABS

Most everyday woodworking tools can be used with ABS, although a saw that does not have hardened teeth may be dulled more rapidly than if you are cutting wood.

Power saws are a problem. The heat generated by friction causes ABS to melt in contact with a circular saw, leaving smears of plastic on the sides of the blade. These smears melt again when you are cutting something new, and can be sticky enough to grab the material and throw it at you with great force.

Plastic-cutting blades are available, made of thicker steel that absorbs more heat. Blade lubricant can also help, but ABS is so soft, I use a handsaw even for cutting the full length of a 96" sheet.

Unlike plywood, ABS doesn’t splinter, and a tenon saw with hardened teeth will make a fairly clean cut. A handy item known as a deburring tool can smooth ragged edges while adding a narrow bevel, just with a single pass. This is much more efficient and satisfactory than using sandpaper.

The tool is shown in Figure 15-1. It has a sharp edge (you can see it reflecting the light in the photograph), but this terminates in a rounded tip that makes the tool quite safe to use. Wearing gloves is still a good idea, just in case.

The way in which a deburring tool removes a thin ribbon of plastic from the edge of ABS is shown in Figure 15-2.

Heating ABS

To bend or curve a sheet of ABS, you have to raise its temperature to 105 degrees Celsius or about 220 degrees Fahrenheit, just above the boiling point of water. There are two ways to do this.

The easiest way is the expensive way, using a plastic bender consisting of an electrical element in a long, ceramic channel. An example is shown in Figure 15-3. You plug it in, wait about 10 minutes for it to get hot, and then lay a piece of plastic over it. The element heats the plastic along the line where you want the bend. After 30 to 60 seconds (depending on the thickness of the plastic), you can bend it with reasonable precision—usually within ¹/₁₆".

Unfortunately, this type of plastic bender is not cheap. If you go online, you can find plans and videos suggesting how to make your own version, but that kind of DIY project, using a hot element powered with house current, seems a bit iffy to me.

I think you should use a heat gun. This is not only less expensive, but can make multiple bends that would get in the way of each other on a plastic bender.

A heat gun is like a hair dryer, but more powerful. (A hair dryer is not hot enough to soften ABS.) In addition to bending plastic, it has other uses. If you are doing hobby-electronics, heat-shrink tubing is designed to shrink when you apply a heat gun. Sticky labels will unstick themselves more easily if you blow hot air at them, and if you have a cold workshop, epoxy glue flows more easily and sets more quickly when you apply some heat. Quite often, I find myself thinking, “Maybe a heat gun can help with this little problem.”

You can buy either a full-size heat gun, using about 1,000 watts, or a small-size version that consumes approximately 350 watts. For our purposes, the smaller, less expensive type will be sufficient. An example is shown in Figure 15-4. It costs less than the larger type, and is safer to use—so long as you use it sensibly.

Caution: Burn Risk

At the risk of emphasizing the obvious, heat guns do get hot. Don’t point one at yourself, or at other people. Don’t put your hand close in front of it to check that it’s working, and don’t lay it down and walk away from it while it’s running. Also, a heat gun should not be used with materials that burn easily, or if there is flammable vapor in the air.

If you are wearing 100 percent synthetic clothing such as polyester, nylon, or spandex, there is the potential risk of melting the cloth if you point the heat gun toward yourself accidentally at close range.

Higher-powered heat guns often incorporate a steel tube to direct the heat, and this tube will remain hot enough to burn your hand for a while after you switch off the power. Therefore, don’t leave a heat gun lying around where children may pick it up or pets may be hurt by it. And unlike the character in Figure 15-5, you should wear heat-resistant gloves while bending plastic. Pure cotton gloves or oven mitts are acceptable.

Focus the Heat

When hot air emerges from a heat gun, it tends to spread out. This is okay if you want to make a gentle curve in the plastic, but if you are hoping for a sharply defined bend, such as the corner of a box, you will need a way to confine the heat to a narrow strip.

For this purpose, you could use small pieces of plywood as heat shields. However, a heat gun is hot enough to scorch wood, and can even make wood burn if you run it for long enough at short range.

I think a better idea is to use a nonflammable material, and ceramic floor tiles are a good choice. You can buy them at any big-box hardware store, and three of them will be sufficient.

A Test Bend

To see how easy it is to bend ABS, cut a piece measuring about 4" x 2" and place it between two tiles on your work area, with the end sticking out, as in Figure 15-6.

Hold the third tile to cover the part of the plastic that you want to protect from the heat, and use the heat gun on the narrow strip that is exposed, as in Figure 15-7.

Most heat guns have two settings. If you are using a small heat gun, use the high setting; if you are using a large heat gun, use the low setting. Keep the tip of it 2" away from the exposed ABS while you direct the hot air up and down the strip in a steady rhythm. After about a minute, when you press on the plastic, you should find that it isn’t as springy as before. Switch off the heat gun, and see if the plastic will bend as in Figure 15-8. If it resists, heat it a little more.

You don’t necessarily have to bend the plastic while it is clamped between the tiles. You can take it out and bend it in your gloved hands, and you should still get a well-defined folded shape. This is because while you were using the heat gun, the tiles not only blocked the heat but absorbed some of it.

Figures 15-9 and 15-10 show the concept. If you heat plastic that is unprotected, the plastic conducts some of the heat along its length, so the hot area is relatively wide. If you clamp the plastic between tiles, they conduct heat away, so that only the area under the heat gun gets hot enough to bend.

How long should the heating process take? This depends on several factors.

• ■ Thin plastic heats much more quickly than thick plastic.
• ■ A wider or longer exposed strip of plastic takes more time, because a fixed amount of heat is spread over a larger area.
• ■ The distance of the heat gun from the plastic will make a difference.
• ■ If you bend multiple pieces of plastic, each one may take less time than the last, because the tiles become hotter. The heat gun also becomes hotter with use.

If you overheat ABS, you will scorch it. First it turns yellow, and then brown. This change is not reversible. If your plastic becomes soft in less than 30 seconds while using a small heat gun, you’re probably making the plastic too hot.

When making a bend, always remember to curve the plastic away from the hot side, so that the hot surface stretches around the outside of the bend. If you try to do it the other way, the hot surface may bunch up or create an ugly fold inside the bend.

After you make a bend, use a speed square to check the angle, and when it looks the way you want it, you can spray it with a thin mist of water or wipe it with a wet sponge. It should stiffen almost immediately.

You may be tempted to use a pencil or pen to indicate where you want a bend to be. This is not a good idea, because the heat can make the mark permanent. I generally mark a bend with a tiny dot on the edge of the plastic. This can be scraped off later with a utility knife.

If you’re using large tiles, and the one that you’re holding is too big and heavy, you can break it into smaller pieces. You can try to control the break by scoring the tile with a glass cutter, if you have one. Either way, you can snap the tile across a length of two-by-four. If you are reluctant to do this with your hands, and you have a floor that won’t be easily damaged, hold down one end of the tile with your foot, and step on the other end.

Be careful with broken edges, which can be sharp.

Paperback Book Stand

I’m starting with this project because it’s the simplest. Just three folds will do it.

If you like to sit and read a book without having to hold it up, a book stand solves this problem. You can buy one, of course, but wouldn’t you rather make one that is exactly the right size for your needs? If you only read paperbacks, the stand can be compact. If you prefer art books, it can be big. I’ll describe a compact one, leaving you to change the scale if necessary.

The plan is shown in Figure 15-11. I’m guessing that you have a piece of ABS 12" wide, because this is the standard minimum width when you buy it online. The plan is drawn with this in mind, as it requires a piece of plastic 11½" x 7".

When you receive a sheet of ABS, it may have a sawn edge, which is likely to be straight but rough. If it has a “natural” edge, it can look like the closeup in Figure 15-12. Either way, you’re going to have to cut your own reference edge, which will be both straight and smooth. This is similar to the procedure that you followed when using plywood in Chapter 10.

To create your reference edge, I suggest you cut along a piece of guide wood as shown in Figure 15-13. A sacrificial piece under the plastic isn’t necessary, because ABS doesn’t splinter, and a tenon saw with hardened teeth will make a fairly clean cut.

The two-by-four under the plastic is only there to provide some support beyond the work area. A ¹/₈" thick sheet of ABS is not very rigid, so it needs support when you are cutting it. Sawing it closer to the edge of your work area is not an option, because the clamps would get in the way.

Saw gently, being careful to keep the side of the saw vertical. When you complete the cut, you can clean the underside with a deburring tool or a few strokes of a sanding block.

Now use your speed square to draw a line at 90 degrees from your reference edge, as in Figure 15-14. Measure along this line and make a mark at 7". I’ll call it Point A.

Measure 11½" along the reference edge, as in Figure 15-15, bearing in mind that the piece you need to make your paperback book rest is 11½" long.

Use your speed square to draw another 90-degree line at the 11½" mark, as in Figure 15-16. Extend this line and mark it 7" from the reference edge. I’ll call this Point B. Now you can draw a line connecting Point A and Point B, and it will be parallel with your reference edge, and the same length. You can cut along this line, as in Figure 15-17, and then cut the two other edges of the rectangle to its finished size. (The saw happened to be held at this angle when the photograph was taken, but should be used at a shallow angle while making the cut.)

Now you need to make marks on the edges to define where the bends will be, as shown in the plan in Figure 15-11. The easiest way to do this is to clamp the ABS against a piece of two-by-four, so that you have something to rest the ruler on, as in Figure 15-18.

After you make marks along one edge, you can use your speed square to copy them across to the other edge, as in Figure 15-19.

You’re ready to start bending. The plan in Figure 15-11 assumes you’ll want the textured side of the ABS on the exposed face of the book stand. Don’t forget: you always bend the plastic away from the heat, because the hot side has to stretch around the bend. The outside of the bend is a longer distance than the inside.

Beginning at the top and working downward, your first bend, at the 4" mark, requires you to heat the textured side. So, the plastic goes between the tiles textured-side-up. You should be able to see the edge marks about ¹/₈" beyond the tiles. Check that the plastic is at 90 degrees to the tile edge by using your speed square, as in Figure 15-20.

Apply the heat gun as in Figure 15-21. When the plastic has softened, remove it quickly, hold it between your two hands, and bend it along the line that you heated till it makes a sharp angle as in Figure 15-22. To see why the sharp angle is necessary, look ahead to the finished book stand in Figure 15-26.

For the next bend, the plastic goes into the tiles smooth-side-up, as in Figure 15-23. Before you apply the heat gun, add a piece of tile to protect the exposed area beyond the bend.

When the plastic is sufficiently soft, your second bend is at 90 degrees, as shown in Figure 15-24.

For the third bend, the plastic goes into the tiles smooth-side-up, as shown in Figure 15-25. Only ½" of the plastic remains inside the tiles, so you’ll need to clamp it firmly. A short bend is always more difficult than a long one.

After the third bend—that’s it!

Use sandpaper to round the four corners, and the job is done. The finished paperback book stand is shown in Figure 15-26.

Now consider how you would have made this out of plywood. Probably you could have used two triangular side pieces, to support the slanting book rest.

But how would you have made the lip at the bottom? I don’t think it would have been quick or easy, and the end product would have weighed more while probably not looking as nice.

So what else can we make with ABS?

Adjustable Paper Towel Dispenser

I decided that I wanted a paper towel dispenser which will allow me to adjust its turning resistance. I think this concept is useful, because the towel roll should be loose enough to turn, but stiff enough to resist when you tear a towel along its perforations.

The design in Figure 15-27 consists of a simple bracket to mount on the wall, and two inserts that push into the cardboard tube in the center of a roll of towels. You have to squeeze the lugs that stick out of the inserts when you push them into the tube. Once inside the roll, the lugs are springy enough to grip it. You adjust the turning resistance by tightening or loosening a ¼" bolt at each end of the roll holder.

The plan for the wall bracket is shown in Figure 15-28. This is longer than the likely 12" width of your ABS sheet, unless you decide to make it in two pieces. I’ll leave that to you. It’s a very simple design, requiring just two bends. I think you can make those without any need for photographs, at this point. The holes are centered vertically between the two long edges.

A plan for each end piece is shown in Figure 15-29. Saw cuts are in red. The circles indicate holes that you drill through the sheet. I put a cross in the center of each one so that if you enlarge and print this plan, you can easily prick through the center of each circle into the plastic.

Making the ¼" hole in the center shouldn’t be a problem, but a ³/₈" drill bit grabs the plastic, digs in, and can make a mess. You can minimize the problem by countersinking to the limit of the holes established by the straight lines, as in Figure 15-30. Then use a ⁵/₁₆" drill bit, and finally the ³/₈" bit. Make sure the plastic is firmly clamped, and run the drill as slowly as possible.

You may wonder why the ³/₈" holes are necessary. The reason is that whenever you have two saw cuts meeting inside a piece, you should always drill a circular hole first, and then saw into the holes, as shown in Figure 15-31. If you allow two saw cuts to meet at a sharp point, and a bend line is nearby, the plastic will tend to split where the cuts meet. The curve at the inside of the hole allows the plastic to stretch instead of splitting.

You have to angle the saw up till it is almost vertical as it approaches each of the holes. Proceed cautiously with the last few millimeters of the cut. If you stop just before the hole, ABS is soft enough to let you wiggle or twist the piece away. Any remnants can be sanded or pared away with a utility knife, so long as you cut down into some scrap wood, as shown in Figure 15-32. Don’t pull the knife toward you.

Bending the lugs on the end pieces is very straightforward. All the bends can be smooth-side-up. Figure 15-33 shows one of the end pieces with three of the lugs bent, and one remaining.

Test your first end piece to make sure it’s a tight fit in a roll of towels, as in Figure 15-34. You can always reheat the plastic to bend the lugs in a bit or out a bit.

Use a 1" long, ¼"-size bolt, two 1” fender washers, and a locknut to mount each end piece in the bracket that holds the towels, as in Figure 15-35. The threads on the nut and the bolt must match (usually, 20 per inch). If you built the pantograph in Chapter 14, these items will be familiar to you. Tighten the bolt to increase resistance to rotation.

The towels in the dispenser are shown in Figure 15-36. I happened to have flat-headed ¼" bolts, so I countersunk them into the bracket for a cleaner look. Pan-headed bolts would do just as well.

Shower Caddy

Maybe you already have one of these. I’m talking about a little rack or basket that contains shampoo and other essentials, hanging from the shower head in your bathroom. Even if you have one, it may not be the right size or shape for the bottles that you want to put in it. This is a good reason for designing your own, as part of the pleasure of making things is that you can get exactly what you want.

If you make a smaller version, it can be a soap dish that hangs from a suction cup on the tiling around your shower. My design in Figure 15-37 has no dimensions on it, because you can adjust the scale to suit your needs.

The first step in designing your own folded ABS object is always to draw the plan on a piece of paper, cut it out, fold it, and see if it looks good. Once you have it the way you want it, tape the paper to the smooth side of the ABS and draw around it. The drawing doesn’t have to be super-neat. My version, in Figure 15-38, certainly wasn’t.

After drilling holes where cuts will meet, you can cut around the outline using a tenon saw for straight edges and a coping saw for curved edges.

This is a simple object to bend, because all the bends are in the same direction, and there are only four of them. I don’t think you’ll need step-by-step photographs, so I’ll just show the finished object in Figure 15-39.

Origami Crane

This is a slightly more difficult fabrication project because it mixes bends in opposite directions. After each bend becomes rigid, it tends to get in the way of the next bend.

Be careful to make the bends in the correct sequence. The numbers in the plan tell you what the correct sequence is. See Figure 15-40.

After you cut and drill the shape in the same way as in previous projects, start the bending sequence with the tail. By the time you get to the second wing (bend number 5), you’ll have to be creative to avoid reheating previous bends by using vertical pieces of tile, as shown in Figure 15-41.

The finished crane is in Figure 15-42. If you like the look of it, why not fold a couple more, and use them in a mobile?

I think you can see from this chapter that a bendable material opens up some fascinating design possibilities. But glue and screws also have their uses, as I’ll show you in the next two chapters. After that, I’ll describe a concept that applies glue, screws, and bending to plastic of two different types.