By Ken Tarlow
I use plastic for most of my prototypes and continue to be pleased with the quality models I can produce. You can design on paper what you want to build and many of the things you design can be constructed from pieces of tubing or flat material that can be purchased at any good plastics store in your area. Become familiar with the stock shapes so you can get an idea of what's available to work with.
Once you know what the standard shapes are and which ones you want to use, make a list of the parts you want and exactly how you want them cut. Then, take your list to the plastics store. Look in the Yellow Pages under "Plastic, Acrylic Sheets, Rods, and Tubes" and find a store that not only sells those materials, but will also cut them to your size. They can also buff and polish the edges or fabricate the entire model for you, although that's more expensive than doing it yourself. However, it's not excessively expensive and most stories do very good, quality work.
1. SAFETY
First of all, you'll want to work in a well-ventilated room. Many of the glues and other spray materials that you'll use in building a plastic model can be harmful to your respiratory system and you'll need good ventilation. I also advise wearing (especially when using the glues and spray materials) a good mask that fits over your nose and has an activated charcoal filter built into it. Most hardware, paint or automotive stores have them.
In addition, purchase a good pair of safety glasses whenever you're cutting or drilling any plastic. You don't want to endanger yourself with little flying bits of plastic or unexpected cracks, so I recommend eye protection in all cases.
2. ADJUSTABLE SPEED DREMMEL TOOL
You can make plastic models without having sophisticated shop equipment. I recommend that you get an adjustable speed Dremmel tool. Dremmel is a brand name. Sears has them under the Craftsman brand name. (There are other companies that sell these handheld motorized tools, but Dremmel is the most popular). With this tool and a assortment of tips that go with it, you'll be able to do most of your prototyping activities, especially if you've gotten your plastics store to cut all the pieces to the size that you need. If you're not doing any major cutting and just the more detailed shaping and cutting, this is really the only piece of power equipment you'll need.
"Cut Off" Wheels
For your Dremmel tool, you'll want to make sure you have a good supply of thin "cut off" wheels. These are disks that are made of very abrasive material, but are very thin. There's also a shaft that these discs go onto (they screw on with a little screw head that's supplied).
When you turn your Dremmel tool on, this disc spins. The disk is one inch in diameter and will cut through metal and in most cases, through virtually anything. So rather than having big expensive saws and tools and a giant shop, you can really do all the cutting you need to do with this versatile little tool. If you have to cut more than a few inches of material at a time, ask your plastics store to cut it for you. Just do the little detail cutting and shaping with the Dremmel.
Drum Sander
The other piece you'll need for the Dremmel is called a drum sander. It's a shaft with a rubber drum shaped device on the end of it. A cylindrical sanding drum slips over the rubber tip and allows you to sand into all kinds of tough places. You can round off edges and smooth out rough spots with this sanding drum.
Disk Sander
Another tip that you want to get for your Dremmel is a disk sander. It's a small flat rubber disk with an area for little round disks of sandpaper to stick to it. You can sand flat areas and do special sanding and shaping with the sanding disk. You'll see,it comes in very handy.
Rasp
You will want a tip that works like a rasp. It looks a little like a drill bit, but instead of going in just one direction like a regular drill bit, the flutes of this bit go in two directions and look like little cross hatched "X"s. With this bit, you can clear away plastic or other materials in a kind of grinding action to make any kind of irregular hole or shape that you want. It gives you the ability to clear away material very precisely.
3. DRILL PRESS
Many times when making prototypes, you must drill holes of various sizes and a small drill press is the way to go. You can get these for around $150 and sometimes less if they are on sale. Again, Sears or any other store that sells power tools will have a small drill press that suits your needs and your budget.
When you drill holes in acrylic sheet, you need special drill bits that are designed for drilling into plastic. Ask your plastics store to get you some drill bits for the size holes that you want to drill. If you use a regular drill bit to drill through plastic, when you've gone through the plastic and the bit is about to got out the other side, it may chip the material. So the special plastic cutting bits are truly necessary.
4. GLUE
You will also need the glue necessary to adhere the plastic pieces together. There are several types of plastics glue.
Acrylic Cement
Acrylic cement is very watery and comes in a bottle or can. You pour part of the contents into a smaller bottle that your plastic store will sell you which has a tip like a syringe. When you want to glue two flat pieces of plastic together, you put them together the way you want them. Right where the pieces touch, you flood the area with this thin, watery cement. It actually seeps into the joint and fills it by itself, by a method similar to capillary action. You need to hold it there for perhaps 30 seconds and then the joint will be strong enough to stay on its own. Best of all, it dries completely in about half an hour to an hour.
Five-Minute Epoxy
For joints that are not perfectly smooth, you need to use something that has more filling ability. For this I recommend five-minute epoxy. You can get this at any hardware store. The two parts of this epoxy are mixed together in equal amounts, using a popsicle stick. You can glue joints together and create a little filling action at the same time.
Cyanoacrylate Glues
If you want to get an instant rock-hard bond and get some filling action as well, I recommend the cyanoacrylate type of glues like "Super Glue." Thee are other brand names also (like "Zap Gap"). You can use these glues with an accelerator that comes in a little spray bottle. Apply the glue neatly and be careful not to get any on your fingers. Then, spray the glued area with one spray of the accelerator and instantly the joint will turn into a rock-hard seal. It's really quite miraculous!
However, this is one of the more toxic glues, so I really recommend using it in a very well-ventilated area. Turn a fan on, have the window wide open, and use a good mask that will screenout some of these fumes.
Auto Body Filler
If you want to create a blend between two pieces to create a look that is more appropriate for a consumer product, you can use autobody filler, like "Bondo" that you can get in any auto parts store or plastics supply store. It comes in a large can, which is the filler, accompanied by a tube of hardener. You take about a golf ball size worth of the filler and squeeze out of the tube about a one-inch length of the hardener and mix it up thoroughly. Then you can apply this with an ice cream stick or any other kind of device that you want to spread this material out. Now you can fill any kind of gap. You can create fillets. You can blend two pieces together any way you want. "Bondo" dries quite hard in about 15 minutes. It sands very nicely and you can use your Dremmel tool with your drum sander or your disk sander and sand the parts away that you don't want.
5. WET OR DRY SANDPAPER
Sand with wet or dry sandpaper to get a really smooth finish. You can start with 180 grit sandpaper and then progress to finer papers--400 is the finest. Make sure to get wet or dry sandpaper. This looks black and it has a cloth back. You can take pieces of it and keep a tray of water next to you and as you sand, you dip the sandpaper in the water to clear away all the material that you've been sanding that clogs the sandpaper. With this method using auto body filler, you can actually make any shape you want because you'll be sculpting it and sanding it to the desired shape and dimensions.
Once it's sanded smooth, you can then use a glazing putty, available in an auto parts store, to smooth out small areas. It's a very thin, toothpaste-like material. It comes in a tube and is best when applied less than one-sixteenth inch at a time. It's used for doing the final detail body work, filling in pinholes and other slight irregularities. Once it's dry, you can then sand it with 400 grit wet or dry sandpaper. When you're finally done, you can coat it with a sandable spray primer paint. When that has dried, you can fill it some more with body putty if needed.
From this point, you're ready to go right to a final lacquer or enamel paint. The paints are available in your auto parts store or a good hardware store. When you're done, you can create some very finished, professional-looking prototypes.
The above article was excerpted from Tarlow's MIND TO MONEY, a cassette tape/workbook package that can help you develop a new product from the idea stage to the marketplace. MIND TO MONEY may be ordered from the Dream Merchant at $59.95 plus $4.95 CA sales tax and$5 shipping and handling ($69.90 total). Send orders to the Dream Merchant, 2309 Torrance Blvd., Suite 104, Torrance, CA 90501.
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