Corrugated cardboard is great for prototyping because it is easy to work with. It's inexpensive, light, stiff, and is really easy to cut. There is a wavy length of paper in the center, which helps stiffen up the sheet without adding much extra weight. Cardboard is a good choice for quick prototyping activities like figuring out dimensions, exploring architecture options, and making structures quickly.
For higher fidelity models, foamcore is a great choice. It has a layer of foam sandwiched between two sheets of paper, which allows for some additional modeling details like different types of corners and joints. While more expensive than cardboard, foamcore is still an inexpensive prototyping material. Foamcore takes a little longer to work with, but because of it's clean surface and rigid foam, foamcore is a great choice for sturdier models or models needing a clean look.
Click a tool to learn more about it!
Bending sheets is usually the first process you plan for when making sketch models out of sheets because it is faster than joining with glue. The general process is to mark out your bend, line up the edge of a straight-edge, and give it a good whack with a mallet to make a dent.
Cardboard and foamcore both have a grain direction, which means they behave differently in different directions. For cardboard, when you are laying out your model, prioritize bending across the grain, as this will leave you with a precise, tight bend right where you dented the sheet. Bends along the grain will still work, but you may end up with a "crushy" edge if the cardboard flutes interfere with the denting process.
Foamcore tends to resist bending a bit more than cardboard, resulting in a springy-hinge-type bend that may or may not be useful. One way to make foamcore a bit more flexible it to skin one paper side off of the foamcore using a hotwire. To learn more about using a hotwire, visit the page on Foam.
Cutting sheets with a utility knife is a core technique for making sketch models. It is also the technique that requires the most caution, as it is really easy to cut yourself with the blade. It's important to keep the blade sharp because that requires less cutting force (which is safer) as well as making the edges of your model clean and free of pilling.
The Fletcher is a wall mounted tool used primarily for straight cuts in sheet materials. It makes precise square cuts quickly and easily. It is also equipped with a ruler and a stop to help you make repeat cuts to the same width. Keep the Fletcher in mind to really save some time!
Remember to keep your cutting angle low. This helps reduce the cutting force and keeps the exposed blade in contact with the material, resulting in cleaner, safer cuts.
Although cutting and bending are useful techniques, most models can't be made without attaching one sheet to another. Hot glue guns are the primary tool used to join sheets together. Strive to use just enough glue in your models, as too much glue will take a long time to dry, whereas not enough glue will result in a poorly bonded joint.
Often times gluing joints and bends alone results in models that won't properly withstand testing. Add ribs and gussets to your model to help add stiffness and make your prototype more robust.
Corner details (also referred to as foamcorners by nobody else but me) are part of what makes foamcore a more versatile material to work with over cardboard. Different corner details have different advantages and disadvantages, so if you are making a higher fidelity foamcore model it will be important to be able to choose the right foamcorner for the job. Bonus: this video has another foamcore specific tool, the circle cutter!
There are three main categories of corner details for foamcore. The first is rounded corners, which are useful if you want your model to have soft, rounded edges. The second category is exposed edge corners, which are the result of using a butt joint to join materials together. These types of joints are fast, but the exposed edge makes the model look less finished and is not a great choice for looks-like models. The final category is clean edge corners, which hide the foam layer, resulting in clean looking models. A few different joint types, like lap or miter joints, result in a clean edge.
Round Corner: folded round corners are the result when you bend foamcore. You can make these bends more precise by scoring the foamcore through the first layer of paper and the layer of foam (but not through the final layer of paper). To make the foamcore hold it's edge, add glue to the scored section. This type of joint is fast and good for when you want your model to have a soft, rounded edge, but it is not very structural so consider adding stiffeners.
Exposed Corner: a butt joint is formed when two formcore edges are "abutted" and glued into place. This is the fastest type of joint (when one sheet of foamcore is attached to another). Butt joints are a good choice for quick models that do not need to look very clean, but are used for exploring other things like function or architecture. Butt joints do not have much glue holding the surfaces together, so stiffeners may be needed.
Clean Corner: a lap joint is made when a strip of foam is removed along the edge of a sheet, resulting in a flap of paper, creating a feature called a rabbet. This can be done with an Olfa knife, but a rabbet cutter can also be used to make quick work. A rabbet edge meets a standard edge to form a lap joint, which had more surface contact between sheets, so it is sturdier than a butt joint. The flap of paper hides any foam from being exposed, making the edge detail very clean, but this flap of paper can be turned up and bent if the model is handled roughly. You may still need to add stiffeners, but because of the speed of making this joint with a rabbet cutter, it's slightly improved structure, and it's clean edge, lap joints are a very useful corner detail.
Clean Corner: a miter joint is the result when two beveled edges are glued together. The resulting joint is structural, stiff, and doesn't peel up. A miter joint is a high quality foamcore joint, but the main disadvantage is it requires skill to execute quickly, and even special tools designed for making the angled cuts needed require some finesse. If you try to make a beveled edge but it comes out rough, you can use sandpaper and a sanding block to smooth out the edge.