Model Complex Solid Shapes With Cardboard.

This is a technique to model complex (or simple) solid shapes.
The idea is to cut your model into slices and cut cardboard with the shape of your model slices. When staking the slices in the correct order you get your model in rough finish to start sanding.

The final model will have really good weight and resistance. A great advantage of this method it's its precision since the model comes out almost exact as the 3d computer model. A disadvantage is the amount of time you may spend cutting and sanding.

This is kind of a replacement for a laser cutter and MDF plaques. For me it was faster and more controlable than laser cutting MDF. Hope it helps!

In dedication to my design classmates with whom I learned this technique. | Dedicado a mis compa�eros de dise�o con quienes aprendi y sigo perfeccionando la tecnica.

www.combaideas.com.ar !

Step 1: Make Your 3d Model

Model your object in your favorite 3d modeling software. You don't need it to be exact, round corners can be later sanded so don't bother to do your model highly detailed.
I use Rhinoceros 4.0.

Step 2: Slice Your Model

Try to slice your model in the direction in which you get less slices, this will save you cutting and gluing time. Make the separation of the slices equal to the thiknes of the cardboard you have. Slice the part of the model that you find convenient for this method (non geometric shapes you can't get by folding or curving other materials). Fo the saw I only sliced the body since I needed it to be solid and strong to support the weigh of the blade, base and protection of the blade.
Rhino has a special tool to slice your model in any direction you like. Just type "_Contour" and hit enter to start the tool. Make sure "grouping objects by cutting plane" is on so all the curves of each slice are grouped togheter.
In the second example shown I have chosen to slice the model in a diagonal direction. This tool only creates curves, it doesn't really cut your model so don't worry about your model being cut.

Keep in mind that the thinner your slices are, the thinner and easier to cut your cardboard will be BUT you'll have more slices to cut. You'll also get more exact models with thinner cardboard. It all depends on what you'll do and what results are you looking for.

Step 3: Print Your Slices

Now accomodate your new curves so you can print them out. You can print them directly from Rhino or export them to another software like Adobe Illustrator or Corel.

You can print them on regular paper or on sticky paper so you can forget about adding glue later.

Step 4: Cut Your Slices

Now you have printed your sliced model you have to cut your cardboard with their shape. The quickest way I found was to glue the printed slices with Pritt or Uhu (glue on a bar) to the cardboard and cut it. This type of glue will let you unglue the paper later when you assemble your model. Remember to number your slices before your loose the correct order.


(The first picture shown is of the handle of the gardening spoon, didn't take pictures of this part of the process for the saw. The second photo is of a handle of a screwdriver a classmate of mine was making.)

Step 5: Glue Your Slices Togheter

The glue you use is very important for what you will be doing later (sanding). I always use regular white glue. If you use any other type of glue remember that it has to solidify enough to be sandable later.
Unstick the paper before you glue your cardboard parts together.
Apply the glue with a big brush so it applies evenly. It is important to apply glue evenly in the borders of each slice so you can sand worryless later.
Press and let dry for a few hours.

Step 6: Sand, Add Plastic Putty, Sand, Paint, Finish

Sand corners, add plastic putty, sand some more. I use Zeocar or Tersuave (brands you can find here in Argentina), its the type of putty to fix car scratches. Add a thick layer of putty until you can't see the cardboard anymore, otherwise when you apply the paint it will be absorbed differently on the surface.

I recommend you apply some primer before you paint to even the surface.

Practice a few times because it's a technique that gets better with it. Share your experimentations with others. Thanks for reading and the best of luck!