Lab: Foam Core Construction

Overview: 

In this lab, I learned how to construct a simple box made of foam core by first mastering the creation of corners (joint, lap, and larger radius) then developing a larger box.

Getting Started:

Before I began cutting the foam core, I familiarized myself with the tools and tips. 

• The X-Acto knife is the most important tool for this lab and keeping it sharp is imperative.
• A metal straightedge is helpful for keeping sides straight and at 90 degree angles. 
• A large and cut proof surface keeps the knife from dulling and simplifies the work.
• Adhesives like hot glue are important because they hold separate parts together (lap joints and folds)
• Proper cutting techniques
• use the whole blade instead of just the tip
• don't cut through foam core all at once
• Joining techniques include sharp, lap, and larger radius joints.

After understanding the basics, I began each corner the same way. I started out by using the metal straightedge and the X-Acto knife to give me straight sides and then to make the corners perfect 90 degree angles. Once complete. I was ready to start on the individual joints.

Cutting straight edges with the X-Acto knife and the straightedge.

Joint: Sharp

I cut through the straight-edged rectangle with the knife to the second sheet of paper (TO not THROUGH) and then bent the foam core back on itself to reiterate the cut. I then took the opposite end of the knife (being careful of the sharp edge) and forced a furrow along the line multiple times until the furrow is as deep as the thickness of the foam. Then I rotated the knife in the furrow to mold it into 45 degree angles.

Furrowing the foam core into a 45 degree angle. 

Using the hot glue to hold the sides together, I folded the foam into a 90 degree angle and glued along the cut line. I allowed the glue to dry before letting the foam core sit on its own. 

Holding the foam core at a 90 degree angle until the glue was dry.

The completed sharp joint.

Joint: Lap

Starting again with the straight-edged rectangle, this time I cut the foam core all the way through to give my two separate pieces. I laid one piece flat on the table and placed the other perpendicularly and flush on top of it. With my knife, I made soft slits where the vertical edge met the horizontal surface. This gave me a line of equal thickness as the width of the foam core. I then followed the lines with a deeper cut to the opposite side but not through it. I "flicked" off the edge of the cut side with a flat head screwdriver being careful not to break the back paper (just taking off the top layer and the foam inside). I ran the hot glue gun on the edge with no foam and then pressed my second piece directly on to the flap perpendicularly from the first piece creating a 90 degree angle. 

The first piece after cutting the edge to equal the width and flicking off the top and middle layer.

Completed lap joint.

Completed lap joint (you can see how the two separate pieces are joined perpendicularly to one another)

Joint: Larger Radius

This joint is a little more intricate than the others. Starting with the same straight-edged rectangle, I worked from the center of the piece and cut out 1/8" strips of foam, going about halfway through and removing the top layer of paper CAREFULLY leaving the foam attached. Then I bent the foam closed going past the intended angle. If you are not satisfied with your angle, you can cut out more slits in the foam until you get a good angle. I then hot glued over the notches and set my desired angle. 

Cutting the small slits in the foam board. 

Completed larger radius joint. 

Simple Box:

With all the joint practice, it was then time to put my knowledge to work and create a box starting out with two squares and one longer rectangle of foam core. Starting out at one end of the rectangle I measured three inches from the edge, and using my straightedge I cut a deep slit. I used the techniques from the sharp joint and made the first joint. I then measured five inches from the new edge and created another sharp joint. I continued the three inches and five inches once more until I had a cube shape with some excess overlap. I cut the excess off with a knife and made a lap joint to hold the two unattached edges together. I then measured the openings of the box on both sides and cut the measurements out on the two square pieces. I then made lap joints from these pieces and hot glued one to its appropriate side. With the last opening I also did a lap joint; however, I did not glue the pieces together! Instead I just made very exact measurements so that the pieces fit together tightly, but were still able to be taken apart when needed. This is important so that I can use the box to hold the breadboard or whatever else needs to be inside. 

Creating the sharp joints for the three corners.

First joint completed.

Second joint completed. 

Four joints completed!

After assembling the two sides!

All in a day's work in the lab!

Problems:

When working on the larger radius joint, I found it difficult to only remove the top paper layer and accidentally removed some foam. This was difficult because the paper was pre-laminated and therefore very attached to the foam. Use patience when removing this section because you do not want gaps in your joint. 

Helpful Links:

For more information about foam core construction:

• Basics with steps
• Foamcore (helpful pictures)