Mechanical Engineering Student
Zhe Yi Soo
Sustainable Foam Core Chair Project
This designing project focused on building a chair without using any fasteners
or glue. The chair had to be under 500g and yet able to support a 80kg person. Techniques of drawing lines of force were used to identify stress concentrations and designs were improved through adding fillets, chambers, or reinforcements.
The seat height had to be between 480mm to 530mm, the seat depth and the seat width had to be between 380mm to 420mm, and the back height had to be between 250mm to 450mm. No fasteners or glue was able to use in this project and all of the parts had to be made out from 18” x 24” x 3/16” foam core board.
Design Process
In order to get the best design among the six designs, a decision matrix was used. Five criteria were taken into consideration in this decision matrix and the five criteria are weight, durability, safety, functionality, and easiness to use. Each of the criterions was weighted as one point. The first design is a rocking chair, it
was comfort but it was heavy and unsafe. Design 2 is durable but there are still a lot of unnecessary parts in this design. Design 3 is safe but heavy too. Design 4 is durable and easy to use but the bottom parts took too much of materials and made it heavy. Design 5 might not be able to support in the middle part of the seat as it was hollow in the middle part. Design 6 was light and simple but the back still need
some parts to strengthen the back of the chair. According to the design matrix, design 6 got the highest marks and was decided to make some bridges on between the legs of the chair.
Prototyping
The prototype of design 6 was built. The parts were cut
out from foam core board using laser cutting machine. The chair was set up but some parts are hard to fit in because the connection holes are too small to fit in with the connection parts. This situation has led to some cracking while setting up the chair.
Since the chair first broken down in the middle of the
legs, it can be assumed that an insufficient leg support was the main reason of the failure. Theoretically, when a person sits on the chair, the force will be normally distributed on the chair hence the force exerted on the seat will create a moment. The moment at part C had
caused cracking. Besides, it can be seen from the line of force that part C is a weak part that sustains a lot of force. Thus, adjustment has been made to prevent the cracking.
Results
The chair was weighed 0.482kg. It was able to support a
80kg person successfully and every part was able to support the pressure.
To see this project in a more detailed report form,