Manufacturing (Resistant Materials)

Methods of Production (Injection Moulding)

Teachers notes Programmes of Study

The Robin Day Chair (Polyprop)
The following article which may be found in the Guardian Archives examines the work of contemporary designers and inventors. Once you have read the article answer the following questions.
The article is concerned with Robin Day and The ''Poyprop''chair

The people's chair March 13th 1999

1. I
n what year was injection-moulded polypropylene first invented?

2. Describe Day's design philosophy? In your answer you need to explain what he feels are the important design factors and considerations.

3. For which famous Hall did Day design the seats?
In which year did he design the seats and give a detailed descripion of the seats, with regards to the materials used and their construction?


This injection moulded polypropylene seat is based on an enamelled bent tubular steel base.

This familiar chair is common throughout schools, businesses and shops. We are all guilty of taking this classic piece of furniture for granted.

Inspired by the Eameses ''Plastic Shell'' Day developed this low cost, stackable, single-form seat.

The seat is made from polypropylene which is inexpensive, durable, lightweight, easy to clean thermoplastic. A single injection mould can produce 4000 seat shells per week.

From 1963 to the present day over 14 million chairs have been sold.

From left to right;

1. The Polyprop 1962 to 1963.

2. The Upholstered Polyprop 1963.

3. The Polo Chair 1975.



1. Moulds used in Injection moulding should be hardwearing and durable. Choose which material should be chosen to make a mould for a run of 10,000 mouldings?

Stainless Steel

2. In an Injection moulding machine the plastic is forced into the mould by?

Air Pressure
A Hydraulic Ram
Pneumatic Pressure

3. Name three thermosetting plastics which are commonly used to create Injection Moulded products ?

4. Injection Moulding usually uses which type of plastic?

Thermosetting plastics

5. Which type of screw is used to carry the plastic to the mould?

Half Round
Archimedean Screw
Slot Head

6. Explain how gears were made before the introduction of Injection moulding?

7. II the gears were made individually instead of on mass what effect would this have on the unit cost of each gear?