Injection molding has evolved significantly since its origins in the mid-19th century. John Wesley Hyatt patented the first injection molding machine in 1872, which used a plunger to inject melted plastic into a two-part mold. This early machine was crude compared to modern screw-based machines. In 1946, James Watson Hendry built the first screw injection machine, which gave better control over injection and improved quality. Screw machines now make up 95% of injection molding machines. Major developments in available plastics occurred from the 1930s-1950s, and robots were introduced to the injection molding process in 1972.

1. Injection Moulding History &
Facts
1847 Jons Jacob Berzelius produces first condensation polymer: polyester, derived
from glycerin (propanetriol) and tartaric acid. Berzelius is also credited coining the
chemical terms allotrope, catalysis, isomer and polymer.
1861 The first man-made comercial plastic invented in Britain in by Alexander
Parkes.
1862 Alexander Parkes publicly demonstrated his plastic at the 1862 International
Exhibition in London, calling the material he produced “Parkesine.” Although
expensive to produce, brittle and flammable, Parkesine could be heated, moulded and
retain it’s shape once cooled.
1868 American inventor John Wesley Hyatt develops a plastic material he
named Celluloid, made from a process that combined cellulose nitrate and camphor.
Originally developed as a substitute for ivory in billiard balls. He improves on Parkes’
invention so that it could be processed into finished form.
1872 John Wesley Hyatt, together with his brother Isaiah, patent the first injection
molding machine (see fig. 1). This machine was relatively crude in comparison to
machines in use today, working like a large hypodermic needle. It used a plunger to
inject melted plastic through a heated cylinder into a two part mold. The industry
progressed slowly over the years, producing products such as collar stays, buttons,
and hair combs.
1909 Leo Hendrik Baekeland of Ghent, Belgium discovers phenolformaldehyde
plastic, originally called Bakelite. While the reaction of formaldehyde and had been
investigated by Bayer in 1872, Baekeland was the first to control the substance and
make it’s use viable on a large scale.

2. 1930s Saw the initial development of major vinyl thermoplastics still used widely
today: polystyrene, PVC (polyvinyl chloride) and the polyolefins. During this period,
the ICI laboratories produce Perspex (polymethyl methacrylate).
1938 Polystyrene invented by Dow. The plastic is still used widely today.
1939 WWII creates a massive demand for cheap, mass-produced materials.
1941 Nylon, developed brilliantly by Du Pont as a fibre in the mid-l930s, was first
used as a moulding material. Also in 1941 a patent taken out by Kinetic Chemical Inc.
described how R. J. Plunkett had first discovered polytetrafluoroethylene.
1945-1955 Polyethylene, polystyrene and other previously rather expensive special
purpose materials, are produced more cheaply and start to replace older materials –
not only other plastics but more traditional materials such as metals, woods, leather
and glass.
1955 General Electric begins marketing Polycarbonate.
1959 DuPont introduces Acetal homopolymer.
1946 American inventor James Watson Hendry builds the first extrusion screw
injection machine (see fig. 2). The rotating screw gave much better control over and
injection speed and therefore the quality of the articles produced. Coloured or
recycled materials could be added to virgin materials because of the mixing action.
The action of the screw also now aids the heater bands in the heating of the plastic
due to the friction, thus reducing energy usage. Screw machines nowadays make up
approximately 95% of all injection moulding machines.

3. Fig. 2: Patent drawings for the Hendry injection moulding machine.
1955-65 In the mid-1950s a number of highly useful new thermoplastics become
available. High-density polyethylenes produced by the Phillips process and the
Ziegler process are marketed and shortly followed by the discovery of polypropylene.
Acetyl, ABS and polycarbonates are also developed.
1956 W. H. Willert reciprocating screw plasticator patent issued – the next
development from the extrusion system (see fig. 3). In reciprocating systems the
screw moves backwards and forwards during the mould cycle. After mixing, the
screw stops turning and the entire screw pushes forward, acting like a plunger for
injecting material into a mold. During plastication, the screw moves backward against
the hydraulic back pressure.
Fig. 3: Drawings for the Willert reciprocating injection moulding machine.
1960s Polysulphones, the PPO-type materials, aromatic polyesters and polyamides
introduced.
1970s James Watson Hendry went on to develop the first gas-assisted injection
molding process, which permitted the production of complex, hollow articles that
cooled quickly. This greatly improved design flexibility as well as the strength and
finish of manufactured parts while reducing production time, cost, weight and waste.
1972 Parts removal robots used in injection moulding process.
1973 OAPEC oil crisis. First real point of considering dependence on plastics on oil
and other materials.
1979 Plastic production overtakes steel production.

4. 1985 All-electric molding machine produced by Japanese firm.
1990 Aluminum molds first used widely in injection molding.