Fuzzy pid based Temperature Control of Electric Furnace for Glass Tempering Process

2.1 Introduction glass Tempering Process 
 
2.1.1 History of Tempered Glass 
Deliberately tempered glass was first patented in June/July1874 by the Frenchman Francois 
Royer de la Bastie but not developed until the early 1900s and the first patent for a process to 
produce tempered glass is said to be held by Rudolf Seiden, an Austrian chemist who 
immigrated to the United States in 1935. Prior to this time the only documented use of 
deliberately tempered glass was the production of Prince Rupert Drops which were novelty 
items [1][2]. 
Back in the early 1600s a German in Mecklenburg discovered that if he dropped molten glass 
into a bucket of cold water he produced tadpole shaped pieces of glass that were unbreakable 
until the tail was fractured. When the tail was broken the tadpole of glass then disappeared, as 
if by magic, in a cloud of dust [1][2]. 
How these were made was kept a secret and they were sold as novelties throughout Europe. 
In 1660 Prince Rupert, Duke of Bavaria, gave some to King Charles II, who in turn gave them to 
the Royal Society for further investigation and they discovered that the 'drops' were in fact 
molten glass that had been stressed by dropping into cold water. The resultant temperature 
differences present in the glass as it became solid produced very high compressive stress in the 
surface and high tensile stress in the core of the glass. When the tail was fractured a shock 
wave that is followed by a fracture front, travelled through the glass breaking it completely into 
extremely small particles [1][2]. 
 Tempered glass has greater mechanical strength and thermal resistance than heat 
strengthened glass. It is about four to five times more impact resistant than regular non-
tempered glass. In the event of breakage, tempered glass will break with a high energy release 
of small fine round pieces [2]. In the 1940's, Henry Ford started using tempered glass for the 
side and rear windows of his automobiles and its use in vehicles became common place in the 
1950's. Architectural tempered glass started to become popular in the 1960's as the benefits of 
the stronger, safer glass became more widely known.

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Fuzzy PID Based Temperature Control of Electric Furnace for Glass Tempering Process
M.Sc. Thesis, Addis Ababa University, December 2016 
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