News and events - Tampere University of Technology

Modelling creates significant cost savings in the design of glass tempering machines

In his doctoral thesis, Master of Science Mikko Rantala developed calculation methods for modelling heat transfer in various heat treatment processes for glass.

Plate glass can be heat-treated using methods such as tempering, bending and laminating. Heat treatment improves the strength of glass, changes its shape or makes its break patterns safer. The construction of a new heat treatment machine starts with decisions about the goals set for the production. Next, process design aims to carry out the execution together with mechanical, electrical and automation designs. Finally, the drawings are refined into practical elements in the assembly.

“The machine prototype can already be the final form of a new machine with no need for additional corrections. If modelling is used in the process, several rounds of upgrades become unnecessary. Process devices and structures affecting the process can be directly scaled in order to achieve the best possible compromise between the requirements of a process designer, the possibilities of a mechanical designer and the wishes of a cost accountant,” says Rantala, describing the benefits of modelling.

When a machine is ready, it is important to measure the realised output to ensure that the modelling accurately represents reality. The result of modelling is a tailored modelling programme for new glass treatment machines. Such a programme can be applied to any call for offers simply by changing the initial data.

Using modelling in the operation and automatic adjustment of machines is still in its infancy. Theoretical know-how also adds extra value to the company brand. Modelling is a relatively cheap method that could be utilized to an increasing extent.

When glass is tempered, it is first heated to 600 degrees Celsius using resistors and hot air jets, and then cooled down with air jets. Heat is also conducted into the glass through the points at which it touches the roller transporter on which it moves through the furnace. Some tempered glass is subjected to a second round of heat treatment to prevent spontaneous breakage during use. In this heat soak resistance test, tempered glass is heated by hot air circulating between the glasses.

“Heat radiation is challenging to model, as some of it is directly absorbed into the surface of the glass, some inside the glass, and some goes through it. Additional modelling challenges are posed by the surface coating of energy-efficient glass. Depending on the wavelength of the radiation, heat radiation is reflected off the coating,” Rantala explains.

His doctoral thesis proposes a new solution to these problems.

Public defense of a doctoral dissertation on Thursday, 26 November

M.Sc. Mikko Rantala’s doctoral dissertation in the field of mechanical engineering and industrial systems entitled ’Heat Transfer Phenomena in Float Glass Heat Treatment Processes‘ will be publicly examined at the Department of Mechanical Engineering and Industrial Systems of Tampere University of Technology (TUT) in Auditorium K1702 in Konetalo building (address: Korkeakoulunkatu 6, Tampere, Finland) at 12 noon on Thursday, 26 November 2015.

The opponents will be Dr. Norbert Siedow (Fraunhofer, ITWM) and Dr. Jaakko Saastamoinen (Technical Research Centre of Finland, VTT). Professor Reijo Karvinen from the Department of Mechanical Engineering and Industrial Systems at TUT will act as Chairman.

Mikko Rantala (44), from Tampere, Finland, works as a research scientist and patent engineer at Glaston Finland Oy.

Further information:

Mikko Rantala, tel. 040 050 8985

News submitted by: Tiina Leivo
Keywords: science and research, glass tempering, heat transfer, heat treatment