A robot arm takes over the fully automatic handling of the test melts in a glass screening unity. Image: Knud Dobberke for Fraunhofer ISC |
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and more frequently, the electronics in automobiles are being moved
closer to the engine block. Materials used for the seelectronics must
resist increasing heat, so the glass solder being used as glue must be
continually optimized. For the first time ever, a robot takes on the
task of developing new types of glass and examining their
characteristics. Researchers will introduce this robot at the
“productronica“ trade fair to be held in Munich, Germany, Nov.15-18,
201.
For
laymen glass looks like glass—it might be a window, a drinking vessel,
or a lens for an automotive headlight. But there is much more to the
transparent material: glass can consist of 50 to 60 different elements.
Experts are constantly being asked to create glass with certain
characteristics out of these elements, since new applications require
new materials quite often.
The
car is a good example: the electronic components in a car’s engine
compartment are being brought ever closer to the engine and so must
increasingly be resistant to heat and corrosive gasses. This also
applies to the glue, a glass solder. In the development of fuel cells,
the demand for new types of glass is also great: the use of new metals
requires that the glass solder also be adapted. In addition, over a
period of approximately 100,000 hours, the glass must withstand thermal
heat of 900 C without being damaged.
In
order to develop glass with new characteristics, experts select about
ten compounds from potential elements, mix them and then heat the
powder. They heat it in a furnace until it is soft, then they pour it
into a mould and let it cool slowly and in a controlled fashion, down to
room temperature.
During
that process small samples from the viscous glass are taken to test it:
how viscous is it? How well does it wet metals? How does it crystallize
out? To produce the glass samples by hand and to test them requires a
lot of time: one employee needs approximately two weeks to process 16
samples.
Researchers
of the Fraunhofer Institute for Silicate Research ISC in Würzburg have
developed a unit that carries out all these steps automatically.
“It
needs only 24 hours to process 16 samples,” says Dr. Martin Kilo,
manager of the expert group for glass and high-temperature materials at
the ISC. “For this reason we are able to develop glass elements more
cost-effectively than previously, by up to 50%.”
The
core piece of the unit is a robot: it puts a mixing cup on a scale and
moves it under 14 storage vessels, from which a certain amount of powder
is filled into the cup. Then the robot mixes the individual ingredients
by closing the cup and shaking it, just like a bartender does with a
cocktail shaker. The robot arm then grabs a crucible, puts it onto the
scale, fills it with a certain amount of the mixed powder and puts the
crucible into one of the five furnaces available in total. The robot
repeats this steps several times, since gases build up when the powder
is heated and foam could form otherwise. In addition, the powder shrinks
during the melting process. Finally, the furnace heats the fully filled
crucible to a higher temperature, causing the gas bubbles in the glass
to rise to the surface. Once the glass is viscous, the robot arm removes
the crucible, pours the glass into a new mould and places it in a
stress-relieving furnace. Here, the glass cools slowly and in a
controlled manner, from 600 to 800 C down to room temperature.
An
additional central element of the unit is the analysis unit. It works
according to the thermo-optical measurement principle. Looking through
two measurement windows, the shade the sample projects in a backlight
test system is recorded by a CCD camera. The changes in the contour make
it possible to determine characteristics such as sample volume,
hemisphere point and wetting angle. This test unit measures how viscous
the melt is, and if and how it crystallizes and wets metals. The test
unit can also be used independently of the glass screening unit. The
unit also determines and records the ability of the glass to conduct
heat.