Master Thesis - Fachbereich Informatik

1.2. PROBLEM STATEMENT 3
hazards, risk of explosion, x-rays, radioactive material, loud noise levels, etc. [7]. On the
other hand, in applications that require aseptic conditions as in the food or pharmaceutical
industry, a human operator can be a ‘polluter’ as a source of dirt particles (hair, danders,
bacteria, etc.). In this case, a MV system is a clean alternative.
Machines usually exceed humans in all kinds of accurate vision-based measurements.
Human vision performs well in comparing objects and in detecting differences for example
in shape, color or texture [27]. Large deviations can be detected quickly. As the difference
is getting smaller, however, the time of inspection increases or the deviation can not be
detected at all without technical tools. With respect to the task considered in this thesis,
a human is not able to determine the length of an object at sub millimeter precision just
by looking at it. Manual measurements are slow and not practicable in line production if
100% control is desired, and can thus be used only for random inspection of few objects.
MV systems on the other hand can measure the length (or other features) of an object
without contact up to nm precision - depending on the optical system and the size of the
object [16]. Furthermore, humans soon reach limits, if the number of objects to inspect per
minute increases significantly. Many manufacturing processes are so fast that the human
eye has problems to even perceive the objects, not to mention the ability to accomplish
any inspection task. MV systems, however, can handle several hundred objects per minute
with high accuracy.
Although MV systems have many advantages for manufacturers, there are also drawbacks.
Usually, a MV system is designed and optimized for a specific task in a constraint
environment. If the requirements of the application change, the system has to be adapted,
which can be difficult and expensive [7]. Furthermore, the system can be sensitive to a
lot of influences of the (industrial) environment like heat, humidity, dirt, dust, or ambient
lighting. Respective precautions have to be taken to protect the system. Finally, like in
general in automation, vision systems that exceed the power of a human at some specific
task, replace human operators and will therefore supersede mostly low-skilled jobs in the
future. Addressing this problem in more detail is outside the scope of this thesis.
1.2. Problem Statement
A large variety of heat shrink tubes of different sizes, material and shrinking properties is
available on the market. The focus in this thesis will be on the DSG- Canusa DERAY-
SPLICEMELT series. These tubes are commonly used for insulation of cable splices in
the automotive industry (see Figure 1.1 for an example). A film of hotmelt adhesive inside
the heat shrink tubes provides a waterproof sealing around the splice after shrinking. In
addition, the DERAY- SPLICEMELT series shows a strong resistance against thermal,
chemical and mechanical strains. The easy and fast handling allows for an application in
series production. Accordingly, if the heat shrinking is performed in an automated fashion,
the accuracy demands increase.
In production, the heat shrink tubes are cut into lengths from a continuous tube. During
this process, however, deviations from a specific target length can occur. In terms of quality
assurance, any deviations above a tolerable level must be detected so that failings can be
sorted out.