Master Thesis - Fachbereich Informatik

48 CHAPTER 3. HARDWARE CONFIGURATION
Figure 3.11: Air pressure is used to sort out tubes that do not meet the tolerances. The
blow out unit consisting of an air blow nozzle, light barrier and a controller (not visible in the
image) is placed at a certain distance behind the measuring area.
the function room darkening. For industrial use this interim solution has to be replaced
by a more robust and compact (metal) case that excludes environmental illumination and
protects the whole measuring system against other outside influences in addition. A slight
overpressure inside the closed case or an air filtering system could be integrated to avoid
dust particles from entering the case through the required openings. Any accumulation of
dust or other dirt on the lens is critical and must be prevented.
3.4. Blow Out Mechanism
After a tube has passed the measuring area the measured length is evaluated with respect
to the given target length and tolerance. The result is a binary good/bad decision for
each particular tube. Good tubes are allowed to pass the blow out unit, which is placed
behind the measuring area at a certain distance. On the other hand, tubes that do not
meetthetoleranceshavetobesortedout. Thisisdonebyairpressure. Aairblownozzle
is arranged to blow out tubes from the conveyor. Therefore, the guide bars have to end
behind the measuring area. The whole blow out setup can be seen in Figure 3.11.
The visual inspection system sends the good/bad decision over a RS-232 connection
(serial interface) to a controller unit in terms of a certain character followed by a carriage
return (‘\r’). The used protocol can be seen in Table 3.4. Once the controller receives an
A or B this message is stored in a first-in-first-out (FIFO) buffer.
Message Code
TUBE GOOD ‘A\r’
TUBE BAD ‘B\r’
RESET ‘Z\r’
Table 3.4: Protocol used for communication between the inspection system and the blow
out controller.