Learning Event 2:
DESCRIBE THE MAJOR SYSTEMS OF THE AUTOMATIC FILM PROCESSOR
1.
Film drives and transport systems.
a. Probably the most important area of machine design is the film drive
system. The film must be transported through the solution tanks at a constant
speed.
The operator must be able to adjust this film drive speed as the
situation warrants. Also, the speed must be reproducible. In other words, if
a particular type of film is to be processed at speed of 10 feet per minute, a
second roll at 20 feet per minute and a third at, again, 10 feet per minute,
the first and third rolls, (both processed at 10 feet per minute) must produce
identical results.
b. An ideal transport system would be one in which the film is moved
through the processing machine without the film being touched by the processor;
it could never be damaged.
Research is being conducted on a liquid bearing
transport which would do exactly that: move the film through the processor
without contact between them.
An ideal drive system would provide a uniform
rate of speed throughout the system, one in which there would be no slack or
stress on the film at any point. Finally, an ideal drive system would also be
exact, one in which the speed of travel could be set with considerable
accuracy.
Many film drive and transport systems approach these ideals,
particularly in the areas of uniformity and accuracy. Drive systems generally
consist of a motor, a variable speed transmission, and a drive chain which
produces rotation of the transport rollers, usually through a system of
c. The type of transport system found in a processor is dependent on the
size (width) of the film to be processed and the desired quality of the end
product. In processors designed for narrow film widths, the film is generally
transported by gangs of rollers. If the film being processed is perforated,
sprocket drives may be employed to transport the film.
In other cases the
rollers are flanged and the film is guided between the flanges.
If
misalignment of this type of roller occurs because of a worn shaft or bearing,
the film could climb the flange causing crimped edges, creases lengthwise along
the film or, in severe cases, film breaks due to the film running off the
roller.
d. On the other hand, processors designed for larger (wider) sizes of film
usually have single roller transports instead of ganged rollers. These single,
wide rollers depend on proper alignment for accurate film tracking. Because of
their width some lateral movement of the film is possible, allowing the film to
"find its own path" through the processor.
This lateral movement, however,
increases the possibility of side strain on the film. If the rollers become
misaligned, one edge of the film may rise up off the roller resulting in damage
to the film.
e. Another factor to be considered is the diameter of the individual
rollers. Smaller diameter rollers use considerably less space, allowing more
of them to be placed within a small area. The disadvantage of smaller rollers
is that they exert more strain on the film as it bends around them. The
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