COOLING AND EXHAUST SYSTEM.—Excessive amounts of heat or ammonia vapors should
NOT reach the room in which the machine is
located because of the installed exhaust and cooling
system. The system consists of twin blowers,
driven by a motor that exhausts fumes and
hot air from the machine enclosure through a
vent to the outside atmosphere. Therefore, a partial
vacuum is created within the machine covers,
thereby causing air to flow into the machine
rather than the counterflow that would otherwise
exist. A blower time switch operates the
blower motor independently of the rest of
the machine thereby ensuring the removal of
vapors and hot air after the mercury-vapor lamp
is turned off. The switch may be adjusted to
operate for any given length of time up to 30
MACHINE OPERATION.—A short warm-up period is required before material can be fed into the machine. Always follow the manufacturer’s instructions during machine operation. When starting the machine, make sure that the developer drain tube is inserted in the residue bottle (fig. 3-64). Then, fill the storage tank with ammonia. If bubbles are encountered in the feed system because of increased temperature or high altitude, dilute the ammonia with cold water. Usually, a one-eighth to one-fourth dilution is sufficient.
After the ammonia storage tank has beenfilled, turn on the main switch, and adjust the ammonia feed to 50 to 60 drops per minute. At high speeds (30 ft per minute and above), the rate of drops per minute can be increased. On virtually all modern, large-size diazo machines, ammonia feed is automatically increased and decreased to correspond with variation of machine speed.
During machine operation, the ammoniafeed regulator should NEVER be turned completely off. If the machine is left running and no moisture is entering the developer section, the evaporation tray and heater rods are likely to be warped because of excessive heat.
After a short warm-up period, the machine isready for operation. The machine should be run for approximately 20 min or until the operating temperature is between 180°F and 210°F. Time and temperature may vary; therefore, always follow the manufacturer’s instructions. Feed the material into the machine with the original on top, adjusting the speed of the machine so that a clear print is obtained.
Printing speed is dependent on the trans-lucencyof the original, the density of the opaque image, and type of sensitized material used.
Running the machine at speeds that are toofast will result in a background on the print. Running the machine too slowly will cause the image to be weak or missing from the print altogether. The only positive method for obtaining the correct speed for your machine is by running a test because each machine’s light intensity changes with age.
When stopping the machine, turn theammonia flow off, then feed a sheet of porous wrapping paper, 16 in. wide, into the machine. Stop the machine with the paper in position around the printing cylinder and between the sealing sleeve and the perforated tank. This will prevent the sleeve from sticking to the perforated tank top and will also protect the belts from the heat of the cylinder while it is cooling.