Termocouples are necessary to record mold temperature and help alert the metalcaster when a mold is too hot or too cool and may lead to casting
defects or misruns. Bubblers
Bubblers are used for targeted cooling where a larger circuit is not practical due to geometry constraints. For example, they may be located at the center of a deep metal core. Te fluid comes from the main cooling channel and enters at the bottom of the bubbler, then flows up through an inner tubular device and cascades inside the unit. Te fluid then flows
Fig. 3. A center core and slide water lines were added to the mold to realize the short cycle time through fast cooling.
down through an outer tubular device and exits back into the main cooling channel. Exiting water carries heat from the bubbler into the main cool- ing medium.
Cycle Times A cycle time refers to how long
each casting is in the mold. Part mass, heavy sections, surface areas and how long a mold is open all affect cycle
time. Changes to the casting design to reduce heavy sections or change their locations can aid in solidification. If that’s not possible, some metalcasters may alter the time a mold is open or a casting is extracted from the mold to allow the die to return to its optimal temperature for the start of a cycle.
Controls and Measurements Termocouples are necessary to
Fig. 4. Extraction tabs were added to the side for a stiff feature because the feeder was still in the mushy zone at extraction and could be stressed. Two small regions of porosity were predicted requiring further thermal management in the tool.
February 2017 MODERN CASTING | 29
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