What calibration methods can be used when extruding Eastman Provista™ copolymer in a water bath?
Plates [usually not more than 0.64 cm (0.25 in.) thick] can be fabricated at a relatively low cost as long as a vacuum jig is attached to the back of the front plate. This vacuum prevents water from migrating along the profile towards the die. If this happens, the water will most likely freeze off part of the plastic and prevent it from entering the front plate. Because these plates are submerged, it is not necessary to plumb for cooling. Blocks are usually more desirable as they incorporate the most efficient cooling technique—”Heat of Evaporation.” With “Heat of Evaporation,” vacuum and water are alternated within the block structure such that when steam is produced (as water is injected), it is immediately removed by the vacuum and replaced by cool water, which turns to steam and the process repeats. This expedited removal of heat makes “Heat of Evaporation” the cooling method of choice.
