To cool or not to cool, this is sometimes the question. Some systems use water-cooled jaws as a means of maintaining the jaw at a relatively constant temperature. These systems then, may demand an excessive amount of energy to overcome the heat loss into the cooled jaw. When a water chiller is utilized, excessive cooling is often the case. Cooling below the dew point will result in undesirable moisture condensation on the jaws, particularly in humid environments.
When using high response temperature control, the controller supplies only enough heat to make the seal. Much of the heat is carried away by the material that has been sealed, the remainder is not too great and will be absorbed by the mass of the aluminum Heatseal Jaw Bar. If the jaw bar gets warmer during prolonged operation, the controller will continue to sense only the actual temperature of the Heatseal Band and will automatically reduce the amount of energy to the band; thereby assuring that the band temperature during each impulse cycle is always the same.
When doing impulse sealing at high speeds, 50-60 or more seals per minute, cooling of the Heatseal Jaws can be helpful in accelerating the cooling cycle. This reduces the time required for the seal to set and permits operation at higher speeds. Some polymeric materials, like polypropylene, may become brittle when cooled too rapidly. It is, therefore, important to know the character of the film before developing a processing protocol for sealing it. The skillful use of water that is temperature controlled can be a valuable aid when the investment is justified by greater productivity. A cooling passage is included in
Tâ—†Oâ—†Sâ—†S Heatseal Jaw Bars as a standard feature. It is there if it is needed.
In any event, if one elects to use cooling water, it is imperative that the Heatseal Jaw not be over-cooled. A carefully calculated balance must be maintained between the time required to heat the seal and the time required to cool it.
Air cooling is occasionally employed to accelerate the cooling of the heat sealed material. This technique is more often utilized to cool seals that have been made by the constant heat mode.
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