Hair dryers are essential for many people to complete their daily routine. Most people don’t have the time to wait for their hair to dry naturally so they reach for a hair dryer to speed things up and achieve a specific look or style. Hair dryers have to meet a number of important design criteria. First, they cannot be so hot that they burn the user during operation. To prevent this, engineers have developed temperature cut off switches. A common type of switch is a bimetallic strip. This consists of sheets of two metals that expand at different rates. As the temperature of the hair dryer rises, the bimetallic strip bends and trips a switch that cuts off power to the heating element. Some models also use a thermal fuse, which will blow and break the circuit if the heat and current become excessive.
The outside of the hair dryer must be lightweight and easy to hold while it is in operation. To make this happen, the plastics used for the body of the hair dryer are created by injection molding – a process in which hot, molten plastic is injected into a stainless steel die and allowed to harden. The parts are then separated and assembled.
When selecting a hair dryer, look for one with multiple heat and air settings as well as a nozzle. A medium heat setting works best for most hair types as it provides the most versatility in drying. High heat can distort curly hair, while low heat is great for straightening strands. A blast of cool air helps set a style by closing the hair cuticle and locking it in place. hairdryer