The purpose of pre-setting is to prevent the cloth from creasing, and the process plays an important role in producing cloth that exactly matches the length and width planned in advance. Generally, the higher the temperature for heat setting, the greater the effect. However, if the process fails, sometimes the breaking stress of fiber decreases depending on the blend ratio between polyester and polyurethane and the types of product distributed by textile makers who manufacture polyester/polyurethane blended yarn.

In the case of polyester, the appropriate temperature for heat pre-setting is, commonly, 180°C x30 sec., however, it is recommended that appropriate temperatures and time should be decided after testing the breaking stress of fiber.