Regardless of fabric, type of garment or the machinery and equipment employed, the majority of pressing operations have the same components.
The Components of Pressing
The purpose of using pressurised steam is to relax the fibre structure of the fabric and make it pliable enough to be moulded by manipulation and pressure. Steam itself is an odourless, invisible gas consisting of vaporized water, and its white cloudy appearance is caused by minute water droplets interspersed in the vapour.
In factories steam is generated by boilers fired by electricity or fossil fuels such as coal, gas or oil. Depending on the number of pressing work station in the factory, steam can be distributed from central boiler room by small boiler located close to the work station.
There are also independent pressing units which have a built in boiler for generating their own steam.Steam is a flexible, adaptable and efficient component of pressing.Some of its outstanding features are:
- It has very high heat content.
- Its heat is generated at a constant temperature.
- It can be easily distribute and controlled.
- Water is relatively cheap and plentiful.Steam has been used through out the centuries for pressing and it is still the best medium for this purpose.
The components of Pressing
After steaming, manual or mechanical pressure is used to change the geometric fibre lay of the area being pressed. A simple example of this change is the pressing open of a regular seam. This structural change is typical of the majority of pressing operations.Drying
Following the application of steam and pressure, the area which has undergone these processes hasto be dried and cooled in order that the fabric can revert to its natural moisture content and stable condition. The drying process is usually performed by a central vacuum pump which is connected to pressing units, or by pumps built in to ma machine it self. The vacuum action removes the residual moisture from the material while it is lying on the pressing area.Time
The length of time to which a component or garment ifs subjected to steaming, pressure and drying is a combined function of steam temperature, garment construction and the physical properties of the fabric being pressed. Whilst there are no fixed rules for the duration of these components,experience is a good teacher. Accurate control of the four components of pressing is essential to the maintenance of uniform quality. This is one of the main reasons why modern pressing machines can be programmed for the duration, operating conditions and sequence of all of the elements with in a specific pressing operation.