Know What You Wear

Saturday, December 2, 2017

Pressing Equipments and Methods Used in Garment Industry

Pressing:
It is the process of application of heat, pressure and moisture to shape or crease garments or garment components into the geometric forms proposed by the designer. The pressing process influences the final garment appearance and hence the garment appeal. Finishing and pressing machines contour the semi finished garment panels as well as finished garments by bringing down the fibers in the fabric to an elastic state and then deforming and setting them.

Purpose of pressing:

  • To flatten out the undesirable wrinkles, creases and crush marks.
  • To make creases where the garment design needs it.
  • To mould the garment to the silhouette of the body.
  • To prepare garments for further sewing.
  • To refinish the garment after completion of the production process.
Basic components of pressing:
The main elements of the pressing process are heat, pressure and moisture, which deform fibres, yarns and fabrics to accomplish the required effect.

1. Heat – It is necessary to soften the fibres, stabilise and set the fabric in the desired shape. Temperature must be selected based on the fibres, yarns and fabrics.

2. Steam (Moisture) – It is fastest way of transmitting the heat onto the fabric. Steam and heat are essential to ease the fabric from tension and make the fabric with adequate flexibility so that it can be moulded to get the required contour.

3. Pressure – It is applied to change the form and increase the durability of the moulding. Pressure could be applied by means of a mechanical device or steam.

4. Drying – Subsequent to the steam and pressure application on the fabric, the garment panel or finished garment must be dried and cooled; thus, the fabric can return to its regular moisture content and steady condition. This could be done by removing the surplus water from the fabric by means of a vacuum action which cools it at the same time.

5. Time – The time period for which the garment is exposed to steam, pressure and drying depends on the type of fabric being pressed and there will be an optimal time period for each component.

Types of pressing equipments and methods in apparel industry:

There is a large range of equipment available for the pressing of garments, from the simple hand steam irons to the sophisticated vertical front and back pressing robot. In this article, let us see about the use of various pressing equipment and methods. The various equipment used are iron, steam presses, steam air finisher, steam tunnel, pleating and permanent press.

Pressing equipments of garments
Fig: Pressing equipments of garments
Classification of pressing equipment:
The pressing machines are classified in three major categories based on how the machines are pressed.

1. Solid Pressure Equipment (Pressing Equipment)

  • Pressing irons
  • Buck presses
  • Mangle presses
  • Block presses
  • Form presses
  • Pleating presses
  • Creasing machines: Edge folders
2. Moisture Pressure Equipment (Steaming and Wetting)
  • Wetting tanks: London shrinkers and auxiliary equipment
  • Sponging machines
  • Decaters
  • Steam guns and jets
  • Steam chambers
  • Autoclaves
3. Heat Energy Equipment (Heating and Baking)
  • Thermoelectric machines
  • Hot plates
  • Casting equipment
  • Dry heat ovens
Types of Pressing Equipment:
Solid surface pressing equipment uses a firm surface to apply pressure while steam and heat mould the fabric, garment or garment parts. Pressure may be applied through a rolling action, gliding action or compression.

Hand irons:
Iron which is known commonly as iron box has been in existence for a very long time with the traditional one being used with heat generated using charcoal. There were also irons which were heated by gas flame inside the metal casting and it was mainly used in touching up of men’s jackets. However in recent times, steam and electric irons are used commonly.

Hand iron
Fig: Hand iron
The two basic kinds of irons used today are:
  1. Dry iron
  2. Electric steam irons
Normally, hand irons are available in different shapes and weights:
  • Narrow hand irons are used for seam opening on sleeves and trouser legs. The wrinkle marks on the garment are evaded by the narrow sole construction of the steam iron as well as curved and narrow ironing bucks. Teflon-coated soles should be used for ironing fabrics that are sensitive to lustre
  • Wide ones for flat shapes
  • Pointed shape
Iron table:
The significant factor for the proper selection of an ironing station is the air flow through the garment to cool it and set it. Some types of ironing tables are listed below:

  • Jacket seam ironing station
  • Trouser seam ironing station standard
  • Sleeve seam ironing station
  • Dress board ironing tables
  • All purpose table
  • Flat top ironing tables
  • Blouse and shirt ironing station
  • Trouser leg ironing station
  • Hip-bow ironing station
  • Concave ironing station
  • Convex ironing station
  • Curtain ironing table
The stability of the covering of the ironing table is based on several factors such as hydrolysis resistance, pressure resistance and heat resistance of the used materials. All layers of fabrics in an ironing table together are accountable for the even distribution of steam. The covering starts at the metal surface of the ironing table.
  1. Rough wire mesh – Besides the steam spreading it also improves the vacuum suction.
  2. Lower padding – It should be durable as well as heat resistant.
  3. Lower layer – Polyester wire screen mesh which distributes the steam.
  4. Intermediate padding – This provides the softness of the covering.
  5. Upper layer – It is a polyester wire mesh with inlet.
  6. Final top cover – It must be less heat resistant than other lower layers.
Steam press/buck press:
Steam presses commonly consist of a static buck and a head of complementary shape closing onto it, thereby sandwiching the garment to be pressed. It consists of a frame housing the buck which is normally in round shape for pressing different garments and linkages to close the head by a scissor action.

Steam press
Fig: Steam press
Steam is passed to head and buck using a pipe system. Adequate controls are provided for controlling head closure and vacuum. Vacuum is created to provide suction through the buck using a vacuum system. The typical pressing cycle is as follows:
A garment need to be pressed is fixed in the buck

The buck head closes and locks

Then steam is applied to the head or the buck to press the garment for a predetermined time

The buck head is released

Vacuum is applied to the garment to cool and dry it

The garment then moved around the buck for the next part of it to be pressed

Similar operations are carried out for completing the pressing of the garment and then the garment is hung on the hanger. It should be ensured that the garment is not damp or distorted after pressing. Various types of presses are used in steam pressing. The different steam presses used for different parts of the garments are collar press, sleeve press, shoulder press, back and front press, collar master.

Carousel press:
Carousel press is a new development in pressing operation in which a pair of bucks is provided that rotates between operator and the head. The head can be of single or double based on the bucks being identical or an opposite pair for pressing the left and right of a garment part. In this press, scissor action and vertically acting heads can be used.

Carousel press
Fig: Carousel press
Trouser pressing:
Trousers include a wide variety of garments, ranging from jeans, women’s trousers with simpler construction and requiring a less sharp crease, men’s trousers including four pockets, and suit trousers. The trouser pressing is carried out in two operations along with underpressing of the seam. The first operation is done for legging on a flat press to set and crease the legs and the second operation for topping in a series of lays around the top of the trouser on a contoured press.

trouser pressing
Fig: Trouser pressing
Double legger-pressing machine:
Double legger-pressing machine is used for pressing trousers, and in this machine both the legs are pressed simultaneously with the top hanging down between two separate bucks. These machines consist of vertically acting heads, carousels and microprocessor controls. Heat resistant silicone foam is used for covering bucks of steam presses and tables used with irons and vacuum boards and the outside being covered with a woven polyester cover. Sometimes stretch nylon is used with the highly contoured bucks.

Steam finisher:

This equipment is known as a form press or a ‘dolly’ press. It has a compressed air system, frame for a steam distribution system and a pressing form made of a canvas bag in the suitable silhouette of the garment to be pressed. The pant steam finisher and universal steam finisher are shown in below figure .

steam finisher
Fig: Steam finisher
Tunnel finisher:
Tunnel finishers are used for finishing knitted goods. They can be used for manmade fibre garments and their blends also. This garment finishing process involves no pressure application and reduced handling of garments in steam tunnel. In this finishing process, the garments are put on hangers and fed through a cabinet using a motorized rail. The garments pass through sections with superheated steam and it is dried by blowing air. In some cases garments are loaded onto frames and passed through the tunnel on a conveyor.

Tunnel finisher
Fig: Tunnel finisher
Steam helps to relax the fibres in the garment and the tunnel helps in avoiding the need for any other pressing process before or after this operation. In some cases, it completely eliminates the other pressing processes. These tunnels are incorporated with infrared drying in some cases. As the garments are vertically hung, the turbulence of blown air provides additional energy to remove wrinkles in woven fabrics. Proper care should be taken during pressing operation for fibres where excessive agitation causes fabric deformation.

Press cladding:
Bucks of steam presses and the ironing tables used with hand irons are normally covered with silicone foam. This is covered on the outer side normally by a top cover of polyester woven fabric. The heads of the steam presses could be covered with several layers of materials like a layer made of metal gauze for uniform steam distribution, a layer of synthetic felt to shield the next layer, the main layer of cotton knitted padding, and a last layer of outer cover as on the buck.

Creasing machines:
This unique kind of small press performs an exceptionally useful function. Creasing machines are used to fold over and press the edges of clothing components such as pockets or cuffs to prepare them for easy sewing.

Blades are used to create creases and folds. The component is kept over a die with blades aiding in forming creases around it and required pressure is exerted during pressing cycle. Creasing machine is actually preparation underpressing machine. Creasing machine principles and components are basically alike regardless of type or style of the section being creased by the machine.

Pleating:
Pleating is the process of creating pleats in the garment. Pleats are a type of fold actually formed during stitching by doubling fabric upon itself and securing it in place. However, these pleats can also be introduced in pressing by creating a set of creases in the garment and making it set by pressing. The pleats can even be according to a geometrical pattern. Pleating is done by using pressure, moisture and heat. There are two types in machine pleating.

One is a blade machine in which pleats are formed by the action of blades and then set by heat and pressure when they pass through a pair of rollers and the other type is a rotary machine in which the rollers are fitted with complimentary dies. Crystal pleating, hand pleating, box pleats and fan-shaped pleats are some of the examples shown in below figure.

Crystal pleating, hand pleating, box pleats and fan-shaped pleats
Fiig: Crystal pleating, hand pleating, box pleats and fan-shaped pleats
Block or Die pressing:
In die pressing, the fabric is kept over a fixed die prior to the application of steam, heat and pressure. This is normally used for shaping and moulding of hat and gloves during the manufacturing process. Another variety of an automated die pressing machine is utilised for combined folding and creasing of patch pockets as well as pocket flaps, in which the operator has to keep the components to be pressed over a die and engages the machine for folding and creasing.

Permanent press:
The permanent press method normally results in reduction of fabric strength. This method was developed for producing better crease recovery of cellulosic fabrics. The process involves processing the fabrics during its manufacture with a resin. A permanent press fabric is processed after the resin treatment and is then made into garments. The method is commonly used for trousers to introduce the creases at the seams and hems and down the front and back. The garments are then passed through an oven to cure the resin in the fabric.

Future trends in pressing:
We have already seen the trend of increased automation in pressing together with increases in the use of computer technology to not only monitor production but also reduce the effect of human error in the pressing operation. It is clear that this trend will continue. Pressing will become more automated, and pressing pressures, temperatures and the moisture content of steam will be critically controlled using appropriate software integrated into a network. Similarly, automation is applied to other garment finishing operations. Wet finishing and dyeing processes will continue to be modified as the range of fibres and fibre mixtures increases. Furthermore, consumers are continually demanding increased comfort properties from their garments. These properties will be enhanced by the addition of specific chemical finishes to the garment together with differing fibre mixtures.

The concept of nanotechnology is also making its way into garment finishing. New nanotechnology-based concepts such as ease release, quick wick and rare care finishes further improve the functionally of the textile by imparting the various properties such as soil release, anti-pilling effect, water/oil repellency, hygiene effect, easy care and odour-free effect.


References:
  1. Apparel Manufacturing Technology by T. Karthik, P. Ganesan, and D. Gopalakrishnan
  2. Garment Manufacturing Technology by Rajkishore Nayak and Rajiv Padhye
  3. http://fashion2apparel.blogspot.com/2017/01/methods-equipments-garment-pressing.html