A Brief Discussion on the Principles of Garment Ironing and Equipment Selection

Expert Liu Qi, Expert Committee of the China Commercial Federation Laundry and Dyeing Industry

Expert Profile of Liu Qi
In August 1992, joined the ironing workshop of the Jing'an Temple main store of Shanghai Zhengzhang Laundry Company; since September 1996, served as the director of the ironing workshop of the chain department of Shanghai Zhengzhang Laundry Co., Ltd.; from September 2000 to present, serving as the production manager of the chain department of Shanghai Zhengzhang Laundry Co., Ltd.
This article elaborates in detail the different functions and classifications of garment ironing. By actually measuring the temperature-time curve of garment ironing, it analyzes the principles of garment ironing in detail; the article also provides a relatively detailed introduction to different types and uses of garment ironing equipment, and based on research, offers insights into the development trends of today's garment ironing technology.

Garment ironing is a shaping method that uses the basic principle of fabric wet-heat setting, applying appropriate temperature, humidity, and pressure to change the structure and surface state of the fabric. Broadly speaking, garment ironing refers to all heat treatment processes performed on garments. Ironing is the most important process in garment manufacturing. There is a traditional saying in the garment industry: "30% sewing, 70% ironing." Although somewhat exaggerated, it reflects the importance of the ironing process.
In garment sales, when people decide to buy a piece of clothing, the main basis is often not just the style and color, but more importantly the feel of the garment, which directly depends on the quality of the ironing. Experience tells us that the production of high-end garments must be matched with corresponding ironing equipment.
      
1. The Role of Ironing
The importance of garment ironing lies not only in its ability to compensate for defects in sewing but also in completing tasks that cutting and sewing cannot achieve. From a broad perspective, the functions of garment ironing mainly include four aspects: shaping, flattening, pleating, and bonding.
1. Shaping. Shaping is the process of using ironing to create the three-dimensional shape of garments. We know that the process from fabric to garment is a transition from a flat surface to a curved surface. Certainly, through certain garment piece structure design and dart processing, some three-dimensional effects can be achieved, but structural design alone is insufficient. Ideal shaping must rely on ironing technology to change structural factors such as fabric density and yarn morphology to achieve the three-dimensional shaping of garments. Thus, shaping corresponds to what is commonly called "pushing, returning, and pulling." This process can be done manually with an iron or, to some extent, by mold ironing machines designed with corresponding upper and lower mold shapes.
2. Flattening. If shaping uses ironing to bend and pull fibers and yarns to meet three-dimensional shaping requirements, flattening is the opposite. It uses ironing to smooth out wrinkles caused by storage and handling during processing, making the garment smooth and crisp.
3. Pleating. Pleating (such as trouser creases, skirt pleats, etc.) is an important form to enhance garment aesthetics. Of course, seam pressing at garment piece seams also belongs to a form of pleating ironing. People's requirements for fabric pleating and wrinkling are opposite: pleating requires crease durability, while wrinkling hopes for crease resistance and quick disappearance after formation. There are two types of pleating: one is purely using ironing to bend fibers and yarns to form pleats; the other is so-called permanent pleating, which first uses open seam basting and then ironing to press and fix the sewn crease in place, or combines ironing with chemical treatment to form permanent pleats. During sewing, treatments like pressing the edges of patch pockets before sewing also belong to pleating, aimed at reducing sewing difficulty and improving sewing speed and quality.
4. Bonding. Many garments (such as suits) require reinforcing certain parts with one or more layers of interlining to increase the garment's body and stiffness. Interlining is often bonded to the garment using the principle of hot-melt adhesion, bonding the interlining and garment into one through pressing and ironing. Hot-melt bonding only requires a certain temperature and pressure for a certain time to complete. In large-scale garment production, specialized hot-melt bonding machines are generally used, which are efficient, high-quality, and stable. In small-batch production, irons and some clamping ironing machines are often used, which are less efficient, lower quality, and unstable.
The above four functions are often not independent; in one ironing operation, several functions can be achieved simultaneously, such as shaping and bonding together, which can also achieve flattening. Besides these main functions, due to the high temperatures used in ironing, it also has a bactericidal effect. Additionally, with the cooperation of suction ironing tables, ironing can sometimes also serve to remove dust and clean.

2. The Basic Process of Garment Ironing
Here, we define the basic process of garment ironing in two forms. According to the ironing procedure, it can be divided into intermediate ironing and final ironing; if classified by whether there is a change in shape, it can be divided into restorative ironing and design ironing.
1. Intermediate ironing and finishing. Intermediate ironing refers to the ironing process applied to garment components during the sewing process, such as seam pressing, crease removal, pleating, interfacing, and shaping. It is commonly called "small ironing." Intermediate ironing not only ensures the smooth progress of subsequent sewing operations and improves seam quality but sometimes also saves part of the sewing work. Of course, for certain garments (such as suits), the more important role of intermediate ironing is the thermoplastic shaping treatment applied to the garment. Some garments, relying solely on structural design methods like darts and pleats, cannot fully meet the complex curved surface requirements of the human body. In such cases, intermediate ironing is needed, using the "push, gather, pull" ironing techniques to make the garment look attractive and fit well.
The so-called "push, gather, pull" process means: "gather" refers to bringing together the fabric's structure or its constituent fibers; "pull" means stretching the fabric structure and fibers; "push" is a continuation of gathering, pushing the gathered momentum to a certain position to fix it. Of course, the push-gather-pull technique is not万能 (universal); its extent is limited by factors such as fiber properties and fabric structure. For example, in garments made from non-thermoplastic materials like cotton, linen, and silk, the push-gather-pull technique is mostly limited to altering the density and looseness of the fabric structure.
2. Restorative ironing and design ironing. Restorative ironing and design ironing are two opposite concepts, both indispensable in the garment manufacturing process.
(1) Restorative ironing. Restorative ironing refers to ironing performed to eliminate state changes in garments caused during production, transportation, storage, and wearing. The purpose of restorative ironing is to restore the fabric or garment to its original state, such as smoothing out wrinkles.
(2) Design ironing. Design ironing covers a broader scope; its purpose is to create new shapes for the clothing. Treatments such as bending, folding, shortening the body length, and bulging (shaping) applied to garment materials all belong to design ironing. Design ironing is based on our styling design and process plans. It is much more complex than restorative ironing and often requires multiple methods to meet design requirements.

3. Process conditions for garment ironing
The process conditions for garment ironing are essentially the wet-heat setting conditions for the textile materials constituting the garment. It requires completion under certain temperature, humidity, and pressure conditions within a specified time.
1. Temperature. Temperature is the most important factor in the ironing process; it is the key to deforming and setting the garment materials. If the temperature is too low, the fiber's deformation ability is small, and the purpose of heat setting cannot be achieved; if the temperature is too high, it can cause the garment materials to yellow, scorch, and harden. For synthetic fiber materials, melting and bonding may occur, damaging the fabric's wear performance. The importance of temperature is not only reflected in its level but also in the duration of exposure. After treatment at a certain high temperature for a certain time, rapid cooling is necessary to fix the textile materials in the new shape and achieve a soft, elastic, and excellent hand feel.
2. Humidity. Humidity is also an indispensable factor in the heat setting process. Usually, only under wet-heat conditions can the constituent fibers of the fabric be moistened, expanded, and stretched. Therefore, shaping into the desired form is only possible in a moist state.
3. Pressure. In the garment industry, there is a common misconception that higher pressure is needed to achieve good ironing quality. Experiments have shown that beyond a certain point, increasing pressure does not improve ironing quality but rather increases the occurrence of glare. Therefore, whether in the design of garment ironing machinery or in practical ironing, pressure control must be moderate.
4. Time. From the above discussion on "temperature," we have seen the importance of time control. Good time control affects not only the shaping effect but also the amount of energy consumed. In many garment ironing machines, time control is used to regulate the changes in temperature, humidity, and pressure applied to the garment surface.
4. The physical process of garment ironing
In the development of the garment industry, a set of physical processes has been summarized to meet the above process requirements, namely, "steam application (humidification and heating) — shaping — moisture extraction (dry setting)."
As mentioned earlier, to achieve the designed shape of the garment, the fibers in the garment must be shrunk or stretched to form a new shape, and then the fibers must be rapidly cooled to fix them in the new shape. This physical process is precisely what achieves this purpose.
1. Steam application.
Wet steam is the simplest medium for heat transfer and the fastest and easiest way to transfer heat into the fabric. Moreover, it does not affect the appearance of the fiber surface. By supplying a certain amount of steam, the fabric not only reaches a certain temperature but also gains a certain humidity, providing the conditions for deformation. Different fabrics and garment styles can use different characteristics and amounts of steam to achieve various setting effects.
2. Shaping. After steam passes through the garment fabric, the conditions for deformation are met. At this time, according to design requirements, the parts of the garment that need ironing can be shaped by manually applying certain pressure and pushing force to form the desired shape.
3. Moisture extraction. After the garment reaches the required new shape through the shaping process, if it is slowly cooled and dried, it will revert to the pre-ironed shape, failing to achieve the ironing purpose. Therefore, rapid moisture removal and cooling are necessary. This is similar to the heat treatment setting process of metal materials. In actual operation, this process is often overlooked by operators, so the use of small ironing tables must be emphasized in garment manufacturing.
In modern ironing technology, microprogram control has been widely and deeply applied, enabling the garment ironing process to achieve automation. For different garments, the microcomputer can automatically determine process parameters and complete the entire physical process automatically, which not only improves work efficiency but is also very important for obtaining stable ironing quality.

5. Main Equipment for Garment Ironing
Different ironing equipment should be used according to different ironing requirements. Modern ironing equipment is mainly divided into the following categories.
1. Iron. There are many types of irons, mainly divided into four categories: steam irons, electric irons, steam-electric irons, and full steam irons.
The heat source of a steam iron is hot steam, while an electric iron uses an electric heating element for heating. Neither of these irons can automatically spray water to moisten the fabric and require manual humidification, mostly used for local heat melting and bonding. Steam-electric irons and full steam irons are different; although they use electricity or hot steam as heat sources respectively, they have perforated steam slots and horizontal valves on the soleplate to control steam release, enabling automatic fabric humidification. The quality and shape of the iron's soleplate vary according to different usage requirements. Generally, irons used in sewing are lighter with narrow and pointed soleplates, while those for heavy ironing are heavier with wide and blunt soleplates. For knitting garments, ironing mainly focuses on flattening, so special irons with particularly wide soleplates are often used.
2. Steam generators and suction ironing tables. When irons are in use, they must be equipped with ironing boards, stands, and electrical wires; full steam irons also require necessary steam boiler piping systems. To improve ironing quality, the use of irons must be combined with suction ironing tables for immediate moisture extraction, drying, and cooling to achieve excellent results. Besides the iron's own weight, manual pressure is applied to achieve different pressing effects; also, due to the small footprint and diverse soleplate shapes, irons are very flexible. However, irons have low production efficiency and require high operator skill; improper use often fails to achieve the desired ironing effect.
In actual production, the combination of full steam irons, steam generators, and suction ironing tables is almost involved in every stage of garment ironing operations. The previously used hanging bottle steam irons on sewing assembly lines have almost been replaced by this combination, or at least supplemented with suction ironing tables.
3. Pressing machines. Pressing uses the interaction of upper and lower pressing molds to complete ironing. Pressing machines can be divided into mold pressing and clamp pressing.
(1) Mold pressing. In mold pressing, the garment is clamped by the upper and lower pressing molds of the pressing machine. The pressing molds emit high-temperature steam, giving the fabric plasticity for shaping, and use strong suction generated by a vacuum pump to absorb moisture, cooling and setting the fabric to complete the ironing process. This is used for shaping hats, collars, sleeves, and bra cups.
In mold pressing machines, the upper and lower pressing molds are two key components. Their design must fully consider the garment's shape characteristics to achieve a reasonable and modern look, and the molds must fit together properly. Since the molds are designed according to the shape features of different garment parts, they play a very important role in improving garment quality. However, mold pressing machines occupy large space, consume high energy, and are highly specialized, so they are mostly used for specialized large-scale production and are not suitable for small factories or small batch garment production. The garment pressing assembly line used in suit production is a combination of different types of mold pressing machines.
(2) Clamp pressing. Clamp pressing places fabric or finished garments flat on a specially arranged surface, then applies pressure from another flat surface to achieve heat setting. Clamp pressing machines are mostly standalone units. Their main structure is roughly similar to mold pressing machines, but the upper and lower pressing molds of clamp pressing machines are mostly flat or slightly contoured. Because clamp pressing machines are generally standalone and more adaptable, they are easily adopted by small factories or small batch garment producers, partially replacing the more specialized mold pressing machines. They are also used to some extent in the dry cleaning industry.
(3) Mannequin steam ironing. Mannequin steam ironing, also called three-dimensional ironing or overall ironing, uses an adjustable (manually or automatically adjustable), inflatable mannequin bag that expands under steam and vacuum, raising the garment surface to a certain temperature and moisture level and applying pressure to achieve a steam setting effect.
The main process steps of mannequin steam ironing are: ① taking and placing the garment on the mannequin ironing machine; ② steam blowing ironing; ③ air drying and setting; ④ removing the garment from the ironing machine.
The mannequin ironing machine has a wide range of applications. It can be widely used for ironing various coats, jackets, underwear, etc.; for plush fabrics (such as velvet, corduroy) and fur fabrics, mannequin steam ironing can prevent nap and hair from being crushed; especially for lightweight fabrics (such as silk, rayon), the benefits of mannequin ironing are more evident. Since mannequin steam ironing completes the entire garment in one go, its overall garment ironing and shaping effect is better, although some local effects are obviously inferior to mold pressing and other ironing methods. Mannequin ironing is highly efficient; except for placing and removing the garment, the rest is fully automated, taking only a few tens of seconds. Also, due to the high degree of automation, the equipment is very easy to operate.
4. Pleating machine. Pleating is the process of shaping fabric into a series of pointed or rounded pleats under certain temperature and humidity conditions using a certain pressure. Besides hand pleating, clamp ironing machines, or irons, there are also specialized pleating devices. Especially in forming some more complex and delicate pleats, using a dedicated pleating machine can improve quality, increase production efficiency, and greatly reduce costs.
The main components of the pleating machine include the pleat mold, pleat pushing mechanism, heating elements, cooling and shaping system, and control system. Modern pleating machines use computer control and can create various beautiful pleat patterns according to different requirements. In actual production, considering equipment utilization and to reduce investment, specialized pleating machines are often not used for some simple pleats, instead replaced by other machinery.
5. Hot melt bonding machine. The hot melt bonding machine is specialized equipment for bonding interlining with heat pressing. There are two main types of hot melt bonding machines: conveyor belt type and drum type. The heating element is the main component of the hot melt bonding machine. The process parameters mainly include temperature, time, and pressure, which are determined primarily by the type of hot melt adhesive on the interlining and the fabric's properties.
6. Shirt ironing machine. The main ironing parts of a shirt are the cuffs and collar, so the shirt sleeve ironing machine and collar ironing machine are the main ironing equipment in shirt production. Additionally, the shirt 3D ironing machine is also a key device in shirt making. The use of the shirt 3D ironing machine generally involves three steps: dressing, ironing, and undressing, and one cycle can iron the entire front and back, yoke, and shoulder areas of the shirt.
7. Wrinkle removal hanging steamer. The wrinkle removal hanging steamer uses a small steam generator to produce steam, which is delivered through pipes and a steam nozzle to act on the garment surface, helping to eliminate minor wrinkles formed during storage, transportation, and wearing. This lightweight equipment is mostly suitable for shopping malls, homes, hotels, and other entertainment venues.
The above provides a brief classification introduction of ironing equipment. With the rapid development of science, technology, and the garment industry, various new ironing processes continue to emerge, leading to continuous improvement and updating of various garment ironing equipment.

6. Development of ironing technology
To correctly analyze the development direction of ironing technology, one must first have a clear understanding of its past and present. Like other industries, the garment industry is undergoing fundamental changes influenced by the electronic revolution and new design concepts. We summarize these changes into six aspects:
(1) Cost. Old equipment requires high purchase and installation costs and also needs relatively high investment in spare parts inventory; new ironing equipment is lightweight, flexible to use, and features unique steam and vacuum generators, requiring no steam or air pipelines, thus reducing installation costs.
(2) Energy consumption. Old equipment has inefficient temperature control devices and requires installation of a series of steam and air pipelines, increasing energy loss; new ironing equipment comes with its own steam generator and has no long pipelines, reducing heat loss. Steam discharge can be automatically controlled as needed, no longer manually operated.
(3) Functionality. Old equipment is difficult to use for multiple tasks; new equipment uses entirely standard components and can achieve more functions with a basic system by simply changing the ironing frame.
(4) Operation. Previous mechanical equipment lacked ergonomic design, did not consider the operator's capabilities and limits, was often difficult to operate, and had poor results. Operators had to perform unnatural movements, which over years could lead to health decline; modern equipment design fully considers human anatomy and function, applying ergonomic methods to greatly reduce operator fatigue and improve work efficiency.
(5) Quality. Traditional equipment did not fully consider the physical properties of fabrics, often causing fabric surfaces to shine (gloss) or produce poor ironing effects due to overheating or excessive moisture from steam; new equipment combined with physical testing designs optimal process parameters such as temperature, vacuum, and humidity to achieve the best ironing quality without damaging fabrics, thus significantly improving quality.
       
So far, garment ironing technology has made certain progress. New ironing equipment continues to develop in this direction, meeting the needs of contemporary high efficiency, high quality, and small batch production. New high-efficiency, modular ironing equipment will increasingly gain popularity.