Traditional bras are typically made by cutting cup components from standard fabrics and then sewing them together to form-3-D cups. But the major drawbacks are time consuming and uncomfortable. Fewer seams in a bra mean fewer making-up procedures and make the bra more comfortable to wear. However, with the advent of some of the synthetic fibres we now take for granted, a process was developed for making bra cups without seams. That process involves heating polyester fabric just enough to soften it, while holding the fabric over a desired final shape. So the entire bra is produced as a single piece by the process called moulding. If you picture a waffle iron (without the dimples that hold the maple syrup), you'll see a similarity to a moulding machine; two sides, affectionately known as "male" and "female" are pressed together over the fabric. The heating process actually stretches the fabric in some areas of the bra cup, most notably the apex area. This stretched area is quite visible when holding a stretch moulded cup up to the light. The stripes would be very distorted at the apex, but not necessarily around the perimeter of the wire line. By the way, this process is called "bubble-moulding". The same moulding process was soon applied to foam, and the padded seamless cup was born. The foam starts out as a 1/2" or 5/8" thick slab and as it goes into the moulder, the foam softens, and decreases in thickness according to the mould shape. No seams are required at the edges, nor at the transition points between the other components. This not only improves comfort and reduces making-up costs, it also prevents the bra from attractively showing through the garment worn on top.

Fig. 1 Typical moulding machine

A typical moulding machine consists Male mould, Female mould, Compressor, Temperature regulator, Time controller, Two operation switches and Safety switch.

Male Mould

A pair of male aluminum mould in semi-oval shape, is fixed on a plate. It moves up and down by the power of pneumatic or oil compressor.

Female Mould

The female mould is also made of cast of aluminum and its shape is like a cavity.

Types of moulding process used in intimate apparel industry

Bullet (Bubble) moulding

Bullet (Bubble)-mould is a standard mould used mainly for elastic fabric by which a circular shape is moulded into the fabric and the final shape is given by the female bust. Bubble moulds are available in various diameters and the depths can be adjusted to suit the size and article. The bubble process is suitable for fabrics with two-way stretch. This stretch is obtained by using texturized yarn or by adding elastane into the yarn. For example, polyamide/lycra, or cotton/spandex.

Figure 2. Bubble moulding

Contour moulding

A pair of pads is drawn toward the walls of heated female moulds (cavity) by hot male moulds (press). The foam material is then softened by heat and compressed by pressure for a specified time. The thickness of material depends on the gap between the male press and female cavity.

Figure 3. Contour moulding Typical procedures of moulding a bra:

  1. Lamination - Combine cover fabric and liner fabric
  2. Cutting - Cut the laminated fabric to specific design using a fabric cutting machine
  3. Moulding - Mould the bonded sample to created the designated cup shape
  4. Trimming - Final cuts (or die cut to increase the efficiency) made to the garment to achieve the desired shape
  5. Final assembly - Strips, slides, hooks and eyes are attached to fabric portion of bra.

Moulded bra mainly composed by fabric or foams alone or fabrics laminated with foams together, the following paragraphs will discuss the features of common mouldable materials in bra making:

Common types of mouldable fabric

Early attempts to produce moulded bra cups typically involved moulding nylon fabric. However, with nylon it is difficult to override the partial heat set which is applied when the fabric is produced. As a result, when nylon fabrics are moulded and heat set, it is necessary to approach the melting point of the nylon in order to override the partial heat set, resulting in a high incidence of yellowing and the fabric becoming brittle. This has made nylon commercially undesirable for moulding bra cups. The advent of polyester fabrics has done much to overcome this problem. The partial heat set applied to polyester fabric when it is produced can be easily overriden by only a relatively small increase in the temperature at which the bra cup is moulded (e.g., about 20 degree. above the partial heat set temperature). The other type of mouldable fabric used in bra is cotton with resin finish. The advantage of using this material is air permeable (breathable) and water absorbent. But the disadvantage is it can't stabilize its shape after water penetration.

Mouldable fabric must have enough fabric stretch in the wale and course (warp and weft) directions in order to prevent the non-elastic fibers (i.e., nylon or polyester) from cutting and rupturing the spandex fibers as the fabric is stretched during moulding. Warp-knit or circle-knit fabrics are the standards for molding. Woven fabrics can only be molded when sufficient elasthane has been woven into the fabric.

Recommended Fabric Properties for Moulding:

Warp stretch 210%, plus or minus 10% Course stretch 110%, plus or minus 10% Total fabric stretch 300 to 320% with 95 to 100% minimum.

Common type of mouldable pad

Polyurethane (PU) foams

A polyurethane is any polymer consisting of a chain of organic units joined by urethane links. It is widely used in flexible and rigid foams, durable elastomers and high performance adhesives and sealants. Over three quarters of the global consumption of polyurethane products is in the form of foams, with flexible and rigid types being roughly equal in market size. In both cases, the foam is usually behind other materials: flexible foams are behind upholstery fabrics in commercial and domestic furniture; rigid foams are inside the metal and plastic walls of most refrigerators and freezers, or behind paper, metals and other surface materials in the case of thermal insulation panels in the construction sector. Its use in garments is growing: for example, in lining the cups of brassieres. The major advantages of using foams materials because it can be sculpted and moulded to a cup pad for fitting breasts, provide fit and support for bras with good softness, better air permeability, good memory of shape and remain the shape long after repeated washing and wearing.

Spacer knits are double-layered circular knits with a cushion of air and "spring-like" yarns between the two sides. The space provided by the connecting or pile yarns provides good air permeability. It can be heat-set or molded at lower temperatures which allows better whites and more efficient production.

Figure 4. Spacer fabrics

Characteristics of Spacers compare to foam

  1. on-yellowish after moulding
  2. dimensional stable
  3. breathable
  4. compression resistant
  5. have good physiological properties and are soft
  6. value added with application of anti-microbial, UV- protection.
  7. excellent elasticity.
  8. reducing cost of production as no laminating of external layer required.

Range of temperature :

Range of processing time:

Pressure is constant while moulding and controlled by the compressor.

After moulding, you should have to check the product(bra) in different ways in order to fulfill the customer needs. Here are the common check point:

  1. Defects(Burst, deformed shape, shrinkage) on the fabric
  2. Discoloration (Yellowing on white fabric)
  3. Cup depth of maximum cup size after shrinkage


Figure 5. Cup depth checking

There are different kinds of defects raised in moulding process due to 1)Mechanical, 2)Thermal and 3)Chemical Problem. Mechanical problem mainly related to machine settings such as mould and sensor alignment, distance between male and female moulds. If the mould or sensor alignment is not correct, it will cause the thickness along the cup rim uneven.

Thermal problem mainly related to moulding temperature and time. Moulding temperature and time are crucial to the moulding process. The mechanical properties and appearances of bras would be varied by different moulding temperature and time. For example, the bra cup will become brittle when the moulding temperature is too high or the moulding time is too long. Common defects made by wrong setting of moulding temperature and time are shown as follows:

  1. Moulded cup becomes brittle when the moulding temperature is too high and the moulding time is too long.
  2. Mould ring will appears on the product when mould temperature is too high.
  3. Indistinct details (like ridge for trimming) on the moulded cup when mould temperature is too low or mould time is too less.
  4. Polymeric materials melt and adhere to mould.
  5. Discoloration of dyeing additives(Blue dot) will occur when mould temperature is too high.

Chemical Problem

The defect related to chemical problems is discoloration. Discoloration of PU foams is affected by UV light, oxidation and temperature. The presence of antioxidant BHT in many plastics, can also affect the color.

PU foams made with an aromatic isocyanate will yellow if exposed to UV light. The yellowing is caused by an oxidation reaction in the backbone of the polymer. Since it is the polymer itself which is being oxidized, the yellow color cannot be extracted and the foam will ultimately degrade. So the foam must be placed in the room without UV light or using some covers to prevent the foam under UV exposure. PU foams will discolor if oxidized. Oxides of nitrogen from pollution can cause a foam to oxidize and become yellow. This phenomenon may be more observable in the winter when warehouses are closed up and gas furnaces are in operation. Ozone exposure can also oxidize foam and cause discoloration. PU foams can also become discolored from exposure to heat. This can occur during the foaming process or if the foam is exposed to heat in end use. If the moulding temperatureis too high, yellowing will occur.

Presence of fire retardants and antioxidant BHT can increase the risk of discoloration.

The other defects like Moire shadow on fabric laminate and undulatory surface (orange skin) after moulding; they are basically related to material itself: 1)May be yarn misalignment or mismatch of fabric and foam materials' stretchibility.

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