Sunday, March 11, 2018

Challenges of Automation in Clothing Industry

Difficulties or Challenges in automation:
Unlike the large-scale automation in other industries, garment industries are much slower in adopting the technology. The major problem hovers around proper handling of the fabric, due to high flexibility.

One of the major areas of research for several groups is related to the automation in fabric handling. The major component of clothing is the fabric, and in many operations they need to be moved from an operation or placed for a new operation. For moving the fabrics, they need to be held by an appropriate device and transferred to a movable component and then replaced for another operation. The selection and designing of such devices depend on the fabric properties, the operational speed, accuracy required, and the position of the points on the material for which such accuracy is required. The fabric may need to be gripped and transferred as a single component placed on a surface (e.g., table) or from a bulk of other fabrics. For gripping a single component, a number of approaches can be taken as discussed in Table.

Automation in sewing
Fig: Automation in sewing
Table: Various approaches used for fabric gripping and transfer

Holding tool/method
Influencing fabric properties
Pins or needles
Fabric stiffness
Chances of damaging delicate fabrics
Fabric stiffness and surface friction
May not be effective for limp fabrics
Fabric stiffness and surface friction
Fabric dimensions should be stable
The hardness of the fabric
The device used for penetration must not damage the fabric
Nature of fibers in the fabric, flatness, surface texture
May not be effective in some types of fabrics
Fabric porosity
Hard to handle porous fabrics such as nets
Nature of fibers, effectiveness in postremoval of adhesive
Additional process of adhesive removal is needed
All fabric can be handled. The type of fiber influences the time needed for freezing and heating operations
Additional time needed for freezing and heating operations

Some of the commercial devices based on the holding methods as described in Table are discussed in the following section:

  • Clupicker uses the pinching method to hold the fabrics, which is similar to the human fingers picking up the fabric. When a Clupicker is programmed to grip one component, it will be hard to grip the garment assemblies.
  • Polytex is based on the method of using pins or needles to pick up single fabric component. As these devices are prepared with high precision, they are slightly expensive.
  • Littlewood is also based on the method of using needles, which is a variation of the needle principle used to provide reliability in ply pick up.
  • Walton device is based on the combination of air foil, needle, and suction for picking up “oneply only.”
Although commercial equipment has been designed using the methods in Table, they are not very successful in fabric holding and transferring because of the following reasons:
  • There is lack of fundamental engineering approach,
  • There is lack of quantitative material data, and
  • The original equipment manufacturers (OEMs) do not perform dedicated research to solve the problems.
The detection of fabric before gripping can be accomplished by the application of different sensing techniques such as:
  • Optical: A light source or infrared ray can be used.
  • Mechanical sensing: A mechanical sensor can be used.
  • Airflow: Measure pressure drop of airflow.
All the fabrics used for apparel purposes are flexible materials, and the handling is influenced by fabric stiffness. The other influencing fabric properties during material handling are the friction, which is characterized by coefficient of friction, and longitudinal extension (EM). All these three properties (stiffness, friction, and EM) play important role in fabric handling. The low values of fabric stiffness and friction and high EM make the automatic handling rather a difficult task. Because of high variability of these three factors among different fabrics, it is hard to design automated equipment that can handle all types of fabrics.

Furthermore, these fabric properties change depending on the relative humidity and temperature of the working room. As the working room conditions in many garment industries are not precisely controlled, the change in fabric properties will cause difficulty in materials handling. During automatic placement of cut pattern pieces for sewing operation by automatic machines, mismatching of patterns can occur. Positional errors of 5–10 mm generally occur during the operations such as laying, grasping, folding, and sweeping.

Fabrics are flexible material as they undergo significant out-of-plane bending with the application of small forces. The limpness of the fabric due to low stiffness makes it difficult for automatic handling. Automatic handing is very easy in automotive industry where rigid components are handled by robotic arms. Considering the developments relating to material handling in automotive industry, one would find that almost no progress has been achieved in garment manufacturing. The inherent nature of the fabric for automatic handling has made the universal application of automation a difficult task.

The traditional process of manually joining two fabric components by sewing involves: (1) gripping the fabric components, (2) aligning or matching them at the reference point or notch, (3) stitching for the necessary length, and (4) removing the stitched component and placing them in a position to be picked up by the next operator. Hence, while designing automatic robots for fabric handling and sewing of garments, these operations should be kept in mind. The automatic device should be able to grip and feed the fabric component(s) to a sewing machine, match the reference points, if there are two or more components, form the seam, manipulate the components around the needle, stitch them together, and remove them as the stitching has been finished.

While designing the automatic robots, it is important to consider dimensions of the components to be joined and their range, the physical features of the components (such as stiffness, surface roughness, and porosity), and the amount of stitching needed. There are different ways of moving the fabric from one to the other place such as pick and carry, sliding, rolling, conveying, destacking, alignment, and distortion.

The automation of sewing at high speed can lead to excessive needle heating, which can result in improper sewing and faults in the garment. The detection and remedial action is essential to produce quality garments. To resolve this problem and facilitate high-speed automatic sewing, researchers at the Georgia Institute of Technology (GIT) have developed a device that can identify excessive needle heating and indicate to the operator. The device is based on the use of certain sound frequencies whose amplitudes increase when sewing needles become worn. In the incident of a thread break or when the needle wear exceeds a preset level, the computer alerts the operator by sending a signal that turns on a light. Researchers at GIT are also designing devices to detect sewing problems resulting from needles and thread before they occur. Piezoelectric sensors can be used to monitor the thread movement during sewing, which send the data into a computer and the computer detects the fault.

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