The textile industry requires a high level of expertise and precision. At Smartex, we have been researching textile defects and how to categorize them for better understanding and management. Our research has focused primarily on defects that arise during the knitting process, which can cause significant issues if not promptly identified.
Are you familiar with the 4-point system for classifying fabric defects? It is a popular approach used to categorize defects. However, other systems also exist, and some companies even create their own classification systems that are tailored to their specific processes.
Although it is challenging to devise a classification system for defects that is applicable across the entire industry, we have found that the most general framework for classifying textile industry defects should be based on their upstream effect on the supply chain. This way, companies can comprehend their defect rate and its implications, and make the necessary adjustments. We have identified four parameters to classify defects:
Let's explore each in more detail:
Continuity is an essential criterion as it often affects other criteria. Knitting is circular and repetitive, making it easy for defects to be periodic and recurrent. Continuity usually results from a defective or misaligned element in the production process or from incompatible raw materials. These defects are generally easy to detect, although some, like bent needle defects, can be very hard to spot. Continuous defects in fabric can include barré defects, which are visual patterns of horizontal bars and stripes. These defects can be caused by faulty yarn, uneven thickness, contamination, broken elastane, elastane misplacement, or other factors.
The length and pattern of each defect are key in this classification. A 50 cm defect of broken elastane is not as damaging as a 5 m or 10 m defect. Longer defects usually require cutting the entire roll to remove them, whereas shorter ones may not.
At the opposite end of the spectrum, there are simpler defects which typically appear singularly. These can have different levels of influence on the dyeing process, depending on the defect. Examples include holes (essential for anti-pilling dyeing processes), oil drops, or singular material contaminations.
Subjective defects depend on customer preferences and internal procedures. This means that the likelihood of a defect being accepted or tolerated can be controversial. While some defects may go unnoticed by certain people, others may find them unacceptable. Defects like broken needles or holes are generally agreed upon. However, debates can become heated when assessing subjective defects like irregular yarns, which may or may not be considered defects depending on the customer's standards or procedures.
The Smartex system has alerted customers about highly irregular yarns, leading to significant consequences. In some cases, alerts were ignored and production continued. Other times, the customer's customer was warned and asked to accept or decline the defect. Usually, production continued, but there have been cases where it was stopped, and the yarn supplier was contacted.
The Smartex system is also useful when textile defects are caused by damaged or bent needles, which can give the fabric an uneven column spacing that may or may not be considered a defect.
Reversible defects are critical when considering the impact on the supply chain. These defects can be corrected, reversed, or avoided if their presence and location are known prior to certain manufacturing processes. Examples of reversible defects include oil spots, oil lines, and barré defects. In most cases, oil spots or lines can be reversed after the knitting process if the dyeing facilities use anti-oil procedures. Additionally, some barré defects can be reversed if the fabric is re-dyed with a different color.
The main issue arises when knitting and dyeing facilities lack communication. This can result in fabric with excess oil going through the dyeing process without undergoing the necessary anti-oil applications, rendering the fabric unusable. Similarly, needle-related defects along the edges of the fabric are cut in most jersey fabrics, thus reducing their severity.
Only very well-trained eyes can detect certain knitting defects because they are so small or have such a slight change in pattern that they are invisible to the human eye before dyeing. The visibility of a defect can have a major impact on the supply chain - as less visible defects are much more prone to be undetected and propagate throughout until later stages of the supply chain. There is also a small subset of defects that become much more visible after dyeing - even when they were invisible during inspection before dyeing - the most prominent case here being barré defects caused by yarn lot mixing. Due to the uneven color stickiness of different cotton yarn lots in the mix, this defect can only be seen before dyeing with a UV light.
It's important to note that this criterion isn't applicable to everyone, as factories' quality standards vary depending on production orders and fabric types. Nonetheless, these insights have been gained from studying the industry from both external and internal perspectives.
By categorizing defects according to these four parameters, factories can gain a better understanding of their impact and take steps to improve processes and prevent future issues. Identifying defects in knitting is essential to preserve roll quality in the supply chain and minimize waste. Smartex provides artificial intelligence tools to automate this process, click here to learn more.