1. Process Definition
On Line Quality Control (QC) of knitted fabric is the process of evaluating the greige and dyed yarn prior to knitting and checking the knit circular and flat machine parameter(s), in order to ensure conformity with the fabric specifications required by the customer.
2. Process Requirements
Equipment used for on line quality control of knitted fabrics are:
- Datacolor Spectrophotometer
- Inspection Table
- Light Box.
2.2 Key Accessories
Key accessories used for on line knit quality control are:
- Weighing Balance
- Inch Tape
2.3 Materials/Chemicals Used
Sulphuric acid solution is used for fiber composition.
3. Safety Instractions
In order to ensure floor safety, an Inspector should follow the instructions given below:
- Smoking is strictly prohibited in the factory premises.
- Adequate number of Fire extinguishers are placed in Inspection Area. Floor personnel are trained to use it.
- Do not place fabric stack in front of the electric panels.
- Follow the safety instructions and guideline while operating the machines.
- Take necessary safety precautions (e.g. use of hand gloves) while handling chemicals and other hazardous materials.
4. Operation Procedure
4.1 Operation Staff
Operation stuffs for on line quality control process includes:
- Manager, Quality Control
- Production Executive
- Sr. Inspector
4.2 Check List Before Operation
Supervisor should check the following points prior to operation:
- Required manpower is available.
- All the tools/accessories are available.
- Fabric/yarn is ready for inspection/evaluation.
4.3 On Line Quality Control (QC) Procedure for Knitting
Rihan Textile Ltd. (RTL) considers the customer-approved sample or the specifications as the standard for quality control. However, in absence of customer’s specification(s), RTL follows the standard guidelines as specified in the RTL Quality Standard Specification in order to ensure quality product.
4.3.1 Dyed Yarn Evaluation
A few pieces of collars/cuffs are knitted and washed to match with approved standard visually. Spectrophotometer is also used if decision is to be taken whether the yarn is approved for shade or not in case of DE less than 1.0. Further evaluation is done by Colour Fastness Test to Washing. If blended yarn is used then it is burned out with Sulphuric Acid (70%) to check the shade of other component.
4.3.2 Greige Yarn Evaluation
One roll of fabric is knitted to evaluate the yarn and it is processed as soon as possible. Based on the fabric appearance both Greige and Dyed yarns are evaluated. Refer to Greige Yarn Evaluation Report for other parameters that are checked and recorded.
4.3.3 Machine Parameter Checking
Following machine parameters are checked during on-line QC:
|Machine||Parameters to be Checked|
|Circular Knit Machine||Stitch Length|
|Flat Knit Machine||Yarn Tension|
4.3.4 Yarn/Fabric Quality Checking
Every yarn cone/package is checked before using it in circular and flat knitting machine. Each of 30 Circular and 55 Flat knit machines are checked randomly while they are in running condition. Different faults and specifications like Needle line, GSM, width, Barre mark, thick/thin, unevenness, etc. are checked for tube/open fabrics. In case of collars and cuffs the width, length, ply, tube, and appearance are checked.
4.3.5 Fabric Roll Monitoring
The Online Knit QC Supervisors continuously monitor all the processes to identify various faults or defects, like crease mark, needle line, patches, holes, etc, and to take immediate necessary action.
Based on the sequence of Greige Inspection, the Inspector serially numbers each roll ensuring that all the rolls are having the Knit Card with complete details of the roll. This newly assigned number is termed as “Hole Number” and it is written on the Knit Card and on the corresponding roll. Refer to Greige Inspection Process Specification for details.
The roll numbers and weights are written on the backside of the Batch Card against these “Hole Numbers” assigned by the Griege Inspection department (as shown in the following example), and required number of holes are made on the fabric (50cm from the edge) using a hole creator.
|Hole #||Roll #||Qty (kg)|
Then the fabric roll moves to the Batch Preparation section along with the Knit Card. Refer to Batch Preparation Specification for details.
At Dyeing section, a new column “Tube” is added to the existing data mentioned on the backside of the Batch Card. Here, the number of the tube, in which a particular roll is loaded for dyeing, is recorded against the corresponding roll number (as shown in following example). This number has two parts. The first part i.e. T1, T2, or T3 denotes the tube number of the machine (assigned from left to right for each machine). The tube number is followed by the nozzle codes, i.e. a, b, c etc. (assigned depending upon the machine capacity).
The hole marks should not be removed during processing.
|Hole #||Roll #||Qty (kg)||Tube|
The Online Knit QC Supervisors keep track of each roll using these data along the process line; i.e. Hydro-extractor Machine, De-water Machine, Slitting Machine, Compactor Machine and Stenter Machine. They also ensure that the hole mark is not removed from the roll during processing as it helps to identify a particular roll easily during Final Inspection.
4.3.6 Laboratory Testing
Color Fastness to Wash and Water, TPI and yarn strength are tested in RTL QC Laboratory. Due to unavailability of required arrangements, some parameter(s) can not be checked at RTL QC Lab. In that case, these are sent to BTL QC (for fabric)/PTML QC (for yarn) for testing. The Yarn Quality Report is used to record the details of yarn testing done at PTML.
4.4 Sample Test
Sample is sent to laboratory for testing. Refer to Specification on Off Line QC Test for Finished Fabric for details.
4.5 Response to Faults
4.5.1 Response to QC Faults
Following response are to be taken in case of any QC faults:
|Greige Yarn Fault||Inform Yarn Supplier (Spinning)|
|Dyed Yarn Fault||Inform Yarn Dyeing Department|
|Knitting Fault||Inform Knitting Department|
4.5.2 Response to Machine Faults
Following response are to be taken in case of any machine faults:
|Any Electrical Faults||Inform Electrical Maintenance Department|
|Any Mechanical Faults||Inform Mechanical Maintenance Department|
5. Applicable Forms and Documents
5.1 Forms and Documents Used
Following forms are used for Online Quality Control process:
- Daily Knit Machine and Yarn Evaluation Report
- Greige Yarn Evaluation Report
- Dyed Yarn Evaluation Report
- Lot-wise Yarn Consumption Report
- Knit Card
- Batch Card
- Yarn Quality Report
- On Line Circular QC Report
- On Line Flat QC Report
5.2 Document Flow
Document flow for the above documents are as follows:
👉Daily Knit Machine and Yarn Evaluation Report is maintained to keep record of Yarn and process faults for each order. Supervisor records detailed information in this form and signs on it and the area in-charge puts his signature upon verification.
👉Greige Yarn Evaluation Report and Dyed Yarn Evaluation Report are filled out by the QC department upon testing the quality of the sample yarn. Three copies of these forms are sent to planning, knitting and stores. If the yarn quality meets the specification, stores places bulk order.
👉Lot-wise Yarn Consumption Report is prepared to keep record of total yarn consumption per lot. Supervisor prepares the document on put his signature. The Area In-charge signs on it upon verification.
👉The Greige Inspector records all the details of greige inspection result on the Knit Card. It includes information like order no., style, quality, greige GSM, roll quantity, reject quantity, knitter, shift, date, etc. He also puts his signature and comments (i.e. approved or rejected) on the Knit Card, which moves with the fabric along process line.
👉Batch Card includes detailed information related to fabric like order no. customer, quantity, type and quality of fabric and yarn, GSM, shade, etc. On the other hand, Job Card includes information related to collars and cuffs for the same order.
👉The Yarn Quality Report is used to record the details of yarn testing done at PTML. The person performing the testing signs on it after recording the test findings and the section head sign on it upon verification. This document is used as an internal document and maintained for future reference.
👉The On Line Circular QC Report and the On Line Flat QC Report is used to record the findings of on line random checking of parameters mentioned in section 4.3 of this document. Inspector fills this out and the supervisor submits it to the section head, QC upon verification.
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Founder & Editor of Textile Learner. He is a Textile Consultant, Blogger & Entrepreneur. He is working as a textile consultant in several local and international companies. He is also a contributor of Wikipedia.