How Does a Metal Detector Work in Garments industry | SOP of Metal Detection Procedure

Introduction: A metal detector is a machine that is widely used for finding out the metal parts such as broken needles, pins, any sharp metal tools broken parts, broken metal buttons, etc. from the final garment to ensure the safety of the product.  

Types of Metal Detector Machines: There are two types of metal detectors used to find out the unwanted metal in the garment industry.

1. Conveyor belt system metal detector.
2. Hand-held metal detector. 

Metal Detector Machine

Working Principle of Conveyor Belt System Machine: This type of machine is used to confirm the metal's presence in the garment. 

• In this machine, the product is passed through the place of the electromagnetic induction channel of the machine. 
• If there are any metal substances in the garments, the machine sensor sends an automatic signal to the electronically integrated system & the alarming light pops up. 
• Finally, the machine stops passes the product & sends it back to the start point.

Working Principle of Hand-Held System Machine: This type of machine is used to find out the exact location of the metal in the garment if the metal parts aren't found easily after being held by the conveyor belt machine.

• In this process, the product is placed flat over the table.
• The hand-held machine moves over the product from left to right. 
• The machine creates the same electronic magnetic field to find the metal parts.
• If the machine finds the metal part's location, it makes a sound with a pop-up light alarm.

Why is the metal detection method applied by the garment manufacturer?

1. This procedure is mostly used when a needle is broken during sewing & operator doesn’t find the broken needle. Then she informs the concerned person. After that, they do the metal detection procedure to ensure the presence of broken needles in the garment. If don’t find any needle again operator starts sewing the garments.

2.  The final metal detection is applied before the product is packing & cartooning. Here the main purposes for doing this are to ensure product safety & pack a metal-free product in the carton.

3. It is mandatory for all children's wear, and it varies according to the buyer's needs.

4. Finally & most importantly meet customer satisfaction.

SOP of Metal Detection Procedure:

Before operating any machine, you have to check, if is it ready for work or needs some maintenance? If everything is ok you can proceed with your work. Below are the steps of product metal detection;

Step-1- Machine Preparation: Make sure the machine is neat & clean. Always operate the machine by a trained & authorized person to avoid any kind of mistakes. To calibrate the machine, here we need a ferrous text card & a stand. Card size should be 0.8 mm, 1.2 mm, 1.5 mm, & 2.0 mm. Stand has 3 spaces in the top, middle, & bottom sides for holding the card. It could vary as per different customer requirements. 

Ferrous Card

Step-2- Machine Calibration Procedure: Metal detection is a continuous process in the finishing area. But it needs to be calibrated every time after restarting the machine. The machine has a conveyor belt to pass the product. It is divided into 3 zones left side, center, & right side of belt for calibration. The stand is also divided into 3 points top, middle, and bottom. Here we count the points according to stand position A = bottom, B = middle, C = top, & the zone according to belt 1 = left side, 2 = center, 3 = right side.

So, the 9 points are A1, A2, A3, B1, B2, B3, C1, C2, C3. We keep the ferrous card into the 3 points of the stand & 3 placed on the belt to check the machine sensitivity. If every time the card doesn't pass the machine then the machine is ok. Otherwise, the machine is not ok and needs maintenance. Conveyor-type metal detection machines should be used for the garment's metal detection method. Small flat table-type metal detection machine can only be used to check accessory products.

9-Points of machine calibration
Position	Left Side	Center	Right Side
Top	C1	C2	C3
Middle	B1	B2	B3
Bottom	A1	A2	A3

We can do Metal detection for semi-products / finished products only after the metal detection machine has passed “9-point calibration” or the machine performance has been properly adjusted.

Step-3- Metal detection of Product: After completing all the checking points of finishing for quality & finishing items attached like price tag, hangtag, etc. the product must pass through the metal detector machine. The machine is established in a place where one part (opening of the machine or conveyor belt) is outside & another part is in a room surrounded by glass. Only authorized persons can enter the room to collect the metal pass product for cartooning. No one can be allowed to enter the room with any metal tools (needle, stapler, scissors, cutter, etc.). This zone is also known as a metal-free zone.

1. Firstly, we placed the product over the belt and pressed the start button of the machine.

2. The product is passed through the machine, then it is ready for packing & cartoning.

3. All checked product quantities should be kept separate and clearly marked from unchecked quantities to avoid mix-ups. Here the operator makes reports hourly basis.

4. If the product isn’t passing the machine, then it should be checked by the hand metal detector.

5. If the metal part is still not found, the operator makes a report with the correct information & keeps it in a specific box. Finally, the product should be destroyed as per the company rules or customer instructions.

The final product of the garment should be metal or needle-free; Otherwise, it may harm the user. In the garments industry, this procedure is 100% maintained by the manufacturer. It is highly recommended by each & every fashion brand to follow this operation.