Metal Detection Before Shipment for Packaged Products

Why foreign object risk matters before shipment

The U.S. FDA Compliance Policy Guide on hard or sharp foreign objects (CPG Sec. 555.425) notes that such contaminants in food may cause traumatic injury, including injury to the mouth, throat, stomach, or intestine. Metal contamination is not only a quality issue — it is a safety, recall, and customer trust risk that can have serious regulatory and commercial consequences.

A single contamination incident can trigger a product recall, damage brand reputation, and result in regulatory action. For manufacturers shipping food, pharmaceutical, cosmetic, or industrial products, inline metal detection before shipment is one of the most effective controls available to prevent contaminated product from reaching the end consumer. Detecting and removing suspect units at the production line is far less costly than managing a recall after distribution.

What products need inline metal detection

Metal contamination risk exists across a wide range of product categories. Inline metal detectors are commonly used for:

• Food products: Sugar, salt, meat, packaged snacks, baked goods, frozen foods, and other processed or packaged food items
• Pharmaceutical products: Tablets, capsules, powders, and liquid medicines in sealed packaging
• Cosmetics: Creams, powders, and personal care products in bottles, tubes, or sachets
• Textiles: Garments and fabric products where broken needles or metal fasteners may be embedded
• Toys and hardware: Products where metal fragments from manufacturing processes may remain
• Chemical industry products: Packaged chemicals and industrial materials where metal contamination affects product purity

In each of these categories, the contamination source is typically the production environment itself — worn machine parts, broken tooling, or metal fragments introduced during processing. Inline detection at the end of the line catches these contaminants before shipment regardless of their origin.

Detecting ferrous, non-ferrous, and stainless steel contaminants

Not all metal contaminants are the same, and detection difficulty varies significantly by metal type. Ferrous metals (iron-based) are the easiest to detect due to their strong magnetic properties. Non-ferrous metals such as aluminum, copper, and brass are detectable but require higher sensitivity settings. Stainless steel is the most challenging — it has low magnetic permeability and high electrical conductivity, making it difficult to distinguish from some product signals.

The JZ-M300 is designed to detect ferrous, non-ferrous, and stainless steel foreign bodies, including fine metal particles embedded within products. Its sensitivity specifications reflect this range: Fe ≥ 0.8 mm, Non-Fe ≥ 1.2 mm, and SUS304 stainless steel ≥ 2.0 mm. For products with high stainless steel contamination risk — such as those processed on stainless steel equipment — confirming detection sensitivity against your specific product and packaging is an important step before line integration.

JZ-M300 for narrower packaged products

The Metal Detector JZ-M300 is suited for inspecting narrower packaged products on a conveyor line. Key specifications:

• Detection aperture: 300 mm width × 100 mm height
• Belt height: 750 ± 50 mm (customizable)
• Maximum belt conveyor speed: 25 m/min
• Delivery capacity: 10 kg/time
• Power supply: AC 220V, 50–60Hz
• Sensitivity: Fe ≥ 0.8 mm, Non-Fe ≥ 1.2 mm, SUS304 ≥ 2.0 mm
• Frame material: SUS304 stainless steel
• Belt: FDA-certified food-grade PU belt
• Protection rating: IP65

The IP65 protection rating makes the JZ-M300 suitable for washdown environments, and the FDA-certified food-grade PU belt supports deployment in food and pharmaceutical production lines. The 300 mm aperture width accommodates most standard pouch, sachet, and small carton formats.

JZ-M400FB for wider conveyor inspection

The Metal Detector JZ-M400FB provides a wider detection aperture for larger packaged products or multi-lane conveyor configurations. Key specifications:

• Detection width: 400 mm
• Detection height: 80 mm
• Belt height: 750 ± 50 mm (customizable)
• Maximum belt conveyor speed: 25 m/min
• Delivery capacity: 3 kg/time
• Power supply: AC 220V, 50–60Hz
• Frame material: SUS304 stainless steel
• Belt: FDA-grade PVC belt
• Protection rating: IP65
• Product memory: 99 programs

The 99-product memory program capability is particularly useful for multi-SKU production environments where different products run on the same line. Each product can be stored with its own detection parameters, allowing operators to switch formats quickly without recalibrating from scratch.

Digital signal processing and product effect compensation

One of the most common challenges in metal detection is the product effect — the signal generated by the product itself as it passes through the detection coil. Wet, conductive, or high-mineral-content products (such as meat, cheese, or certain packaged sauces) can produce signals that interfere with metal detection, leading to false rejects or reduced sensitivity.

The JZ series addresses this through digital signal processing (DSP), automatic phase tracking, and automatic product-effect compensation. These features work together to distinguish the product signal from genuine metal contamination signals, maintaining detection stability across different product types and packaging formats. Automatic phase tracking continuously adjusts the detection phase angle to match the product signal, reducing false rejects without sacrificing sensitivity to actual contaminants.

Alarm and rejection options

When a metal contaminant is detected, the system must take action to prevent the suspect product from continuing down the line. The JZ series supports multiple response options:

• Alarm shutdown: The conveyor stops automatically when a contaminant is detected, allowing the operator to locate and remove the suspect unit
• Buzzer alarm: An audible alert notifies the operator of a detection event without stopping the line
• Optional rejection mechanism: An automatic rejection device (such as a pusher, diverter, or air jet) can be integrated to remove suspect products from the conveyor without stopping production

The choice of alarm and rejection method depends on line speed, product value, and the acceptable level of operator intervention. For high-speed lines where stopping the conveyor would cause significant disruption, an automatic rejection mechanism is the preferred option. For lower-speed or lower-volume lines, alarm shutdown with operator removal may be sufficient.

Where to place a metal detector in the production line

Metal detector placement depends on the product format and the point in the process where contamination risk is highest. The most common placement is at the end of the production line — after filling, sealing, wrapping, or cartoning — so that the final packaged unit is inspected before it enters the shipping carton.

Typical placement sequences by product type:

• Food pouches and sachets: After VFFS or premade pouch sealing → Metal Detection → Checkweighing → Case Packing
• Pharmaceutical bottles: After capping and labeling → Metal Detection → Cartoning
• Cartons and boxes: After cartoning → Metal Detection → Case Packing

In many lines, metal detection is paired with a checkweigher to combine contamination inspection with weight verification in a single pass. The Online Checkweigher JZ-150 can be integrated before or after the metal detector depending on line layout and inspection priority. Combining both systems reduces the number of non-conforming units that reach the shipping stage and provides a more complete quality gate before dispatch.

Ready to configure your metal detection system?

Contact Keypack Intelligent to match your product size, conveyor width, detection sensitivity, rejection method, and factory inspection workflow with the right metal detection system. Our engineering team will review your line requirements and recommend the appropriate model and configuration.