SNB’s Blog

Many manufacturers may look at their current inspection equipment and question whether they have the correct rejection system for their application. It is key to have a rejection system fitted on any inspection equipment as it stops contaminated product continuing on the production line.
With so many rejection systems to choose from, it can seem difficult to make a decision. To correctly choose, there are variables that need to be considered such as product details, weights and lines speeds.

Alarm Belt Stop

Alarm Belt Stop also known as ABS or Stop on Detect, is the simplest form of  metal detector. On detection of contamination, the metal detector stops the conveyor line and alarms through a beacon and sounder. Once an operator has removed the contaminated product, the metal detector can run again.
This type of reject is suitable for systems that are bulk product, heavy or award shaped. Products can be up to 30kg heavy. An ABS is also ideal for manufacturers that have small foot print as it allows the conveyor length to be shorter.

Air Blast

This mechanism does what it says on the tin. It works by a nozzle being attached on the outfeed conveyor and the metal detector blasting air on detection. The product is blasted by air into a rejection bin, making it an automated process and stopping the production line from being disrupted.
Air blast reject systems are best suited to products that are light weight and underneath 500-600g depending on the product type. This system isn’t suited to products that are easily breakable due to the drop into the bin.

Kicker / Pusher

A Kicker or pusher mechanism has a plastic or stainless steel blade that pushes contaminated product off the conveyor length and into a bin. The mechanism tends to be attached to the side of the inspection equipment.
This mechanism type is suited to products that are wrapped and in rigid packaging. The kicker mechanism would not be suited for a poly-bagged product unless a brush strip is fitted to the kicker. We recommend the maximum weight on a kicker/pusher to be 5-10kg. Anything above this would need a heavy-duty mechanism.

Retract Band

A retract band system is a conveyor that retracts the belt towards the metal detector to create a gap on the conveyor enabling an area for a contaminated product to drop into a rejection bin. Once the product has dropped, the conveyor expands again.
Retract bands are suitable for loose packaged products such as sachets or ready meals in plastic. Remember to measure the retraction gap to identify whether your product would drop with ease.

Divert Flap

Divert flap rejects are ideal for products that loose or bulk.
The flap is attached at the end of the unit and will direct the contaminated product off the conveyor into a rejection bin.

Divert Arm

Similar divert flap, the product is diverted off the conveyor and into a bin. However on a divert arm (also known as plough or diverter) the product is directed off to a rejection bin on the side. This rejection type is best for products that are fragile and have slower line speeds.

Lift Tables & Drop Tables

On one of these systems, the outfeed conveyor either has a mechanism arm to lift or drop the outfeed table, therefore diverting the product into a rejection bin.
This rejection type is suitable for products under 1kg.

If you are looking to upgrade your system to a different rejection system or would like advice, get in touch with SNB today on 01977 689555 or email SNB@metaldetector-rentals.co.uk