Getting the correct aperture size on a metal detector is essential and the first step to ensure that we can achieve the best sensitivity levels possible to detect metal contamination within your product however “Product effect” will also determine what test piece sizes we can pick up.
Two things the metal detector is looking for:
1: How magnetic a pack is
2: How conductive a pack is
Other factors regarding product effect are:
Wet (Conductive) vs Dry product
Fresh (Conductive) vs Frozen
High Salt content (Conductive)
Plastic packaging vs Foil packaging
Ferrous is both magnetic and conductive so it is easily detected. Non-ferrous is non-magnetic but a good or excellent conductor so it is relatively easily detected. Stainless steel is the most difficult contaminant to detect as it is usually non-magnetic and a poor conductor.
Stainless steel comes in various grades, some of which are magnetic and varying to completely non-magnetic. Their conductivity also varies but is generally low. Both of these factors contribute to poor detectability.
There are so many variations with product effect to consider which is why it’s not as simple as choosing a large enough aperture just so the pack can fit through it.
This is why QPM LTD and Loma Systems will always ask for all pack details so that we can spec up a suitable system for your production line.