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Contaminant detection in the plastics-processing industry

From blocking hot runners to crashing extruder screws or breaking blades in shredders, metallic contaminants can cause many problems for plastics processing. We have the right contaminant detectors to prevent damage to machinery and production downtime.

Sesotec specialises in systems for industrial contaminant detection and has more than 40 years of experience in the plastics industry.

We provide a complete range of leading technology that includes metal detectors and magnet systems for the reliable detection and removal of contaminants in a wide variety of applications. Our systems can target ferrous metals, stainless steel and non-ferrous metals, such as aluminium, copper or brass − regardless of whether the metals are magnetic or not, coated, painted, loose or embedded in material.

The Circular Economy: a challenge for plastics processing

The model of a circular economy presents the plastics processing industry with a compelling framework by which to close the plastics cycle. However, in using recyclate, plastics processors are often confronted with challenges in the form of contaminated materials.  

In order to enable the large-scale use of recyclate, contaminants must be avoided and eliminated. The right process technology is critical in this regard. The use of contaminant detectors, flake sorting equipment, and material analysis systems from Sesotec are key to establishing an efficient, profitable circular economy.

Read in our Circular Economy Blog about "How plastics processors use recyclates profitably"
Sesotec's strengths
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over 40 years of experience and reliability

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Personal support in the after-sales area

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Long-term reliability for spare part supply

Learn more about our solutions for the plastics recycling industry



Why is contaminant detection and removal important for processing plastics?

Machine protection is key, as costly equipment − including injection-moulding machines, blow-moulding machines, twin- and single-screw extruders, and calenders − are at the heart of plastics processing. The aim therefore is to protect machinery from damage to prevent expensive repairs and production downtime. Particular focus is placed on the detection and removal of metallic contaminants, as they can quickly cause blockages and damage.  

Quality assurance is another important factor. Metal particles in the final product are not the only reason for compromised quality. Blockages and tool damage can also result in defects from too little or too much injection of the materials. Metal detectors ultimately help to detect bead wire breaks.

Product example PROTECTOR

What kinds of contaminants could appear?

Metal particles made of iron, stainless steel or copper which are hidden among the plastic granules are the most common type of contamination in the plastics-processing industry. They can come from a variety of sources:

  • Contaminated input materials (granules, recycled materials, additives)
  • Wear and tear from machines or pipes
  • Open material containers that contaminants can enter
  • Personal items belonging to staff (pens, jewellery, etc.


Where do plastics-processing plants use our machines?

Common applications for metal detectors, flake sorting systems and material analysis systems include the following :

  • Quality management and incoming goods inspection of recyclates, granules and additives after delivery
  • Inspection of granules in conveyor pipes
  • Inspection of granules and additives right at the material inlet of the processing machine
  • Inspection of production waste and other recyclable parts before shredding/recycling
  • Inspection of finished plastic parts on a conveyor belt before packaging


As you can see, we support you in all steps of the process. We would be happy to advise you personally to find the right solution for your need together.


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White Paper

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  • … the differences between post-consumer and post-industrial recyclate
  • … the problems plastics processors may face when using recyclate
  • … how to future-proof your processes to effectively handle increasing volumes of recyclate

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While processing virgin glass-filled material together with regrind, the same problem was coming up up over and over again. Metal inclusions were clogging the hot runners of the molds, leading to as many as 10 emergency stops and 2 to 3 costly repairs per month. After careful consideration of the production environment and manufacturing specifications, the metal detection system PROTECTOR 40 was installed along with the magnet system SAFEMAG at the feed hopper of the injection molding machine.

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