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Contaminant detection in the production of plastic compounds

The use of a number of raw materials from different suppliers is common in the compound industry. As a result, there are many potential sources of contaminants. Our metal detectors and separators protect your production equipment and assure product quality.

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.

Plastics compounding and the circular economy

Compounders are processing more recyclate than ever before. This is due to a combination of factors: rising consumer demand for recycled goods, improvements in the recyclability of virgin plastics, and the low cost of recycled materials.  

Just like manufacturers and processors of plastics, compounders must ensure they are working with the highest quality materials. Especially when working with recyclate, quality controls are of key importance. A circular economy is only possible if it yields usable recyclate in consistent and sufficient quantities.

Systems from Sesotec reliably detect and eliminate contaminants from material streams, thereby minimizing rejection rates, increasing plant availability, and improving material efficiency. By eliminating the risks associated with the use of recyclate, Sesotec systems play an important and lasting role in the establishment of a profitable circular economy.
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 it important to detect and eliminate contaminants in the production of plastic compounds?

It is crucial to detect and eliminate contaminants in order to protect important, expensive machinery and assure product quality. From masterbatch and various additives to recycled and other materials, the sheer number of different raw materials from a wide range of suppliers increases the risk of contamination. Metal particles in particular can quickly cause damage to plasticising screws and cylinders, and block melt filters and nozzle tools. Any one of these things can halt production and lead to downtime and repair costs.   Particles that end up in the product reduce their quality, which is why customers expect metal-free compounds. With our metal detection systems, which are also able to reliably detect and remove non-magnetic particles embedded in a product, you can prevent customer complaints and boost your competitiveness.
Product example RAPID PRO-SENSE 6

Which contaminants can cause problems for plastics compounders?

Metals such as iron, stainless steel and copper very often interfere with the production of compounds. They make their way into the manufacturing process at various points:

  • The input materials can be contaminated.
  • Pieces of metal from machinery or pipes end up in the product through wear and tear.
  • Contaminants can make their way into open material containers.
  • Staff can lose personal items, such as pens or rings.

Recyclate can often contain different plastic types, colors, and other materials that detract from overall material purity. 

  Learn more about our solutions for the plastics recycling industry 

Where do manufacturers of plastic compounds use our machines?

One common application is the inspection of granules. Such inspections are a sensible course of action in various process steps:

  • Checking incoming goods
  • During production in conveyor pipes, right at the material inlet of an extruder, after a screening machine, etc.
  • Checking outgoing goods (before or after packaging)

Learn more about our devices in practical use in our case study about Sitraplas

We have standardised systems for a wide range of applications and would be happy to advise you personally to help you find the best solution for the set-up of your processes!


Product Categories
Content type
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White Paper

Keeping plastic compounds free of metallic contaminants

The Whitepaper explores the challenges that metal contamination poses to compounding and masterbatch production and considers the key features that metal separators must have to provide an adequate solution.

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White Paper

The circular economy: Challenges and opportunities for Recyclers and plastics processors

The plastics industry is under pressure. Between climate change, excessive consumption of finite resources, and vast amounts of plastic waste in the world’s oceans, plastics are coming to be seen in a different light by politicians, businesses, and consumers alike. Read in our e-book about the most important factors of a functioning circular economy, especially which challenges and opportunities exist for recyclers and plastics processors.

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White Paper

Using recycled materials in plastics processing

In the new Sesotec White Paper "Using recycled materials in plastics processing" you will learn about

  • … why there is increasing pressure on plastics processors to use more recyclate
  • … 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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Case Studies

Machinery protection at Starlinger
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Case Studies

For decades Brückner has been relying on Sesotec metal separators
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Case Studies

SABIC chooses Sesotec high performance metal separator
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Case Studies

Metal detector protects Wanner granulators from damage

Case Studies

Sitraplas: Risk-free recyclate processing

Separately purchased recyclate often contains various different polymers as well as metal contaminants such as aluminum, brass, and stainless steel. Learn in our Case Study how Sitraplas has solved this problem.

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Case Studies

OPC UA for production without machine downtime

SITRAPLAS GmbH is a producer of high-performance engineering plastic compounds. Unplanned downtime is a nightmare for every company, but especially for continuous production facilities. When metal separators are networked with plastic processing machines, the flow of information between machines can be monitored.

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Case Studies

Machine protection during PVC granulation

To avoid any metal in the powder, CIPSA wanted to inspect the PVC compounds before they enter the pelletizer. This was to protect the extruder screw from damage and avoid expensive production stops.

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Case Studies

How a metal separator saved this plastics manufacturer 75% in maintenance costs and increased output by 20%

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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Case Studies

Product purity for chemical products through precise quality control

The quality requirements of the chemical industry are particularly high. Metal detectors play an essential role in the refinement of solids to ensure a consistently high product quality and safety. At the same time, the customers expect quick setup times to achieve high flexibility and efficiency.

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Industry Brochures

Economy meets Ecology

Sorting and Detection systems for every stage of the Circular Economy in the plastics industry.

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Industry Brochures

All about PET
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Product Brochures


Hochleistungs-Metall-Separator für Freifallanwendungen

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Product Brochures

RAPID 4000

Metal separator for free-fall applications

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Product Brochures


Metall-Separator für Extruder, Spritzgieß- und Blasformmaschinen

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Metall-Separator für Spritzgießmaschinen, Extruder und Blasformmaschinen

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Metall-Separator für pneumatische Förderleitungen

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Plate type metal detector for installation in conveyor belts and material chutes

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Splitable metal detector for installation on conveyor belts and material chutes


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Flächen-Metalldetektor zum Einbau in Förderbänder und Materialrutschen

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Product Brochures


Metall-Detektionssystem für Förderbandanwendungen

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Conveyor based Metal detection systems

Varicon compact

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Kompaktes Metall-Detektionssystem mit Förderband zur Untersuchung von Stückgütern

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Product Brochures


Rohr-Magnet für Freifallanwendungen

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Product Brochures


Rohr-Magnet für Spritzgießmaschinen, Extruder und Blasformmaschinen


Product Brochures


Rohr-Magnet für Spritzgießmaschinen, Extruder und Blasformmaschinen

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Product Brochures


High-performance metal separator for resin and compound manufacturers

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Product Brochures


Analyzing system for the plastics industry

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Product Brochures


Mobile metal separation unit for material recovery

Sesotec live! - Our upcoming exhibitions
Circular Economy
White Paper
Case Studies
Latest news and blog articles
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Circular Economy
How the pre-sorting of regrind contributes to profitable and highly efficient plastics processing
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Speed meets quality: Sesotec metal separators on their way to the customer in five days
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Sesotec at Fakuma trade fair 2023 - "Economy meets Ecology“
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Plastics Circular Economy 2023 - an Update
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Using recycled material in the production of preforms, blow-moulded parts and plastic bottles - how it works!
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