High-power magnetic grates with permanent magnets are a simple and highly effective solution for the separation of metal contaminants from plastic granules and regrind materials. Installed in the hopper of an injection molding machine, extruder, mill or regranulation line, they protect key components of the plasticizing system against damage caused by steel chips, screws or small metal parts.
What is the purpose of a magnetic grate in plastics processing?
Magnetic grates are an essential protective component in the plastics processing industry. Their main functions include:
- Separation of ferromagnetic contaminants (steel, iron) from granules and regrind.
- Protection of the screw, cylinder, and nozzle in injection molding machines or extruders.
- Reduction of downtime caused by machine failure due to foreign particles.
- Improvement of molded part quality by eliminating metal particles from the process.
How does a magnetic separator in a feed hopper work?
Magnetic grates use an advanced magnetic circuit design and a labyrinth of round stainless-steel bars. As material flows through the grate, fine iron and steel particles are attracted and held on the surface of the magnetic bars.
The system operates continuously, without stopping the production process. Contaminants accumulate in the lower part of the protective tubes, from where they can be removed periodically.
Where are magnetic grates installed?
Magnetic grates are designed for installation in the feed hoppers of:
- Injection molding machines
- Extruders
- Mills and crushers
- Regranulation and recycling lines
By selecting the proper size, the separator can be easily fitted into an existing hopper. The magnetic grate rests on the sides of the hopper at a defined height and usually requires no machine modifications.
Key advantages of our magnetic grates
- Specifically designed for feed hoppers of plastic processing machines.
- Available with samarium-cobalt (SmCo) and neodymium (NdFeB) magnets.
- Compact, hygienic stainless steel 304 construction.
- Easy cleaning and simple daily operation.
- Wide range of sizes to fit different hopper diameters and material flow rates.
SmCo or NdFeB magnets? Comparison of solutions
For various plastics processing applications, we offer two types of magnetic grate separators – with SmCo (samarium-cobalt) magnets or NdFeB (neodymium) magnets.
| Samarium-Cobalt Magnet (SmCo): | Neodymium Magnet (NdFeB): |
| -Magnetic induction approx. 1240 Gauss – Depending on size, from 3 to 11 bars, diameter about 24 mm – Large separator surface creates a dense labyrinth highly effective at capturing ferromagnetic impurities – Economical solution in terms of purchase cost – In some materials, larger surface area may slightly affect material flow | – Magnetic induction approx. 9000 Gauss – much higher magnetic strength than SmCo – Depending on size, 3 to 5 bars with a diameter of 22–24 mm – Smaller active surface that usually does not disturb material flow – Higher purchase price compared to SmCo grates, justified by significantly better performance – Ideal where very high separation efficiency is required in limited installation space |
Available models and dimensions of magnetic grates
SmCo Magnetic Grates
Parameters:
- Magnetic induction: approx. 1240 Gauss
- Bar diameter: approx. 24 mm
- Stainless steel 304 housing
Models:
| Model | Number of rods | Mounting plate width | Rod length | Plate height |
| MR3 | 3 | 90 mm | 100 mm | 80 mm |
| MR5 | 5 | 150 mm | 115 mm | 80 mm |
| MR7 | 7 | 190 mm | 200 mm | 80 mm |
| MR9 | 9 | 240 mm | 240 mm | 80 mm |
| MR11 | 11 | 300 mm | 295 mm | 80 mm |
NdFeB Magnetic Grates
Parameters:
- Magnetic induction: approx. 9000 Gauss
- Bar diameter: approx. 24 mm
- Operating temperature: up to 80°C
- Stainless steel 304 housing
Models:
| Model | Number of rods | Mounting plate width | Rod length | Plate height |
| M3 | 3 | 150 mm | 150 mm | 40 mm |
| M4 | 4 | 200 mm | 200 mm | 40 mm |
| M5 | 5 | 250 mm | 250 mm | 40 mm |
How to select the right magnetic grate?
When selecting a magnetic grate separator, consider:
- Type of raw material: virgin granules, regrind, crushed waste, additive blends
- Diameter and geometry of the feed hopper
- Required separation efficiency (standard protection or high-risk applications)
- Installation height and its impact on material flow
- Working conditions – especially temperature of the material and environment
If you send us details about your machine, hopper dimensions, processed material, and expected contamination types, we will select the optimal SmCo or NdFeB magnetic grate separator.
Frequently Asked Questions (FAQ)
Q: Can a magnetic grate be installed in an existing injection molding machine without modifications?
A: In most cases, yes. The grate rests on the hopper walls and requires no mechanical interference. Just select the correct grate size to match the hopper diameter.
Q: How often should the magnetic grate be cleaned?
A: It depends on the contamination level. In practice, many factories clean the grate after each material change or once per production shift.
Q: When should I choose a NdFeB magnetic grate instead of SmCo?
A: The neodymium magnetic grate is recommended where maximum magnetic capture of very fine metal particles is required or where installation space is limited but high material flow must be maintained.
Contact us
If you need help choosing the right magnetic grate separator for your injection molding machine, extruder, mill, or regranulation line, contact us.
Based on your machine and material data, we will propose the optimal SmCo or NdFeB solution and prepare a customized quotation.
Please provide:
- Type of machine
- Feed hopper dimensions
- Type of processed material and potential metal contamination
We will select the appropriate magnetic grate type (SmCo or NdFeB), recommend the correct size, and prepare a quotation tailored to your application.
