As the screen (or mesh) with its specific hole diameter is one of the most critical components determining the final size of the recycled plastic flakes.

As a leading manufacturer, XINYI MACHINERY understands that selecting the correct screen hole diameter is essential for optimizing the entire recycling process. Here’s a detailed breakdown.

What is the Screen (Mesh) in a Plastic Grinder?

The screen is a perforated metal plate that lines the grinding chamber. As the rotating blades cut the plastic, particles small enough to pass through the holes in the screen are ejected. Particles that are too large remain inside the chamber to be cut repeatedly until they are small enough to pass through.

Standard Hole Diameters and Their Applications

Screen hole diameters are typically measured in millimeters (mm) and occasionally in inches. The choice depends entirely on the type of plastic and the desired end-use of the regrind.

Here is a general guide to common hole diameters and their typical applications:

Key Factors Influencing Screen Hole Diameter Selection

When XINYI MACHINERY advises customers on screen selection, we consider the following:

o Type of Plastic Material:

o Brittle Plastics (e.g., PET, PS, ABS): These break cleanly and can be ground with smaller screens (e.g., 4-6 mm) more easily.

o Tough & Ductile Plastics (e.g., LDPE, HDPE, PP): These materials are "chewy" and require more cutting. Using a screen that is too small can cause heat buildup (degrading the plastic) and overwork the motor. A slightly larger screen (8-10 mm) is often better, with the option to re-grind if a finer flake is needed.

o Desired Final Particle Size:

o For Pelletizing: The flake size should be consistent and small (often 6-8 mm) to ensure efficient and uniform melting in the pelletizing extruder.

o For Direct Extrusion/Injection Molding: A fine, uniform flake (4-6 mm) is preferred to ensure smooth material flow and a homogeneous melt.

o For Washing Lines: A slightly larger flake (8-12 mm) is often used to prevent material loss and improve separation in wash tanks.

o Machine Throughput and Power:

o A smaller hole diameter restricts material flow out of the grinding chamber. This requires more power and can reduce the overall throughput (kg/hour) of the machine. A larger screen allows for higher throughput.

o Material Form and Feed Size:

o The screen hole diameter should be smaller than the feed size of the plastic parts. You cannot put a whole PET bottle through a 6mm screen; it must be pre-cut or shredded.

The "Mesh" vs. "Hole Diameter" Distinction

You may hear the term "mesh" used. In industrial grinding, we almost always refer to the hole diameter in millimeters.

· "Mesh" technically refers to the number of holes per linear inch in a sieve. A 10-mesh screen has larger holes than a 30-mesh screen.

· In plastic grinding, specifying "a 10mm screen" is unambiguous and standard practice. It directly states the size of the holes that the plastic flakes must pass through.

Conclusion and Recommendation from XINYI MACHINERY

There is no single "best" hole diameter. The optimal screen is a balance between your desired flake size, the material type, and your production goals.

· For most standard recycling applications (e.g., grinding HDPE bottles or PP caps), starting with an 8mm or 10mm screen is a safe and efficient choice.

· For high-quality, clean regrind intended for direct manufacturing, a 6mm screen is often ideal.

· For initial size reduction of large items, a 12mm or larger screen is used.

As a professional manufacturer, XINYI MACHINERY typically provides a range of interchangeable screens with our industrial grinders, allowing our customers to easily swap them out to suit different materials and production requirements. We recommend consulting with our technical team to select the perfect screen for your specific recycling operation.