What happens between cutting and discharge?
In a screened granulator, material is cut in the cutting area and can leave through the screen when its shape and position allow passage. The aperture helps control discharge; it does not mould the material into identical pieces.
The RHONG standard R catalogue, for example, lists a 6 mm screen aperture for RG-1619R, RG-1626R, RG-2136R and RG-2142R. This is a catalogue configuration reference, not a measured particle-size distribution or a promise that every particle’s longest dimension is below 6 mm.
Why a long piece may pass through a smaller opening
Length and passing cross-section are different measurements. As a simple geometric example, a long, narrow piece may present its narrow end to an opening. Its length can exceed the aperture while the section passing through fits. Flat or flexible pieces can present different shapes as they turn or bend. This explains a possibility, not how often it occurs in a particular machine’s output.
“Maximum particle size” therefore needs a measurement definition. The longest dimension found during inspection and the material retained by a particular test sieve are different observations. Neither can be calculated from the machine’s nominal screen aperture alone.
The hole has depth as well as an opening
Nominal aperture is only part of a screen’s geometry. Hole shape, its direction through the plate and the working plate thickness describe the passage a particle encounters. Manufacturer literature distinguishes straight, conical and slanted holes. These examples explain why screens with the same nominal aperture are not automatically equivalent; availability on the quoted RHONG model needs separate confirmation.
| Record | What it describes |
|---|---|
| Screen specification | Nominal aperture, hole geometry and working plate thickness of the proposed screen. |
| Particle shape | Long, narrow or flat pieces that an aperture figure does not fully describe. |
| Sample distribution | How a sample separates across the stated test-sieve sizes. |
| Downstream acceptance | The size fractions, fines and elongated pieces the next process can accept. |
Use the sample to answer the output question
Record the test-sieve openings and the proportion in each fraction, together with the sample’s material and cutting conditions. That gives two sample results a common basis for comparison. Assess long pieces separately where their shape matters; a sieve fraction is not a complete shape description. The sampling and acceptance method should match the downstream requirement.
A smaller aperture is not automatically a better specification. Material properties, rotor speed, cutting conditions and screen construction act together. The useful target is acceptable regrind, rather than the smallest number in the quotation. For assessing quality and output together, see how to read a granulator capacity claim.
Pair the quoted screen specification with a representative sample’s recorded distribution and an observation of elongated pieces. Compare those with your downstream criteria. Passing a size assessment alone does not establish an approved reuse ratio or finished-product performance.
Technical references: Cumberland: Granulator Screens; WITTMANN innovations 4/2025, pages 16–17, screen construction and sample assessment.