Grinding & Milling Equipment

Grinding and milling: four parameters that decide the mill type

Every wet-grinding specification reduces to four variables. Get them wrong and the mill will either fail to reach the target fineness or run hot and wear out early.

1. Target fineness (D50). Above roughly 5 µm, a basket mill or a triple-roller mill is usually sufficient. Between 1 and 5 µm, a horizontal disc mill is the practical choice. Below 1 µm — and certainly below 300 nm — you need a pin-type or static-disc mill running small zirconia media with tight separation.
2. Feed viscosity and solids loading. Low-to-medium viscosity (up to about 20,000 mPa·s) suits horizontal bead mills. High-viscosity pastes above 50,000 mPa·s are better handled by a triple-roller mill or a planetary mixer rather than a bead mill, because the media cannot fluidise the product.
3. Batch or continuous. A basket mill grinds and disperses inside the batch vessel in one step, so it suits multi-product plants with frequent colour changes. A horizontal bead mill recirculates product through a closed chamber and gives better fineness repeatability at higher throughput.
4. Contamination tolerance. Metal-sensitive products — battery slurries, electronic materials, bright white pigments — need ceramic or polyurethane wetted parts. Standard stainless is fine for architectural coatings and most inks.

What this range covers

Ten platforms in this category span laboratory trials through to 1,500 litre batch production. Each is a different answer to the four parameters above, not a bigger or smaller version of the same machine.

Horizontal bead mills

• Pin Type Bead Mill — horizontal pin-type chamber supporting media down to 0.2 mm, with centrifugal separation and forced cooling. The workhorse for nanometer-range coatings, inks and pigment dispersions. Capacity range 0.5–1,000 L.
• Dynamic Disc Type Horizontal Bead Mill — disc rotor geometry that distributes media evenly across the chamber, giving consistent fineness in medium-to-fine grinding without the higher pressure drop of a pin design. Capacity range 0.5–1,000 L.
• High Efficiency Static Disc Bead Mill — static centrifugal separation allows media down to 0.1 mm, which is where ultrafine and nano work begins to be practical rather than theoretical. Capacity range 0.5–1,000 L.
• Ceramic/PU Pin Type Nano Bead Mill — ceramic or polyurethane rotor and chamber lining for products where metal contact is unacceptable, such as battery materials and electronic pastes. Capacity range 0.5–1,000 L.
• 20L Pin Type Bead Mill — a 20 litre pin-type platform used for pilot batches, formulation screening and small-volume ink production before committing to a larger chamber. Capacity range 0.5–1,000 L.

Basket and vertical mills

• Basket Mill (SBM) — submersible basket that grinds, disperses and homogenises in the batch vessel itself, removing the need for a pump, buffer tank or external separator loop. The standard choice for paint, ink, pigment and latex production with frequent product changes. Capacity range 30–1,500 L.
• 1000L Basket Mill for Pigment — the large-batch version of the same principle, sized for pigment plants that grind a full batch in a single vessel rather than recirculating through a separate mill. Capacity range 0.5–1,000 L.
• Vertical Pin Type Bead Mill — vertical pin geometry for batch and semi-continuous nano and fine grinding of low-to-medium viscosity materials, where floor space rather than throughput is the constraint. Capacity range 0.5–1,000 L.

Triple-roller mills

• PTM Triple Roller Mill — three-roll shear for paint, printing ink, pigment and plastic compounds, particularly where the product is too viscous for bead media or where a paste must be de-agglomerated rather than wet-milled. Capacity range 0.5–1,000 L.
• Hydraulic Triple Roller Mill (PHM) — hydraulic roll-pressure control instead of manual adjustment, which keeps the gap consistent across a long production run and reduces operator dependence. Capacity range 0.5–1,000 L.

Typical process routes

Three configurations cover most of what this category is bought for. The order of operations matters more than the individual machine choice.

1. Coatings and inks (recirculation route)

High-speed disperser for pre-mix and wet-out, then a horizontal bead mill in either pass or recirculation mode, followed by filtration and filling. Pre-dispersion quality sets the ceiling on what the mill can achieve — a poorly wetted pre-mix cannot be rescued by running the mill longer. See our bead mill working principle guide for how energy transfers from rotor to media to product.

2. Pigment concentrates (single-vessel route)

Basket mill grinding directly in the batch vessel, then let-down and filtration. Fewer transfer steps means less product loss and faster colour changes, which is why this route dominates smaller pigment and ink plants.

3. High-viscosity pastes (roll route)

Triple-roller mill in multiple passes, with gap settings progressively tightened. Used where the product cannot be pumped or fluidised well enough for bead media, such as certain sealants, plastisols and highly filled pastes.

Comparing the mill variants

Type	Typical fineness	Batch mode	Best fit
Horizontal pin-type bead mill	D50 150–350 nm (coatings)	Pass or recirculation	Coatings, inks, pigment dispersions at volume
Horizontal disc-type bead mill	D50 0.5–3 µm	Pass or recirculation	Medium-to-fine grinding with lower pressure drop
Static-disc bead mill	D50 below 300 nm	Recirculation	Ultrafine and nano work with 0.1 mm media
Ceramic/PU nano bead mill	D50 below 300 nm	Recirculation	Metal-sensitive battery and electronic materials
Basket mill	D50 5–18 µm	Single vessel	Multi-product paint and ink plants, frequent colour changes
Vertical pin-type bead mill	D50 below 500 nm	Batch / semi-continuous	Nano grinding where floor space is limited
Triple-roller mill	D50 2–10 µm	Multi-pass	High-viscosity pastes that cannot be pumped

Fineness figures are indicative industry ranges for typical formulations, not guarantees. Media size, solids loading, binder system and pre-dispersion quality all shift the achievable result — which is why we recommend a trial on your own slurry before a chamber size is fixed.

Frequently asked questions

How do I choose between a bead mill and a basket mill?

Choose a horizontal bead mill when you need fineness below about 1 µm, higher throughput, or tighter batch-to-batch repeatability. Choose a basket mill when you run many products or colours in the same vessel and want to avoid pump, piping and transfer losses. A basket mill is a batch device: throughput is set by batch size and cycle time, not by flow rate.

What fineness can these mills actually reach?

Indicative ranges on typical formulations: D50 150–350 nm for TiO2 coating slurries, below 250 nm for solvent inks, below 600 nm for ceramic and battery pastes, and 5–18 µm for basket-mill paint batches. Reaching the finer end depends on media diameter, separator tuning, cooling capacity and pre-dispersion quality rather than on the mill alone.

Which grinding media should I specify?

Yttria-stabilised zirconia at 0.2–0.4 mm is the default for sub-micron coatings. Larger 0.6–1.0 mm beads raise throughput on coarser feeds but cap fineness. Glass and zirconium-silicate beads are used where contamination is not critical and cost matters. Media charge is a commissioning parameter: being 5–10 % off shifts both fineness and wear.

Why does chamber cooling matter so much?

Grinding energy ends up as heat. If the chamber cannot remove it, the product temperature rises, viscosity drops, residence time changes and fineness becomes unstable — and heat-sensitive binders may degrade. Jacket cooling with an optional chiller loop is standard on these platforms; the required capacity depends on specific energy demand, which is higher for nano work than for micron-level dispersion.

What is the difference between disc and pin rotors?

Disc rotors give broad, uniform shear and suit pigments and coatings. Pin or peg rotors concentrate impact energy and handle hard, coarse feeds more effectively. Neither is universally better: match the rotor to the feed, then validate on your own slurry. Premium European mills often ship multiple rotor kits per platform; our dynamic-disc and pin options cover the same functional range.

When is a triple-roller mill the right answer instead of a bead mill?

When the product is too viscous or too highly filled to be pumped and fluidised by media — typical of some sealants, plastisols and heavily filled pastes. The roller mill de-agglomerates by shear rather than by media impact, and it handles paste consistency that would simply stall a bead mill.

How do I estimate the capacity I need?

Start from batch size and required cycle time rather than from a headline throughput figure. Then confirm specific energy demand for your formulation: kWh per kilogram, not litres per hour, determines whether a given chamber size can reach your fineness in an acceptable time. A 60 L horizontal mill typically covers around 500 L/h of architectural coating at D50 0.3 µm, which is a useful planning anchor but not a substitute for a trial.

How long does a colour change take?

On a basket mill, the change is largely a vessel cleaning activity — the grinding tool is lifted out, so there is no separator loop to flush. On a horizontal bead mill, the chamber, separator and piping must all be flushed, and the media charge may need partial replacement. If colour changes are frequent, this difference usually outweighs the throughput advantage of a horizontal mill.

Related technical guides

• Bead Mill Specifications and Selection Guide — chamber size, media, tip speed and separator selection in detail.
• How to Choose a Bead Mill for Ink and Paint — application-led selection for the two largest product families.
• Zirconia vs Glass Grinding Media — how media choice changes fineness, wear and contamination.
• Bead Mill vs Ball Mill — when a rotating drum is the right machine and when it is not.
• Horizontal Bead Mill vs Basket Mill — the trade-off between fineness repeatability and changeover speed.