THORby CI
ProductsPin Mill

THOR Pin Mill

Screenless impact milling for a narrow particle-size spread.

Pin mill opened for inspection, showing the intermeshing rotor and stator pin rings and the drive motor
Impact · screenless

Impact milling without a screen

Two discs face each other, each carrying concentric rings of hardened pins — one spins up to 110 m/s while the other stays fixed. Feed enters at the centre and is flung outward through ring after ring of impacts.

Mechanism
Impact · screenless
Fineness
20 – 200 µm
Capacity
10 kg/h – 10 t/h
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Working principle

No screen means nothing to blind or tear: the residence time is milliseconds, heat stays low, and the size spread comes out naturally narrow — which is why food and pharma plants pick it first.

FEEDPIN ZONECOLLECT

What the material passes through

  1. 1Feed hopper & dosing screwMeters the feed into the disc centre at a steady rate
  2. 2Rotating pin discUp to 110 m/s tip speed — the impact energy source
  3. 3Static pin discIts pin rings interleave the rotor's, doubling impacts per pass
  4. 4Grinding gapParticles zig-zag outward through 3–5 pin rings
  5. 5Outlet to cyclone / bag filterAirflow carries the powder out to collection

What is a Pin Mill?

A pin mill is an industrial dynamic-impact grinding machine engineered to achieve fine to micro-fine particle-size distributions. THOR by CI offers the series in two core configurations: Screened and Screenless.

The Screened Pin Mill surrounds the milling chamber with a high-precision sieve to enforce a strict mechanical cut-off size. The Screenless Pin Mill relies entirely on centrifugal aerodynamics to sweep fine particles out — bypassing physical meshes and completely circumventing screen-plugging (blinding). This flexibility lets one platform process dry, crystalline, brittle, oily and soft materials into fine powders.

Where Pin Mill sits on the particle-size scale

5 mm
1 mm
200 µm
50 µm
10 µm
Pin Mill
CoarseSub-micron

Three mills in one base machine

The peripheral insert is fully interchangeable — change the cut, change the mode, on the exact same chassis.

Screened — Strict mechanical top-cut

An interchangeable sieve screen at the discharge boundary lets only sub-aperture particles pass — tight control over maximum particle size.

Screenless — Air-swept, no blinding

A smooth-bore spacer ring replaces the screen; the rotating disc's air current sweeps fines to a peripheral chute — eliminating any chance of screen blockage.

Liner-equipped — Impact + friction attrition

A segmented, high-durability ribbed grinding liner (breaker ring) slides in — projecting particles against heavy ridges to combine pin impact with aggressive shear.

Advantages & limitations

What the THOR-PM does exceptionally — and where pin-mill physics sets a ceiling.

Advantages

  • Standardized 3-in-1 platform

    Swap screened, screenless and liner modes on one base machine — slashing CAPEX and spare-parts inventory.

  • Hygienic clean-in-place design

    316L stainless, mirror-polished surfaces and seamless welds — a true micro-pulveriser for food and pharma.

  • Narrow particle-size distribution

    Precise intermeshing pin geometry yields a tight PSD — consistent product, minimal over-grinding.

  • Operational versatility

    Runs standalone for intermediate fine grinding, or couples downstream with dedicated classification.

  • Modular classifier compatibility

    For separation down to 10 µm, couple the discharge to a THOR-AC Air Classifier that returns coarse to the mill centre.

Limitations to plan for

  • Vulnerability to abrasive wear

    Quartz, silica or sand (Mohs >3.5) wears the pins fast — risking contamination and frequent pin replacement.

  • Screen blinding in screened mode

    Cohesive, fatty or hygroscopic feeds can bind the sieve — switch to screenless or an air-classification loop.

  • Friction heat accumulation

    High rotor speeds heat the chamber and can melt fats, chocolate or sugar unless water-cooling or LN₂ dosing is fitted.

  • High idle power draw

    Spinning the disc to 18,000 rpm demands substantial power to overcome drag and inertia, even when empty.

Milling, mixing & bulk handling

The THOR-PM Series drops into automated, continuous process lines.

Controlled gravity feeders

Variable-speed rotary valves or electromagnetic vibratory feeders meter the central inlet to prevent over-feeding.

Dust-free pneumatic receivers

Fine powder discharges straight into a vacuum conveyor or positive-pressure transport line — no ambient contamination.

Dynamic air-classifier loops

Couple to a THOR-AC Air Classifier in a closed pneumatic circuit to tune the product top-cut D97 in real time.

Other products

See the other four

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