FLEXO · LOW VISCOSITY · HIGH VOLUME
Flexographic inks are low-viscosity, high-volume products. The line is built for throughput and repeatability: fast pigment wetting, controlled milling to a stable fineness, and filtration that removes oversize particles before the ink reaches the anilox roller.
Flexo ink production is a throughput problem more than a fineness problem: low-viscosity ink runs in large batches, so the disperser and the mill must be sized for continuous flow, and filtration quality decides press performance.
Varnish is prepared in a stirred tank, then pigment and additives are wet out in a high-speed disperser. The millbase is milled to the target fineness, let down to final viscosity, filtered and filled.
Because flexo ink viscosity is low, the mill can run in a single pass or in recirculation with a letdown tank. Recirculation gives tighter distribution at the cost of longer cycle time.
A single-shaft high-speed disperser handles pigment wetting for most flexo formulations. Where powder loading is heavy or the batch is large, a double-shaft disperser gives better circulation and faster wet-out.
For milling, a disc-type horizontal bead mill suits high-volume micron-range production. A pin-type mill is chosen when the target fineness is finer or the pigment is harder. Basket mills are used where colour changes are frequent.
Most losses come from inconsistent filtration and from running the mill past the point where fineness stops improving: energy goes into heat, not into dispersion, and temperature rise can shift viscosity and colour.
A second common cause is poor pigment wetting upstream. If the premix still contains unwetted pockets, the mill has to do work the disperser should have done, and throughput drops.
| Stage | Equipment | What it decides |
|---|---|---|
| Pigment wetting | High-speed disperser (single or double shaft) | Wet-out speed and dispersion quality |
| Milling | Disc-type or pin-type horizontal bead mill | Fineness and throughput |
| Letdown | Letdown tank with agitation | Final viscosity and colour adjustment |
| Filtration | Bag filter | Oversize removal before filling |
| Filling | Filling machine | Pack accuracy and foam control |
A typical line includes a varnish tank, a high-speed disperser, a horizontal bead mill, a letdown tank, filtration and filling. Capacity is set by the mill, which is usually the slowest stage.
Yes, with cleaning between products and compatible seals and contact materials. Solvent-based production needs hazardous-area rated motors and controls.
Flexo inks are usually milled to a micron-range fineness with a narrow distribution. The exact target depends on the anilox volume and the print application, and should be confirmed on the actual formulation.
Low viscosity and surfactant content make foam likely. Reducing free-fall, filling below the surface and controlling pump speed all help; the filling machine configuration matters as much as the formulation.
Send the ink type, the pigment system, the target fineness, the batch size and whether the line must run solvent or water-based products. POLYC MACHINE engineers will confirm the configuration and state where a trial is required before performance is guaranteed.