A practical screening guide for free-flowing, cohesive, dusty and blended powders.
Many fine, dusty, cohesive and moderately free-flowing powders can be candidates for auger dosing. Suitability depends on flowability, bulk density, particle distribution, moisture sensitivity, aeration, compaction, inclusions, dust and the required pack. A product name is not enough to make the decision.
Representative trials are especially important when a powder bridges, floods, changes density after transport, contains fragile pieces or leaves residue where the pack must seal.
Assess how the powder behaves during storage, refill, agitation, dosing, stoppage and settling—not only how it looks in a sample bag.
| Observed behaviour | Why it matters | Trial focus |
|---|---|---|
| Bridging or rat-holing | The auger may not receive a consistent charge. | Hopper geometry, agitation, refill level and pause/restart behaviour. |
| Very free flow or flooding | Powder may continue moving after the screw stops. | Tube, outlet, cut-off, head pressure and pack position. |
| Aeration or compaction | The same volume may have a different mass over time. | Loose/settled density, refill, transport and settling conditions. |
| Dusty release | Product may escape or contaminate a rim or seal area. | Drop height, outlet, enclosure, displaced air and source capture. |
| Large or fragile inclusions | Pieces may bridge, segregate or be damaged by the screw path. | Particle limits, blend uniformity and comparison with another dosing method. |
Flowability affects how reliably powder reaches and leaves the auger, while bulk density connects the controlled volume to the delivered mass. Cohesive powders may need assisted hopper flow; very free-flowing powders may need tighter control at the outlet. Density changes must be reproduced during trials.
Record both loose and settled density where possible, plus the events that create each condition.
Direct link to answerAn auger filler may handle some blends containing small particles, but the inclusion size, shape, fragility and proportion must suit the screw, tube and outlet. Larger or irregular pieces can bridge, segregate, be damaged or make each volumetric charge less consistent.
Use a representative blend sample and inspect both fill weight and ingredient distribution after dosing.
Direct link to answerTest another dosing method when the product is too coarse, fragile, irregular or free-flowing for a stable auger charge, when ingredient distribution is critical, or when weight-based combination is more appropriate than volumetric screw dosing. The comparison should use the same product, target pack and acceptance method.
The existing auger versus weigh-filling guide explains the main trade-offs.
Direct link to answerSafety note: powder hazards must be assessed from the actual substance and process. For Great Britain, HSE guidance covers COSHH assessment and fire and explosion risks under DSEAR. Machine suitability does not replace a competent workplace assessment.
Include product safety information, fill range, packs and known differences between batches or suppliers.