Wet granulation is complete when the binder has distributed uniformly and the granule population has reached its target size — in practice, read from the mixer torque curve: impeller torque rises as liquid is added, peaks near saturation, and the endpoint is set at a defined fraction of that peak. A granulator that displays torque in real time turns this from operator judgment into a repeatable number.
Why the Endpoint Matters
Stop too early and the batch is under-granulated: fine, dusty granules with poor flow and wide size spread. Stop too late and the mass over-wets: large, dense lumps that dry slowly and mill into fines. Between the two sits a window where granule size, porosity and downstream behavior are reproducible — and the whole point of endpoint control is hitting that window batch after batch.
How Torque-Based Control Works
As binder solution is sprayed (typically via a wet granulation spray gun) the wet mass resists the impeller more and more. The motor current or torque signal therefore traces a characteristic curve: baseline, rise, inflection and saturation. The endpoint is usually defined at a fixed percentage of the maximum torque or at a torque slope change — a value locked during development and then repeated in production. Because torque tracks the mass itself, it responds to real granulation progress rather than to clock time.
Practical Signals to Watch
- Torque rise onset — first liquid contacts the powder mass
- Inflection point — granule growth accelerates
- Plateau approach — pores filling, saturation near; stop inside the window, not at saturation
- Post-granulation checks — granule size spread and fines ratio confirm the chosen endpoint
Equipment That Supports Endpoint Control
Benelabo high-shear wet granulators (0.15–640 L working volume) display mixer torque in real time so the endpoint can be defined, recorded and repeated — and the binder is delivered by a matched spray gun for even, clog-resistant addition. After granulation, the wet mass moves straight to fluid bed drying without a transfer-induced size change.
FAQ
Is torque the only endpoint method?
No — power consumption, hand squeeze and inline NIR are also used. Torque is the most practical to instrument on high-shear mixers and correlates directly with wet mass consistency.
Does the endpoint percentage change between formulas?
Yes — each formula has its own torque curve, so the endpoint window is locked during development and then repeated batch to batch.
Can we verify the endpoint on our own material before buying?
Yes — granulation trials run on your formulation record torque curves and granule data; see the sampling process.