Fixed vs. Variable Gap Roller Compactors: How the Right Choice Impacts Granule Quality
Roller compaction is a widely used method for improving powder flowability — especially in pharmaceutical applications. While much attention is paid to formulation and compaction force, one technical detail is often overlooked: the design of the roller compactor.
There are two principal types of roller compactors:
- Fixed Gap Roller Compactors
These machines maintain a constant gap between the rollers throughout the compaction process. The gap can typically be adjusted before starting but remains unchanged once the process begins.
What does this mean in practice?
- If powder flow from the feeding unit fluctuates — which is common with poorly flowing materials — the compaction force will fluctuate as well.
- This leads to inconsistent ribbon densities and, ultimately, to variability in granule properties.
- Variable Gap Roller Compactors
In these systems, one roll is mounted on a flexible mechanism that allows the gap to change slightly during operation, depending on the amount of powder being fed.
The key benefit:
- The compaction force stays constant, even if the powder input varies.
- The process becomes more stable, and ribbon density — and therefore granule quality — remains consistent.
Why It Matters in Pharma
When producing high-quality granules for solid oral dosage forms, consistency is everything. Variable gap systems offer better control, fewer deviations, and easier scale-up — making them the standard for pharmaceutical dry granulation.
Conclusion
Choosing between fixed and variable gap roller compactors isn’t just a mechanical decision. It’s a strategic one that impacts process robustness, product quality, and regulatory compliance.
At Solids Development Consult, we exclusively work with variable gap roller compactors — in R&D and in scale-up — because only they deliver the consistency and control required in pharmaceutical environments. If you’re evaluating your roller compaction setup or struggling with granule consistency, we’re here to support you with insight, testing, and optimization.
Let’s ensure your process is as reliable as your formulation deserves.