A rugged or robust process must included 3 qualities: high-quality product must be prepared within the expected time cycle; the process must accommodate relatively broad purity ranges for the inputs, whether prepared or purchased; and the process must operate within parameter ranges, e.g. temperature and pH, which are readily obtainable during the expected process time-cycle. Unless the process is rugged, additional time is incurred, and the quality of the drug substances may be jeopardized. Appropriate in-process controls (IPC) are necessary to maintain low operating costs. Processes must be as simple as possible, but superficially simple (simplistic) processes may be eventually prone to errors.
An "edge of failure", or the conditions at which process failure will result, lies at the limits of the PAR (proven acceptable range) or beyond them at some undetermined point. After appropriate optimization a robust manufacturing process will "tolerate the expected variability of raw materials, operating conditions, process equipment, environmental conditions, and human factors."**
In general, rugged processes operate comfortable far from the edge of failure.
The Kilomentor approach to process development is geared towards the simple, rugged and dependable process step and avoids the technically demanding step, which uses sophisticated and expensive equipment. This keeps with the tenor of the times wherein so much process work is being moved to the developing economies where at least for now labour is plentiful, so long as the work process is rugged.*Anderson, N.G.; Burdick, D.C.; Reeve, M.M. "Current Practices of Process Validation for Drug Substances and Intermediates." Org. Process. Res. Dev. 2011, 15, 162-172.
**Process Robustness - A PQRI White Paper. Pharm. Eng. 2006, 26(6), 1; http://www.pqri.org/pdfs/06ND-online_Glodek-PQRI.pdf