In the manufacturing environment, the sequencing and scheduling plays a crucial role in decision making. The sequence is the process to establish the job order, to reduce the queue length and to minimise the idle time of the critical machine in the shop floor. This makes the objective of critical machine utilisation as essential, but the major objective of any shop floor is due date. In this research work, a set of solution methods with a new heuristic and corollaries was proposed to optimise both these objectives. A case study was done in a gear manufacturing environment with implementation of the proposed solution methods. The solution methods yield a better result, but handling of critical machine is difficult in flowshop environment. To switch over from traditional flowshop to flexible flowshop is one of the successful ways to avoid the critical machine situation; it is discussed and proved through the simulation models. The makespan was achieved below three days of time, i.e., 4,154 minutes with practical feasibility. The makespan was achieved almost below 1/2 of the standard schedule time. © 2016 Inderscience Enterprises Ltd.