04 Feb Production Optimisation Methods
The optimization, in general, is the activity of selecting, from the possible solutions of a problem, the best one, which is assessed after a predefined criterion. Optimization Theory is one of the most important and fastest growing ﬁelds among all the decision sciences. It is deﬁned as the art and science of ﬁnding the best possible solution(s) according to some predeﬁned measure(s) within a feasible domain/space deﬁned by a given set of constraints.
An optimization problem supposes three components:
- The objective function
- The variables vector
- The restrictions
For different processing methods (cutting, plastic deformation, welding, sintering, etc.) optimization problem has specific forms.
If the optimization criterion is the manufacturing cost, in (Liu and Feng, 2014) the primary objective is to find the optimal sequence of jobs and the optimal resource allocation separately. The authors propose two separate models: minimizing a cost function of makespan, total completion time, total absolute differences in completion times and total resource cost; minimizing a cost function of makespan, total waiting time, total absolute differences in waiting times and total resource cost.
In order to solve the optimization problems are used classical approaches of the existing methods, different combinations between these methods and some new and original developments of the existing methods. The most suitable approach of the optimization for the manufacturing activities seems to be integrated process planning and scheduling (IPPS). It is required an update of the performance indicators of manufacturing process and of objective functions used in optimization, which must have a synthetic character and reflect as well the interest of the manufacturers. Optimization should be multi-criteria or to be performed separately for many objective functions, in order to create an efficient Decision Support System (DSS) for the manager of the manufacturing activities. Generally, the optimization of the manufacturing activities doesn’t have a flexible character, taking into account the conditions from a given moment, without considering the perturbations which may appear or other influences. Energy efficiency and environmental impact of the manufacturing processes must be considered at least as restriction, if they are not considered even as objective function, according to the actual legal requirements (Afteni and Frumuşanu, 2017).
- Afteni, C., Frumuşanu, G. (2017). “A Review on Optimization of Manufacturing Process Performance”. International Journal of Modeling and Optimization, Vol. 7, No. 3.
- Liu, Y., Feng, Z. (2014). “Two-machine no-wait flowshop scheduling with learning effect and convex resource dependent processing times”. Journal of Cleaner Production, vol. 75, pp. 170-175.