Sigma -Six. Lean and Theory of Constraints


Sigma-Six. Lean and Theory of Constraints

Thereare many process improvement methodologies that have been developedin past few decades (Nave, 2002). Among these the most prominentmethodologies have been the six- sigma, the TOC and the lean theory.The key aspect is to establish which methodology works within thecurrent organization structure and culture (Nave, 2002). Even thoughthe ultimate objective of the three methodologies is to maximizeprofits their more immediate objectives to attain this differsignificantly. For the Six Sigma methodology, the immediate goal isto consistently attain clients’ expectation for Lean methodology isto increase value for the clients while for TOC the goal is toaugment throughput (Nave, 2002).

SigmaSix, Lean and Theory of Constraints

Sigma-six is designed to help the organization have an deep understandingof all the elements in all the process making the system so as toreduce variation as much a s possible. The central assumption is thatthe end result of the whole process will improve by reducing thevariation f all the elements (Nave, 2002). To understand theelements in the process there are five key steps that ought to befollowed define, measure, analyze, improve and control. Processinvestigation thorough the precepts of the five steps is intended togenerate re-evaluation of the value added status of the variouselements within the processes. In this analysis some of the elementscan be transformed while others can be withdrawn.

Whenelements are improved it s expected that mistakes will reduces whichwill improve the volume of process output, reduce variation andincrease quality (Nave, 2002).

Leanmethodology focuses on the elimination of all unnecessary elementswithin the process so as to improve flow.

Toachieve this objective lean has five key steps establishingthe elements that create value, establishing the sequence ofactivities, making the activities flow, allowing the clients to pullproduct and finally perfecting the process (Nave,2002). Even though the primary goal is to remove waste, there aresecondary effects such as improvement in quality, reduction invariation and lowering the chances of damage. System constraints areeliminated as an organization looks at all the elements in the valuestream (Nave, 2002).

Theoryof constraints is designed to streamline processes in organizationoperational network that reduces the speed through which services andcommodities go through system. There are five key steps in thisprocess identifyingand exploiting constrains, subordinating other process to theconstraint, and elevating and repeating the cycle (Nave,2002).

Themain aspect that makes the TOC methodology different from the othertwo is the fact that it pays considerable focus to the system’sconstraints. Lean and Sigma six are not formulated to address thiscomportment. Due to the fact that TOC main focus is leveled on theconstraints in the system yields positive impacts to the organizationby increasing the speed through which process in the system arecompleted (Nave, 2002).

Despitethe fact that it sound enticing to many organization to makeimprovements to various processes within the operational framework,the truth is that there are usually limited resources to conduct sucha endevour. In this respect, theory of constraints state that it isonly logical that organizations should make improvements for theleast investment (Nave,2002). Attempts to make improvements to the individuals process inthe organization’s system at the same time can in actual sense bedetrimental to the capacity and ability of the firm to attain theneeds of the clients and offer the commodities and services that arerequired at the lowest cost. Another fundamental consideration isthat the theory of constraints can only focus on a particularconstraint at a given time, and as such it calls for localizedexertion. Consequently, far-reaching data analysis and participationof all employees is not vital to success as they are in the case ofye lean and six-sigma methodology(Nave,2002).

Inthe event that an organization opts to employ one of theaforementioned approaches, there are ways through which theapproaches can implement each other, particularly in relation toexploiting a constraint highlighted through a theory of constrainteffort. Six-sigma methodology can be a tool for attaining morethroughput out of a constraint, and lean approach can play a crucialrole in getting rid of any waste linked to it (Nave, 2002).

Comparingthe methods

Theymay also be employed to fuel out variation and lower waste linked tonon-constraints processes that impede the constraint. TOC assistorganizations to channel attention and efforts on system constraintsat the same time offering fast throughput and cutback of inventory.Theory of constraints is a logic-driven model where organizations cancreate a set of procedures and techniques to establish and optimizesuch constraints (Nave, 2002). In this light, an organization can useSix-sigma and the Lean methodology in theory of constraints to removeany waste and augmenting throughput out of a constraint. Use of Sixsigma approach can amplify the consistency processes. Nonetheless, onits own Six-sigma can not take in hand the question of how theorganization can optimize process flow. Additionally, Six-sigma doesnot attend to the competitive elements of speed (Nave, 2002). On theother hand when leans applied unaided with other methodologies, itwill assist the organization to reduce the complexity of processesbut it will not redress the question relating to reliability. In thisvein by combining these two methodologies, organizations can redressimportant competitive components such as complexity, reliability andspeed.

Leankey assumptions are that waste reduction will invariably lead to theincrease in the business performance. It is clear that this is one ofthe central assumptions but the problem is that it is not legitimatein all situations (Nave, 2002). Moreover, the central assumption madeby Six-sigma that minimizing variability in all processes willinvariably result to an overall systems improvement is also notlegitimate in all environments.


Nave,D. (2002). How to Compare Six Sigma, Lean and the Theory ofConstraints: A framework for choosing what’s best for yourorganization. Available at: