Lean management uses principles from lean manufacturing to focus on delivering value with less waste. Lean management is the comprehensive adoption of other lean concepts like lean construction, lean manufacturing and lean thinking into a project management context. Lean project management has many ideas in common with other lean concepts; however, the main principle of lean project management is delivering more value with less waste in a project context. Lean project management has many techniques that can be applied to projects and one of main methods is standardization. Key techniques are those "inherited" from Agile software development like: blame-free employee involvement, the need for a strong facilitator, pipelining, etc.
Six Sigma seeks to improve the quality of process outputs by identifying and removing the causes of defects (errors) and minimizing variability in manufacturing and business processes. It uses a set of quality management methods, including statistical methods, and creates a special infrastructure of people within the organization ("Champions", "Black Belts", "Green Belts", "Orange Belts", etc.) who are experts in these very complex methods. Each Six Sigma project carried out within an organization follows a defined sequence of steps and has quantified financial targets (cost reduction and/or profit increase)
Six Sigma projects follow two project methodologies inspired by Deming's Plan-Do-Check-Act Cycle. These methodologies, composed of five phases each, bear the acronyms DMAIC and DFSS. DMAIC is used for projects aimed at improving an existing business process, while DFSS is used for projects aimed at creating new product or process designs.
The DMAIC project methodology has five phases: First, define the problem, the voice of the customer, and the project goals, specifically. Second, measure key aspects of the current process and collect relevant data. Third, analyze the data to investigate and verify cause-and-effect relationships. Determine what the relationships are, and attempt to ensure that all factors have been considered. Seek out root cause of the defect under investigation. Forth, improve or optimize the current process based upon data analysis using techniques such as design of experiments, poka yoke or mistake proofing, and standard work to create a new, future state process. Set up pilot runs to establish process capability. Last but not least, control the future state process to ensure that any deviations from target are corrected before they result in defects. Implement control systems such as statistical process control, production boards, visual workplaces, and continuously monitor the process.
The DFSS ("Design For Six Sigma") also contains five phases: First, define design goals that are consistent with customer demands and the enterprise strategy. Second, measure and identify CTQs (characteristics that are Critical To Quality), product capabilities, production process capability, and risks. Third, analyze to develop and design alternatives. Fourth, design an improved alternative, best suited per analysis in the previous step. Last but not least, verify the design, set up pilot runs, implement the production process and hand it over to the process owner(s).
In summary, lean focuses on elimination of waste while Six Sigma eliminates process variation. Lean is about just-in-time processing. The materials and/or information arrives just as it's needed. The goal of lean is to avoid having input sitting around waiting to be used and to have as little output as possible beyond what customers are expecting. Six-Sigma is focusing on elimination of variation. Its goal is to produce output that is consistent and free of defects. Defective output requires re-work and re-work is waste. Inconsistent output is the result of a flawed process. Six-Sigma seeks to identify the flaws, determine their cause, and eliminate them.
It is recommended to do lean before six sigma because you don't want to perfect wasteful processes. If something doesn't need to be done there is no point in doing it well. Lean and Six Sigma are complimentary, but neither is dependent on the other. Lean tends to be more applicable to Service sectors (or process) while Six Sigma tents to be more often used in manufacturing. Depending on the project goals, project managers will need to choose the right approach.