Basic of Six Sigma#
Defining a Procee Y = f(x)#
A process transforms inputs into outputs. Consider that inputs to Amazon are products such as books, the process receives and stores them, the goods are then delivered to the customer and represent the output of the process
$$ Y = f(x) $$Y is the process output, x is the process inputs. There may be several imputs, in that case, x can be a vector.
Voice of the customer (VOC)#
The customer is the basic focal point for designing, improving, monitoring and control processes. In Lean Six sigma, their wants and needs are referred as the “VOC”. The VOC drives the system of inputs, processes, and outputs.
Critial to Quality (CTQ)#
Critial to Quality(CTQ) represents the characteristics or specification of the product or service necessary to meet the wants and needs of of the customer.
CTQs align the design function with the voice of the customer(VOC)
- VOC
- CTQ
- Process Design
- Output to customer
Example:
CTQ across the originization
The concept of CTQ can be applied across the enterprise. It can be used to define the quality or attributes of a purchased part, a service provided by the company, or after market product support to customers.
Voice of the Process (VOP)#
Every process is capable of delivering a product or service within its own limits, called the VOP.
Cost of Poor quality (COPQ)#
Lean six sigma promise efficient and consistent output at appripriate level of quality. But poor quality does happen? So how do we avoid it?
One way to emphasize the problem is poor quality is to put a price on it, it then makes it clear that poor quality have measurable consequences. COPQ is the cost associated with the gap between the desired and actual product or service quality.
It can be measure by:
- Cost of labor to fix problems
- Cost of extra material used
- Cost of lost opportunities, since the process must focus on fixing problems
- Potential loss of market share
- Lower customer service levels
- Higher cost of processing, including lower profits.
Note that COPQ doesn’t include the cost of detection and prevention. What it certainly would include is the cost to repair items that are returned during a warranty period.
Here are some examples of COPQ. These issues can be prevented if proper monitoring and control systems had been in place.
- Faulty ignition switch installed on automobile
- Lead paint on children’s toys.
- Breach of security in online systems.
Fundamental Challenges#
Lean Six Sigma address three major challenges:
- Minimization of delays, defects, waste and errors -> Associate with Lean
- Minimization of output variation -> Associate with Six Sigma
- Establishment of monitoring and control systems. -> Associate with Six Sigma
Continuous Improvement#
Kaizen#
Kaizen mean continuous improvement. Continuous Improvement focus on small changes to establish processes. These changes occur in all corners of the organization.
The Five Steps (5S)#
5S focus on five specific steps to help improve efficiency while reducing delays and waste. The five steps include:
Sort#
Improve workplace layout in a way that promotes efficient use of equipment, inventory or supplies. There are two approaches to improve this:
- Sort items into different groups(Always used, Sometimes used, Rarely used)
- Sort by product families.
Set in Order (straighten)#
Set in order address two important operational issues.
- First, focuses attention on at the detail level. For example, a clear labeling system or fixed location for storing supplies, can avoid delays and wasted motions.
- Second, focus on process flow. It assures that materials, staff, jobs and customer flow through a process as efficiently as possible.
Shine#
Shine focuses on a clean work and storage environment. A clean and pleasant work environment affects worker morale and motivation
Standardize#
Standardize what has been accomplished. By standaradizing these processes, all staff will better understand what is expected of them.
Sustain#
Once the challenge of improving workplace efficiency has been addressed, and standards have been set, the next step is to ensure that a new mindset or culture has been established so that these new standards endure over time.
Visual Control#
Visual control relies on visual and other sensory devices to communicate info through media rather than the printed word. Whenever possible, visual control are preferred over the written word becuase visual info is easier to understand and often requires just a glance to capture the information that is needed at the time
Cycle time#
Cycle time represents the total time it takes to process a person, order, part from the beginning of a process until the process is completed or delivered to the next stage of a larger process. It includes process time, during which is acted upon to bring it closer to an output and delay time, during which a unit of work is spent waiting to take the next actions.
This is an Important metric since one of the major objective of process design or redesign is to minimize the length of time of the overall process.