DMAIC roadmap

Define, Measure, Analyze, Improve, and Control (DMAIC) is a data-driven quality strategy used to improve processes. The letters in the acronym represent the five phases that make up the process.

 

Feel free to refer to and download the infographic below for the DMAIC process steps.

 

If you want more such resources on Lean Six Sigma, Keep following this blog.

 

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Basic notes about variations

Three types of variation : 

1.within a piece

2. piece to piece

3. time to time

variations wrt to process:

Continuous and batch process

Sources of variation :

1. equip.

2. matl.

3. environment

4. operation

Sources of Variation in Production and services process :

Common causes :

Random causes that we cannot identify

Unavoidable

Cause slight difference in process variable like dia, weight, service time, temp. etc.

Assignable causes of variation :

Causes can b identified and eliminated

Typ. causes are poor employee training, worn tool, machines needing repair etc.

Basic principles :

A process that is operating with only Chance causes of variation present is said to be in statistical control.

A process that is operating in the presence of assignable causes is said to be out of control.

The eventual goal of SPC is the elimination of variability.

)_________

Types of control charts :

1 Variable Control charts: This applies to data that follows a continuous distribution

2.Attributes control charts: These charts are applied to data that follow a discrete distribution.

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Process Capability analysis and Baselining

In the Measure phase, we are learning about Process Stability, Process is Capable or not, and finally Baselining.

Baselining: Discrete data:

Unit:  It is an item being processed. for example, a drawing, application, Request for Service.

Opportunity: is any event/characteristic/attribute that is essential and measured from a customer's perspective. It provides a chance of not meeting a customer's requirement.

for example each of the 10 attributes on the trade draft form.

Defect: is an event of non-conformity to the customer requirements. for example, any of the 10 attributes incorrectly drafted.

Defective: is a Unit with one or more defects. for example, a Trade draft with one or more of the 10 key attributes incorrectly drafted. 20% defectives if 20 out of 100 Trades had at least one defect (at least 1 key attribute incorrectly drafted)

example 1

example 2

DPU = 18/1000 = 0.018 (1.8%)

DPO = 18/(1000 x 5) = 0.0036

DPMO = 0.0036 x 10,00,000 =  3600

Sigma level = 4.15

example 3

Say, 500 opportunities, # of Defect oppurtunies per unit= 2, Defetcs = 20.

DPU = 20/500= 0.04 (4%)

DPO = 20/(500 x 2) = 0.02

DPMO = 0.02 x 10,00,000 =  20,000

Sigma level = 3.55

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Baselining: Continuous data:

Voice of Customer defines Specification limits (LSL, USL)

Voice of Process defines Control limits (LCL, UCL)

Process Capability (Cp) is a statistical measurement of a process’s ability to produce parts to the tolerance range. 

Reducing variation in the process is the most desirable way of improving Process Capability.

Cp= Tolerance range / Process Spread

Cp = (USL - LSL) / 6 Std.Dev.

Cp = (33 - 27) / 6 = 1.0

If the data is Stable and Normal. We do Capability analysis.

Process Capability (Cpk) is a statistical measurement of a process’s ability to meet the target (center), or in other words, it describes how well the process mean is close to the specification target.

Cpk = Minimum (CpU , CpL)

example1

CpU = (USL - mean)/ 3 Std. dev.

CpU = (33-33) / 3 = 0

CpL = (mean - LSL)/ 3 Std. Dev.

CpL = (33-27)/3 = 2

Cpk = Minimum (0,2) 

Cpk =  0

example2

CpU = (USL - mean)/ 3 Std. dev.

CpU = (33-33) / 6 = 0

CpL = (mean - LSL)/ 3 Std. Dev.

CpL = (33-27)/6 = 1

Cpk = Minimum (0,1) 

Cpk =  0

So, Finally

Ppk is used to assess the long-term, overall variability, whereas

Cpk is the capability index for short-term, potential variability.

The higher the Cp and Cpk values are, the better the process

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Six Sigma Project Identification and Selection

 This is my first post on the blog. I have started this blog with an intention of keeping all my learnings of Six Sigma in one place and I expect no financial benefits out of it. So, if you are reading this blog. I welcome you and request you to read my posts and give your valuable comments too.

PROJECT IDENTIFICATION & SELECTION

Since Six Sigma's whole purpose is to improve performance, the first step in the Define phase of the

D-M-A-I-C cycle is to identify what to work on - a project. That selection is based on an evaluation of

three characteristics. 

1. Project Payoff analysis tells us whether the project is worth doing. 
2. Project Scope tells us whether the project can be done. 
3. Project Alignment tells us whether the project is consistent with the overall mission of the business.

1. Project Pay- off analysis can be done using Cost-Benefit Analysis:

• Calculate the cost involved to complete the project

• Calculate the Benefits Expected out of the project

Cost Benefit Analysis = (Cost / Benefit)

2 & 3. Use the below matrix (the parameters can be added or removed as per your choice).

To find these, you can take the help of the Project Selection matrix as shown below, Where you can rate the project you are thinking of taking up.

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Generally, there are two types of Six Sigma projects :

Methods to Identify a Six Sigma Project are :

1. VOC (Voice of Customer)

• What do my customers complain about most frequently?

• Queries

2. Lean tool - VSM

• Which process does not add value, but we still do it?

• Which process is always broken?

3. COQ (Cost of Quality)

• Rework

4. Trend Analysis

• Processes where Quality, Productivity & cost on –ve trend

• Look for variation in the process

5. BenchMarking

• How our peers (Internally/External) are performing the process?

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