Chapter 6

Chapter 6

Engineering Management Six Sigma Quality Engineering Week 6 Chapter 6 (Analyze Phase) Chapter 6 Outline Process Map Inputs characteristics Cause & Effect Fishbone Diagram (Minitab) C&E Matrix (Excel) FMEA Process Capablity Cpk Cp

Normality Analysis Detailed Process Map Example (Y's) Surface cleanliness - Removel of sand - Removal of rust - 'Defect free' UNCOATED FITTINGS PICKLE (Y's) Uniformity of flux No excess flux (removed by Drying Ov en) (x's) C Speed of chain / time in bath C Temperature of ly e bath C Make up of lye bath S Cleanliness of lye bath N Geometry of parts S Pendant style / orientation of work S Amount per pendant S Weight of product per minute put through bath

(Heat removal + heat pickup) S Time from shotblast N Humidity (x's) C Speed of chain S Temperature of tunnel N Geometry / Mas s of fittings N Humidity S Air velocity SHOTBLAST HANG ON PENDANTS STAND (x's) C Time C Shot size / mix of sizes N Humidity S Type / Material / Original size of grit N Effectiveness of seperator N Product geometry N Condition of machine N Dust arrestor condition

S Amount of work being shotblast C Time between pickle and shotblast N Operator (x's) C Time N Product geometry N Operator S Rocked / Not rocked S Method of packing (Y's) Dry castings Warm castings DRYING TUNNEL (Y's) Surface cleanliness (dust / rust free) Surface roughness RINSE (x's) C Make up of mix, Concentration and % of Hydrochloric Acid, Hydrofluoric Acid, Activol, Water C Pickling time

S Age of mix / SG N Quality of work / container N Containers / tank N Product geometry S Packing method N Operator S Shotblast prior to pickling LYE BATH (Y's) Acid free Debris removed (Y's) Coating Quality - Thickness of zinc / zinc alloy layers - Uniformity of cov erage - Total coverage - Appearance - Roughness / tex ture - Composition of c oating DIP IN ZINC BATH / BUMP (x's) S Quality of supplier / materials

C Temperature of zinc S Lev el of dross S Lev el of lead N Geometry / mass of fittings N Operator (Skimming surface / agitation of pendants) S Quality of pendants N Spec ifiacation (BS, ISO, EN) S Rate of withdrawal S Fluidity of zinc N Power of bumper unit (Y's) Zinc : Zinc Alloy thickness Appearance (brightnes s) Removal of ash (cleanliness) Fitting temperature WATER SPRAY COATED FITTINGS KNOCK OFF (x's) S Water volume N Water temperature C Speed of chain

N Mass / Geometry of fittings (Rate of cooling) (Y's) Appearance Smooth Finish RUMBLE (x's) C Time C Number of fittings per load N Geometry of fittings S Condition of rumbling barrel Characterising Inputs Inputs can be classified as one of three types Controllable (C) Things you can adjust or control during the process Speeds, feeds, temperatures, pressures. Standard Operating Procedures (S) Things you always do (in procedures or common sense things) Cleaning, safety.

Noise (N) Things you cannot control or don not want to control (too expensive or difficult) Ambient temperature, humidity, operator... Example Machining a shaft on a lathe C C C C C C C S C N N N S Inputs (xs) Rotation speed

Traverse speed Tool type Tool sharpness Shaft material Shaft length Material removal per cut Part cleanliness Coolant flow Operator Material variation Ambient temperature Coolant age Outputs (Ys) Diameter Taper Surface finish The Eight Steps in Cause and Effect Analysis Define the Effect Identify the Major Categories

Generate Ideas Evaluate Ideas Vote for the Most Likely Causes Rank the Causes Verify the Results Recommend Solutions Cause & Effect (Fishbone Diagram)

Objectives To understand the benefits of Cause & Effect Analysis To understand how to construct a C & E Diagram Analysis A method a work group can use to identify the possible causes of a problem A tool to identify the factors that contribute to a quality characteristic Uses of C & E (Fishbone Diagram) Visual means for tracing a problem to its causes Identifies all the possible causes of a problem and how they relate before deciding which ones to investigate C & E analysis is used as a starting point for investigating a problem C&E (Fishbone Diagram)

Effect The problem or quality characteristic The effect is the outcome of the factors that affect it Effect Causes (Fishbone Diagram) All the factors that could affect the problem or the quality characteristic Five Major Categories Materials Methods People Machines Environment Machine Environment

Effect Material Methods People Cause and Effect (Matrix) Benefit Gain new knowledge and perspectives by sharing ideas with others Helps us understand our processes Provides a basis for action Whenever a problem is discovered, using C&E analysis forces us to take a proactive stance by seeking out causes Rating of Importance to Customer 2 1

2 3 4 5 6 7 8 9 10 11 12 13 14

15 1 5 & 6 Total Process Step Process Input Lower Spec Target Upper Spec 0 0 0 0 0 0

0 0 0 0 0 0 0 Total 0 0 0 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0 0 0 0 0 0 3 1 2 3 4 5 6 7 8 9 10 11

12 13 14 15 16 17 18 19 20 4 C&E Matrix Instructions This table provides the initial input to the FMEA and experimentation. When each of the output variables (requirements) are not correct, that represents potential "EFFECTS". When each input variable is not correct, that represents "Failure Modes". 1. List the process output variables 2. Rate each output on a 1-to-10 scale to importance to the customer 3. List process input variables (from the process map) 4. Rate each input's relationship to each output variable using a 0, 1, 3, 9 scale 5. Select the high ranking input variables to start the FMEA process; Determine how each selected input variable can "go wrong" and place that in the Failure Mode column of the FMEA.

FMEA It is an approach to: Identify potential failure for a product or a process Estimate risks that are associated with causes Determine actions to reduce risks Evaluate product design validation plan Evaluate process current control plan FMEA types There are two types: Process: Will focus on Process Inputs Design: Will used to analyze product designs before they are released to production The use of the FMEA Improve

processes before failure occur (Proactive approach) Prioritize resources to ensure process improvement efforts are beneficial to customers Track and document completion of projects It is a living document. It will be updated and reviewed all the time Inputs & Outputs to FMEA Inputs Process Map C&E Matrix Process History Process technical procedures Outputs Actions list to prevent causes Actions list to detect failure modes Document history of actions taken FMEA step-by-step For each process input, determine the ways in which the input can go wrong- the failure modes. What can go wrong with input

Potential Causes What causes the input to go wrong? O C C How often does cause of FM occur? Potential Failure Effects What is the impact on the Output Variables (Customer Requirements) or internal requirements? How sever is the effect to the customer? Process Potential Failure Step/Input Mode

What is the In what ways does the process input go wrong? step/input under investigation? S E V FMEA step-by-step For each failure mode associated with the inputs, determine the effects of the failures on the customer. What the effect on outputs? Potential Causes What causes the input to go wrong? O C C

How often does cause of FM occur? Potential Failure Effects What is the impact on the Output Variables (Customer Requirements) or internal requirements? How sever is the effect to the customer? Process Potential Failure Step/Input Mode What is the In what ways does the process input go wrong? step/input under investigation? S

E V FMEA step-by-step Identify potential causes of each failure mode. What are The causes? Potential Causes What causes the input to go wrong? O C C How often does cause of FM occur? Potential Failure Effects What is the impact on the Output Variables (Customer Requirements) or internal

requirements? How sever is the effect to the customer? Process Potential Failure Step/Input Mode What is the In what ways does the process input go wrong? step/input under investigation? S E V FMEA step-by-step List the current controls for each cause or failure mode (Prevent/Detect). How are these Found or prevented?

Current Controls Prevent Detect What are the existing controls and procedures (inspection and test) that prevent/detect either the Cause or Failure Mode? Should include an SOP number. FMEA step-by-step Create Severity, Occurrence, and Detection rating scales. Severity of effect- importance of effect on customer requirements. It is a safety and other risks if failure occurs. 1= Not Severe, 10= Very Severe Occurrence of cause- frequency in which a give Cause occurs and creates Failure Mode. Can sometimes refer to the frequency of a failure mode. 1= Not Likely, 10= Very Likely FMEA step-by-step Create severity, Occurrence, and Detection rating

scales. Detection- ability to: Prevent the causes or failure mode from occurring or reduce their rate of occurrence Detect the cause and lead to corrective action Detect the failure mode 1= Likely to Detect, 10= Not Likely at all to Detect FMEA step-by-step Risk Priority Number: After rating we get the output on an FMEA Risk Priority Number. It is calculated as the product of Effects, Causes, and Controls RPN= Severity X Occurrence X Detection Effects Causes Controls FMEA step-by-step Dynamics of the Risk Priority Number: The team defines the rating scales 1-10 for the

severity, Occurrence, and Detection ratings. The team choose the levels and numbers: How severe is it: Not Severe =1 Somewhat =3 Moderately =5 Very Severe = 10 FMEA step-by-step Dynamics of the Risk Priority Number: The team defines the rating scales 1-10 for the severity, Occurrence, and Detection ratings. The team choose the levels and numbers: How often does it Occur? Never/rarely =1 Sometimes =3 Half the time =5 Always = 10

FMEA step-by-step Dynamics of the Risk Priority Number: The team defines the rating scales 1-10 for the severity, Occurrence, and Detection ratings. The team choose the levels and numbers: How well can you detect it? Always =1 Sometimes =3 Half the time =5 Never = 10 FMEA step-by-step Determine recommended actions to reduce high RPNs: What can be done? How well can you detect cause or FM?

D E T R P N Actions Recommended Responsible Actions Taken What are the Who is What are the actions for responsible for the completed actions reducing the recommended taken with the occurrence of the action? recalculated RPN? Cause, or Be sure to improving

include detection? Should completion have actions only month/year. on high RPNs or easy fixes. S E V O C C D E T R P N FMEA step-by-step Take

appropriate actions and recalculate RPNs Assign responsible Parties How well can you detect cause or FM? D E T R P N Actions Recommended Responsible Actions Taken What are the Who is What are the actions for responsible for the completed actions reducing the recommended taken with the

occurrence of the action? recalculated RPN? Cause, or Be sure to improving include detection? Should completion have actions only month/year. on high RPNs or easy fixes. S E V O C C D E T R

P N Process Capability Study Cpk & Cp Cpk incorporates information about both the process spread and the process mean, so it is a measure of how the process is actually performing. Cp relates how the process is performing to how it should be performing. Cp does not consider the location of the process mean, so it tells you what capability your process could achieve if centered. Process Capability Study Non-normal distributions Use Capability Analysis (Nonnormal) to assess the capability of an in-control process when the data are from the nonnormal distribution. A capable process is able to produce products or services that meet specifications. The process must be in control and follows a nonnormal distribution before you assess capability. If the process is not in control, then the capability estimates will be incorrect. Nonnormal capability analysis consists of a capability histogram and a table of process capability statistics Questions? Comments?

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