OutLine Design for X
•Trade-offs in Satisfaction
•Robust design
•Failure Modes & Effects Analysis
•Tolerance design
Customer
Needs
(CN)
Functional
Requirements
(FR)
Design
Parameters
(DP)
Process
Variables
(PV)
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Robust Design - Engineering Design and Analysis - Lecture Slides, Slides of Engineering Drawing and Graphics
These are the Letcure Slides of Engineering Design and Analysis which includes Need for Physical Testing, Acceptable Appearance, Tolerance Analysis, Interference Analysis, Product Function, Stable and Repeatable, Realistic Chance, Proof of Concept etc.Key important points are: Robust Design, Failure Modes and Effects Analysis, Tolerance Design, Functional Requirements, Design for Robustness, Probabilistic Optimal Design, Statistics and Probability Theory
Typology: Slides
2012/2013
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OutLine Design for X
• Trade-offs in Satisfaction
• Robust design
• Failure Modes & Effects Analysis
• Tolerance design
Customer Needs (CN)
Functional Requirements (FR)
Design Parameters (DP)
Process Variables (PV)
Basic Design Engineering Goals
- Design Engineering Goals for Product:
- “performs as expected”
- “works all the time” & “lasts long”
- “is easy to maintain”
- and THAT
- no damage occurs to product
- no damage or harm to environment
- no harm or injury to operator or user
Design for Robustness
- Methods to reduce the sensitivity of product performance to variations such as: - manufacturing (materials & processes) - wear - operating environment
- Currently used methods
- Taguchi Method
- Probabilistic optimal design (Monte Carlo)
- Both Taguchi and Monte Carlo methods use statistics and probability theory
Failure Modes & Effects Analysis
- The FMEA Method seeks to systematically identify and correct potential product or process deficiencies before they occur
- The Process
- Identify EVERY Way in Which Product Can FAIL; i.e., determine the Failure MODES
- Analyze the CONSEQUENCES of Every Failure; i.e., determine the EFFECTS
FMEA Example Log Splitter
- FMEA considers Both DESIGN and MANUFACTURING Deficiencies
- Example Hydraulic Log Splitter
- Hydraulic hose, on a home-use log splitter, begins to leak.
- The leak reduces the pressure to the piston/ram resulting in poor splitting.
- The leak drips oil on ground, creating a mess, costly too!
- Upon examination, a weak spot is found on hose due to poor manufacturing!
FMEA Main Concepts
- Failure Mode : the “way” a part fails to perform
- e.g. failure mode: hose leaks
- Effect : adverse consequence of failure mode
- e.g. hose leak results in oil spills, refill costs
- Effects can be severe or hardly noticeable.
- Cause : why it fails (or may fail)
- e.g. poor hose manufacturing, improper pressure
- Causes occur with some likelihood or probability
- Dectectability : the ability to discover the cause before the part is shipped from the factory. - e.g. conduct a pressure test to detect leaks?
RPN Calculation
- Step 1: determine the failure modes
- From:
- Engineering design specifications
- Function decomposition diagrams
- functions ---- matter, energy, signal
- HoQ
- free body diagrams
- force flow diagrams
- process flow diagrams
- configuration sketches / drawings
- From:
RPN Calculation
- Step 2: determine potential effects of each failure mode
- Step 3: determine a severity ( S ) rating for each effect from the Severity rating table.
- Step 4: determine an occurrence ( O ) rating for each cause from the Occurrence rating table.
- Step 5: determine a detection ( D ) rating for each cause from the Detection rating table
Occurrence Rating Criteria
Occurence (O) Rating Likelihood Description (^10) Expected >30 % > One per day 9 Very likely 30 % (3 per 10) 8 Probable 5 % (5 per 100) One per week (^7) Occasional 1 % ( 1 per 100) One per month 6 More plausible 0.3 % (3 per 1,000) One per three months 5 Plausible 4 Remote 0.006 % (6 per 10^5 ) One per year 3 Unlikely 0.00006 % (6 per 10^7 ) One per three years 2 Very unlikely (^1) Improbable < 2 per 10^9 events > five years per failure
Detection Rating Criteria
Detection (D) Rating Detectability Description 10 Impossible Impossible to detect, or no inspection 9 Very rare 8 Rare 7 Possible Some chance of detecting, or 50% inspection 6 Quite possible 5 Somewhat likely 4 Likely Quite likely to detect, or 75% inspection 3 Quite likely 2 Almost certain (^1) Certain Will be detected, or 100% inspection
RPN Calculation Summary
- RPN Calculations are Usually Tabulated or put in a SpreadSheet
Severity (S) Occurrence (O) Detection (D)
Failure mode Effects
S Rating Causes
O Rating
controls tests
D Rating RPN
Recommended Action
RPN Example Hose Failure
- Log-Splitter RPN & Remediation Severity (S) Occurrence (O) Detection (D)
Failure mode Effects S Rating Causes O Rating controls tests D Rating RPN Recommended Action hydraulic hose leaks
poor log splitting oil mess costs to refill
7 (harmful) weak spot 7 (1%) none 10 490 implement pressure test
Define Safe Product/System
- No injury to user, (products liability)
- No injury to consumer/society
- No injury to production worker
- No damage to personal property
- No damage to real property or the environment
Hazards
- Hazard ≡ a source of danger which has the potential to injure people or damage property or the environment
- Partial Hazard List
- Entrapment – pinch, crush
- Contact – heat, sharp edges, electric
- Impact – hammer, robot arm
- Ejection – grinder sparks, saw dust
- Entanglement – hair, clothing
- Noise & Vibration – hearing loss, HAVS