What is the key difference between Prevention and Detection Control (FMEA)?

The biggest difference between money and time: You always know how much money you have but you never know how much time you have: Unknown

Introduction

If annual health checkup is a preventive or detective control? I think both! As it helps the person to detect if there is an ailment at the moment (Sugar, Fatty Acid etc.) and it also helps to know that how is my cholesterol and other parameters in comparison to previous years. If they are slowly inching towards the borderline, it is a time to take preventive action like yoga, morning walk, Ayurveda etc.   

Objective

The FMEA is a deep dive analysis process of identifying possible internal and external failures. When the organization could identify the criticality of the possible failure, it becomes easy to define its existing and possible prevention and detection controls.

The objective of the process controls is to control the process either by the preventive control, to the extent possible, the cause of failure (FC) from occurring or detect the failure cause (FC) or mode (FM), should it occur.  

The preferred approach is to use preventive controls which will result in the reduction of the occurrence rating when prevention is integrated as part of the process. SPC (Statistical Process Control- AIAG 2nd Edition) is one such preventive control.

Definitions

Prevention: Eliminate (prevent) the Failure Cause (FC) or the Failure Mode (FM) from occurring or reduce its rate of occurrence.

Detection: Identify (detect) the Failure Cause (FC) or the Failure Mode (FM) leading to the development of associated corrective actions.

Detailed Information

FMEA (Failure Mode & Effect Analysis) is a team-oriented, systematic, qualitative and analytical method to identify, analyze and mitigate the technical risks related to the ‘product and manufacturing process design.

The FMEA is the ‘Before the Event’ and not the ‘After the Event’ exercise.

Failure Chain:

  • Failure Modes (FM): It means the ways, or modes, in which something might fail.
  • Failure Effect (FE): It refers to studying the consequences of those failures’ mode.
  • Failure Cause (FC): A indication of why failure mode could occur

Risk Analysis:

  • Severity (S): Severity of the Failure Effect (FE)
  • Occurrence (O): Occurrence of the Failure Cause (FC)
  • Detection (D): Detection of the Failure Cause (FE) and/or Mode (FM)

Current Preventive Controls:

Prevention Type Design Control: describe how a cause, failure mode, or effect in the product design is prevented based on current or planned actions; they are intended to reduce the likelihood that the problem will occur and are used as input to the occurrence ranking.

  1. Should consider the margin of safety in the design
  2. System design according to the simulation
  3. Technical specifications in the drawing (Heat Treatment, sensor performance)
  4. Error proofing

 

Prevention Type Process Controls: describe how a cause, failure mode or effect in the manufacturing or assembly process is prevented, based on current or planned actions. They are intended to reduce the likelihood that the problem will occur and are used as input to the occurrence ranking.

  1. Process Planning: Optimal process planning to minimize the possibility of failure occurrence like the adequate layout in the production facility.
  2. Production Process: For an organization to effectively implement current preventive controls, the focus and action starts during the new development process and are verified for their effectiveness during

Some of the key examples to reduce or avoid the failure cause (FC) or its occurrence includes

  • 2 Hand operation of the machine for Safety
  • Poka-Yoke (Fool proofing/Error Proofing)
  • Periodic Equipment maintenance (Preventive/Predictive)
  • Operator skill up-gradation (Training-on the job/classroom)
  • Work instruction with pictures and less content (language and access)
  • Process Control (Job setup, periodic monitoring, SPC)
  • Job set up verification (4M- every shift, tool change, operator change, Alternate machine)

 

Current Detection Controls: It detects the existence of a failure cause (FC) or the failure mode (FM) either by automated or manual methods before the product leaves a particular process or it is despatched to the customer or is released for production. The current detection controls should be clearly and comprehensively described.

Detection Type Design Controls: describe how a failure mode or cause in the product design is detected, based on current or planned actions, before the product design is released to production, and are used as input to the detection ranking. Detection controls are intended to increase the likelihood that the problem will be detected before it reaches the end-user.

  • Functional check
  • Tests like Burst, environmental, endurance
  • Design of Experiment (DOE)

Detection Type Process Controls: describe how a failure mode or cause in the manufacturing or assembly process is detected, based on current or planned action, before the item is shipped from the manufacturing or assembly plant, and are used as an input to the detection ranking.

  • Visual Inspection (Checklist, sequence)
  • Optical inspection with the camera (Product/Component, Master/Limit sample)
  • Attribute inspection (Gauge, fixture, jig)
  • Dimension check (Micrometer, Vernier, CMM, Roughness tester, coating thickness)
  • In-process/Final inspection (as per schedule like 2 hours/every shift)
  • End of line Testing (Fitment, key characteristics)

The effectiveness of the current preventive and detection control should be confirmed.

If the FMEA team wishes to add, modify or delete design or process controls they should use the recommended action column.

If no prevention or detection controls are applicable for a given failure mode/cause, the FMEA team should leave the corresponding column blank.

Example:

Design FMEA Controls:

Item: Power Steering Pump

Function Delivers hydraulic power for steering by transforming oil pressure at inlet [xx] Bar) into higher oil pressure at outlet ([yy] Bar) during engine idle speed
Failure Mode Inadequate outlet pressure (less than [yy] Bar)
Failure Effect Local (Pump): Low-pressure fluid goes to the steering gear
Next Level (Steering Subsystem): Increased friction at the steering gear
End-user: Increased steering effort with a potential accident during steering movement
Failure Cause Fluid incorrectly specified (Low viscosity)
Prevention Control  Design guidelines for hydraulic fluid selection (Viscosity & Grade)
Detection Control Vehicle Durability Test #ABC

 

Process FMEA Controls:

Process Step: Induction Hardening of the Shaft

Function Induction harden shaft using the induction-hardening machine, with minimum hardness Brinell Hardness Number (BHN) “X”, according to specification #ABC.
Failure Mode Shaft hardness less than BHN “X”
Failure Effect Local (In-Plant): 100% scrap
Customer End: May crack during assembly
End-user: Potential shaft fracture with complete loss of performance
Failure Cause Induction machine electrical voltage/current settings incorrect
Prevention Control Shaft hardening: Job setup verification as per procedure
Detection Control In-process inspection of the shaft hardness

Present Challenges

  • How often the documented preventive and detection controls in the FMEA are similar to what is implemented on the shop floor?
  • How often do the organizations review their existing preventive and detection controls when in-process or final rejection is more than target?
  • How often do the organizations review the effectiveness of existing prevention and detection controls when they receive the customer complaint/warranty/recall?

References:

IATF 16949: 2016

FMEA Handbook (AIAG-VDA 1st Edition June 2019)

Industry Experts

 

This is the 122nd article of this Quality Management series. Every weekend, you will find useful information that will make your Management System journey Productive. Please share it with your colleagues too.

In the words of Albert Einstein, “The important thing is never to stop questioning.” I invite you to ask anything about the above subject. Questions and answers are the lifeblood of learning, and we are all learning. I will answer all questions to the best of my ability and promise to keep personal information confidential.

Your genuine feedback and response are extremely valuable. Please suggest topics for the coming weeks.

 

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