FMEA - Failure Modes And Effects Analysis

FMEA – Failure Modes And Effects Analysis

FMEA – Failure Modes And Effects Analysis is an analysis method used to determine potential failure modes and their causes. FEMA tool can analyze and evaluate various possible risks, and improve product design and production processes according to the magnitude of the risk.

What is FMEA?

FMEA is a preventive planning tool and its main purpose is to discover and evaluate potential failures and their consequences in the product/process; find measures that can avoid or reduce the occurrence of potential failures and continue to improve them. FEMA tool can be used so that

(1) The product or process can be modified easily and at low cost, thereby reducing the risk of post-modification.

(2) Find and implement measures that can avoid or reduce the occurrence of these potential failures.

FEMA’s working principle is:

(1) To identify potential failure modes and score the consequences of failure;

(2) Objectively evaluate the possibility of various causes, and when a certain cause occurs, the company can detect the possibility of the cause;

(3) Sort various potential product and process failures;

(4) Focus on eliminating problems in products and processes, and help prevent problems from recurring.

FMEA is subdivided into:

—-> DFMEA: Design FMEA

—-> PFMEA: Process FMEA

—-> EFMEA: Equipment FMEA

—-> SFMEA: System FMEA

Among them, design FMEA and process FMEA are the most commonly used.

What is DFMEA?

DFMEA refers to the analysis of potential failure modes in the design stage. Design FMEA (also denoted as DFMEA) is a means to control product quality prevention from the design stage. It is used as a control tool for how to meet product quality Because of the similarity characteristics of the same type of products, the DFMEA stage often draws on the advantages and disadvantages of the previous mass-produced or in-production products and evaluates the advantages and disadvantages of the products before making improvements and changes to the new products.

Therefore, although DFMEA does not rely on process control to overcome design defects, it can consider technical/objective constraints in the manufacturing/assembly process, thereby providing a good foundation for process control.

Performing DFMEA helps:

The trade-off between design requirements and design schemes;

Initial design of manufacturing and assembly requirements;

Improve the possibility of considering potential failure modes and their impact on systems and products during the design/development process;

Provide more information for the formulation of comprehensive and effective design test plans and development projects;

Establish a priority control system for improving design and development testing;

Provide references for future analysis and research on site conditions, evaluation of design changes, and development of more advanced designs.

What is PFMEA?

Process FMEA is analyzed in the unit of production process (for single and centralized process mode of process method, basic analysis can be performed in process method as the unit, and then called during process FMEA analysis.), generally before the preparation of production tooling. The process feasibility analysis stage begins or before, and all manufacturing processes from individual parts to assemblies must be considered. The objects of its evaluation and analysis are all new parts/processes, changed parts/processes, and original parts/processes with changes in application or environment.

It should be noted that although PFMEA does not rely on changing product design to overcome process defects, it must consider the product design characteristic parameters related to the planned assembly process in order to ensure that the product meets the user’s requirements and expectations to the greatest extent.

PFMEA generally includes the following:

Determine the potential failure modes of the process related to the product;

Evaluate the potential impact of the failure on users;

Determine the cause of failure in the potential manufacturing or assembly process, and determine the process control variables that reduce the occurrence of failures or find out the failure conditions;

Compile a classification table of potential failure modes and establish an optimal system for corrective actions;

Document the manufacturing or assembly process.

Preparation process of FMEA

Step 1: Determine the start time of FMEA preparation and establish a problem-solving team

The timing of FMEA preparation must be ahead of the specific data design and manufacturing engineering data; in terms of personnel composition, if the problem cannot be solved independently, notify the relevant personnel to form a team.

Step 2: Describe the problem

Explain to the team when, where, what may happen, severity, current state, how to deal with it urgently, and show photos and collected exhibits. The clearer the details, the faster the team will solve the problem.

Step 3: Implement temporary countermeasures

If the real cause has not been found, decide what method can be used to prevent the problem as quickly as possible for the time being? Such as full inspection, screening, automatic change to manual, inventory check, etc.

Step 4: Find out the real cause of the problem

When looking for the real cause of the problem, it is best not to blindly change the current state of production. First, observe, analyze, and compare. List all the production conditions you know (i.e fishbone diagram), observe one by one, and see which conditions change will cause the failure mode to occur? Fixtures, operators, suppliers, transporters, processes, dimensions, weights, voltage values, CPK, withstand voltage and other defects always have causes, and data analysis can often reveal clues. This kind of analysis can help you narrow the scope and get closer to the core of the problem. When the analysis is complete, list the items that you think are most likely, and then make some adjustments and changes one by one, and analyze the extent to which some changes can restore the quality to normal and affect the variation, and then find the real cause of the problem.

When looking for the real cause of the problem, pay attention to distinguish the direct cause from the root cause. Don’t just stay on the surface and direct causes of the problem, but do in-depth analysis of the root cause and initial cause of the problem. The root cause can be found by asking a few more “whys”.

Step 5: Choose a permanent countermeasure

After finding the main cause of the problem, you can begin to formulate countermeasures. There may be several countermeasures, such as repairing or updating molds. Try to list the pros and cons of the possible options. How much does it cost? How much manpower? How long can it last? Then make the best choice of possible methods, and confirm that such countermeasures will not produce other side effects.

Step Six: Implement and verify permanent countermeasures

When the permanent countermeasures are ready, you can start to implement and stop the temporary countermeasures. for example, the observation defect rate can be reduced from 4000PPM to 300PPM, and the CPK increased from 0.5 to 1.8. The downstream section and customers can fully accept it and no more problems will occur.

Step Seven: Prevent recurrence

For other similar productions, although no problems have occurred yet, synchronous improvements are needed to prevent recurrences. At the same time, such failures should also be included in the FMEA of the next product development section for verification.

Benefits of FMEA:

FMEA helps managers:

Identify potential failure patterns and severity of impact of these errors
Objectively assess the possibility of errors occurring
Assess the ability to detect errors
Categorize potential product or process defects that may occur
Focus on eliminating the causes of material errors

For manufacturers:

FMEA is truly a powerful tool for product design and improvement of product and process.

FMEA helps us to reduce design time and cost

Summary

FMEA management is an upgrade of quality management, which raises “continuous improvement” to “prevention in advance”. This requires relevant personnel to change their thinking and change the previous model of “solving problems when they occur” to “avoiding all risks before acting”. Not only that, the entire development process and development plan must also provide sufficient time and qualified personnel for the preparation of FMEA, so as to ensure that the operation of FMEA preparation is more practical and the real effect of FMEA is guaranteed.

FMEA – Failure Modes And Effects Analysis