Failure Mode Analysis (FMEA)

FMEA is known as a risk assessment tool used to discover potential failures even in the design phase of a product. By applying this technique, teams can create a safe and functional product regarding customers’ requirements. The goal of the FMEA is to highlight the weak points of the product and process, which may cause serious issues after releasing it in production.

Exists two main types of FMEA:

  1. DFMEA – Design Failure Mode Analysis
  2. PFMEA – Process Failure Mode Analysis

Design Failure Mode Analysis DFMEA

The Design Potential FMEA supports the design process in reducing the risk of failures by:

  • Evaluating the initial design for manufacturing, assembly, service;
  • Assuring the potential failure modes and their effects have been considered in the design/development process;
  • Establishing a priority system for design improvements, development, and validation testing/ analysis;
  • Providing lessons learned for evaluating design changes and developing advanced designs.

The DFMEA is a living document and should:

  • Be initiated before or at design concept finalization
  • Be continually updated as changes occur
  • Be completed before the drawings are released for tooling

The DFMEA takes into consideration technical limits as:

  • Necessary mold drafts
  • Limited surface finish
  • Assembling space/ access for tooling
  • Limited hardenability of steels
  • Tolerances/process capability/performance

Process Failure Mode Analysis PFMEA

Purpose of the Process Potential FMEA:

  • Identifies the process functions and requirements;
  • Identifies potential product- and process-related failure modes;
  • Identifies process variables, which to control or to detect;
  • Develops a list of potential failure modes, establishing a system for preventive actions;
  • Assesses the effects of the potential failures on the costumer;

The PFMEA is a living document and should:

  • Initiated before or at the feasibility stage;
  • Before tooling for production;
  • Take into account all manufacturing operations, from individual components to assemblies;

The PFMEA assures the final product will meet the design intent.

In the next scheme, it can be observed the relationship between FMEA columns.

 In the beginning, it is quite difficult to make difference between Design and Process FMEA, so in the next example, we present some of the possible failure modes of a Headphone in the design and manufacturing phase.

undefinedIn the DFMEA, the focus lies on the end customer, which aspects could be unpleasant using the product, or how can the product lose some of the functions? As a customer, what are my expectations from this headphone? To be comfortable and lightweight to wear, easy to connect, high-quality sounds, durable material, adjustable and secure fit, etc.

On the other hand, in PFMEA, we are focusing on the process to create the desired product. How could each process fail, executing the product as described in DFMEA? Here we talk about equipment, or machine failure, resulting in injection marks, tolerance between parts, glue leaking, transparency of the plastic, etc. 

Take a look at the next table, where is listed some of the potential failure modes, of the Design and also Process FMEA.

Design FMEA-HeadphoneProcess FMEA- Headphone
Doesn’t fit every head size Holes position tolerance are big
Too heavy to wearCracks, marks, flow lines after injection
Uncomfortable to wearThe roughness of surfaces is big
Sound is not clearTolerance between components is small
Doesn’t stay fixedAdjusting mechanism breaks during the assembly
Material is too weakThe headband is deformed, thick, thin
The adjusting mechanism is blockedWire breaks during the assembly
Ear pad doesn’t cover the earsGlue leaking marks on ear pads
The surface material isn’t smoothEar pads are not fixed properly on the support

FMEA could have a different focus, so for this reason, we distinguish three main cases:

Case 1: New Design/ Technology/ Process. The scope of the FMEA, in this case, is to complete process, design, or technology.

Case 2: Modification of existing design or process. In this case, there is already on FMEA made for the existing process, design. The scope of the new FMEA should focus on modification and possible interactions with the design process.

Case 3: Use of existing design, or process in a new location, environment, application. Like in the second case, already exists an FMEA to use as a base point. The goal of the new one is the impact of the new environment on the existing design or process.

NOTE: Better the FMEA is made, more potential failure modes will be preventively detected and controlled, so the product could meet the customers’ expectations. With more potential failure modes remaining left out, it took more time, and money for the product launch, because of the appearance of unexpected problems.

The FMEA template is a complex document, therefore we dedicated to this topic two more articles, one for Design FMEA and the other one for Process FMEA.

Until then, you should familiarize yourself with the FMEA Template.

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