FMEA Pitfalls and Limitations

Pitfall 1:  Prioritizes, Doesn’t Correct

• The initial output of an FMEA is the prioritizing of failure modes based on their risk priority numbers.
• This alone does not eliminate the failure mode. Additional action that might be outside the FMEA is needed.

Pitfall 2 Only as Good as the Team

• Identifying failure modes is a team brainstorming activity.
• If the team forgets to list it, an important failure mode could be left alone, waiting to occur.

Pitfall 3 Time Consuming

• It takes time to get into the details.

Pitfall 4 Unknown Unknowns

• Might miss a failure mode or an effect outside the experiences of the company.

Pitfall 5 Not Customizing Rating Scales

• Rating scales should be meaningful to everyone in the organization.
• The generic rating scales might be confusing to some teams.
• Management will not be able to compare RPNs in order to prioritize activities between teams.

Pitfall 6 Not Starting in the Design Stage

• The earlier in the design process an FMEA is started, the better.
• A DFMEA can catch where design verification is needed.

Pitfall 7 Taking on Too Large a Scope

• Taking on an entire process may be a daunting task.
• Break a large process down into manageable chunks.

Pitfall 8 Not Including Operators

• Experienced operators should be on the team to add their perspective.
• They often have good information on failure modes and on the effectiveness of control systems.
• They might have information on occurrence as well.

Pitfall 9 Not Including Customers

• Customers, especially end-users, often have a better view on failure modes than internal personnel.

Pitfall 10 Not Including Suppliers

• Suppliers also bring an outside perspective to the team.
• Might be able to tie your process in with theirs.

Pitfall 11 Becoming a Full-Time Job

• Sometimes people use an FMEA as an excuse to get out of doing their regular job.
• You can’t afford to have people who are just conducting FMEAs.
• Won’t get their regular work done.
• Even if FMEAs are made their “regular” work, they will lose touch with the process and the FMEA will become mere paperwork.

Pitfall 12 Not Using Concept of a Process

• This will cause the team to forget some failure modes.
• The team should brainstorm failure modes in each of People, Methods, Equipment, Materials, and Environment.

Pitfall 13 Not Getting into the Details

• A superficial look at the process will miss many failure modes.

Pitfall 14 Forgetting there are Internal- and External-Related Failure Modes

• Many FMEAs focus only on the customer requirements (specifications).
• Sometimes internal productivity losses, equipment damage, scrap, and rework have very severe effects on the company.

Pitfall 15 Confusing Root Cause and Failure Mode

• Teams often have root causes as failure modes.
• A failure mode is the failure to perform the intended function.

Pitfall 16 Not Looking at Each Product

• Templates are great but every product being made in a process is not exactly the same.
• The template should be used as a starting point and each product should be evaluated:
  • Could this failure mode occur with this product?
  • Would this effect occur?
  • Is this the correct root cause?
  • Are these controls applicable?
  • Should any of the three ratings be changed?

Pitfall 17 Assuming Detection Controls Are Better Than They Are

• Some controls are not as good as they are perceived to be:
• High repeatability and reproducibility.
• Don’t test for what we think they test for.
• Only test part of the product.

Pitfall 18 Assuming Detection Controls Apply When They Don’t

• A control might apply to one effect of a failure mode but not another.
• For example, final inspection is a control against a defect impacting a customer, but it may not be a control against rework or scrap.

Pitfall 19 Not Linking with Mistake-Proofing

• FMEA is a prioritization tool. It doesn’t eliminate failure modes or effects by itself.
• Companies need to apply tools such as mistake-proofing to eliminate the root causes of failure modes.
• This is especially true with failure modes that have very severe effects.

Pitfall 20 Not Tying into Control Plans

• The control plan tells people how to react when a failure mode occurs.
• The FMEA will not be a living document if it is not tied to the control plan.

Pitfall 21 Failing to Update the FMEA

• As new potential failure modes are identified, they should be added to the FMEA and control plans developed for them.
• It is critical that the template also be updated.