Fishbone Analysis for Maintenance: Turning Causes into Corrective Work

Fishbone analysis is useful when a maintenance team knows a failure is repeating but does not yet know why.

The method is also called Ishikawa analysis or cause-and-effect analysis. It helps teams organize possible causes before jumping to conclusions.

For maintenance teams, the value is simple: stop guessing, structure the discussion, verify the causes, and turn findings into corrective work.

When to use fishbone analysis

Fishbone analysis is useful for problems such as:

• Repeated bearing failures
• Frequent motor trips
• Conveyor belt misalignment
• Pump seal failures
• Hydraulic leaks
• Compressor overheating
• Poor lubrication discipline
• Sensor drift
• Quality defects linked to equipment condition
• Breakdowns that return after every repair

It is not needed for every small issue. Use it when the cost of recurrence is high or when the team keeps fixing symptoms.

The basic fishbone structure

The problem is placed at the head of the fish. Possible causes are grouped into categories.

Common maintenance categories include:

• Machine
• Method
• Manpower
• Material
• Measurement
• Environment
• Maintenance system

Each category helps the team explore different causes instead of blaming the technician or replacing parts repeatedly.

Example problem

Problem statement:

Packaging conveyor stops repeatedly during second shift.

Possible causes may include:

• Machine: worn rollers, misaligned belt, weak motor, damaged sensor
• Method: cleaning procedure skipped, tension setting not standardized
• Manpower: operators not trained to identify early belt tracking issues
• Material: cartons are damp or inconsistent in size
• Measurement: no record of motor current, stop frequency, or sensor faults
• Environment: dust buildup near photo sensors
• Maintenance system: PM checklist does not include belt tracking inspection

This structure keeps the conversation broader and more disciplined.

Evidence matters

A fishbone diagram is not proof. It is a list of possible causes.

The team still needs evidence:

• Work order history
• Breakdown timestamps
• Photos
• Technician remarks
• Operator observations
• Spare part replacement history
• Meter readings
• Inspection results
• Trend data
• Production conditions when failure happened

This is where a work order management software and asset history become important. Without records, fishbone analysis becomes opinion-based.

Ask better questions

Good fishbone analysis depends on the quality of questions.

Instead of asking:

Why did the motor fail?

Ask:

What changed before the failure?
Was the load higher than normal?
Was the same spare replaced before?
Was the PM completed as planned?
Was the alignment checked?
Was there an abnormal reading?
Did the issue happen after cleaning, changeover, or startup?

These questions move the team closer to practical causes.

Convert causes into actions

The most common failure of fishbone analysis is stopping at the diagram.

Every validated cause should become an action.

Examples:

• Update the PM checklist
• Add an inspection point
• Replace a weak component with the correct specification
• Train operators on early signs
• Add a reading or photo requirement
• Improve lubrication frequency
• Correct an installation method
• Create a follow-up work order
• Review spare part quality

A breakdown maintenance software process should connect the analysis to actual corrective work.

What to avoid

Avoid these mistakes:

• Listing causes without evidence
• Blaming people too quickly
• Treating all causes as equal
• Not assigning owners
• Not setting due dates
• Closing the analysis without verifying results
• Failing to update PMs or SOPs
• Not checking whether the failure returns

Root cause analysis is only useful when it changes future behavior.

Bottom line

Fishbone analysis helps maintenance teams organize possible causes of repeat failures. But the diagram is only the beginning.

The real value comes when teams use evidence, validate causes, assign corrective actions, update PMs, and track whether the same problem returns.

MaintBoard supports this by connecting breakdowns, asset history, work orders, inspections, preventive maintenance, corrective actions, and reports in one maintenance workflow.