A Guide To Vibration Analysis

Vibration analysis allows technicians to detect abnormal vibrational patterns within machines and solve issues to prevent further damage. Vibrational monitoring, calculations and formulas help technicians identify the root causes of high vibrations in precision machine tools, allowing them to perform preventive maintenance and restore machines to proper operational performance.

A guide to vibration analysis can help you understand how the process works and the type of results you can expect. This type of analysis reveals conditions such as misalignment, imbalance, poor lubrication, bearing failures, pump cavitation, critical speeds, loose components and gearbox failures.

What Is Vibration Analysis?

Vibration analysis is an essential part of predictive and preventive maintenance because vibrations can damage machinery and hinder operations. Vibration analysis allows professionals to monitor tools and machines and use vibration data to detect potential complications. This process measures a machine’s vibration frequencies and levels, providing data about the machine and its components’ health.

Vibration Analysis Tools

Vibration monitoring and analysis tools gather vibration data without interfering with normal machine operation. A machine’s components create vibrations while it operates, and an attached accelerometer measures the vibrations. The accelerometer produces a voltage signal corresponding to the machine’s vibration amount and frequency.

An accelerometer is the most common vibration data collection tool, but another tool is also available. Laser sensors use advanced technology to detect even more vibrations than accelerometers. These high-speed sensors make no contact with machines, and they can collect more accurate data, allowing technicians to use more methodology in their analysis.

Vibration Analysis Explained

Vibration can significantly affect a machine’s inner components and operation. Vibration analysis detects problematic vibrational patterns, and professionals use it to determine necessary maintenance and repairs.

Technicians perform vibration analysis by calculating various vibration forms with complex formulas while monitoring a machine’s inner components and operations. An accelerometer typically measures how many vibrations a machine produces per minute or second. Professionals can evaluate vibration in the following forms:

  • Velocity: Velocity refers to movement speed.
  • Displacement: Displacement is the distance a measuring point moves.
  • Acceleration: Acceleration is how rapidly movement speed changes.

After an accelerometer or laser sensor measures a machine’s vibrations, it sends the data to data collector software. This software can record the signals in the following ways:

  • Time waveform: Time waveform measures a signal as amplitude versus time.
  • Fourier waveform: Fourier waveform measures a signal as amplitude versus frequency. This is also referred to as a spectrum.

Computer program algorithms analyze collected vibration data. Experienced vibration analysts or engineers further analyze the collected data to evaluate a machine’s condition.

What Does Vibration Analysis Detect?

Vibration analysts can use vibration measurements and data to identify and repair the following complications:

  • Imbalance
  • Bent shafts
  • Misalignment
  • Critical speeds
  • Bearing failures
  • Poor lubrication
  • Gearbox failures
  • Loose components
  • Electrical motor faults
  • Natural frequencies and resonance
  • Pump cavitation, such as bubbles or excess space

Vibration Analysis Principles

The principles of vibration analysis provide essential information about a machine’s vibrating parts and operating conditions. Basic vibration analysis principles consist of the following:

Time Domain

The time domain is amplitude versus time. Waveforms are vibration signals in the time domain.

Frequency Domain

Frequency versus amplitude is a spectrum inside the frequency domain. This spectrum appears when a waveform is subject to spectrum analysis. The frequency domain is common for in-depth analysis.

Modal Analysis

Modal analysis places a machine’s measured frequency response functions into a computer model. The model can then show various vibration modes through animations. Professionals can also adjust the model to add or remove factors such as stiffness or mass to evaluate results.

Joint Domain

The Gabor-Wigner-Wavelet technique is a joint time technique. This technique calculates variations of fast Fourier transform (FFT). Calculating more than one vibration spectrum at a time is beneficial because vibrations can change with time.

Vibration Analysis Forms

Professionals can use various algorithms, calculations and analysis forms to evaluate the following vibration analysis aspects:

Time Waveform and Fast Fourier Transform (FFT)

Time waveforms measure time versus acceleration and show raw vibration in a short time sample. A time waveform reveals information about a machine’s condition that frequency doesn’t reveal.

The FFT algorithm uses time waveforms to calculate spectrums. It breaks signals down into all their frequencies and can convert a time-domain signal into a frequency domain. Technicians often use FFT to detect imbalance or misalignment.

Order Analysis

Order analysis is another type of FFT, and professionals often use it to quantify machine vibrations with various revolutions per minute (RPM). While frequency analysis expresses the frequency axis in orders of hertz, order analysis expresses the axis in orders of RPM.

Phase Measurement

A phase measurement measures two signals in units of angle instead of time. The signals must have the same frequency. Professionals can use phase measurement with FFT to identify imbalance, loose components and misalignment.

Power Spectral Density

Professionals calculate power spectral density (PSD) by multiplying the FFT’s amplitude by its various forms. This calculation normalizes the FFT with the frequency bin width. PSD evaluates random vibrations at several different frequencies and signal lengths.


Professionals can measure orbit by placing two probes 90 degrees apart in a journal’s bearing house. They can then display the resulting data digitally and use it to detect shaft vibrations and determine if oil whirling is moving the journal.

Envelope Analysis

Envelope analysis detects low-energy impacts that other vibration signals typically hide. Professionals use this analysis method to detect damaged roller bearings and gear teeth.

Resonance Analysis

Resonance in a machine indicates high vibration that could result in damage. Resonance analysis measures a machine’s natural frequencies and vibrations to detect if vibrations could reach damaging levels.

Trust Setco With Your Machine Repairs

Vibration analysis is vital for preventive maintenance of machines and machine tools. High vibrations can affect various components, and vibration analysis detects potential complications before they cause further damage.

Technicians use various vibration analysis monitors, calculations and formulas to identify complications such as poor lubrication, misalignment, imbalanced components, loose parts, bent shafts, electrical motor faults and problematic speeds. Detecting these complications before they cause further damage helps them last longer and work properly.

Setco offers precision repair services to keep machines operating with top performance. Setco is a leader in the machine tooling industry, and we are dedicated to providing the highest quality services and products. Our trained technicians inspect and repair spindles, milling heads and slides to restore them to exact specifications. Contact us to learn more about our high-quality repair services and how we can restore your precision machine tools to their highest operation.

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