How to Calculate the Required Excitation Force for a Vibration Shaker

• Vibration shakers are generally not designed for continuous operation at maximum excitation force.
  Operating at or near maximum excitation force significantly increases the risk of system instability and component failure. In practical testing, vibration levels are typically limited to approximately 60% of the shaker’s maximum excitation force, while factory shipment settings are usually configured to 85% of the rated maximum force.

When the calculated required excitation force is close to the shaker’s maximum force rating, a safety factor of 1.2 may be applied for system selection. A safety factor of 1.3 provides sufficient performance margin, whereas long-term operation with a safety factor below 1.2 may negatively affect the service life of the vibration shaker.

• Displacement is commonly specified in inches.
  One inch of displacement is approximately 25 mm. The most commonly used displacement ratings are 2 inches (51 mm) and 3 inches (76 mm).
  For example, if the required displacement is 40 mm, selecting a 2-inch (51 mm) displacement shaker is generally sufficient.

• When calculating the required force for configurations using a horizontal slip table, the total moving mass must include the weight of the slip table bearing adapter.
  This is because the vibration shaker is rotated from a vertical configuration to a horizontal configuration, and an additional bearing and connection assembly is installed between the shaker armature and the slip table.
  Therefore, the mass of the bearing adapter must be included in the total load calculation (as illustrated in the diagram showing the vertical-to-horizontal shaker conversion).

Calculation Example:

1. Test Requirements & Parameters

• Specimen Weight: 40 kg
• Specimen dimensions: 800mm*800mm (L*W)
• Fixture/Expanders: 800 mm Square Vertical Shaker Table (70 kg)
• Armature Weight (Moving Coil): 11 kg
• Total Moving Mass (M): 40 + 70 + 11 = 121 kg
• Required Acceleration (A): 5 g

2. Force Calculation (Newton’s Second Law)

The theoretical force required is calculated as:

F = M x A = 121 kg * 5 g = 605 kgf

3. Safety Margin & System Evaluation

To ensure system longevity and account for potential peaks or signal noise, we apply a safety coefficient.

• Standard Calculation (20% Margin):

605 kgf x 1.2 = 726 kgf

• Proposed Solution: SNEV207 Shaker System (Rated Sine Force: 700 kgf)

4. Technical Conclusion

While the calculated requirement with a 1.2 safety factor (726 kgf) slightly exceeds the SNEV207’s rated thrust of 700 kgf, the solution remains viable based on the following:

• Safety Factor Flexibility: While a 1.3 factor (786 kgf) is ideal for heavy-duty cycles, a 1.2 factor is often acceptable for standard testing profiles.
• Margin Overlap: The raw required force is 605 kgf, which is only 86% of the shaker's capacity. This leaves a 14% real-world overhead.
• Optimization: If the test profile is extremely demanding, we recommend verifying the center of gravity (CG) to ensure no additional overhung moments are straining the armature.

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