Example #1

Machine Failure Analysis

The Problem: A mechanical punch press utilized for punching and forming truck chassis fails due to vibration at half-rated speed. Identify the cause and solution. (Breach of Contract)

[Exmpl1-1]

Test data is taken on the drive shaft. (Only part of the transfer press is schematically depicted.)


[Exmpl1-2]



The test data is obtained and shown above. The test data is obtained by placing strain gauges on the main drive shaft of the "giant" press. The test data is then "curve fit" by means of a mathematical Fourier analysis. Vibration components are identified. The portion in red is a trace obtained on the drive shaft of the press at 16 stampings per minute. Below is the mathematical trace utilizing 30 coefficients. Below the theoretical trace of torque versus rotation angle is the excitation frequencies, along with magnitudes of torque that produce the actual torque on the driveshaft.

[Exmpl1-3]"

Finally, a theoretical analysis is "derived" based on the shape of the cam that defines the motion of the mechanical drive train (portion of calculation shown below). The machine is modeled mathematically as a single degree of freedom vibratory system with Coulomb friction.

[Exmpl1-4]"

Structural analysis of a large mechanical component identifies a flexible element that causes the machine to vibrate at the frequency identified in the Fourier curve fit of the test data and is supported by the theoretical analysis. The solution is to stiffen the mechanical element to eliminate the offender component and reduce vibration to acceptable levels. Below is a portion of a computer program used for theoretical analysis:

[Exmpl1-5]"

Home Page | Return to Analysis

Copyright © 2005 Meridian One, Inc. All Rights Reserved. No portion of this publication may be
reproduced by any process without express written consent of Meridian One, Inc.