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STEP 6 - TEST THE PRODUCT/PACKAGE SYSTEM
Once the package design is completed, the prototype package system is tested to
ensure that all design goals were met.
SHOCK
The package must be able to fall from the design drop height, set in STEP 1, and
transmit less than the critical acceleration to the unit. An accelerometer
mounted to a rigid portion of the product near the center of gravity can be used
to monitor the acceleration level transmitted through the cushioning material
into the product. A rigid location is selected so that the input to the product
as a whole can be observed during the impact, and thus directly compared to the
results of the Step Acceleration test. It may be desirable to monitor additional
locations during the tests, such as certain critical components, however the
only effective way evaluate package performance is to monitor a rigid location.
Packaging itself does not directly change the response of the product to a given
input, but it can modify the input which eventually reaches the product.
Flat drops are usually thought to be the most severe drops
possible in terms of the acceleration level transmitted to the product. Flat
drops focus all of the input along one axis of the unit and little energy is
lost to the crushing of corners or edges of the package, or to package rotation.
Flat drops, therefore, are used to measure the performance of the package
system.
Corner and edge drops, however, often cause damage to the
structure of the package which similar flat drops do not. These types of drops
are often used as part of a test sequence to verify the package's ability to
hold together during shipment.
VIBRATION
Ideally, the package system will attenuate or filter out vibration at those
frequencies where the unit is most sensitive. To accomplish this most
effectively, the package system should have a natural frequency less than one
half that of the product's lowest natural frequency.
To run the package response vibration tests, the product
is again fitted with a response accelerometer attached at a rigid location. The
product is then placed in the prototype package system and secured to the table
of a vibration test machine. The package is subjected to a low level sinusoidal
input over
the same frequency range which was used to test the bare product. In this test,
however, it is the response of the package system rather than the product
components which is monitored. A transmissibility plot of the package response
is generated and used to verify that the package is working properly.
Once the package resonant frequencies have been
determined, dwell tests are performed at those frequencies. In addition, dwell
tests may be performed at each of the product resonant frequencies. Random
vibration tests may also be conducted in which the vibration system is
programmed to mimic the real world motions of transportation vehicles.
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