To
solve practical cushioning problems detailed information is
needed on the product to be shipped, how it is to be shipped,
and methods of handling.
Fragility
of the Item
The
so-called "educated guess" of the G factor for a given
item can be dangerous for two reasons. First, if the guess is
too low, the package may be over-designed resulting in higher
package costs than necessary. Second, if the G factor is too
high, an under-designed package and high damage claims are likely.
Unfortunately, the degree of fragility for most products has
never been determined, or it is not generally known. But with
the advent of ultra-sensitive electronic testing equipment, it
has become necessary to determine fragility factors.
Table
1 may be used as a guide where the G factor of a product
is known, but is should never be considered a substitute for
test information on a specific product.
Handling
of the Item
The
anticipated height of drop, based on potential hazards that might
be encountered during shipping and handling, must be determined.
Also, a line between "normal handling" and "rough
handling" must be drawn. A heavy item may not be dropped
higher than 12" to 18" during normal handling, but
during rough handling, such as falling from the back of a truck,
a drop height of 42" may be encountered. If an item is light-weight
and could be thrown by baggage handler, a drop height of 36" is
realistic. A guide for estimating anticipated drop heights is
given in Table
2.
Common
Foams for Cushioning
Polyurethane
foam is a low-cost, cellular cushioning material with predictable
and excellent characteristics in the broad temperature range
(0° to 250°F.). The ease of fabrication into a variety
of shapes makes polyurethane foam especially adaptable for use
as a multi-cavity cushion material. It is available in flat sheet
stock and can be die cut to your requirements. This is probably
the most frequently used cushioning material, particularly in
military packaging.
Polyethylene
foam is a moderately priced cellular cushioning material with
predictable performance characteristics. The virtue of this
material lies chiefly in its ability to withstand high bearing
loads and its extremely low water-absorption factor.
