proceedings of the fourth us water jet conference - Waterjet ...

THE USE OF HIGH PRESSURE WATERJETS IN CUTTING FOAM
S. Yazici and D. A. Summers
High Pressure Waterjet Laboratory
Rock Mechanics Facility
University of Missouri-Rolla
Rolla. Missouri
ABSTRACT
Expanded plastic foam is increasingly being used as a light, inexpensive yet
effective method for providing object support in packaging. However, the most effective
use of this support requires that the packaging material be carved to roughly conform to
the shape of the packaged object. While this is a relatively easy accomplishment when
the surrounding void is filled with small pieces of foam, it becomes more of a problem
when the object contours must be generated in solid foam pieces. Solid foam, however,
has the advantage of providing a more uniform loading of the object and holds it more
rigidly in position. These requirements mandate that a simple but effective method be
available for carving the foam to shape. The most prevalent of the current methods relies
on either manual carving of the solid block, using heated scoops or wires, itself an
expensive and relatively slow procedure, or that the foam support be composited by the
glueing together of the different component parts, each of which has previously been
manually carved to its required shape. Both of these processes can be relatively slow and
therefore also expensive.
High Pressure waterjet cutting systems have been developed for use as industrial
cutting tools, with significant market penetration having occurred within the last seven
years. The majority of the applications for this novel tool have, however, been directed at
cutting harder and more difficult materials, with the use of abrasive injection, or for the
cutting of relatively soft materials. The range of foams which must be considered for the
current operation lies over a range of densities which fits between these two extremes.
The cutting of foam, in general, provides a material which it is extremely easy to cut at
relatively rapid rates. This, in part, allows observation of cutting parameters at different
ranges from those normally essayed. One requirement for the current program is,
however, different to that sought for most industrial cutting where the cuts are made
through relatively thin thicknesses of material. In contrast, in this operation, in order to
cut the required contours of some of the objects to be packed, cutting depths on the order
of one meter should be achievable.
PROGRAM PLAN
As a means of assessing the parameters required to achieve the required cutting
performance, a full factorial experiment was designed. The experiment utilized a pump
(Ingersoll Rand 1 ) which w a s capable of generating pressures of up to 400 MPa at flow
rates of up to four liters/min. Nozzle diameters for the factorial experiment were chosen
to insure that the full factorial could be completed within these limitations. The
1 The use of trade names is for the purpose of identification only and should not be taken as an endorsement
of any one particular product.
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