Metal Foams: A Design Guide

Chapter 15
Cutting, finishing and joining
The cellular structure of metal foams requires that special techniques are
required to give high-quality cuts and joints:
ž Rough cutting is practical with conventional machine tools, but with some
surface damage.
ž High-quality surfaces require the use of electro-discharge machining, chemical
milling, water-jet cutting or high-speed machining.
ž Adhesives work well as bonding agents for metal foams.
ž Welding, brazing and soldering are all possible.
ž Threaded, embedded and bolted fasteners require careful design if they are
to function well, and are sensitive to fatigue loading.
Guidelines for the design and use of joining methods are assembled in this
chapter.
15.1 Cutting of metal foams
Conventional cutting and machining techniques (bandsawing, milling, drilling)
cause severe surface distortion or damage to low-density metal foams.
Accurate cutting is possible by electro-discharge machining (EDM), by
chemical milling, by water-jet cutting or by the use of very high-speed flycutters.
When making test samples of metal foams for characterization (see
Chapter 3) it is important to use electro-discharge machining or chemical
milling unless the samples are very large, because surface damage caused
by other cutting methods influences the properties.
15.2 Finishing of metal foams
The cut surface of a metal foam has open cells, a rough texture, and is vulnerable
to local damage. The surface can be filled with an epoxy or other resin,
or clad (creating a sandwich structure) with a skin of a material compatible
with that of the foam. Syntactic structures have a natural skin, which can be
polished, etched, anodized or coated by conventional methods.