INTRODUCTION TO PROCESSING OF BIOMATERIALS - Advanced Biomaterials: Fundamentals, Processing, and Applications - page 244

Open die
Close die
Hot rolling
Cold rolling

Forging

Forming
operations

Rolling

Extrusion

Drawing

Metal fabrication
techniques

Sand

Die

Casting
operations

Investment

Continuous

Miscellaneous Power metallurgy lens ®

Figure 8.2. Schematic representation of techniques used for fabricating primary devices
(bars, wires, sheets, rods, plates and tubes) from raw metal.

8.3.1.2.2 PROCESSING OF RAW MATERIALS [1, 25, 26] . Various forming and
castings steps (Figure 8.2) are used to produce stock shapes from raw metal that
are subsequently converted into primary devices such as bars, wires, sheet, rods,
plates and tubes.
The strength of these stock shapes is improved by heat treatment and pre-
cipitation hardening. Conventional metal fabrication techniques that involved
the use of dyes for the production of stock shapes are being gradually replaced
with modern techniques such as computer-aided machining (CAM/CAD) and
automated processing for fabrication of preliminary implants [27, 29-32]. These
modern techniques reduce production cost, processing time and shop-fl oor area,
while providing greater manufacturing fl exibility and precision on the shapes of
the primary devices. The primary devices, once formed, then undergo surface
fi nishing to incorporate desired changes in surface properties and aesthetics of
the device.

8.3.1.2.3 SURFACE FINISHING. Surface fi nishing is the method of processing
of stock shapes/preliminary devices to improve physicochemical properties [33]
such as corrosion resistance, friction control, wettability, adhesion, and appear-
ance. The two main types of surface modifi cation techniques are adding/altering
the surface and removing/reshaping the surface. However, there are other surface
fi nishing techniques that are specifi cally used at lower scales (micro/nano-meter
scale) and have been included under the section on 'processing by scale' in this
chapter.
Metal processing techniques are gradually changing from the conventional
techniques to more sophisticated techniques such as CAD/CAM and rapid
prototyping that have enabled the fabrication of metallic implants with desired