Chapter 16 Tabletting

Publisher Summary Powder pressing is a forming process used in a wide range of industries, such as powder metallurgy, industrial ceramics, pharmaceutical tablets, food, detergents, fertilizers, batteries, magnets, and nuclear and hard metals. The process is fast, economic and lends itself to high-volume production. In spite of the broad range of powder materials and applications, powder pressing has common features in various industries. The operation consists of filling a die with powder, compressing using rigid punches, followed by ejection from the die. During this process, the loose powder bed is made compact according to a given shape and microstructure. Powder metallurgy compacts are required to have sufficient strength to withstand handling and have a dense, uniform, and defect-free microstructure. Compaction is followed by sintering to achieve near-full density and maximum strength for structural applications. The properties of a powder compact depend on the characteristics of the powder and the choice of process parameters during compaction. In order to achieve the desired compact properties the powders are mixed with other ingredients having specific functions. For example, lubricants are added to reduce the friction and wear of the tools and equipment. Steel powders may be mixed with graphite, which acts as a lubricant during compaction and alloying material can be mixed during sintering. Hard metal cutting tools are compressed by embedding the hard ceramic component into a soft metal matrix. In pharmaceutical tablets, the active ingredient is mixed with excipients such as lubricants (to control the friction between powder and tooling), glidants (to improve flow), binders (to improve strength), and disintegrants, which are polymers that swell in contact with water.