Due to the advancements in mechanization and automation, many types of product work-pieces are now being processed on machinery devices. Objects as large as the 9th generation LCD panels to chip mounted components as small as several micrometers, automated processing are performed while the work-pieces are being held. The work holding principles and technology will be explained in the following.

(1) The basics of work holding

• Work holding technology is needed for all fixturing, automated assembly, and processing.
• Mechanisms to hold work-pieces by some means (retaining, gripping, chucking) are called "Work Holders".
• There are mechanical, electrical, air, hydraulic means to hold the work-pieces.
• The operational relationship between the work holders and the process tools (manipulators) is the same whether the process is for cutting or assembly.
• The shaping and assembly process are performed by applying desired movements of the tooling on the work-pieces held by work holders.

(2) Classification of work-piece external shapes

• Work-piece shapes can be classified into the following three types.
  1. Flat surface
  2. Cylindrical surface
  3. Compound shape surface
• The flat surfaces include: edges, flanges, steps, surfaces, shoulders, slopes.
• Cylindrical surfaces can be inner circumference and outer circumference.
• Compound surfaces are the ones not belonging to a) or b), and often occurring with formed parts (cast, forged, injection molded parts)

(3) Classification of Locating

Locating can be classified into the following four types (see [Fig.2])

1. Flat surface locating
2. Coaxial locating
3. Radial locating
4. Compound locating