Hierarchy of Workholders
To understand how modular fixtures relate to workholding in general, an awareness of the other two basic forms of workholders is necessary:
General-purpose workholders, the simplest fixtures, include a wide variety of standard clamps, vises, chucks, and similar off-the-shelf components. General-purpose components are reusable and, normally, the least expensive. Although these components represent a smaller initial investment, they are often inadequate or unsatisfactory for complex parts or high-volume production.
Permanent workholders, the most complex types of tooling, are specifically designed and constructed for a single workpiece or family of parts. These workholders, though usually the most efficient, are also the most expensive. Permanent workholders are built with a variety of standard and custom-made parts to meet specific requirements. These fixtures are the best choice for high-volume or repeated production runs.
Modular workholders fall between general-purpose and permanent fixturing in terms of |
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complexity. They can be described as special-purpose workholders assembled from general-purpose components. Figure I shows a typical system of modular-fixturing components. The concept of modular fixturing, rather than a departure from conventional fixturing methods, actually combines the best attributes of both permanent and general-purpose workholding methods. Modular fixtures are built with the accuracy and detail of permanent workholders. But with reusable and universal components, these fixtures compare favorably in cost to general-purpose workholders.
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