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control (QC) to ensure that the dimensions of the workpiece are within the tolerance limits. Stress analysis is to prevent excessive deformation for both the workpiece and the ®xture, which ultimately could minimize the de¯ection and vibration of the whole system. UMJFS, a proven new technological equipment, has been developed based on the highly standardized ®xture elements and subassemblies. It consists of premanufactured standard elements or subassemblies with various shapes and sizes, and can be assembled quickly according to the requirements of manufacturing processes of the workpiece. It has the same advantages as the conventional ®xtures, and furthermore, it can be disassembled after use. Then the ®xtures elements are washed with an oil-based antirust formula, sorted and stored, preparing for the next ®xture assembly. Therefore, UMJFS does not have annoying problems when there is a product change or manufacturing process change due to its ¯exibility. The UMJFS can be used repeatedly and it creates an extremely favorite environment for machining processes with a tremendous cost reduction. The assembly principles of UMJFS are based on the idea of building blocks, utilizing the modern concept of multiple structures, locating with keys and grooves and fastening with bolts and nuts. The following chart shows the actual loop for UMJFS usage:
Design?Assemble?Use?Disassemble?Store
Loop
UMJFS may be pided into three series according to its basic structure characteristics, M16 (large), M12 (medium), and M8 (small). The most popular one is the M12, which is widely used with metal-cutting machining processes. The UMJFS M12 series consists of eight basic kinds of elements. Sections 3.1±3.8 describe these elements.
3.1. Base elements
Base elements may consist of square base, a rectangular base, or their simpli®ed version with limited T-slots, a right angle base, or a circular base with 45, 60 and 90
grooves. Base elements are about 1*1.4% of the total ®xture elements. Base elements include the base of the ®xture itself and the base for mounting other ®xture elements via using location
Towards the design and development of modular jigs and ®xtures 383
keys and fasteners. Base elements are equivalent to the base of the conventional ®xture.
3.2. Supporting elements
Supporting elements include symmetrical and right angle groove square support, rectangular support, symmetrical and multi-groove rectangular support, simpli®ed support, square and rectangular hollow support, 45/60/90mm width single groove stretch plate, and angled support. Support elements are about 12*16% of the total ®xture elements. Supporting elements form the core of the ®xture. There is a lot of varieties and dimensions. They play a major role of connecting various ®xture elements to form the main body of the ®xture.
3.3. Locating elements
Locating elements include ¯at keys, T-keys, eccentric keys, locating pins, diamond pins, locating disks, diamond disks, square and hexagonal locating blocks, end-bore locating supports, V-blocks and V-supports. Locating elements are about 15*16% of the total ®xture elements. Locating elements are used for locating the relative position between the workpiece and the ®xture and ensures the locating accuracy. They sometimes can increase the connecting strength and rigidity of the entire ®xture.
3.4. Guiding elements
Guiding elements include regular drill bushings, quick-change drill bushings, different types of drill guiding plates, bore supports, guiding supports and others. Guiding elements are about 4*6% of the total ®xture elements. Guiding elements guarantee the relative position between the workpiece and the cutting tool, meanwhile providing guidance to the cutter. They can also be used as locating elements.
3.5. Clamping elements
Clamping elements include ¯at clamping plates, stretched clamping plates, U-clamps, circular clamps and others. The clamping elements are about 3*4% of the total ®xture elements. Clamping elements are used for clamping the workpiece onto the ®xture base or some other elements, in order to keep the