APPLICATIONS FOR JIGS AND FIXTURES


APPLICATIONS FOR JIGS AND FIXTURES

Typically, the jigs and fixtures found in a machine shop are for machining operations. Other operations, however, such as assembly, inspection, testing, and layout, are also areas where work holding devices are well suited. Figure 1-7 shows a list of the more-common classifications and applications of jigs and fixtures used for manufacturing. There are many distinct variations within each general classification, and many work holders are actually combinations of two or more of the classifications shown. EXTERNAL-MACHINING APPLICATIONS:
Flat-Surface Machining
   • Milling fixtures
   • Surface-grinding fixtures
   • Planing fixtures
   • Shaping fixtures

Cylindrical-Surface Machining
   • Lathe fixtures
   • Cylindrical-grinding fixtures

Irregular-Surface Machining
   • Band-sawing fixtures
   • External-broaching fixtures
INTERNAL-MACHINING APPLICATIONS:
Cylindrical- and Irregular-Hole Machining
   • Drill jigs
   • Boring jigs
   • Electrical-discharge-machining fixtures
   • Punching fixtures
   • Internal-broaching fixtures
NON-MACHINING APPLICATIONS:
Assembly
   • Welding fixtures
   • Mechanical-assembly fixtures
     (Riveting, stapling, stitching, pinning, etc.)
   • Soldering fixtures

Inspection
   • Mechanical-inspection fixtures
   • Optical-inspection fixtures
   • Electronic-inspection fixtures

Finishing
   • Painting fixtures
   • Plating fixtures
   • Polishing fixtures
   • Lapping fixtures
   • Honing fixtures

Miscellaneous
   • Layout templates
   • Testing fixtures
   • Heat-treating fixtures
Modular Fixtures

Modular fixtures achieve many of the advantages of a permanent tool using only a temporary setup. Depicted in Figure 1-4, these workholders combine ideas and elements of permanent and general-purpose workholding.

Figure 1-4. Modular workholders combine ideas and elements of both permanent and temporary workholding to make inexpensive-yet-durable workholders.


The primary advantage of modular fixtures is that a tool with the benefits of permanent tooling (setup reduction, durability, productivity improvements, and reduced operator decision-making) can be built from a set of standard components. The fixture can be disassembled when the run is complete, to allow the reuse of the components in a different fixture. At a later time the original can be readily reconstructed from drawings, instructions, and photographic records. This reuse enables the construction of a complex, high-precision tool without requiring the corresponding dedication of the fixture components.
Arc Welding:
The arc welding is a fusion welding process in which the welding heat is obtained from an electric arc struck between the work(or base metal) and an electrode. The temperature of the heat produced by the electric arc is of the order of 6000°C to 7000°C. Both the direct current (D.C) and alternating current(A.C) may be used for arc welding, but the direct current is preferred for most purposes. When the work is connected to the positive terminal of the D.C welding machine and the negative terminal to an electrode holder, the welding set up is said to have straight polarity. On the other hand, when work is connected to negative and the electrode to a positive terminal, then the welding set up is said to have reversed polarity. The straight polarity is preferable for some welds while for other welds reversed polarity should be used.
Following are the two types of arc welding depending upon the type of electrode:
(A): Un shielded arc welding:
When a large electrode or filler rod is used for welding, it is said to be un- shielded arc welding.
(B): Shielded arc welding:
When the welding rods coated with fluxing material are used, then it is called shielded arc welding.

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