Jig and Fixture Systems

Shops should consider several factors when deciding on a jig and fixture system.

The costs for jig and fixture systems include the investment needed to create the workholder, maintenance between runs, storage and a depreciation based on repeated usage. For a true comparison, companies should consider lot sizes, the number of times a job repeats, the life expectancy of the jig and fixture.

Modular jig and fixture systems have reusable parts, so component cost should be amortized over the system's typical lifetime by dividing total component cost by 100. Once initial jig and fixture costs are established, further cost comparison suggests the most efficient type of fixturing for a particular operation based on the overall cost per part. Each jig and fixture type offers advantages in some areas.

One suggested formula for figuring the total cost to manufacture a given part:

Run cost is the cost of labor to produce a part. Generally, run costs for dedicated and modular fixturing are about the same, while power workholding lowers labor costs by improving cycle time and reducing scrap.

Setup cost is the labor cost to retrieve a jig and fixture, set it up on a machine and return it to storage after use. Since dedicated fixturing and power workholding are faster to set up, they create lower cost than modular fixturing, which requires assembly.

Lot size is the average quantity manufactured each time the jig and fixture is set up.

Initial Tooling cost is the total of labor and materials to design and build a jig and fixture. Here, modular fixturing is cheapest because parts are reused, while the more complex power workholding systems initially cost more.

Total quantity over tooling lifetime is the lesser of the total anticipated production quantity or the quantity that can be produced before the tooling wears out. Generally speaking, as quantities increase, the efficiency of power workholding yields the lowest cost per part.

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