GlossaryKind of term: Manufacturing termFixture
What is a fixture?
A fixture is workholding built for one part or part family, with its own locators and clamps, so the workpiece sits in the same position every time.
In construction it is a plate or structure carrying rest points, stops or locating pins, and clamps. The workpiece goes into the same position each time, so the work origin need not be found again for every piece. A fixture can hold several parts at once and can sit on a zero-point system, so the fixture itself goes back onto the machine repeatably. Soft jaws machined to the part's shape fall between standard workholding and a dedicated fixture.
How does a fixture work in practice?
A fixture takes design, material, manufacture and proving; in return it can bring shorter setup time, shorter or steadier cycle times and a repeatable position. Whether it pays depends on batch size, how often the part comes back, the setup time saved, the accuracy the drawing asks for and the cost of storing and maintaining it. On a new revision the change decides whether the fixture still fits: a moved hole can invalidate a stop or locating pin, a changed roughness usually does not. Whether you charge the fixture as a one-off item or spread it over the pieces is an estimating convention you agree with the customer.
What is a fixture often confused with?
A fixture is not just any workholding: a vice or chuck is general-purpose, a fixture is made for a given part. Nor is it a jig: a jig guides the tool, for example with drill bushes, while a fixture only locates and holds the workpiece.
Frequently asked questions
When does a fixture pay off?
When the setup time saved and the repeatable result over all expected batches are worth more than the fixture costs. Quantities, repeat frequency, hourly rate and the accuracy the drawing requires all count. On a one-off with no repeat it rarely does.
What happens to the fixture on a new revision?
First check whether the change affects it: different dimensions on locating or clamping faces, or a moved hole, can invalidate stops and the work origin. Sometimes an adjustment is enough, sometimes a new fixture is needed, with a new one-off item.
Who owns a fixture?
Settle it in the quote or the terms. If the customer pays for the fixture as a separate item, it is often the customer's property and the supplier stores it. If its cost is built into the piece price, ownership is less clear-cut.