Workholding: Why is it so important?
In machining workholding is the method with which the workpiece is being held in order for the part to stay in alignment while being machined. How a part is to be machined is the most pivotal factor when determining how a workpiece is to be held, but can also be affected by the material being used and the geometry of the workpiece. If a part is being machined from barstock, the workholding will look much different than if the workpiece is a thin irregularly shaped component.
In machining the workholding can greatly affect the precision, efficiency and safety of the manufacturing process. There are different requirements of workholding if the facility is a job shop or a high volume flow shop. If the facility is a flow shop they may focus more on consistency of workholding device while a job shop may focus more on quick-change of workpieces. Workpiece holding sometimes requires custom solution when the part has especially irregular geometry or is particularly fragile; but will add to the cost manufacture if the workpiece requires a custom workholder for each of the manufacturing steps.
There are several types of workholders:
- Jig: used for hold, support and locating the workpieces while guiding the cutting tool into a specific operation.
- Fixture: used for hold, support and locating the workpiece. There are 4 types of Fixtures:
- Faceplates: mounted to the spindle of the machine
- Baseplates: Mounted to the worktable of the machine
- Angle Plates: Two plates that can be adjusted to various angles.
- Tombstones: Vertically oriented rectangular fixtures to mount the workpiece perpendicular to the worktable
- Locators: only locates the parts in a specific orientation
- Supports: supports the workpiece to prevent workpiece deformation
- Clamps: used for strengthening and holding parts together. Vises and chucks are both considered clamps.
Workholding doesn’t just affect a machine shop’s CNC lathe department but throughout the shop. For example if a part being inspected on a CMM inspection machine is not held properly you can get false passes and fails on parts. Workpiece holding must considered throughout the process to ensure the efficiency and precision of the final component.
