When shopping around for workholding equipment, simple cost comparisons between fixture types may not tell the whole story, according to the Swiftsure engineers at Carr Lane Roemheld Mfg. Co, St Louis, MO.

Overall tooling costs for any type of fixture include the investment needed to create the workholding device, tool maintenance between runs, storage, and costs of repeat usage. Lot size, how many times a job will repeat, and the life of the fixture should also be taken into consideration.

For modular designed systems, with parts that can be reused, the system costs can be amortized more easily, providing additional justification for hydraulic workholding. Once initial costs are established, further cost comparisons will suggest the most efficient type of fixturing for a particular operation based on overall cost per part. Each type offers its own particular advantages.

This total cost methodology applies when assessing the cost of various workholding devices. Certainly, manual workholding is what many shops have always used, and its initial cost is usually considerably less than power (hydraulic or pneumatic) workholding. For shorter runs, manual workholding can also be better for users, but as materials become tougher and more expensive, and setups more complex, hydraulic workholding becomes increasingly advantageous.

"With hydraulic workholding, speeds and feeds can be increased and users can take heavier cuts," says Derek Evans,

This power workholding fixture is custom designed to permanently hold a workpiece, and offers great efficiency for high-volume or repeated production runs.

Swiftsure application engineering manager. "This workholding is designed to securely clamp and support the workpiece to reduce vibration and deflection."

Power workholders introduce a highly consistent clamping process. Since they allow for more precise control of individual machining operations and hold with high repeatability, they can ensure better quality. This means less scrap and rework.

Power workholding provides several advantages over manual workholding, including consistent, repeatable clamping; a uniform clamping force; simplified operation; N/C compatibility; and a high degree of compactness.

The precisely controlled clamping forces plus increased speed and safety are the most notable advantages of power workholding. Since power workholders are controlled by a power source, the pressure and clamping force remain constant. This is safer for the operator, who can get injured clamping part after part. A properly designed system features controls for added safety in case of power failure.