Securing the Part
The previous chapter discussed positioning cylinders, which accomplish the first of the three steps in workholding. In this chapter we look at clamping cylinders, used to implement the second step.
Holding a workpiece in place while working on it is so fundamental that generations of metalworkers have devised countless variations of mechanical clamps such as the one illustrated (Refer to Chapter 3 for more examples).
Hydraulic workholding overcomes those limitations. The tradeoff is that the purchaser must pay more upfront for a hydraulic clamping system. However, the numbers readily show that for any significant production volume, the cost of using hydraulic workholding is lower than for manual clamping. The lower total cost of hydraulic workholding combines with an increased production rate, improved accuracy and repeatability, less congested fixtures, increased safety, and automation compatibility.
“Clamping” is the secure fastening of a positioned workpiece in a fixture. Clamping always requires force transmission through the part. Each clamping force vector should, as nearly as possible, describe a line that extends from the application point of the clamping force through the workpiece to the bearing points and is parallel to the axis of the clamping cylinder and perpendicular to the plane of the bearing points.