Many older-generation hydraulic presses and stamping machines employ simple on-off control of two position hydraulic valves to extend and retract the hydraulic actuator that does the work. In such machines, precise control of the ram position may not be a primary requirement, but velocity control can turn into a big issue. Depending on the application, the use of discrete (on-off) hydraulic valves could impact the quality of production units, and may actually be hazardous to a machine’s health.
With on-off control, the actuator stops abruptly when the valve is moved. In a heavy metal-stamping application, the large inertia of the moving parts can lead to damage of the machine and the work piece. Guyana A better means of control involves the use of a proportional servo valve and electrohydraulic motion controller, which can control the actuator’s velocity and make the motion smoother to avoid the shock of instantaneous accelerations and decelerations.
This is the rationale that drove Albany, Ore.-based TEKFAB Inc., integrator of high-performance production lines, to use proportional valves and a programmable motion controller in a new line it developed for a manufacturer of steel building studs, Figure 1. Before roll-forming the edges of flat stock to make the legs of the studs, access holes are punched in the material using a compound die that first punches the hole and then forms the edges of the hole for strength—all during a single stroke…..
