by Michael Riehn
Servo presses and hydraulic presses have many uses for a wide variety of applications. What happens if you combine their capabilities to form a hybrid machine utilizing many of their advantages? What capabilities and attributes would this machine have?
The Accu-Flex servo-driven hybrid presses, manufactured by Beckwood Press Company, answers these questions. It is designed to provide users with unlimited flexibility with precision performance for both position and force control.
The idea was initiated in order to take advantage of widespread servo-motion technology (particularly vector drives), of VFDs-and combine it with hydraulic actuators in a package that can be far less costly in many true servo-hydraulic press applications.
Servo-hydraulics are the right fit for many challenging applications, but can be very expensive in certain cases. Their maintenance costs, their up-front costs and their complexity can be very high and have been excluded from many jobs that could use its benefits.
The terminology wasn’t always easy. In servo-motion, you’re dealing with velocity and torque. In hydraulics, you’re dealing with pressure and flow. So Beckwood had to work to integrate and blend those two technologies together so that they understood what each one correlated to.
The Servo-Driven Hybrid Press users are able to choose between position control with force override or the inverse, depending on whether precision force or position is more important for that application at hand. The system uses a touchscreen operator interface and is completely programmable: Force, approach speed, return speed, distance and dwell time all can be changed instantly. There’s no parameter in the cycle that you cannot program with these controls.
The control system provides real-time trending that allows users to plot process variables, such as position or pressure, and observe how they interact. An operator can store those scenarios and download them via Ethernet either to a computer database or a printer. For industries with strict certification requirements, such as aerospace or assembly, those capabilities provide the kind of traceability a shop needs.
The system also has built-in go/no-go gauges that can be programmed to accept or reject parts based on certain user parameters that are needed to produce a part correctly. For instance, if you know you need 6 tons of pressure to insert a rod into a bushing 3 in., the system will reject parts if the machine happened to use, say, 5 tons or 7 tons. The machine’s built in report trending will tell you if a bad part has been made.
This makes changes “on the fly” easy. The parameter curve changing dynamically to match what has been programmed.
Beckwood offers the Accu-Flex in tonnages ranging from 5 to 150+ tons. That ‘sweet spot’, marks the range where a ball-screw machine can’t keep up with the tonnage and a true servo-hydraulic or servo press can’t compete with the prices. This is provided that you are in that traditional hydraulic press speed application.