How to Control Hydraulic Press Automation Systems

Hydraulic presses are powerful machines used in a variety of industries, from metal forming to food packaging. Due to their difficulty to operate manually, manufacturers increasingly rely on automated solutions to boost production rates and cut operating expenses.

Southern Manufacturing Group (SMG) had an outdated automation system that lacked the features and functions required to reduce cycle times and enhance part run consistency. They sought a replacement system that could be designed and installed quickly at an affordable price point.

Inductive Sensors

Inductive sensors use currents generated by magnetic fields to detect nearby metal objects. If a metallic object enters the inductive sensor, its proximity alters its inductance of a coil driving an oscillator, producing either an increase or decrease in frequency or current which can be detected and used to activate an external circuit.

Noncontact sensors come in a range of materials, including stainless steel, PPS, PBTB or nickel plated brass. Many are rated for high temperatures so they're suitable for many industries that require constant operation.

For hydraulic presses, Contrinex's C44 range of inductive sensors offers a robust solution to prevent collisions. They offer high accuracy at an economical price point and come with hardwired connecting cables or integral metal connectors as well as being IO-Link compatible for quick integration into Industry 4.0 initiatives.

PLCs

PLCs (programmable logic controllers) are electronic microelectronic devices that automate various production process controls by interacting with field input signals and pre-input procedures. They have become widely used to replace relay-based control systems in industrial facilities.

Modern PLCs can accommodate virtually any programming language. They can be programmed using ladder logic, which utilizes electromechanical relays, or with specially-adapted programming languages like BASIC or C.

Many hydraulic press automation system designers utilize a combination of PLCs and motion controllers for their control needs. These two products work best together, offering optimal performance when combined.

Hydraulic cylinders exhibit nonlinear behavior when their position changes, necessitating advanced processing. This task may not be achievable with a standard PLC and may necessitate using complex algorithms like gain scheduling, feed forward or smoothing techniques to adjust control parameters based on shaft position.

Motion Controllers

Motion controllers are commonly utilized to regulate the position of a hydraulic cylinder. They offer various inputs, such as absolute and incremental encoders and resolvers, that allow for precise positioning control of your machine.

Motion controllers can send commands to proportional directional control valves. This is essential, as it enables the motion controller to monitor pressures within actuators and command the proportional control valve accordingly.

Hydraulic press automation systems can be challenging to regulate due to their complex dynamic behavior. To achieve smooth and precise motion, advanced control intelligence is necessary.

Specialized electrohydraulic motion controllers are often chosen for this type of application due to their superior performance in terms of sample time, I/O and optimized algorithms that close the motion loop with high precision and dynamics. Standard PLCs cannot offer these features; thus, when selecting a motion controller suitable for hydraulic use it should be taken into account.

Control Panels

When operating a hydraulic press, installing a control panel is often recommended. Not only does this make operation of the press easier and safer, but it will save the operator money in the long run as well.

Installing a control panel can be accomplished in several ways. Popular options include installing an electronic PLC, adding touchscreen capability or upgrading an existing system to more powerful controls.

Another option is installing a closed loop system. These systems are commonly used in force control and pressure control applications.

Converting to a closed loop system on a hydraulic press can improve cycle times, positional accuracy and other aspects of production. It also increases capacity of the machine. Some beneficial retrofits include adding distance and pressure capability to the closed loop system, upgrading speed control for hard-to-form materials and increasing cycle rates of the press.