What Is A Servo Press?

Press machines are used in mass production – for example cutting parts in the automotive industry. The machines work by using extreme force to set, shape, cut or stamp metallic components.

Manufacturers have traditionally used mechanical and hydraulic machines, but technological advances have seen many manufacturers switch to servo presses.

Mechanical press machines work by using a flywheel, clutch, brake and crankshaft. Hydraulic presses use hydraulic fluid to generate the force needed to compress metal and shape it. But servo presses use a motor to power the gear that operates the slider of the press. 

Each type of press has its advantages and disadvantages, but servo motors combine many benefits of the other machine types in one.

Mechanical, Hydraulic And Servo Presses Compared

To understand how servo motors work and their advantages, we first need to see how they differ from mechanical and hydraulic press machines. The main comparison points are speed, accuracy, flexibility, cost and stroke length.

Speed in mass production is needed to maximise productivity. Closely related to the speed of the machine is flexibility – measured by slide velocity, which is the speed at which the slide in the press operates. Flexibility in slide velocity means the press can complete a variety of tasks.

Accuracy and reliability are important to ensure precision. For higher adaptability, variation in the stroke length of the machine is beneficial. Stroke length measures the speed range of the machine – the longer the machine’s stroke, the slower it will be.

Mechanical Presses

Conventional mechanical presses can operate at higher speeds, especially for processing surfaces that are somewhat flat with simpler assembly requirements. They feature a fixed stroke length and fixed slide velocity in a single cycle and are less complex to set up. Traditional mechanical presses have lower initial costs and are highly accurate and reliable.

Hydraulic Presses

A hydraulic press powered by hydraulic fluid can’t achieve the same speeds as a mechanical press. It’s slower because it takes time to build speed. It’s best suited to more complicated processes that need substantial materials and do not rely on higher production speed. Hydraulic presses have variable stroke length and slide velocity. They also have reduced accuracy and repeatability, but initial costs are low.

Servo Presses

With a servo press, power is generated via a high-capacity electromechanical motor that converts electrical energy into mechanical power. Servo motors can match the speed of mechanical presses and provide the flexibility of a hydraulic press. For instance, the slide velocity, stroke length and speed can be programmed for a variety of tasks at varying speeds.

Servo motors are suited to tasks that require precise control, often being used in robotics and automation where the motor interprets signals from the controller to execute commands.

Advantages Of A Servo Press

• Servo motors provide more flexibility because they allow for adjustable stroke length profiles. 

• They have higher precision in slide motion and position control across varying stroke length profiles. This means that they can perform complex tasks while adhering to exact dimensions. 

• Servo motors provide highly accurate and variable slide velocity control (even in a single cycle). 

• They can operate at full capacity at any speed, providing cycle speeds comparable to mechanical presses and greater than hydraulic presses.

• Their main advantage is that they have high accuracy and repeatability, but their initial cost is higher in comparison to other press types. 

• Maintenance with servo motors is less frequent and they don’t require seal replacements. 

• Servo motors allow for a more compact and efficient design, generating an overall lower footprint.

Hybrid Options With Servo Capability

Speed and accuracy are critical in mass production. Hydraulic and mechanical systems present challenges to speed and flexibility, especially when performing tasks that require a shorter cycle time or stroke flexibility. A flywheel in a press machine can only manage so many strokes per minute (SPM). When the SPM rate is surpassed, the flywheel is more at risk of damage. In some cases, certain parts can only be assembled so fast, meaning that increasing the SPM speed will compromise quality.

Installing a servo-driven motor to a mechanical press can potentially solve these challenges. Adding a servo motor to a mechanical press to create a hybrid option means the press can open and close quickly and remain at the original speed. In this way, the press machine will use power from the mechanical flywheel and the servo motor drive retrofitted to the press. The flywheel is still performing the same function to press metal, but the servo motor is powering the motion of the slide.

Why Manufacturers Are Switching To Servo

Mass production relies on efficient, high-speed press machines to complete tasks with accuracy and repeatability. Industrial press machines perform a range of tasks, from simple joins to complex stamping and cutting across industries. Automotive and aerospace manufacturers use press machines to assemble parts and to form sheet metal. Other use cases include assembling hardware components and appliances.

The press industry still relies on mechanical and hydraulic press machines, but as the industry evolves more manufacturers are changing to servo motors. That’s because servo motors offer the best of both worlds, combining the benefits of the other press machine types in one. Mechanical press machines offer high speeds and hydraulic machines offer more flexibility in stroke length, but servo motors provide both these advantages and more. Manufacturers are integrating servo motors into their production processes for higher precision and flexibility despite the somewhat higher initial costs.