Servo Press Fundamentals: Power, Precision, and Efficiency Explained

What exactly is a Servo Press?

Servo presses are driven by a servomotor. Just like the traditional press machines, they are made for forming applications. The ability to control the ram position, stroke length, slide profile, load value, torque, and speed makes them very efficient. There is an extremely low energy loss during operation.

Servo presses are high-torque machines. They are able to produce the output pressing force with full energy at any point of an operation. As a result, they are ideal for processing high-strength materials. The full control ability allows them to perform high-precision forming. Secondary processes such as surface finishing are reduced.

 

Janome Industrial Equipment
 

The full control of the pressing actions is realized by a closed-loop feedback system. The system consists of sensors at the ram so that the cycle time and loads are more precisely regulated. As a result, a servo press can carry out tasks that require different torque, speed, slide, and stroke. The common uses include press-fitting, riveting, sealing, bending, drawing, forming, cutting, punching, just to name a few.

 

How Does the Electric Servo Press Work?

The way the ram works is significantly different from that of a traditional mechanical press. In a servo press, there is a lead screw and a nut, instead of a cylinder, that moves the ram. The servomotor is connected to a lead screw with a belt. As the motor drive shaft rotates, the belt pulls the lead screw to spin.

As the lead screw spins, the nut inside the cylinder moves along a guide groove. Unlike the typical electric motors, a servo motor can have the driveshaft spin clockwise or counterclockwise. This controls the spinning direction of the lead screw, and in turn the pushing and retracting of the ram. Below is a video showing how a the press works.

 

Servo Press Mechanism, Mechanism World


 

Types of Servo-driven Presses

 

● Hydraulic

Hydraulic presses work based on Pascal's law. Pressure applied in a confined environment spreads evenly without any energy loss. In other words, the pressure within the closed system is consistent. In conventional hydraulic presses, one piston generates a force in a smaller cylinder. The other piston creates a large force in a larger cylinder.

Compared to conventional hydraulic presses, the servo-hydraulic presses equipped with high-performance servo motors achieve a much higher slide rate in the forming process. They are commonly used for forging, molding, punching, and metal forming applications. Servo hydraulic press is popular in industrial manufacturing for the ability to form intricate shapes with less material waste.
 

● Ball Screw

This type of servo press utilizes ball screws to reduce friction. Unlike conventional screw presses, the sliding speed can be changed during the forming process without a clutch or flywheel. The advantage is that the full slide rate and maximum force can work at any position. It can be applied to a range of applications, fitting the need for long stroke applications such as extrusion.

Also, servo ball screw presses are ideal for forming applications that require rapid motion at the end of the process. When it comes to the maximum load of the ball screw type, you should be aware of the load capacity of the ball screw as well as the reduction of the belt. By increasing the number of servo motors and spindles you can enhance the power of the machine.
 

● Crank

Servo-driven crank presses are an economical alternative for the ball screw types. The servo motor with high torque capacity in the servo crank press can be attached to the driveshaft directly. It is very similar to the traditional mechanical press, the main difference lies in the elimination of the flywheel and the clutch. It works with two connecting rods to enhance the power for high-load applications.
 

● Linkage

The linkage mechanism reduces the slide speed and achieves a higher load capacity of the motor located near the bottom dead center. By slowing down the sliding rate within the stroke, they can increase the approach and return rate. Another benefit is the capability to maintain high loads throughout a relatively long processing stroke.