The control system from Rexroth finds the correct setting for profile extrusion presses

The control system from Rexroth finds the correct setting for profile extrusion presses
Marginal Column

July 2017


A multi-adjustable pressure and flow rate control system improves energy efficiency and availability in profile extrusion.

Foshan Nanhai Jinli Machinery Manufacture Co., Ltd. is a manufacturer of aluminum and copper profile extrusion presses. The company switched to variable speed pump drives a few years ago, including Sytronix from Rexroth. With its dynamic characteristics, the efficient combination of highly dynamic servo drive and fixed displacement pump fulfills the requirements of plastic processing machines and main drives of down stroking servo presses perfectly.

Dynamic characteristics and power

In addition to dynamic characteristics, profile extrusion presses require high levels of power. This power is needed, for example, for a hydraulic cylinder to press copper and aluminum billets through the die. To ensure that a fixed displacement pump can build up this pressure, the servo motor must work at maximum torque with low rotation speed. In high ambient temperatures and with long billets, this can lead to overheating, causing the motor to switch off.

To tackle this challenge, Foshan Nanhai Jinli worked with Bosch Rexroth to develop a drive solution for use in extremely hot countries. It is based on variable speed pump drives with axial piston variable displacement pump A4 and electrohydraulic DFE control. The system not only changes the speeds to suit demand, but also the swivel angle of the axial piston pump. This generates a high flow rate with low pressure for fast movements and high pressure with low flow rate for slow, but extremely powerful movements.

Optimal combination

The SY(H)DFEn software from Bosch Rexroth calculates the optimal combination of swivel angle and speed for the entire drive train based on the required pressure, thus creating a continuously adjustable hydraulic gear. The swivel angle adjustment disconnects the speed from the movement. In pressure-holding operation, the flow rate is reduced by swiveling back the variable displacement pump and the motor speed can reduce accordingly. In the profile extrusion press, SY(H)DFEn controls the main movement extremely smoothly without proportional valves. This reduces throttle losses and heat influx in the hydraulic oil.

Foshan Nanhai Jinli has already delivered the first four profile extrusion presses with SY(H)DFEn to a sub-tropical environment. The electrohydraulic pressure and flow rate control has also proven itself there. The machine manufacturer therefore plans to switch to the solution for new machines and will also offer customers the option of retrofitting the solution on machines already installed.