Eckelmann has automated tube mills – so-called stretch-reducing mills – for many years. The automation of these mills pursues a dual objective: reducing heavy tube ends and increasing quality through precise wall thickness control.
Automation for tube mills
Group drives in stretch-reducing mills are increasingly replaced by separate electrical drives. A large number of finished tube dimensions are made from only a few tube blank sizes. As regards the speed and the exact coordination of the drives, applications of this kind make particularly high demands on automation.
Full control of the rolling process
In seamless tube rolling, the tube ends, for production-related reasons, tend to thicken. Modern drive technology and automation can be used to taper heavy tube walls in a targeted manner. Rejections are reduced, efficiency is increased.
Wall thickness may vary over the entire length of the mother tube. Automatic wall thickness control is used to prevent such variations. For this, wall thickness is measured prior to insertion and subsequently optimised via tension increase and decrease. The quality of the tubes is thus improved.
In principle, the quick control system (2 ms cycle time) assumes the following tasks:
- Exact position tracking of tube head and tube end
- Reduction of heavy ends, so-called heavy end control
- Automatic wall thickness control
- Load compensation controls for adjusting engine torque in a stand
For a major manufacturer of stretch-reducing mills, Eckelmann has developed a hardware platform and the related software for next-generation machines. In this, one of the key tasks was to design a control system with a maximum of flexibility, allowing for the smooth transfer of the solution to future machines. For drive types and number of stands vary depending on the customer.
The automation also comprised the visualisation of process and user interfaces. In addition, a quick data logging system records approx. 1000 measurement values.