MoMAS steps up productivity

The Mobile Measurement- and Automation-System for Extruders (MoMAS) is a system for optimising the operation of extruders for metals with the goal of achieving high productivity and enhance product quality. Basis for the optimisation is the mastering of the thermal processes underlying the extrusion process. In particular MoMAS consists of measurement and control sub-systems which serve to achieve tight control of crucial variables such as extrusion rate and exit temperature. This leads to a high and consistent product quality.

 

 

By virtue of the variety of options it offers, MoMAS provides operators and managers of extrusion plants with a flexible and effective tool which can be employed to achieve various optimisation and automation goals. Thereby the operator can himself select the degree of automation with which MoMAS operates. Most importantly, he can start off by operating the extruder manually and still exploit the information of process variables acquired and supplied by MoMAS. This provision for introducing the automation in steps alleviates its application and makes it easily acceptable on the part of operating personell.

MoMAS controls the exit temperature by suitably varying the extrusion rate automatically. It can be employed to achieve a reduction in the extrusion time per billet by employing exit temperature control in conjunction with a successive lowering of the furnace temperature. In case controlled tapered heating is possible, MoMAS can be employed to obtain constant exit temperature with constant extrusion rate.

A first important and useful function of MoMAS is that it measures various process variables such as exit temperature, extrusion force, ram velocity etc. continuously and displays runs of the runs of these variables in the current and previous cycles. Also displayed is information such as the extrusion time per billet, idle times between cycles and the mean and standard deviation of the exit temperature over the cycles.

The second main function of MoMAS is calculating the optimal input functions employing data of the previous cycles and displaying these at the start of each cycle. The operator can select the run of the input, e.g. the extrusion rate, proposed by MoMAS or a modified version of this and apply it to the extruder. Furthermore, a direct on- line control is superimposed during the extrusion.

The core of MoMAS is the exit temperature measurement and control system which is employed to maintain the exit temperature at a constant predetermined value. The control consists of a combination of Predictive FEeed- Back and Adaptive Feed- Forward (PFEBAFF) control. The extremely robust off- line open-loop control in conjunction with the on- line closed loop permits a variety of possibilities for optimising the extrusion process. The off-line technique facilitates the application of non-causal filtering for lag-free smoothing of the pyrometer signal and the elimination of effects of the inherent sluggishness of the extruder.

MoMAS hardware consists of an industrial PC with Windows operating system, a plug in card for interfacing the computer with the process, an interface to acquire the analog signals, a pyrometer for measuring the exit temperature and a sensor for ram position. This is supplemented by signal processing, control and optimising and data handling software.

All the process data is stored and can be archived and retrieved.