Advanced pass-schedule design in radial forging

The hydraulic radial forging machine SMX by SMS group has been a success story for more than 30 years, where the defining feature of the SMX is given by the hydraulic drive of the four forging dies. Compared to the conventional mechanically driven system, our hydraulic drive offers the significant advantage with regard to the forging process and workpiece quality that the full forging force is available over the entire stroke of each forging cylinder. Hence, a good core penetration as well as flexible forging strategies with a controlled movement of the dies becomes possible.

Nowadays, radial forging processes are mainly designed based on the experience and knowledge of the operator or geometry based pass-schedule calculation. Although this allows a well-proven analysis on the process sequence, forces and kinematics, it gives only a statement on the geometrical evolution of the workpiece and does not provide any further information e.g. on the distribution of equivalent strain or temperature.

On the other hand, a numerical simulation of open-die forging process using FEA (finite element analysis) is complex, requires large numerical effort as well as personnel with technological knowledge and is very time consuming, since forging processes usually consist of up to many hundred forming steps. Hence, the process design in radial forging is often very time-consuming, expensive and leads to pass-schedules, where too large safety margins e.g. regarding the temperature are chosen resulting in a reduced profitability. 

To overcome this challenge and improve the process of radial forging, SMS group presents the newly developed software ComForge^® Property Predictor, which can calculate the temperature and deformation for a given pass-schedule within seconds.

It is SMS group's target to support customers from pass schedule calculation to material properties optimization. Existing technology software ComForge^® is transferred into a forging technology suite now covering all extensions of ComForge^®:

1. ComForge^® PassSchedule Calculator
2. ComForge^® PassSchedule Analyzer
3. ComForge^® Property Predictor

Since its introduction with the first SMX radial forging machine, ComForge^® has proven to be an efficient and powerful tool for creating pass-schedules. ComForge^® allows ensuring a consistent high level of production quality by addressing the main challenges in process design:

• Increase productivity for maximum performance
• Minimum tolerances
• High reproducibility with detailed documentation

Within the new forging technology suite, the known ComForge^® is re-named as ComForge^® PassSchedule Calculator. With data on over 200 materials, the ComForge^® forging technology suite has everything required for calculating relevant forging schedules for all customers. This provides plant owners with a comprehensive database for trouble-free and technologically proven forging processes. After calculation, the pass-schedule is directly transferred to the PLC of the SMX and finally fully automated executed. Here, PassSchedule Calculator offers various forging strategies for the production of round, square and rectangular bars using different tool sets. To ensure a precise prediction of the forging time and the resulting productivity, the characteristics of the machine’s hydraulic are directly implemented into PassSchedule Calculator.

During forging operation, deviations between the planned pass-schedule and the forging operation might occur e.g. because of deviating alloy composition resulting in higher forces or manual action of the plant operator. The PassSchedule Analyzer is used to analyze the recorded process data from the SMX (e.g. speed, position, forces etc.) to identify these deviations. In a next step, these deviation are compared with the intended pass-schedule to check whether a critical impact on the material properties is given.

Property Predictor, as a part of our forging technology suite ComForge^®, is our advanced technology module, which allows a detailed calculation and analysis of radial forging processes regarding the material properties:

• Calculation and visualization of the strain distribution along the cross-section of the workpiece. The strain model is available for all most relevant material classes, where additional material groups or alloys can be implemented upon request. 
• Calculation of the temperature distribution in the cross-section considering radiation, convection, tool contact as well as heating through dissipation. The principle of temperature modelling is based on the Finite-Difference Method (FDM).

Property Predictor can be applied as stand-alone technology solution as well as in combination with PassSchedule Calculator, so that for any pass-schedule the temperature and strain distribution can be directly evaluated in no time. Using calculated pass schedule as input data for Property Predictor you can further optimize the process (see figure 2). The forging technologist can adapt the parameter of the pass-schedule and evaluate the effect of the forging parameter on the resulting strain and temperature distribution.

The software can also be easily used for employee training since it directly allows evaluation of the impact of different forging parameters on the workpiece quality.

Further benefits of ComForge^® Property Predictor are:

• No special FE-simulation software is required, saving high license fees.
• Due to the total integration within the forging technology suite, a simple data transfer directly within ComForge^® is possible and can be handled by process engineer, so that no simulation specialist is required.
• Due to the fast modelling of the strain and temperature, very short simulation times (less than 1 minute) are possible.

In the next step, the forging technology suite ComForge^® will be further developed by coupling  ComForge^® Property Predictor to the microstructure calculation by SMS group to enable direct calculation and optimization of the resulting microstructure in radial forging. This will be available in the forging technology suite under the name ComForge^® Property Optimizer. Furthermore, coupling the models to the control system of radial forging machine will allow for an online analysis of temperature, strain and microstructure in radial forging.

Contact: Martin Wolfgarten, Frederik Knauf