Publications

Wear due to thermal and mechanical stresses is one of the major causes of forging die failure. The assessment of die condition and the associated die life is usually based on experience. This paper presents a method to objectively predict the remaining life of a forging die. With this method a prediction based on optical measurements can be calculated. Practical tests show the possible applications. In addition, force measurements are performed and analyzed to determine how wear affects the force distribution in the die. The assessment based on optical measurements allows objective statements about the remaining tool life of forging dies. The analysis of the force measurements shows potential for predicting tool life but needs further investigation.

You can view the article here.

Process monitoring, wear, optical measurements, force measurement

Tool-integrated process variable monitoring during cross-wedge rolling of hybrid semi-finished products in the context of tailored forming process chains
Components made from several materials offer the potential to improve properties and increase functional integration. For example, it is possible to produce lighter and application-optimised components by combining steel and aluminium. The combination of different iron alloys can improve the mechanical properties of a component and thus increase the service life of rolling contacts, for example. Within the framework of the Collaborative Research Centre 1153 "Process Chain for the Production of Hybrid High-Performance Components by Tailored Forming" at Leibniz Universit¨at Hannover, the production of hybrid components is being researched. In particular, high demands are placed on the production of suitable semi-finished products by means of various joining processes, targeted heating and subsequent forming. Process monitoring of the forming of hybrid semi-finished products by means of cross-wedge rolling is necessary to ensure consistent component qualities and to detect component defects at an early stage. Within the scope of this dissertation, approaches for tool- and machineintegrated process monitoring are investigated. It is shown that by means of different sensor types a reproducible assessment of the process parameters can be carried out and the compliance with process limits can be monitored. Process parameters such as semi-finished product temperature and material as well as tool temperature, speed and position can be used automatically to determine process deviations.

Cross-Wedge Rolling, Process Monitoring, Tailored Forming, Hybrid Components

Process Optimization through Thin Flash Prevention. Due to the good flow properties of aluminum, the material tends to flow into tool gaps during flashless precision forging and produce the so-called thin flash. For the industrial implementation of flashless precision forging processes, an innovative prediction method for thin flash as well as sealing concepts are to be developed in cooperation with an industrial partner. Simulative studies show that local form filling does not correlate with high pressure or an increased potential for thin flash.

thin flash, FEM-simulation, sealing concepts, precision forging, forming technology

In the non-circular rolling, the feasibility of rolling several mutually offset, locally non-round shaped elements into a cylindrical semi-finished product are investigated. One sub-area of the investigations is the rolling of two elliptical sections.

From three different calculation concepts for the determination of the tool engraving, one was chosen for a simulative parameter study. The main influencing variables, including the length and width of the engraving and a process window, were identified.

forming technology, manufacturing technology, FEM

Process monitoring strategies allow wear-related conditions of forging dies to be detected and predicted. The prediction of the wear condition allows intelligent maintenance strategies. This allows residual tool life to be fully utilized, scrap to be reduced and downtime to be calculated. The content of this article is an economic analysis for calculating the payback period of a process monitoring system.

forging, process monitoring, economic efficiency

During flat die rolling, two die plates pass each other and form the cylindrical semi-finished product enclosed within. Non-circular rolling examines the rolling of multiple, locally nonround geometries such as eccentrics. With the aid of statistical experimental design, a simulative parameter investigation has been carried out, main influencing variables have been recognised and process windows identified.

non-round, eccentric, flat jaw tools, preforms, intermediate forms, FEM

IPH has developed an algorithm for the automated design of rolling dies in the DFG project "Non-Circular Rolling". The researchers are using it to perform extensive parameter studies with a wide range of dies.

Non-circular rolling, cross wedge rolling, rolling dies, design, automation, algorithm

In the automotive and mechanical engineering industries, forged parts are used in many applications. The dies for the forged parts are subject to high wear during forging due to high forming forces and temperatures. In order to enable economical production operation, methods to reduce the wear in warm forging have been investigated. One promising method is the use of Diamondlike-Carbon (DLC) wear-resistant coatings.

Warm Forging, Coating, DLC, Wear

In the forging industry, which is dominated by SMEs, the tool life of forging dies is usually determined on the basis of empirical values and subjective decisions. In order to avoid considerable logistical and economic expenses as a result of unplanned downtimes and die failure, the tool life is often set many times lower and a waste of existing residual tool life is caused. One possibility to determine the remaining tool life of forging tools is a combined measuring method, which is to be developed at the Institut für Integrierte Produktion Hannover (IPH) gGmbH.

Forming technology, tool life, process monitoring

Warm forged components have better surface properties and higher dimensional accuracy than hot forged components. Diamond-like-carbon (DLC) coatings can be used as wear protection coatings, which are anti-adhesive and extremely hard (up to 3500 HV), to increase tool service life. In the first funding period of the research project at the IPH – Institut für Integrierte Produktion Hannover gGmbH and the Institute for Surface Technology (IOT) of the Technical University of Braunschweig in cooperation with the Fraunhofer Institute for Surface Engineering and Thin Films (IST), the influence of different coating types and process temperatures on tool wear was investigated. The result is, that DLC coatings can reduce tool wear in some cases significantly, but that their service life is strongly dependent on the temperature. Coating-integrated temperature measurement could not be realised at that point, due to adhesion challenges. During the second funding period, the effect of multilayer DLC coatings on tool wear was investigated. Also, an additional method of the temperature measurement on the engraving surface using thin film sensors was developed in order to correlate the local process temperature and local layer wear. In this work, the development of and the results gathered by the thin film temperature sensors are presented, which enable for more accurate temperature measurements than commonly used thermocouples. Their functionality and durability under high loads were investigated and showed to be promising.

DLC2, warm forging, forging, wear, forming

The Hybrid Forging Process satisfies the needs of modern structural and material lightweight engineering by combining forming and mechanical joining operations within one process. This paper presents an analytical approach for the prediction of symmetrical joining bonds of bulk material and sheet metal. Finite element simulations verify that the analytical approach provides a threshold value for the sheet metal thickness at which the bending elongation is reduced significantly. Furthermore, the analytical approach emphasizes that surpassing the threshold value leads to a saturation of the bending elongation reduction and only marginal benefit is achieved by increasing the sheet metal thickness.

hybrid forging, bonding, joining, elastomechanics, lightweight, multi-material manufacturing

Components manufactured by hybrid forging in progressive dies have a high potential for lightweight construction. The example of a suspension arm shows the advantage of hybrid forged parts creating new possibilities for structural and material lightweight construction. Additionally, it is demonstrated that the heat subjected to hybrid forged parts during the subsequent hardening process does not threaten the potential of material lightweight construction.

progressive compound, hybrid, forging

The Institute for Integrated Production Hannover develops process technologies for the simultaneous forming and joining of dissimilar materials. In the future, they should enable, for example, sheet-metal solid parts and steel-aluminum connections. This expands the possibilities for cost-efficient multi-material construction methods in the automobile.

forging, hybrid, progressive compound

Bulk-formed components are used in many applications in automotive and plant engineering. The conditions under which the components are manufactured, often at more than 800°C and thousands of tons of forming force, lead to high die wear. One way to reduce wear is to use suitable protective coatings. Initial basic investigations showed that the use of hard Diamond-like Carbon (DLC) wear-resistant coatings can significantly reduce the tribological effects on the die surface. With new methods such as the use of multilayer layer coatings and temperature measurement on the die surface by use of thin layer sensors, the potential of wear protection for semi-hot massive forming is to be investigated and expanded.

DLC, hot forging, wear

Lot sizing is an important task of production planning and control: basis of lot sizes are order change costs and costs for storage. Models for lot sizing do not consider lot size dependent maintenance costs. However, for a forging company the tool wear is very important, because the tooling costs represent a major part in the production cost. In this article, the deter-ministic lot size model of Andler is extended with lot size dependent maintenance costs. For this purpose, the correlation between lot size and the tool wear is ?rst derived in order to develop a lot size dependent wear function. The linking of a lot size dependent wear function with maintenance costs results in a lot size dependent maintenance cost function, which can be integrated into existing lot size models with a customized total cost function. The validation of the extended lot size model consists of two parts. In the ?rst part, the functionality of the extended lot size model is validated. In the second part, a sensitivity analysis of the lot size is carried out with regard to lot size dependent costs and unit costs.

lot sizing, tool wear, forging industry, sensitivity analysis

High temperatures up to 1280 °C and high pressures during the forming opperation lead to strong tool wear in forging processes. Increasing tool wear can lead to very high costs. By experiments conducted at the Institut für Integrierte Produktion in Hanover the correlation between tool wear and lot size in hot forging processes was verfied. The findings will help companies to optimise maintenance procedures and therefore reduce cost in the future.

forging, steel, tool wear, lot size

Considering production planning and control, lot sizing is a very important task. Lot sizes are usually resorted to lot size dependent order and storage costs. However, models for lot sizes ignore the aspect of lot size dependent maintenance costs. For forging companies the tool wear has a great economic importance, because the tooling costs represents a major factor in production costs.

production planning and control, lot sizing, process stability

The lecture presents a method for the automated design and calculation of progressive dies. The basis is an automated CAD modeling of progressive dies. From the created CAD models characteristics are derived, which are used as input parameters for prediction models to predict the tool costs.

tool making, quotation costing, data mining, prediction

Many companies can or must reduce energy consumption in their production. The Institut für Integrierte Produktion Hannover (IPH) has developed procedures and a formula with which companies can improve the energy balance. At the same time the quality of products can be increased by this approach.

process management software, quality costs, reliability engineering

The companies in the tool making industry are exposed to a high intensity of competition. To get customer orders, they have to prepare reliable quotes in a short time. The available rudimental and partially incomplete information about the tool is of limited suitability for a reliable estimation of manufacturing costs. This thesis aims to support the tool making companies with tender preparation through a method of feature-based estimation of manufacturing costs. Essential basis forms a digital representation of the tool, which is generated by an automated CAD model building using technical guidelines. The method is implemented in the form of an expert system. The cost estimation is done, firstly, by determining the costs for machining by an analytical method based on the CAD model. Second, the costs for manufacturing processes are determined by means of a data mining based method by features derived from the CAD model and serve as inputs for prediction models. Using practical examples, the application of the expert system is described in practice and the method is evaluated. Thereby the practical applicability and limitations of the method are shown.

tool making, tool shop, quotation costing, data mining, expert system

The method of injection molding is one of the most important processes in the processing of plastics. Thus moldings can be produced economically in large quantities and with a high reproducibility. Besides quality the energy consumption in the production is an important part because of the energy transition and the rising energy prices. In particular, small and medium enterprises from the plastics processing industry in Germany with about 3,000 companies are, therefore, forced to optimize their processes and production equipment energetically.

injection molding, plastics processing, energy optimization, parameter optimization, energy model

Compliance with punctual delivery under the high pressure of costs can be implemented in the forge industry through the optimization of the in-house tool supply. Within the Transfer Project 13 of the Special Research Department 489, a mathematical model was developed which determines the minimum inventory of forging tools required for the production, considering the tool appropriation delay.

production planning and -steering, production management, tool inventory reduction, servicelevel, fo

Forging companies are often suppliers of the automotive industry, which has, by the implemented principles of Just-In-Time production, particularly high demands on the logistics performance of their suppliers. Moreover, the cost pressure in this industry is very high, so forging companies are striving to minimize their logistics costs. One of the factors influencing these logistics costs is the amount tools in a company’s tool inventory. Since the tooling costs have a high percentage of the product costs, strategic positioning between logistics performance and costs in the forging industry holds great potential. However, while a too low number of tools may cause delays in production and more frequent setting-ups caused by division of production lots and a concomitant increase of setting-up times of up to 30%, a possible consequence of too high tool inventories is the increase of process uncertainty by a prolonged and more stray tool circuit pass-through time. A structured approach to the positioning of the tool supply between logistics performance and costs is presented.

production planning and -steering, production management, tool inventory reduction, servicelevel, fo

There is a high potential for optimization in positioning a forging company’s tool supply between logistic costs and performance. Based on a model, which was developed for the improvement of the internal tool supply in the transfer project T13 of the CRC 489, a controlling instrument has been deduced to relate the weighted service level and the stock of the tool supply cycle.

production planning and -steering, production management, tool inventory reduction, servicelevel, fo

Through the use of cooling systems in injection molding, the reduction of cycle time and increasing the quality of molded parts is desired. New manufacturing processes such as selective laser melting enable the layered structure of cooling systems and allow the free design of cooling systems which is close to the part geometry. With these form-fitting cooling systems, for example, the tempering cycle times can be reduced further. However, the degree of freedom in the design of cooling circuits increases with the new production method, which makes the manual design difficult and extends the simulation times. Automated design methods of conformal cooling systems based on geometric and process parameters are currently not available. An innovative software helps by constructing close-contoured channels and reducing the cycle time with minimized engineering effort.

injection molding, conformal cooling systems, design, nature-inspired algorithms