Control of the material flow in sheet-bulk metal forming using modifications of the tool surface

A conceptual framework is introduced for the design of tool surface topographies in bulk metal forming processes. The objective of the design is to control friction to desired levels while minimizing wear of the workpiece and tool surfaces and adhesive metal transfer between the workpiece and tool. Central to the design framework are the tool/workpiece interface properties of lubricant retention and interface permeability. Lubricant retention refers to the capacity of an interface to retain lubricant rather than freely channel it to the exterior of the tool/workpiece conjunction. Permeability refers to the capacity to distribute lubricant to all areas within the conjunction. These properties lead to the concept of two-scale surface topography consisting of a fine scale background of interconnected channels on which is superimposed an array of coarser-scale cavities. Control of friction and wear is achieved by designing the tool surface topographies at these two scales to address the unique tribological conditions of specific bulk metal forming processes. The coarser scale is designed to ensure adequate supply of lubricant within the conjunction. The finer scale is designed to ensure adequate delivery of lubricant to all parts of the conjunction where nascent workpiece surface is being formed. The design concepts are illustrated with results from laboratory experiments using the rolling process as an example, and comparing the performance of various roll surface topographies under similar processing conditions. A two-scale surface topography consisting of hemispherical cavities distributed across a background surface of finer scale, interconnected channels was shown to reduce friction compared to a single-scale ground finish, but not as much as a single-scale coarse topography consisting of densely-packed cavities produced by an electrical discharge treatment. On the other hand, the smoother cross-sections of the cavities, especially when elongated in the direction of greatest relative motion, produced significantly less wear than either of the single-scale tool surface treatments. It is concluded that two-scale engineering of tool surface topographies based upon the concepts of lubricant retention and interface permeability can provide a broad basis for achieving desired levels of interface friction while minimizing workpiece surface wear and adhesive material transfer in many metal-forming processes.

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Material flow control in sheet-bulk metal forming processes using blasted tool surfaces

MATEC Web of Conferences ◽

10.1051/matecconf/201819013003 ◽

2018 ◽

Vol 190 ◽

pp. 13003 ◽

Cited By ~ 1

Author(s):

Marion Merklein ◽

Maria Löffler ◽

Daniel Gröbel ◽

Johannes Henneberg

Keyword(s):

Metal Forming ◽

Material Flow ◽

Simultaneous Occurrence ◽

Tribological Behaviour ◽

Forming Process ◽

Functional Elements ◽

Bulk Metal ◽

Bulk Metal Forming ◽

Main Challenge ◽

Functional Components

Highly-integrated and closely-tolerated functional components can be produced by sheet-bulk metal forming which is the application of bulk forming operations on sheet metals. These processes are characterized by a successive and/or simultaneous occurrence of different load conditions such as stress and strain states which reduce the geometrical accuracy of the functional elements. Thus, one main challenge within sheet-bulk metal forming is the identification of methods to control the material flow and thus to improve the product quality. One suitable approach is to control the material flow by local modifications of the tribological conditions. Within this study requirements regarding the needed adaption of the tribological conditions for a specific sheet-bulk metal forming process were defined by numerical investigations. The results reveal that a local increase of the friction leads to an improved die filling of the functional elements. Based on these results abrasive blasting as a method to modify the tool surface and thus influencing the tribological behaviour was investigated. For the determination of the tribological mechanism of blasted tool surfaces, the influence of different blasting media as well as blasting pressures on the surface integrity and the friction were determined. The correlations between surface properties and friction conditions were used to derive the mechanisms of blasted tool surfaces.

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Investigation on blasted tool surfaces as a measure for material flow control in sheet-bulk metal forming

Manufacturing Review ◽

10.1051/mfreview/2019012 ◽

2019 ◽

Vol 6 ◽

pp. 10 ◽

Cited By ~ 3

Author(s):

Marion Merklein ◽

Maria Löffler ◽

Daniel Gröbel ◽

Johannes Henneberg

Keyword(s):

Metal Forming ◽

Material Flow ◽

Simultaneous Occurrence ◽

Tribological Behaviour ◽

Bulk Metal ◽

Geometrical Accuracy ◽

Bulk Metal Forming ◽

Tribological System ◽

Local Modification ◽

Functional Components

Highly integrated and closely tolerated functional components can be produced by sheet-bulk metal forming which is the application of bulk forming operations on sheet metal. These processes are characterized by a successive and/or simultaneous occurrence of different load conditions which reduce the geometrical accuracy of the parts. One challenge within sheet-bulk metal forming is the identification of methods to control the material flow to improve the product quality. A suitable approach is the local modification of the tribological conditions. Within this study, requirements regarding the needed adaption of the tribological system for a specific process were defined by numerical investigations. The results reveal that a local increase of the friction leads to an improved geometrical accuracy. Based on these results, abrasive blasting as a method to modify the tool surface and thus influencing the tribological behaviour was investigated. For the determination of the tribological mechanism of blasted tool surfaces, the influence of different blasting media as well as blasting pressures on the surface integrity and the friction were determined. Additionally, the functional stability of a modification was investigated. Finally, the correlations between surface properties and friction conditions were used to derive the mechanisms of blasted tool surfaces.

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Controlling material flow in incremental sheet-bulk metal Forming by thermal grading

Procedia Manufacturing ◽

10.1016/j.promfg.2020.08.048 ◽

2020 ◽

Vol 50 ◽

pp. 257-264

Author(s):

Sebastian Wernicke ◽

Ulrich Thier ◽

Marlon Hahn ◽

Erman Tekkaya

Keyword(s):

Metal Forming ◽

Material Flow ◽

Bulk Metal ◽

Bulk Metal Forming

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Innovative approaches for controlling the material flow in sheet-bulk metal forming processes

Manufacturing Review ◽

10.1051/mfreview/2016001 ◽

2016 ◽

Vol 3 ◽

pp. 2 ◽

Cited By ~ 3

Author(s):

Marion Merklein ◽

Michael Lechner ◽

Daniel Gröbel ◽

Maria Löffler ◽

Thomas Schneider ◽

...

Keyword(s):

Metal Forming ◽

Material Flow ◽

Bulk Metal ◽

Bulk Metal Forming ◽

Innovative Approaches

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Improved Sheet Bulk Metal Forming Processes by Local Adjustment of Tribological Properties

Journal of Manufacturing Science and Engineering ◽

10.1115/1.4005313 ◽

2011 ◽

Vol 133 (6) ◽

Cited By ~ 21

Author(s):

H. Hetzner ◽

J. Koch ◽

S. Tremmel ◽

S. Wartzack ◽

M. Merklein

Keyword(s):

Contact Pressure ◽

Metal Forming ◽

Material Flow ◽

System Analysis ◽

Sheet Thickness ◽

Fe Model ◽

Forming Process ◽

Bulk Metal ◽

Bulk Metal Forming ◽

Functional Features

This paper is focused on a combined deep drawing and extrusion process dedicated to the new process class of sheet bulk metal forming (SBMF). Exemplified by the forming of gearings, combined sheet and bulk forming operations are applied to sheet metal in order to form local functional features through an intended and controlled change of the sheet thickness. For investigations on the form filling and the identification of significant influencing factors on the material flow, a FE simulation model has been built. The FE model is validated by the results of manufacturing experiments using DC04 with a thickness of 2.0 mm as blank material. Due to the fact that the workpiece is in extensive contact to the tool surface and that the pressure reaches locally up to 2500 MPa, the tribological conditions are a determining factor of the process. Thus, their influence is discussed in detail in this paper. In the first instance, different frictional zones having a distinct effect on the resulting material flow are identified and their effect on improved form filling is demonstrated. Subsequently, a more comprehensive methodology is developed to define tribological zones of forming tools. For this, a system analysis of the digital mock-up of the forming process is performed. Besides friction, other relevant aspects of forming tool tribology like contact pressure, sliding velocity, and surface magnification are considered. The gathered information is employed to partition the tools into tribological zones. This is done by systematically intersecting and re-merging zones identified for each of the criterion. The so-called load-scanning test allows the investigation of the friction coefficient in dependence of the contact pressure and possible loading limits of tribological pairings. It provides an appropriate tribological model test to evaluate tribological measures like coatings, surface textures and lubricants with respect to their targeted application in particular zones. The obtained results can be employed in the layout of further forming processes to reach the desired process behavior. This can be, for example, an improved form filling, less abrasive wear and adhesive damage or lower forming forces, respectively tool load for an improved durability of the die.

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Analysis of Effectiveness of Locally Adapted Tribological Conditions for Improving Product Quality in Sheet-Bulk Metal Forming

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.794.81 ◽

2015 ◽

Vol 794 ◽

pp. 81-88 ◽

Cited By ~ 10

Author(s):

Maria Löffler ◽

Daniel Groebel ◽

Ulf Engel ◽

Kolja Andreas ◽

Marion Merklein

Keyword(s):

Metal Forming ◽

Material Flow ◽

Operating Time ◽

Wear Behaviour ◽

Bulk Metal ◽

Bulk Metal Forming ◽

Geometrical Features ◽

Tailored Surfaces ◽

Economic Developments ◽

Functional Components

Due to current ecological and economic developments there is a growing demand for functional components with complex and closely tolerated geometrical features. Conventional sheet and bulk metal forming operations leads to products which are often limited in their geometrical and functional variety. A promising approach is the process-class sheet-bulk metal forming (SBMF). SBMF is characterised by the application of bulk and sheet forming operations on sheet metals [1]. This combination leads to locally and temporally varying load conditions regarding stress as well as strain states. In order to get high quality parts, controlling the material flow is of major importance. Modified Surfaces, so-called tailored surfaces represent an innovative approach to control the material flow. The objective of the current study is the experimental investigation of the effectiveness of locally adapted tribological conditions using workpiece-and tool-sided tailored surfaces within SBMF processes. The study has shown that the local adaption of workpiece and tool surface increased the heights of functional elements. Thus, using locally adapted tribological conditions leads to an improvement of the quality of the produced gearing components. In a further step the influence of surface modifications on the surface properties of the manufactured components are analysed. Additionally, investigations regarding the wear behaviour of tool-sided surface adaptions lead to the assumption, that the effectiveness of tailored surfaces is reduced during the operating time of the tools.

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Influence of Surface Modifications on Friction, Using High-Feed Milling and Wear Resistant PVD-Coating for Sheet-Metal Forming Tools

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.639.275 ◽

2015 ◽

Vol 639 ◽

pp. 275-282 ◽

Cited By ~ 12

Author(s):

Dirk Biermann ◽

Dennis Freiburg ◽

Rouven Hense ◽

Wolfgang Tillmann ◽

Dominic Stangier

Keyword(s):

Metal Forming ◽

Material Flow ◽

Functional Integration ◽

Work Piece ◽

Efficient Production ◽

Bulk Metal ◽

Wear Resistant ◽

Structured Surfaces ◽

Bulk Metal Forming ◽

High Feed

Increasing technological requirements, as well as the demand for an efficient production demands high performance materials and enhanced manufacturing processes. The development of a new manufacturing process, sheet-bulk metal forming (SBMF), is one approach to produce lightweight forming parts with an increased number of functional properties while, at the same time, combining the advantages of sheet and bulk metal forming. For SBMF processes, the specific adjustment of the friction between tool and workpiece for a specifically designed material flow, which is called tailored friction, is of great importance. The reduction of friction is essential in order to ensure a homogeneous forming zone. However, a higher friction can be used to control the material flow to increase the local thickness of the work piece for additional functional integration. This paper shows the development of surface structures for SBMF tools by means of high-feed milling. Process parameters like the tilt angle or the feed are varied to influence the surface parameters of the structures, which results in different tribological properties of the forming tool. The structured surfaces are subsequently coated with a wear resistant CrAlN coating, processed by a magnetron-sputtering process (PVD) to enhance the lifetime and performance of the forming tool. Finally, a ring compressing test is used to investigate the tribological behavior of the coated structures.

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Validation and application of a screw method for strain measurement in bulk metal forming

The Journal of Strain Analysis for Engineering Design ◽

10.1243/03093247jsa280 ◽

2007 ◽

Vol 42 (7) ◽

pp. 519-527 ◽

Cited By ~ 2

Author(s):

S J Yuan ◽

J Zhang ◽

Z. B He

Keyword(s):

Numerical Simulation ◽

Plastic Strain ◽

Metal Forming ◽

Material Flow ◽

Physical Modelling ◽

Material Model ◽

Processing Parameters ◽

Bulk Metal ◽

Bulk Metal Forming ◽

Numerical Simulation Methods

A new method for measurement of plastic strain inside a deforming body is advanced and validated through a simple cylinder upsetting experiment. It is also applied to a ring for demonstrating this method in a ring compression test. The experimental results and numerical simulation show good agreement. In contrast with other physical modelling methods, this method utilizes the real metal for a sensor and workpiece, rather than using substitute materials, and can observe and measure material flow and plastic strain inside the specimen without splitting it before deformation. It can be used to study material flow and to predict strain distribution in general bulk metal-forming processes such as upsetting, extrusion, and die forging. It is also useful for verification of the numerical simulation methods when the material model and the processing parameters were uncertain and/or not easily verified.

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