T: +44 (0) 161 4747479 E: info@WildeFEA.co.uk

sheet metal simulation applications

• Joint paper presented at the Confederation of British Metalforming Technical Conference 2001.

• Paper focused on the use of both bulk and sheet metal simulation software to aid process development and improvement.

The Practical Use of Simulation in the Sheet Metal Forming Industry.

Wilde FEA Ltd. 2001

THE PRACTICAL USE OF SIMULATION IN THE SHEET METAL FORMING INDUSTRY

Dr Brian Miller (bmiller@WildeAndPartners.com)

Wilde & Partners Ltd, Brindley Lodge, Adcroft Street, Stockport, Cheshire, SK1 3HS

Richard Bond (cae.solutions@virgin.net) CAE Solutions Ltd, Unit D4, Hilton Trading Estate, Lanesfield, Wolverhampton, WV4 6DW

Abstract Much of the attention on simulation software in recent years has been focused on the modelling of bulk metal forming processes such as forging, rolling and extrusion. However, there are numerous applications for the simulation of sheet forming processes and indeed many pressings suppliers in the automotive industry are more advanced in the use of simulation than their forging counterparts. The type of software most suitable for sheet metal forming depends very much on the activities of the company and even the department. For example, at the part design or sales quotation stage, a quick ‘OneStep’ simulation can be run in minutes that ‘unfolds’ the part geometry to predict potential forming problems such as tearing, wrinkling and insufficient strain. Alternatively, toolmakers and stamping departments developing tooling concepts require a detailed incremental simulation where the various processes involved in the press (e.g. closing of tools, drawing, trimming and flanging) can be modelled accurately. Furthermore, there is an increasing need for tooling geometry to be created more quickly than by traditional CAD systems. Software developers have responded by offering rapid die face generation and morphing facilities within the simulation environment. If these issues are combined with the fact that many sheet forming-type processes such as piercing, bending and fastener clamping are best modelled using bulk metal forming software, the choice of software faced by the sheet metal former considering simulation can become very confusing. This paper aims to clarify the types of software available for sheet forming simulation and detail a number of industrial applications. Furthermore, recent developments in simulation, including the growing use of optimisation methods to automatically design tooling, will be discussed. 1. Introduction The use of simulation software in metal forming processes has increased significantly in recent years as the benefits of troubleshooting and optimising processes on the computer rather than through extensive shop trials have been realised. The rapid development of software technology, together with faster and lower cost computer hardware, have recently enabled many manufacturing operations to be modelled cost-effectively that only a few years ago would have been considered impractical. Many of these advances have been made possible by tailoring and optimising programs for specific applications, which has resulted in the general terms of ‘sheet-forming’ and ‘bulk-forming’ applied to different types of process modelling software. However, the choice of software for an uninitiated company is not always as simple as this classification. For example, sheet metal forming simulation is currently developing much interest in the UK as a means of reducing both the development costs of stamping a new part and the production lead time. These costs are accumulated over the entire

development process from initial part design to the final production tool. The correct software tool will depend on both the application and the stage of product development. As distributors for both a 2D/3D bulk forming program (DEFORM) and a 3D sheet forming program (AutoForm), Wilde & Partners have occasionally encountered confusion from companies involved with sheet metal components who are interested in simulation but are not sure which approach suits their processes. The objective of this paper is to reduce this confusion and highlight practical ‘sheet metal’ applications using both types of program. 2. Types of Simulation Program Available Most analysis software employs the finite element method where the geometry of the component to be deformed is divided or ‘discretised’ into simplified regular shapes called ‘elements’. There is a large range of elements available of varying complexity (or degrees of freedom) that can model different modes of deformation (and temperatures fields, electromagnetic fields etc.) [1]. General purpose finite element codes are not generally suitable for metal forming simulation because they are not optimised for these applications, and often do not include features such as automatic remeshing, robust evolving contact algorithms and a tailored, easy-to-use interface which are essential for practical implementation. In general, the two fundamental types of metal forming simulation software available to the sheet metal forming and fabrication industries can be classified by their element choice:

• ‘Sheet-forming’ programs, such as AutoForm, utilise shell elements which are well suited for large, thin sheet problems, where the stresses and deformation are primarily in the plane of the sheet;

• Implicit ‘Bulk-forming’ programs, such as DEFORM, utilise solid elements that can be superior for thicker sheet forming and certain hydroforming problems where the shell description is considered inadequate, and other sheet metal type problems such as joining and blanking, which are beyond the scope of shell element based simulation packages.

Depending on the objective of the simulation work, sheet-forming programs can also be subdivided into the following 3 main areas: 2.1.1 One Step ‘Inverse’ Programs

One Step programs work in reverse to what is normally expected from a simulation program. The part geometry with or without addendum is ‘unfolded’ back to the flat blank shape or to a curved blankholder profile. A One Step simulation can be used to assess very quickly whether the part is feasible by predicting material thickness distribution, cracks, wrinkles, plastic strain and minimum blank outline. Quicker than an Incremental simulation, an entire OneStep analysis will typically take between 5-15 minutes even for complex parts, including the import of part geometry from CAD, the automatic filling of holes and the specification of process parameters. Refinements to a basic OneStep simulation can be made by including the restraining effect of the addendum/flange area and the application of binder force and friction. The addendum can be generated automatically from part and binder surface geometry by specifying punch opening and flange boundary lines. A full tool analysis can also be performed if the CAD geometry is available or has been created in a ‘Die Designer’ system as described in Section 2.1.3.

2.1.2 Incremental Programs Incremental programs offer a full process model that simulates the forming stages as accurately as possible in the logical order from blankholder closing to final flanging. Consequently, incremental

simulations are computationally more intensive than the equivalent one step analysis, and require tooling information to be input. There are two types of incremental code based on either ‘implicit’ or ‘explicit’ mathematical formulations. Implicit codes such as AutoForm typically solve within 1-4 hours depending on the complexity of the part whereas explicit counterparts tend to be 2-4 times slower. As a ‘virtual tryout’ of the production method, an incremental simulation will often by used to simulate the entire stamping process, with capabilities to model the initial deflection of the sheet due to gravity, blankholder closing, first draws and restrikes, sheet repositioning, cutting operations, flanging and springback. Some codes can also simulate hydro-mechanical (fluid forming) processes for sheets and tubes. 2.1.3 Rapid Parametric Die Design Tools

When tooling information is required in a OneStep or Incremental analysis, the creation of the tooling geometry using a traditional CAD system is often very time-consuming, and can form a ‘bottleneck’ when trying to run several simulations quickly to optimise a die design. Consequently, some simulation programs now include integrated rapid die geometry creation tools that enable tooling concepts to be designed and evaluated by simulation more quickly. Developed specifically for automotive die designers, toolmakers and sheet metal stampers, additional surfaces are created for the addendum and blankholder areas of the tools (Figure 1). It has been estimated that these tools can reduce tooling development time by as much as 50%. Moreover, if the die geometry is parametrically linked to the simulation, optimisation programs as described in Section 6 can automatically modify the tools until the desired process is achieved.

Figure 1. Examples of tooling geometry created using AutoForm DieDesigner from the initial part geometry

3. Matching the Simulation Program to the Application

In principle, the solid element will always model 3D deformation in the most complete sense since it is a true discretisation of the geometry. When using solid elements, the geometry of any component should typically be divided into a number of elements in all directions to capture gradients in field variables and avoid extreme aspect ratios. For large thin sheet applications, this results in huge numbers of elements within the model and impractically long run times. Shell elements simplify the analysis by considering stiffness only in the plane of the element and due to bending. For thin sheet structures shell elements consequently offer a far more computationally efficient solution and work

Part

Addendum

Addendum

Blankholder

well if the primary mode of deformation is stretching and any bending is not severe compared to the thickness [2]. However, if the radii of any sheet bending (e.g. die or punch radius) approach the thickness of the sheet then solid elements can be significantly more accurate. Moreover, if the deformation includes other modes, such as localised compression through the sheet thickness (e,g. rivet installation) or extensive through-thickness shear (as in ironing or blanking processes), solid elements are necessary.

3.1 The Application of ‘Sheet Forming’ Programs

Sheet forming codes are used by companies for simulating the majority of deep drawing/stretching forming processes where sheet thickness is less than 2-3 mm. Typical parts that are assessed with these codes are automotive skin panels, automotive inner parts such as reinforcements, sumps and exhaust manifolds, aerospace engine components and complex white good components. In these cases, the engineer is usually most interested in the forming characteristics of the part including:

• The presence of wrinkles • High tensile strains leading to cracks • Insufficient plastic strain resulting in ‘loose’ material and poor surface finish • Skid lines where the sheet is marked by localised punch contact • Minimum blank outline to ensure sufficient material is available

Many of these characteristics can be conveniently assessed by a formability plot, where the major and minor strains predicted by the simulation are compared to the specific Forming Limit Curve for the material grade to identify potential problems (Figure 2).

Figure 2. AutoForm simulation example providing an assessment of formability (Courtesy BMW AG) The majority of sheet forming software licenses will be found in the automotive industry where the relatively large production volumes result in the greatest pressures to reduce part costs. In the vehicle development process, the design cycle can be separated into 4 phases:

• Concept Evaluation • Design Phase • Prototype Phase • Pre-production Phase

Typically the work performed in these phases will be shared between the OEMs and their first and second tier suppliers. Consequently, sheet forming simulation programs are used by virtually all OEMs (e.g. Land Rover, Jaguar), 1st tier pressing suppliers (e.g. Swindon Pressings, Mayflower), engineering consultancies (e.g. Lotus Engineering) and also smaller tooling development companies (e.g. CAE Solutions). Depending on the development phase and company strategy, different types of sheet forming program are most appropriate. For example, at Concept Evaluation, the part designer is unlikely to know the tooling geometry and indeed will not normally have the expertise to design the tools anyway. However, a simple Part Only OneStep simulation may be run to identify early forming problems that may occur if the part moves to the next phase. In such cases, the results can be used to aid discussions with the stamping engineers and guide necessary modifications to the part to achieve a ‘designed-for-manufacture’ concept. At the Design Phase, as the part is finalised, more detailed OneStep simulations can be run with some approximate tooling concepts involving trial addendum and blankholder developments. At the prototype and pre-production phases, these tooling concepts are refined with detailed geometry from CAD or DieDesigner tools, and then Incremental simulations are performed with the input of drawbeads, blank shape, binder forces, relief cuts and other process parameters. In practice Wilde & Partners have found that the application of the One Step and Incremental sheet forming programs varies widely between companies. In some cases, One Step simulations are used by stamping engineers at advanced stages of development because of their speed and ability to determine a minimum blank outline from the unfolded shape. Alternatively, in other situations, because of reduced run times from improved algorithms and hardware, incremental simulations are being increasing used at relatively early stages of the design cycle. 3.2 The Application of ‘Bulk Forming’ Programs Until recently, the use of solid element descriptions for sheet forming and fabrication simulations was severely limited by requirements on computational speed and memory size. However, the recent advances in software and hardware technology [3] have made it possible to run simulations with 100,000 to 300,000 or more elements in a reasonable amount of time. Simulation codes such as DEFORM are therefore being increasingly used for applications that fall outside the limitations of the sheet forming codes described above. They are also useful for modelling certain operations such as fastener insertion, piercing, and blanking that cannot be simulated using shell elements. In many processes, such as fastener insertion and other joining operations, two or more objects may be in contact with each other, with both objects deforming at once. Not all simulation codes can simulate multiple simultaneously deforming objects and therefore the prospective user may need to check out this criteria. A few applications can potentially be simulated using both approaches. For example, simulations are currently possible for tube hydro-forming with both shell and solid elements, with the best combination of speed, accuracy and ease of use depending on the user and details of the application. However, in most cases, including the following examples for both sheet and bulk forming codes, the most appropriate simulation approach is generally clear and can be determined from discussions with the software developers and distributors.

4. Practical Applications using a Sheet Forming Code (Shell Elements) 4.1 Formability Assessment using AutoForm OneStep In a typical One Step application, the engineer will begin with only the part geometry and perhaps some idea of the likely punch opening line of the tools and the final outline of the drawn sheet (‘the flange boundary’). In the following example of a front fender, this information is first input into AutoForm OneStep as shown in Figure 3(a). To perform the simulation, the program creates a mesh of the entire drawn sheet, including the addendum and flange areas, and fills holes and missing zones in the CAD geometry where necessary. During this stage, the mesh is automatically refined with smaller elements in areas of higher curvature and strain gradients (Figure 3(b)) to maximise accuracy. AutoForm OneStep then ‘unfolds’ the sheet to predict the minimum blank outline and make a formability assessment of the final part (wrinkles, cracks, thinning etc). Figure 3(c) indicates the final thickness distribution with critical thinning zones shown in red.

(a) Inputs for the simulation (b) Automatic generation of addendum

(c) Prediction of finadistribution and bla

Figure 3. Assessment of the formability of a front fender by AutoForm OneStep (courtesy

4.2 Tooling Optimisation using AutoForm Incremental at CAE Solutions Ltd CAE Solutions Ltd provides CAD/CAM/CAE services to the tooling industry, specializinrange of components and tooling variants for sheet metal forming processes. For die development, the company over the past five years have used various sheet forming simufor analysing and predicting formability tendencies. This enables their die designsdevelopments to be firstly ‘Proved’ and secondly fully ‘Optimised’ for successful Through their experience, CAE Solutions have found that one significant advantage forcompanies having simulations conducted on their die designs (apart from the obviousfailure) is the ability to request component concessions early in the manufacturing cycle ifhas any ‘borderline’ forming conditions. Other advantages of simulation for die manufactuminimisation of blank utilisation, allowing binder and die surface sizes to be kept to a mtool weight reductions, and the determination of kinematic and force requirements forplanning and press selection.

Part Geometry

Flange Boundary

Punch Opening Line

Minimum Blank Outline

l thickness nk outline

Audi AG)

g in a wide and process lation tools

& process production.

toolmaking of process the process ring are the inimum for production

4.2.1 Implementation of AutoForm-Incremental AutoForm-Incremental has been implemented into CAE Solutions as the front end simulation code for work with single and multi step draw operations, together with AutoForm DieDesigner for rapid die development due to its ability to automatically generate run-offs and variable draw levels for trials. Before the implementation of AutoForm, benchmarks were conducted with archived simulation projects carried out previously on an alternative ‘explicit’ incremental simulation code. On one particular project, with equivalent levels of accuracy specified, the set-up and run time of the AutoForm simulation was found to be approximately 10% of the original simulation time of 9.5 hours for the previous code. The results confirmed very similar formability characteristics of the component to the original simulation. As Figure 4 illustrates, the AutoForm simulation successfully demonstrated an ‘out-of-control’ process. The blank was shown not to be retained under the blankholder, leading to significant wrinkling at an early stage. After using AutoForm on a range of complex multi stage forming panels of different sheet materials, from high strength ZSTE (high press) through to Stainless grades (441,409,304,430ti), CAE Solutions saw good comparative feedback from their customer press trials to the simulations performed.

Figure 4 An example AutoForm incremental simulation at CAE Solutions Ltd indicating excessive

sheet draw-in and wrinkling (Courtesy: Mapleline) 4.2.2 Case Study of a Stainless Steel Half Shell Exhaust Component A project was undertaken by CAE Solutions Ltd on behalf of Unipart Eberspacher to design the tooling for stainless steel half shell exhaust components. These were to be produced and welded together to form the inter silencer assembly, which is assembled inside the main rear exhaust box. This project was performed in conjunction with Hewmor Products Ltd, who manufactured the tools, and Salop Design & Engineering Ltd who performed the final pressings. An interesting feature of the half shells was the perforations in the shell assembly used to decrease acoustic levels through the system. The part was a high production component and for both thermal and acoustic performance was to be produced from stainless steel grade 441 at 1.5mm sheet thickness. From initial 3D die design, it was determined that the tooling was to be operated manually through four stages of operations at approximately 5 strokes per minute in a mechanical press, as follows (Figure 5):

• Op10 – Developed piercing operation used to create the perforation pattern in the flat blank. • Op20 – Draw operation which allows form to be formed down to body flange level, with ‘Y’

piece & ‘Inlet/Outlet’ ports developed out for trimming and restriking. • Op30 – Trim part all round, with further development local to Y piece and Port regions. • Op40 – Restrike & Flanging operation to calibrate local radii, and flange Y piece & Port walls

to flange level.

(a) Punch Side (b) Die Side

Figure 5. 3D design of 4 Stage Tooling 4.2.3 Development of the Half Shell Tooling using Simulation CAD geometry was imported from the 3D design model into AutoForm, where the tools were defined for the Op20 Draw. A rough blank was generated with a ‘first-off’ trial perforation pattern. It was clearly identified that 90 off 3.5mm holes were required in the half shell. From the first simulation results of Op10 & 20 in Figure 6 it was seen that, when formed, the perforation pattern spread onto the lower flange area, together with gaps appearing on top of the pressing to allow further holes to be introduced. This would be unacceptable to the customer and therefore modifications were required.

(a) Partly drawn initial perforation pattern (b) Tools closed

Figure 6. AutoForm Incremental Simulation of ‘First-Off’ Trial Perforation Pattern

From the initial simulation results CAE Solutions were able to adjust the perforation pattern and optimise the blank to its minimum size before running a second simulation (Figure 7). The results of the second and final simulation proved the perforation pattern to be correct, and enabled the minimum blank size and the required force tonnage to be supplied to customer for early material coil ordering and press selection verification. Op30 initial trim line developments were then simulated in AutoForm, together with the Op40 flange and restrike operations, which highlighted the necessity to reduce material thinning in the ‘Y’ area of the component where trapped metal caused a localised problem. In addition to a reduction in the blank

size that allowed material to flow inwards more easily, CAE Solutions were able to increase the local radii in the Op20 Draw Die CAD model to solve this problem.

(a) Optimised Perforation Pattern (b) Tools Closed

Figure 7. AutoForm Incremental Simulation of Optimised Perforation Pattern 4.2.4 Integration of AutoForm with the Manufacture of the Half Shells With the ability to feedback information from AutoForm to their CAD systems, CAE Solutions was able to quickly update its 3D design CAD geometry to begin preparation of all CAM cycles required for Hewmor Products to begin CNC machining for tool manufacture. Operations 10, 20 & 40 were manufactured complete to the 3D design with slight further development conducted on trimming stage Op30. 4.2.6 Final Outcome of the Half Shell Tooling Development It can be seen from Figure 8 that the actual components achieved in tryout were highly similar to those predicted by simulation. As a further test, the simulated draw model was exported to the toolmaker as an STL file, which was inspected in a comparison test against a ‘hard’ pressing. Results showed the ‘pull in’ boundary of the component to be consistent with errors ranging up to 1-1.5 mm. With the use of simulation techniques, tooling design and manufacture was completed in 6 weeks ready for initial line production. Only 1 day of try-out time was required for the update of trim-line development to cut the final profiles of the Op30 cutting punch, die and stripper. Due to the confidence in the process all tools were manufactured as finished units, not approaching the try-out press until completion. Even the Op30 trim tool was simulated to within 1 mm, allowing the 3D form to be CNC-machined leaving minimum re-machining for the updated development.

(a) Actual perforation pattern (b) Final simulation of perforation pattern

(c) Final thickness distribution

Figure 8. Comparison of AutoForm Incremental simulation results with the actual component at tryout

5. Practical Applications using a Bulk Forming Code (Solid Elements) Forging and extrusion examples of bulk forming simulations have been shown at previous CBM Technical Conferences and elsewhere [3-5]. The following case studies are a selection reported by Fischer and Walters [6] using the 2D and 3D DEFORM simulation systems, applied to sheet metal and fabrication processes. 5.1 Axisymmetric Cup Drawing As mentioned previously, drawing processes where the draw radius of the tool is approaching the thickness of the sheet are typically not well served by sheet forming codes that rely on shell elements, since the bending of the material becomes as significant as stretching and drawing. Furthermore, these

type of programs struggle to model ‘ironing’ processes where shear stresses develop through the thickness between the punch and die. In such cases, particularly if the deformation is near-axisymmetric or plane strain, solid elements offer a superior and fast simulation solution. In one reported industrial application the DEFORM bulk forming code is able to detect corner cracking on thick sheet deep drawn cups using the Cockcroft-Latham damage criteria[6]. Figure 9 illustrates a 2 stage drawing process where the high damage value on the outside surface of the sheet after the second operation indicates potential failure.

Figure 9. Simulation of a 2- step cup drawing process. High damage value in outside corner on

second operation indicates a likelihood of fracture at this location. 5.2 Spinning and Crimping Spinning operations are typically performed to close off the ends of thin walled tubular components in diverse applications from cans to racing car drive seals. In many cases the deformation of the ‘sheet’ material is difficult anticipate and can require significant machine set-up time before the end is not over or under-formed. Figure 10 shows the use of 2D bulk forming simulation to help reduce the development time and expense of a new spinning process at a company. By simulating the effect of varying a number of machine parameters, a final production process was developed that enabled the can to be folded without any buckling or wrinkling occurring.

Figure 10. Simulation of a spinning operation on a thin walled can using DEFORM-2D.

Another process used in can manufacture is crimping, where three rollers are used to join a cap to a canister by forming a groove of a similar depth to the thickness of the sheet. The cylindrical updating capability in DEFORM-3D was used to simulate the localised deformation of the cap, enabling the movement of the rollers to be optimised (Figure 11).

Figure 11. Simulation of three roll crimping process for attaching a cap to a canister

5.3 Fine Blanking The fracture modelling capability in DEFORM has now been used for a number of years to study the localisation deformation of material around the failure zone [7-9]. Since shear-type forming processes develop high gradients of stress through the thickness, the solid elements of a bulk forming code are required. By simulating the effect of process parameters on burr formation during fine blanking in sheets, this capability can be used to aid the optimisation of the punch-die clearance for minimum roll-over and burr formation (Figure 12). Furthermore, by predicting punching loads, simulation studies can also be used when investigating tool wear problems.

Figure 12. Simulation of a fine blanking process. Simulation clearly shows rollover, shear zone, and rupture zone.

5.4 Riveting Simulation of the installation of a blind rivet involves severe deformation of two discrete objects, fracture, residual stress, and complex contact conditions. Since the stress pattern is predominantly

through the thickness of the sheets, solid elements must be used for this simulation. This simulation also requires the ability to simulate multiple deforming objects as shown in Figure 13.

Figure 13. DEFORM-2D simulation of the rivet installation process. Note residual stress in rivet

and sheet metal after installation.

5.5 Stud Mounting Fischer and Walters [6] describe the application of computer simulation by Fabristeel Corporation of Taylor, Michigan to develop their self-piercing mechanically staked fasteners for sheet metal parts. Their patented drawform stud was fully developed using simulation. The development process included simulation of the installation process, modeling pullout strength, and designing the manufacturing process for the part, using the multiple deforming body capability illustrated in Figure 14. Based on damage values in the sheet, the original design was modified to prevent fracture in the panel. Pull-out loads predicted by DEFORM were within 5% of experimental values (Figure 15).

Figure 14. (Left) DEFORM-2D simulation of drawform stud installation. (Right) Photograph of stud after installation.

Figure 15 Simulation of drawform stud pullout, and pullout load curve.

5.6 Wire Twisting An alternator manufacturer was experiencing problems with a wire twist tool jamming on wires during the manufacturing process. The cause of the jamming was not clear, and was not easily observable on production equipment. Simulation of this process required a software package such as DEFORM-3D, capable of modelling complex contact conditions between multiple deforming objects in a three dimensional simulation (Figure 16). The root cause of the problem was identified, and the process was modified to eliminate the jamming.

Figure 16: DEFORM-3D simulation of twisting 4 wires together

6 Recent Developments 6.1 Automatic Optimisation of Forming Processes There is increasing interest in both sheet and bulk forming simulation to automatically optimise the manufacturing operations using either integrated optimisation algorithms or third party software such as iSIGHT. Since the automatic determination of even a limited number of optimal process parameters may require a large number of simulations to be run, its practicality depends very much on processing time. However, it is inevitable that automatic optimisation will become increasingly popular in industry as computer speeds improve.

Optimisation capabilities are currently available within AutoForm, enabling the running of multiple OneStep or Incremental simulations to automatically ‘fine-tune’ die geometry or stamping processes. Indeed, since One Step simulations of thin sheet drawn parts can already be run in minutes, the optimisation of flange boundaries, drawbeads and other parameters is already being performed regularly by some users. Fully integrated within the user interface and parametrically linked to the DieDesigner capabilities, the user is able to determine the optimal tool geometry (radii of part and run-off, drawbar height, wall angles, over-crown etc) and stamping process (binder forces, drawbead strength, blank outline, etc,) based on target objectives such as maximum and minimum levels of strain (Figure 17).

Figure 17. An illustrative example of an AutoForm optimisation of tooling geometry, based on the objective of reducing all major strains below the forming limit curve.

6.2 3D Machining Simulations using Bulk Forming Codes Although not directly associated with sheet forming, a recent application using DEFORM-3D indicates the continued spread of simulation technology into all areas of manufacture. Although 2D simulations of machining simulation have been performed for a number of years [10], until recently, limitations on software and computer technology made the three-dimensional (3D) simulation of chip formation impractical. Simulation was therefore limited to so-called ’orthogonal’ cutting, where the cutting edge of the tool is perpendicular to the direction of cutting. As it is convenient to model, there is still much simulation carried out in this mode, however advances in simulation technology have recently made 3D simulation of metal cutting a practical option. As Figure 18 illustrates, a 3D simulation of oblique cutting indicates the lateral chip curl not seen in an orthogonal process.

Figure 18. DEFORM-3D simulation of an oblique cutting process

7. Conclusions This paper has intended to outline the variety of simulation approaches available to sheet metal forming and fabrication companies depending on their applications. However, perhaps the overall objective has been to demonstrate how simulation technology in general, when correctly used, can solve manufacturing problems, reduce development costs and even make better products. The choice of software is in many ways a secondary decision for a company, and can be made by discussing their requirements and applications with developers, distributors and trade bodies such as the CBM. The first and most important decision is whether a company decides that simulation technology in general may form part of their strategy into the future. 8. Acknowldgements The author wishes to thank Richard Bond of CAE Solutions Ltd for his help with the incremental sheet forming applications, and Hewmor Products Ltd, Salop Design & Engineering Ltd and Unipart Eberspacher for their permission to use this material. Also, thanks go to Fisher & Waters for allowing their bulk forming case studies to be shown, and Audi AG and BMW AG for the additional examples. 9. References [1] NAFEMS, A Finite Element Primer, DTI National Engineering Laboratory, 1986 [2] W. Kubli & J. Reissner, Optimisation of sheet-metal forming processes using the special

purpose program AutoForm, J.Mat.Proc.Tech.50 (1995), 292-305. [3] W.T. Wu, J.P. Tang, and G. Li, Recent Developments of Process Simulation and its

Applications to Manufacturing Processes”, 1st International Conference on Thermal Process Modeling and Computer Simulation, March 28-30, 2000, Shanghai, P.R. China.

[4] B. Miller, Virtual Manufacturing: New Simulation Technology and the Business Case, CBM

Technical Conference 1999. [5] C. Wheelhouse & B. Miller, The Industrial Application of Forging Simulation at UEF Ltd ,

CBM Technical Conference 2000. [6] C E. Fischer & J.Walters, Computer Simulation of Metal Fabrication Processes using

DEFORM, SFTC Paper #363. [7] Y. Kim, M. Yamanaka, T. Altan, Prediction and Elimination of Ductile Fracture in Cold

Forgings using FEM simulations, Ohio State University Engineering Research Center Paper No. 265.

[8] E. Taupin, J. Breitling, W.T. Wu, and T. Altan, Material Fracture and Burr Formation in

Blanking – Results of FEM Simulations and Comparison with Experiments, J. of Materials Processing Technology, 1996, vol. 59, nos. 1-2, pp. 68.

[9] B. Miller, M. Ward & K. Davey, The Numerical Simulation of Potential Forming Problems in

a Railway Wheel Manufacturing Process, Proc. Int. Conf. on Forging, IMECHE, 1998 [10] E. Ceretti, P.F.Bohmer, W-T Wu & T Altan, Application of 2D FEM to Chip Formation in

Orthogonal Cutting, J.Mat.Proc.Tech.,59 (1996), 169-180.