SIMULATION AND VIRTUAL REALITY – A KEY FACTOR IN
FUTURE DEVELOPMENT OF METAL FORMING PROCESSES
Miljenko Math
Prof. Miljenko Math, D.Sc., University of Zagreb, FSB, I. Lučića 5, 10000 Zagreb
Key words: Process simulation, numerical methods, finite element analysis
ABSTRACT
In recent years the metal forming industry utilizes practical and proven CAD, CAM
and CAE techniques. The development of numerical simulation methods has created new
feasibilities with great industrial aspects as regards optimisation of metal forming
processes. By applying such methods of analysis it is now possible to visualize the
internal material transformation and predict the interactions between material properties
and forming process, material flow, form filling and defect formation, optimise process
variables as well as predict die stresses for preventing premature die failure. This paper
summarises the state of simulation technology and reviews various applications in most
important forming processes, forging, stamping, deep drawing and extrusion. As
increasingly demands to manufacturing industry of faster, better and cheaper production
has intensified the research and development of this technique a brief discussion is given
concerning applications and future trends.
1. INTRODUCTION
In the process chain "forming", the simulation of the forming process offers
substantial rationalisation reserves, for example optimising of component and tool thus
also the enhancement of process reliability. The program systems currently in use must
be extended in various directions in order to accommodate the growing practical needs.
For further improved accuracy, along with the focuses of development discussed here it
will be necessary in future also to make allowance for better representation for the elastic
properties of the tool. The ultimate consequence of this is that, for complete simulation,
the elastic properties of the press or hammer also will be taken into account. The results
of this simulation will be constitute the basis for optimising the stiffness and weight of
tools.
In metal forming, process simulation is used to predict metal flow, strain,
temperature distribution, stresses, tool forces and potential sources of defects and
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failures. In some cases, it is even possible to predict product microstructure and
properties as well as elastic recovery and residual stresses.
In massive forming, simulation of 2D problems, e.g. axisymmetric and plane or
near-plane strain, is truly state of the art. The application for 3D problems is still not widely
used in industry because it is not always cost effective and requires considerable
engineering and computation time. In sheet forming, however, 3D simulation are
extensively used in stamping industry.
The main reasons of process simulation are:
a) reduce time to market
b) reduce cost of tool development
c) predict influence of process parameters
d) reduce productions cost product quality
e) improve product quality
f)
better understanding of material behaviour
g) reduce material waste
while the goals of manufacturing using these techniques are.
a) accurately predict the material flow
b) determine the filling of the swage or die
c) accurate assessment of net shape
d) predict if laps or other defects exists
e) determine the stresses, temperatures, and residual stresses in the work piece
f)
determine optimal shape or perform
Moreover, using simulation it is possible to:
a) determine material properties such as grain size
b) determine local hardness
c) predict material damage
d) predict phase changes and composition
e) simulate the influence of material selection
As simulation allows to capture behaviour that cannot be readily measured it provides
deeper insight into manufacturing process.
The principal steps involved in integrated product and process design for metal
forming are schematically illustrated in Fig.1., where there are based on functional
requirements, the geometry (shape, size, surface finishes, tolerances) and the material
are selected for a part at the design stage. It is well known that the design activity
represents only a small portion, 5 to 15 percent, of the total production costs of a part.
However, decisions made at the design stage determine the overall manufacturing,
maintenance and support costs associated with the specific product.
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Fig.1. Product and process design for metal forming
Once the part is designed for a specifics process, the steps outlined in Fig. 1 , lead
to a rational process design.
The application of computer aided methods in generally forming processes and
partly today especially important precision or net shape forming processes involves:
a) the conversion of the assembly-ready part geometry into a formable geometry
b) the preliminary design of tools/dies necessary to perform the operations used for
forming the parts
c) the analysis and optimisation of each forming operation and the associated tool
design, to reduce process development and trial and error, and
d) manufacturing of tools and dies by CNC milling or by EDM or another similar
technology
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The ascertaining of process-specific factors in production engineering by means of
process simulation serves the efficient manufacture of products of specified properties.
Three objectives are emphasised:
a) review of the feasibility of an existing concept for the manufacture of a product
b) assessment of product characteristic
c) enhancement of understanding as to what really goes on in a process for the
purpose of optimising the manufacturing technique
To achieve these goals, however, it only makes sense to use process simulation if
this is more economical in the long run than experimental repetition of the actual process.
2. SIMULATION OF METAL FORMING PROCESSES
It is precisely prior mentioned, this prerequisite of efficiency that lend process
simulation great significance in metal forming as compared with other manufacturing
techniques. The substantial cost of tool production and the high cost of the forming
machines compel the increasing use of modern, efficient methods and procedures of
process simulation. However, the variety of elements in the system of metal forming and
the complex mechanics of the forming process proper (geometric and material nonlinearities), make it difficult to deal with the problem so as to meet the rising requirements.
Fig.2. Simulation techniques in metal forming
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The historic development of the numerical and analytical i.e. mathematical
methods and techniques of simulating forming operations can be divided into two periods.
as can be seen on Fig.2.
In the period prior to economical utilisation of the computer (prior to approximately
1960) mostly empirical simulation procedures were employed. Through the systematic
experimental study of parameters (partly involving the use of similitude mechanics)
foundations were created for determining forming forces, material flow and failure
phenomena. The theoretical simulation methods were based mainly on elementary
plasticity theory and sought to compute the forming forces and roughly estimate the
stresses. A detailed description of the elementary plasticity theory is contained, for
example, in [1]. To a smaller extent, methods based on slip line theory and upper bound
methods were applied [2].
The decisive aspect of the theoretical procedures was that they involved simple,
closed analytical calculation rules, or that these theories were applicable by graphic
methods (slip line theory). In view of the complexity of the mechanics of the deformation
zone, the theoretical simulation techniques consequently entailed rough assumptions and
simplifications, which, in turn, strongly impaired the meaningfulness of the data
established with them. For this reason, around 1950 the first experiments were
undertaken to simulate the forming process proper with the modelling materials [3].
With the availability of the computer, a real revolution in the field of theoretical
simulation of forming processes began. Existing approaches that made use of higher
plasticity theory could then be applied. They were reformulated so that they can be used
with numerical techniques which in turn were easy for computers to process. The
development began with finite difference methods, went further with the consummation of
error method, finally advancing around the year 1970 to the application of the finite
element method. But it should be emphasised that the last mentioned techniques are only
"numerical tools" for applying the plasticity theories. Thanks to these numerical tools it is
now possible to determine in advance the flow of materials, the stresses, shape and
failure phenomena, making full use oof the foundations of plasticity theory.
Several issues, such as material properties, friction conditions, geometry
representation, computation time, and remeshing capability, must be considered in cost
effective and reliable application of numerical process simulation or modelling:
a) geometry-depending on geometrical complexity, a metal forming process can be
simulated as a two dimensional, axisymmetric or plane strain, or a threedimensional problem. In general, in order to have an efficient simulation it is
possible to remove all minor geometrical features, like small radii in forging dies if
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these features do not have a significant effect on the metal flow. However, in some
specific applications like microforming processes, tube hydroforming, or deep
drawing the size of effects should be taken into account in the simulation [4]. There
are basically two ways to introduce an existing model into FEM for meshing:
-
use a model from solid modelling as the most common method
-
read a file as a file from an outside CAD system
-
a third way to produce a model for meshing is to create it inside FEM with
geometry functions that are on disposal in particular FEM code
Major things to bear in mind are selecting the right element types and generating
the proper number of elements to accurately describe the physical behaviour of a
component-while keeping the number of DOFs small enough to let the problem
solve within reasonable time. One has to bury on mind that the goal of building an
FE model is to make a model that behaves mathematically like the structure but
not to make it that look like a structure. In general, the more subdivided model, the
more the solution converges on an correct answer. The only sure way to know if
one has sufficiently converged on an answer is to make more models with finer
grids of elements and then check the convergence of solution. But knowing when
to stop subdividing is also important-a solution that gives precise answer but takes
hundred hours to solve is hardly workable.
b) mesh and remesh-in forming processes the workpiece generally undergoes large
plastic deformation, and the relative motion between the deforming material and
the die surface is significant. In the simulation of such processes the starting mesh
is well defined and can have the desired mesh density distribution. As the
simulation continues, the distortion of the workpiece mesh is significant. Hence, it
is necessary to generate a new mesh and interpolate the data from the old mesh
to the new mesh in order to obtain accurate results. The mesh density should
conform to the geometrical features of the workpiece at each step of deformation.
These capabilities are available in commercial codes used in industrial practice. In
some today's solver it exists the so called rezoning option that overcomes too
strong distortion of an element that can cause inaccurate solution and even may
result in elements turning inside out. The element mesh rezoning philosophy does
consist of three steps. A continuous field for all position dependent variables is
determined by means of local smoothing techniques. In these continuous fields a
new finite element model is defined. And all variables are calculated by
interpolation, while the state at the beginning of an increment serves as the
reference state for calculation of the incremental values. Moreover, this procedure
can be done automatically, according to relevant prior determined criteria.
c) workpiece and tool material properties-in order to accurately predict the metal
flow and the forming loads it is necessary to use reliable input data. The stress
strain relation or flow curve is obtained from a compression test in massive forming
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and tensile or hydraulic bulge tests in sheet forming. In most simulations the tools
are considered rigid, thus, die deformation and stresses are neglected. However,
in precision forging and sheet forming operations, the relatively small elastic
deformations of the dies may influence the thermal and mechanical loading
conditions and the contact stress distribution at the die-workpiece interface.
Therefore, elastic deflection of the dies must be considered, whenever the
conditions require it. Today's software, however can handle those requirements
although the required computation time will increase.
d) interface conditions, (friction and heat transfer)-the friction and heat transfer
conditions (in warm forming) at the interface between the die and the workpiece
have a significant effect on the metal flow and the loads required to produce the
part. In massive forming simulation, due to the high contact stresses at the
interface between workpiece and the die, the constant shear friction factor gives
better results then the Coulomb friction coefficient, which is appropriate for use in
sheet metal forming.
e) characteristics of the simulation code (reliability and computation time)-several
commercial codes are available for simulation forming processes, some of them
only for massive forming or for sheet forming operations, but there are also the
commercially available FE programs for simulations practically every particular
forming technique. Some of these are presented in Table 1.
Here, it can be generally emphasised that the accurate and efficient use of metal
flow simulations requires not only a reliable FE solver but also:
1. software packages for interactive pre-processing to provide the user with control
over the initial geometry, mesh generation and the input data, automated
remeshing to allow simulation to continue when the distortion of the old mesh is
excessive, and interactive post-processing that provide more advanced data
analysis such as point tracking and the flow line calculation.
Table 1. Commercially available FE programs for forming process simulation
Application
Name
Manufacturer. country Type
ABAQUS
HKS, USA
Implicit
generally non-linear
MARC
MARC, USA/NL. D
Implicit
generally non-linear
NIKE3D
LSTC, USA
Implicit
generally non-linear
LARSTRAN
LASSO, D
Implicit
generally non-linear
INDEED
INPRO, D
Implicit
sheet metal forming
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ITAS3D
Prof. Nakamachi, J
explicit, static
sheet metal forming
DYNA3D
LSTC, USA/
explicit, dynamic
crash,
bulk,
sheet
metal
PAM-STAMP
ESI, F/D
explicit, dynamic
sheet metal forming
Optris
Dynamic Software, F explicit, dynamic
sheet metal forming
MSCDYTRAN
MacNeal-Schwendler explicit, dynamic
sheet metal forming
ABAQUS-explicit
HKS, USA
explicit, dynamic
crash,
bulk,
sheet
metal
AUTOFORM, CH
AUTOFORM
Spec.formulation
implicit
sheet metal forming
Autoforge
MARC, USA/NL, D
elastic-viscoplastic
bulk, forging
DEFORM
Batelle, USA, D
rigid-viscoplastic
bulk, forging
FORGE2/3
CEMEF, F
rigid-viscoplastic
forging
ICEM-STAMP
Control Data, D
one-step method
sheet metal forming
IS0-PUNCH
Sollac, F
one-step method
sheet metal forming
One- AUTOFORM, CH
one-step method
sheet metal forming
FASTFORM
FTI, Canada
one-step method
sheet metal forming
SIMEX2
SimTech, F
one-step method
sheet metal forming
AUTOFORM
step
2. software packages for interactive pre-processing to provide the user with control
over the initial geometry, mesh generation and the input data, automated
remeshing to
3. allow simulation to continue when the distortion of the old mesh is excessive, and
interactive post-processing that provide more advanced data analysis such as
point tracking and the flow line calculation.
4. appropriate input data describing thermal and physical properties of die and
workpiece material, heat transfer and friction at the die-workpiece interface under
the processing conditions being researched, and flow behaviour of the deforming
material and the relatively large strains that occur in practical metal forming
operations.
5. analysis capabilities that are able to perform the process simulation with igid dies
to reduce calculation time, and use contact stresses and temperature distribution
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from the process simulation with rigid dies to perform elastic plastic stress
analysis.
The time required to run simulation varies depending on the computer being used
and the amount of memory as well as the work load such a computer has. However, with
today computers it is possible to run a simple 2D forming in a couple of hours, while a 3D
simulation may take days to be completed.
3. APPLICATION IN MASSIVE FORMING
a) die and process sequence design in forging
In establishing cold forming operations, it is often appropriate to use a knowledgebased approach at early stages of the design process. However during the detailed
design of the tooling stages, it is necessary to predict the forging lo, the stresses acting on
the tools, and the metal flow to assure that no flow induced defects at any of the forging
stages. Process modelling is used routinely for this purpose by the industry and by the
researches. For reasons of confidentiality, however, there are very few published
industrial results.
Through appropriate experiments it is possible to determine how process
variables, i.e., strains, temperatures and strain rates influence the microstructure
development and properties of the formed part using the results of process simulation.
Examples of such application are available for forging microalloyed steels [5], cold forging
[6]. and hot forging of connecting rods [7].
b) prediction of fracture and laps in forged parts
In recent study, the concept of a critical damage value was introduced by
evaluating several ductile fracture criteria with a FE code: Experiments and numerical
simulations shows that some of used criteria could successfully predict ductile fracture in
cold forging with reasonable accuracy [8]. The application of the damage value concept
and the simulation results for forward extrusion sequence have been researched in [9],
where in first and second phase crack can be seen, while in third pass this cracks can be
eliminated owing to enough degree of deformation. This algorithm is now incorporated into
the commercial FEM code DEFORM and SUPERFORM, and used for predicting and
eliminating the probability of internal fracture in cold forging.
An important advantage of the forging process is that a smoothly contoured grain
flow, one that conforms closely with the die configuration, can be obtained in controlled
directions. To ensure this, certain design precautions and processing adjustments are
employed. Design adjustments for best producibility of ribs may include relocation of the
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parting line to obtain preferred grain direction. Moreover, it can include changes in die
sequences and configurations, or changes in equipment, lubricants or die and forging
temperature. Some of these elements are today incorporated in for example MARCSUPERFORM FEM code to simulate possible forming of laps and prevent possible
defects owing to that reason.
c) tool life and fracture
Numerical process simulation was used to perform the stress and fatigue analysis
of an arbitrary die in cold forging [10]. The capability of process modelling an predicting
the pressure distribution at the material-die interface was used for improving the die
design and service life. The geometry of the highly stressed punch is shown in Fig. 5a,
where by few iterations it was possible to reduce the peak stresses and distribute the
punch more evenly as shown on Fig. 5b. As a result, the punch life could be increased 6
to 8 fold.
Fig.3. Damage evolution in a pinion gear shaft
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Fig.4. Possible forming of laps and its prediction through simulation technique
c) tool life and fracture
Numerical process simulation was used to perform the stress and fatigue analysis of
an arbitrary die in cold forging [10]. The capability of process modelling an predicting the
pressure distribution at the material-die interface was used for improving the die design
and service life. The geometry of the highly stressed punch is shown in Fig. 5a, where by
few iterations it was possible to reduce the peak stresses and distribute the punch more
evenly as shown on Fig. 5b. As a result, the punch life could be increased 6 to 8 fold.
Fig.5. Examples of tool failure analysis to increase tool life in cold forging
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d) closed die forging of a connecting rod without flash
Process simulation was used to develop the tool and perform design for precision
flashless forging of connecting rods. The perform shape and volume, and forging
pressures were predicted [11] (see Fig.6). 3D simulations and physical modelling
experiments showed that the volume distribution and control in the perform must be very
accurate in order to avoid flash formation entirely. Therefore, the preparation of performs
with close tolerances, required for flashless forging, was found to be not practical.
Consequently, this study is now redirected to design a process where a minimum amount
of flashing is allowed.
e) crankshaft forging
This automotive hot forged automotive crankshaft is a well-known application for
three-dimensional simulation. This critical structural component of an internal combustion
engine requires proper grain flow and forging practice to produce a satisfactory part.
Geometry is critical, deformation is large and there is a very limited opportunity to take
advantage of symmetry. Simulating the thin flash requires a robust 3D system with
automatic enmeshing and a fast FEM engine. Fig.7 demonstrates a typical crankshaft
forging that can run on a personal computer or engineering workstation.
Fig.6. Deformations sequence for flashless precision forging of a connecting rod
Simulation and virtual reality
Fig.7. An automotive crankshaft forging simulated using DEFORMTM_3D
Fig. 8: The simulation of a hot forged gear without flash
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f)
integrated heat treatment analysis
In hot forming operations such as forging and extrusion although the last one is in
most cases in semi hot conditions it must be taken into account the heat transfer and
influence of temperature on stresses and metal flow. Sometimes, even in cold forming
operations the temperature can rise considerably owing to great plastic strain of material
and relative velocity between deforming material and the die. In such cases one need
coupled analysis both thermal and mechanical, but here it is pointed out yet another
possibility of numerical simulation: it is shown in [11] in simulation of the forming of a
medium carbon, manganese steel bevel gear that was analysed using DEFORMTM3D on
a personal computer. Mesh density windows were applied for local mesh refinement
during simulation. After deformation, the gear was austenized by heating to 15600 F and
cooled in 60 seconds with a heat transfer coefficient representative of an oil quench. All
that was successfully simulated and the volume fraction of martensite transformation and
the found the areas indicating a mixture of bainite and pearlite.
4. APPLICATIONS IN SHEET FORMING USING HARD DIES
The design of a sheet forming process and the dies involves, in principle, steps
similar to that considered in massive forming, Fig. 1. In sheet forming, however, it is often
necessary to conduct a “one step” product validation analysis, prior to die and process
design. This step allows the product designer to estimate the formability of the design and
make changes if necessary [10]. Simulation of stamping operations is widely accepted by
the automotive industry and its suppliers [11]. A few recent examples illustrate the state of
technology.
4.1 Product Evaluation and Optimal Blank Shape –Excavator Instrument Cover
Forming
Technologies
Inc.
has
provided
their
one-step
FEM
code
FAST_FORM3D and training to the ERC/NSM for the purpose of benchmarking and
research. FAST_FORM3D projects the final part geometry onto a flat plane or
developable surface and repositions the nodes and elements until a minimum energy
state is reached. It can evaluate formability and estimate optimal blank geometries.
An instrument cover for an excavator cabin from Komatsu Ltd. Of Japan is shown
in Fig. 7a. An optimal blank geometry was predicted with FAST_FORM3D and was
compared to the experimentally developed blank shape as shown in Fig. 7b. The
experimental and analytical blank shapes are similar but have some minor differences.
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Simulation of stamping with both blanks, predicted and experimentally developed, showed
that the simulation with the FAST_FORM3D blank gave more accurate results.
(a)
(b)
(c)
Fig. 7: FAST_FORM3D simulation results for instrument cover validation.
In order to study the die design process closely, a cooperative study was
conducted by Komatsu Ltd. Of Japan and the ERC/NSM. A production panel with
potential forming problems was chosen by Komatsu. The geometry was simplified into an
experimental laboratory die, while maintaining the main features of the panel. Experiments
were conducted at Komatsu. A forming limit diagram (FLD) was developed for the
drawing-quality steel using dome tests and a vision strain measurement system. Three
blank holder forces (100, 300, and 500 kN) were used in the experiments. Incremental
simulations of each experimental condition was conducted at the ERC/NSM using PAMSTAMP (Engineering Systems International).
At 100 kN, wrinkling occurred in the experimental, but at 300 kN, the wrinkling
was eliminated. These experimental observations were predicted with PAM-STAMP
simulations as shown in Fig. 11. The 300 kN panel was measured to determine the
material draw-in pattern. These measurements are compared with the predicted material
draw-in in Fig. 7c. Agreement was very good, with a maximum error of only 10mm. At 500
kN, an obvious fracture occurred in the panel. Strains were measured with the vision
strain measurement system for each panel. The predicted strains from FEM simulations
and measurements agreed well regarding the strain distributions, but differed slightly on
the effect of BHF. Nevertheless, these results show that process simulation can be used
to assess formability issues associated with the die design.
4.2 Pressline and die simulation
Computer-aided production engineering (CAPE) tools allow manufacturers to
create a complete virtual pressline including feeders, orientation stations and handling
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robots based on the original CAD geometric shape, or geometry, of these parts. The
realistic 3D environment enables manufacturers to visualise, simulate, verify and optimise
stamping operations in the early stage of the design process.
a) conventional design process
Sheet metal parts are usually manufactured on multi-stage press lines. In every
stage the part is drawn or formed. A process known as "methods design" defines what
shape each geometry must have after every stage and which tasks have to be performed
to produce this shape. This is usually done with the help of FEM-based drawing simulation
systems.
The die design itself is modelled on the geometries defined in the methods design.
It is usually done using CAD-based die design systems. Dies are complex tools,
consisting of several internal parts, e.g. matrices, driver slide devices, cutting steels or
scrap chutes. These parts perform different tasks simultaneously. This can cause
functional problems which may not be detected in CAD systems.
The state-of-the-art process with special software tools for the methods design, the
die design and later for NC programming and manufacturing allows the use of CAD data
throughout the engineering process. This shortens the engineering time, but does not
permit the verification of results until the first parts are manufactured in hardware.
The dies must be integrated into the press line. Since the parts flow from each
stage to the next is often done with rigid kinematics its motion track is usually not variable.
Therefore the die must be designed to ensure a collision free parts transport. Up until now
a die designer only had the 2D motion curve of the feeders to assist him in designing the
parts flow. This might suffice to avoid obvious collisions, but is not able to detect errors in
detail or to determine an optimal part flow.
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b) design process with 3D simulation
Fig.8. Steps involved in design process including 3D simulation
Transporting parts within the press line can cause collisions. As the space in the
open die is very limited, the dies and the toolings must be precisely adapted to take this
constraint into account. The engineers' main challenge is to design the die and the
toolings so as to prevent collisions between the parts and the die. Today the toolings are
not designed until the prototype of the press is set up (see fig. 8). Here the first die parts
are set up in hardware.
In some cases the parts transport is carried out flexibly using robots instead of
rigid kinematics. The set-up and programming of these robots takes place on the real
prototype. This testing phase with a prototype press occurs very late in the development
process. Thus any design changes made at this phase are very costly both in terms of
time and money. This may lead to a delay in the set-up of the pressline and thus in the
production of the parts.
Using CAPE tools to build up a virtual stamping line enables the developer to
verify the stamping line prior to the test with the real prototypes. Ensuring the correct
functioning of the die requires a lot of time and experience. The 3D simulation helps the
die designer to visualise and check all the movements with the help of the collision check
and other features. The functioning of cam kinematics can also be verified. The complete
pressline can even be build up as a virtual model including the environment as feeders,
orientation stations, or handling robots. The goal is to verify and optimise the complete
press line early in the design process. Therefore, AnySIM Simulationssysteme, a
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company of the Tecnomatix group, has developed in co-operation with customers in the
automotive industry, "AnyPRESS" an application based on existing 3D simulation
technology. AnySIM software is used for verification of manufacturing processes (e.g. NC
machines), robot applications or automated and manual assembly.
c) die design verification
Simulation enables the developer to analyse the results of the methods designs
before the first CAD model of the die has been constructed. By moving the parts CAD
model it is possible to calculate swept volumes of the moving part along its motion curve
(see fig. 8). Those swept volumes can be transferred back to the CAD System.
Having the swept volume of the part along its track reminds the developer that he
has to keep this space free for the parts flow. This helps die designers to avoid collisions
right from the beginning of the die design.
Fig.9. Calculating swept volumes at a very early stage of stamping line design
Dies usually have internal functionalities. Tasks, such as punching holes in a
direction other than that of the press movement, or trimming borders of the sheet metal,
require internal moving parts. These parts are usually driver slide kinematics called
"cams". The cams are usually driven by closing the die through the press movement.
Drivers attached to one half of the die force the slides to move when the contact faces
touch (see fig. 10). The actual tool, e.g. a cutting steel, is fixed to the slide.
At this phase, the pressline simulation is used for the function verification. The die
geometry is imported via CAD import functions from the die design system. The driver
slide kinematics of the cams are defined, and the actual part is loaded to the simulation
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environment. The kinematic structure of the die model is built up by defining kinematic
axes.
A special interface of AnyPRESS to the die design system "debis-VAMOS" from
debis Systemhaus GmbH allows the importing of the complete die model in a single step.
The simulation of the special cam kinematics with its drivers and slides is normally not
supported in kinematic simulation systems. The AnyPRESS application however enables
a comprehensive function verification by featuring realistic driver slide movement.
With the collision check function design errors in the cam design can easily be
detected during the simulation. It is used to eliminate collisions in the driver slide
kinematics as well as collisions between the part and the die.
Fig.10. Elements of a die design model and cam movement
e) press line simulation
The press line simulation helps the engineers to ensure a collision free parts flow
within the press line. The complete press line can be built up in the simulation
environment. Each press is modelled according to its geometric and cinematic qualities
and then placed in its correct position. The die models are attached to the appropriate
press machine. Feeder devices and orientation stations are positioned between the press
stages. With the first tooling design and the actual part model the geometric models of the
complete press line scene are now set up. The movements of all kinematic elements must
then be coordinated. The most common technique for synchronising movements is the
use of signal exchanges between individual kinematic elements. As there are numerous
kinematic elements in the scene, each with its own behavior and motion curve, it is very
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difficult to synchronise the elements' motion using signals. Therefore a special function
was developed in AnyPRESS which determines kinematic motion by defining its motion
curve with numeric tables. All available motion curves of all the feeder devices are loaded
into the simulation. AnyPRESS then automatically coordinates their motions to the 360
degree cycle of the leading press machine (see fig. 11).
In addition to this synchronization mechanism it is also possible to integrate
programmable kinematic devices (e.g. robots or programmable feeders) to the simulation
environment. They are synchronised by signal exchange.
Fig.11: Synchronisation of feeder devices to motion curve of the press machine
Once this environment has been set up it is possible to verify the functioning of the
whole press line (see fig. 12). AnyPRESS simulates the parts flow in detail showing the
interaction of the press machines, the feeder devices, the orientation stations and the
dies. The collision detection functionality detects and reports every single collision that
occurs during the stamping process.
Simulation and virtual reality
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Fig.12: Simulation model of the whole press line (presses bodies made invisible)
The option of calculating an offset for each part provides the required safety
distance for the dynamic movements of the sheet metal. The complete setup with all
feeder devices, orientation stations and handling robots can be tested, changed and
optimised without having to block an actual press line. The die and press line simulation
helps manufacturers to design, simulate and optimise stamping processes. This virtual 3D
environment enables them to optimise the die's functionality. Simulating all kinematic
devices along with their actual motions, it allows a verification and optimisation of the
stamping line prior to setup in hardware. This eliminates costly and time-consuming
errors, helps to eliminate risks and uncertainties and enables the manufacturer to
generate design alternatives. Finally, CAPE technology represents a first step towards
optimising cycle times.
The 3D simulation increases cooperation by improving communication both within
the company and with suppliers. The program delivers animation sequences, pictures and
plots, which reduce the hardware setup time by giving a clear understanding to all those
involved.
Overall the stamping line simulation reduces engineering time of new die designs,
toolings and part flow processes and makes the actual stamping process more reliable.
M. Math
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5. LITERATURE
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moje iz Nafemsa
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