Overview of Modeling

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Casting Process Modeling Using SOLIDCast
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What is SOLIDCast?

• SOLIDCast is the worlds best-selling casting
  process modeling software from Finite Solutions,
  Inc. This package, formerly sold as AFSolid 2000,
  is now in use in more than 400 companies and
  schools in over 40 countries around the world.
• SOLIDCast is a PC-based software tool that
  simulates the pouring of hot metal of virtually
  any casting alloy into sand, shell, investment or
  permanent molds, and the subsequent
  solidification and cooling process.

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What makes SOLIDCast Work?

• SOLIDCast uses the Finite Difference Method(FDM)
  of heat transfer calculation, combined with a
  unique tracking of volumetric changes in the
  metal, to predict the temperature and volume
  changes in a casting as it is poured, solidified
  and cooled.
• This combined thermal-volumetric approach has
  proven to be an extremely accurate method of
  predicting various casting problems, including
  micro- and macro-porosity, hot spots and other
  defects.

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What is Casting Process Modeling?

• Casting Process Modeling is a mathematical way to
  let the computer predict(simulate) what will
  happen when a casting is poured on the shop
  floor.
• Virtually anything that can be modified in the
  foundry can be simulated using Casting Process
  Modeling. Simulation allows you to fine tune your
  casting process in much less time, and without
  the waste of expensive materials, than shop floor
  trials.

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What are the benefits?

• Shorten Lead Times
• Help Solve Problems
• Optimize Existing Jobs
• Train Employees
• Improve Customer Relations
• Attract More Jobs Through Improved Market Image

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So, how does Casting Process Modeling work?

• Select Materials and Properties
• Build Casting/Mold Model
• Mesh Model/Run Simulation
• Evaluate Results
• Modify and Re-simulate

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Select Materials and Properties

• The first step in modeling is to select the
  materials that will be used in the simulation.
  This includes the casting alloy, as well as all
  mold materials. SOLIDCast contains databases
  with over 230 casting alloys in all the major
  groups, plus data on all common mold materials.
• You can also use chills, insulation, exothermics
  and cooling/heating channels in permanent mold
  dies.

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Select Materials and Properties

• Properties That Control Heat Flow in a Mold
  Material
• Thermal Conductivity
• Specific Heat
• Density
• Initial Temperature(s)

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This screen capture of the Mold Tab shows typical
properties for a cast iron chill. All common
molding sands are included, plus insulating and
exothermic materials. You can add, modify or
remove materials at any time.
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Select Materials and Properties

• Casting Alloys Also Require
• Solidification Temperature
• Freezing Range
• Latent Heat of Fusion
• Solidification Curve
• Volumetric Change(Shrinkage) Curve

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The Casting Tab has additional data, since the
casting alloy will change from a liquid to a
solid during the simulation.
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The Solidification and Shrinkage curves define
the freezing behavior for each casting alloy.
These can be modified by the user, and cast iron
curves can be developed based on chemistry and
molding method.
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Select Materials and Properties

• Heat Transfer Coefficients Control Heat Flow
  Between Materials
• Mold Coatings
• Air Gaps
• Cooling Channels
• Convection/Radiation

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Heat Transfer Coefficients(HTCs) are used to
define how heat flows across surfaces. They are
most often used in permanent mold casting, to
show coating effects, and in investment casting,
to show radiation effects from the hot shell.
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The top pictures show 2 investment casting models
The bottom pictures show the radiation view
factors
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Build Casting/Mold Model

• Once youve created a Materials List, which
  tells the system what materials will be used in
  your simulation, you need to build the
  casting/mold geometry.
• This step is the most user-intensive part of the
  process, but, as you will see, there are many
  time saving ways of building models.

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Model Building Techniques

• Direct import of 3D CAD data
• Import of 2D CAD data gt 3D
• Blueprints
• Digitizing
• Shapes, Drawing, 2D CAD

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3D STL File Import

• Most CAD systems have it
• Triangles cover the part surface
• One file for each material(casting, chills,
  cores)
• Binary smaller than ASCII

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This model of a cylinder head was created using 4
STL files, one for the casting, two for core
assemblies and one for the sleeves.
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2D DXF File Import

• Every CAD system has it
• Auto-trace utility can extract cross-sections
• Extrude, rotate or blend sections to create 3D
• Exact data as created by CAD operator
• Drawings may have problems, but can be corrected

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The 2D DXF file shown above became the 3D solid
shown at the right. Sections from the CAD file
were extruded, rotated and blended to create 3D
geometry.
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Working With Blueprints - Digitizing

• Fast input
• Multiple scales are ok
• Hardware is inexpensive
• CAD looks better, but simulation results are the
  same

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With a digitizing tablet and a blueprint, you can
trace 2D sections that will be rotated, extruded
or blended into 3D models, such as the investment
cast valve bodies shown at the right.
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Working With Blueprints Shapes, Drawing, 2D CAD

• Requires greatest time and operator effort
• Good for gating/risering systems
• Doesnt require other software
• Works best when all dimensions are listed

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This aluminum permanent mold casting took over a
day to build, using only a blueprint and 2D CAD.
However, the improvements made due to simulation
saved the foundry over 700,000 per year on this
part alone! (Note that the die pieces have been
removed for clarity.)
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Run Simulation

• Once you have the Materials List and the
  casting geometry, you can put the two together in
  a process called Meshing. The meshed model is a
  series of cubes, called nodes. Each node has
  different material properties, as defined in your
  materials list.
• The meshed model is like a big series of Lego
  bricks, all of which are shaped like cubes. A
  meshed model may have millions of cubes, and the
  heat transfer equations are applied to each cube,
  over and over.

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This pictures shows a meshed model of casting
plus risers, including insulating and exothermic
sleeves and chills. The number of cubes used in
a mesh is limited only by available memory.
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This picture shows the mold cavity as it is being
meshed. This can be done automatically using
SOLIDCast.
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Temperatures During Filling Sequence
During the mold filling simulation, the relative
temperatures are shown on the screen, so you can
see hot and cold spots develop. Heat is being
lost to the mold and surrounding air.
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Temperatures During Solidification Sequence
After mold filling is complete, you can watch the
progression of solidification. Gray areas show
solidified metal, and temperatures can be seen in
the cooling metal. Notice that volumetric feeding
is calculated at the same time as temperature.
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Interpreting Results

• Once a simulation is complete, you can look at
  various pieces of data to decide whether you have
  made a good part or a bad one.
• Since this decision may be based on different
  factors for each casting, SOLIDCast provides
  many types of data for your use.

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What Data Can be Plotted?

• Temperature During Fill and Solidification
• Displayed during the simulation, or as a single
  time plot
• Time
• Liquidus
• Critical Fraction Solid
• 100 Solid
• Local Solidification
• Hot Spots (Isolations)
• Based on CFS
• Based on 100 Solid

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What Data Can be Plotted?

• Temperature Gradient
• Cooling Rate
• Material Density
• Criteria Functions
• Niyama
• FCC (Micro-porosity)
• User Defined Functions

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How Can Data Be Plotted?

• CastPic Plot
• 3D color plot at any orientation
• Cut planes can be active
• Iso-Surface Plot
• Surface at a given value
• Surrounds worse values
• Good for time or density plots
• Cut-Plane Plot
• 2D slice from the 3D model
• Good detail, plus individual data
• CastScan Movies
• Color plot on a transparent casting
• Progressive or rotating

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This CastPic plot show the progression of
Critical Fraction Solid (CFS) Time on a valve
body casting. The casting has been cut in half so
you can see what is happening internally.
Progressive Solidification Critical Fraction
Solid Time Range (CastPic Plot)
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This screen is an iso-surface plot of the FCC
Criterion, used to predict microporosity in
castings. Notice that the tendency towards
shrinkage varies depending on position in the
mold.
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This is a Cut Plane Plot. You can drag the cut
plane through the model, and a 2D plot will be
created instantly. This plot also shows CFS Time,
which shows when feeding ends.
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Movies Animating your plots

• Each of the plot types can also be created in a
  movie format. You can control the number of
  frames, how fast the movie runs, and the range of
  data displayed.
• These movies are saved in the Windows standard
  AVI format, so you can send copies to your
  customers and they can run them on any Windows
  PC, without any extra hardware or software.
• The next screen shows samples from a movie.

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Modify Model and Re-simulate
Simulation is an iterative process. Once you have
evaluated results, most often you will find
something that needs improvement. When you do,
you have a number of options available.
Basically, anything that can be changed on the
shop floor can be simulated to a certain extent
using SOLIDCast. For example, you can

• Change Geometry
• Change Process Parameters
• Change Rigging

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The Payback - Casting Examples

• Steel Investment Cast Food Processing Part
• Aluminum Permanent Mold Automotive Part
• Steel Sand Cast Elevator Part
• Cast Iron Sand Cast Compressor Body

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Investment Casting - Steel

• 3 patterns via rapid prototyping
• 2 failures by conventional methods
• 13 simulations in 1 1/2 weeks
• 500,000 per year new business
• saved 26-39 weeks lead time

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The figure on the left is the initial rigged
geometry. The iso-surface plot on the right shows
material density. You can see shrinkage-prone
areas moving from the gating system into the
casting.
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The final model, with a top ring riser, gives
acceptable results. Note that shrinkage was not
completely eliminated in this case, but was
reduced and moved into an acceptable area of the
casting.
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Permanent Mold - Aluminum

• High Volume Brake Component
• 7 Shrinkage Rejects on Machining
• Now lt0.4 Rejects
• 700,000/Year Savings

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With the original gating, the last place to
freeze was in the casting, not the riser. When
this area was bored out, the shrinkage was
exposed and the casting was scrapped.
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By changing the riser shape and increasing the
contact size, the last point to freeze was moved
into the riser, and the casting is now
shrink-free.
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Sand Casting - Steel

• Behind in delivery of new casting
• 9 risers but still had shrinkage
• 12 simulations with feedback
• 10 working days to complete job
• 5-6 yield improvement
• Better quality at a reduced cost

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Without simulation to show the hot spots, this
casting was over-risered, yet still had
unacceptable shrinkage.
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Simulation pointed out where the real problems
lay, allowing an intelligent risering scheme to
be applied, resulting in higher yield AND higher
quality.
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Sand Casting - Cast Iron

• Gray iron compressor body
• High yield, but shrinkage in green sand
• Simulations run for green sand and no-bake
  molding systems
• No-bake provided good results

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This gray iron compressor body was cast in the
green sand process, but had internal
porosity. By switching to a no-bake process, the
mold was more rigid and shrinkage was eliminated.
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Simulated X-ray results. Green Sand
Mold No-Bake Mold
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