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Shape Optimization of Coils
Introduction
This model demonstrates how to design a coil geometry using gradient-based shape optimization. The objective is to achieve a uniform magnetic field along the coil axis and a field minimum near the axis ends. The model assumes azimuthal symmetry, but one can use the optimization result as inspiration for a 3D design.
Model Definition
The model is set up with six inner coils and one coil at each end with the opposite current direction. The current in the two outermost coils at each end is also optimized to mimic the effect of having coils with partial turns. The result of the shape optimization is shown in Figure 2, while the initial geometry for this model is shown in Figure 1.
Figure 1: The initial geometry.
The Transformation and Free Shape Domain features are used to allow the coils to move in the radial direction. There are 8 control variables for the coil positions and one for the current in the outer coils. The IPOPT optimization can solve such problems fast.
The objective function, φ, consists of two terms:
The setup of the first objective function is simplified by the use of the Standard Deviation feature.
Results and Discussion
Figure 2: The optimized geometry.
Figure 2 shows the optimized design. The first and second objectives are reduced by around 90% and 50%, respectively. The strength of the magnetic field on the axis is illustrated in Figure 3.
Figure 3: The optimization increases the magnetic field in the middle domain and decreases it in the outer domains.
Notes About the COMSOL Implementation
This model can be constructed in a way that exploits symmetry in the xy-plane, leading to a reduction in the computational time.
Application Library path: Optimization_Module/Shape_Optimization/coil_shape_optimization
Modeling Instructions
From the File menu, choose New.
New
In the New window, click  Model Wizard.
Model Wizard
1
In the Model Wizard window, click  2D Axisymmetric.
2
In the Select Physics tree, select AC/DC > Electromagnetic Fields > Magnetic Fields (mf).
3
Click Add.
4
Click  Study.
5
In the Select Study tree, select General Studies > Frequency Domain.
6
Click  Done.
Geometry 1
1
In the Model Builder window, expand the Component 1 (comp1) > Geometry 1 node.
2
Right-click Geometry 1 and choose Insert Sequence.
3
Browse to the model’s Application Libraries folder and double-click the file coil_shape_optimization_geom_sequence.mph.
4
In the Geometry toolbar, click  Build All.
5
Click the  Zoom Extents button in the Graphics toolbar.
The geometry should now look like that in Figure 1.
Global Definitions
Geometry Parameters
1
In the Model Builder window, under Global Definitions click Parameters 1.
2
In the Settings window for Parameters, type Geometry Parameters in the Label text field.
Parameters 2
1
In the Home toolbar, click  Parameters and choose Add > Parameters.
2
In the Settings window for Parameters, locate the Parameters section.
3
In the table, enter the following settings:
Name
Expression
Value
Description
f0
1[kHz]
1000 Hz
Frequency
lastTurns
0.5
0.5
Outer loop current factor
dmax
3[cm]
0.03 m
Maximum coil translation
Add Material
1
In the Materials toolbar, click  Add Material to open the Add Material window.
2
Go to the Add Material window.
3
In the tree, select Built-in > Air.
4
Click the Add to Component button in the window toolbar.
5
In the tree, select Built-in > Copper.
6
Click the Add to Component button in the window toolbar.
7
In the Materials toolbar, click  Add Material to close the Add Material window.
Materials
Copper (mat2)
1
In the Settings window for Material, locate the Geometric Entity Selection section.
2
From the Selection list, choose Objects to Mirror.
Magnetic Fields (mf)
Domain Coil 1
1
In the Physics toolbar, click  Domains and choose Domain Coil.
2
In the Settings window for Domain Coil, locate the Domain Selection section.
3
From the Selection list, choose Inner Coils.
4
Locate the Coil section. Select the Coil group checkbox.
5
In the Icoil text field, type 1[kA].
Domain Coil 2
1
Right-click Domain Coil 1 and choose Duplicate.
2
In the Settings window for Domain Coil, locate the Domain Selection section.
3
From the Selection list, choose Outer Coils 2.
4
Locate the Coil section. In the Icoil text field, type 1[kA]*lastTurns.
In a 2D axisymmetric model, specifying a coil with a fraction of the total current is a way to represent a coil with partial turns. Similarly, specifying a current with the opposite sign represents a coil that is wound in the opposite direction.
Domain Coil 3
1
Right-click Domain Coil 2 and choose Duplicate.
2
In the Settings window for Domain Coil, locate the Domain Selection section.
3
From the Selection list, choose Outer Coils.
4
Locate the Coil section. In the Icoil text field, type -1[kA]*lastTurns.
Mesh 1
Mapped 1
1
In the Mesh toolbar, click  Mapped.
2
In the Settings window for Mapped, locate the Domain Selection section.
3
From the Geometric entity level list, choose Domain.
4
From the Selection list, choose Infinite Domains.
Distribution 1
1
Right-click Mapped 1 and choose Distribution.
2
In the Settings window for Distribution, locate the Boundary Selection section.
3
From the Selection list, choose Infinite Domain Boundaries.
Free Triangular 1
In the Mesh toolbar, click  Free Triangular.
Size 1
1
Right-click Free Triangular 1 and choose Size.
2
In the Settings window for Size, locate the Geometric Entity Selection section.
3
From the Geometric entity level list, choose Domain.
4
From the Selection list, choose Deforming Domain.
5
Locate the Element Size section. From the Predefined list, choose Extremely fine.
Size 2
1
In the Model Builder window, right-click Free Triangular 1 and choose Size.
2
In the Settings window for Size, locate the Geometric Entity Selection section.
3
From the Geometric entity level list, choose Boundary.
4
From the Selection list, choose Whole Axis.
5
Locate the Element Size section. Click the Custom button.
6
Locate the Element Size Parameters section.
7
Select the Maximum element size checkbox. In the associated text field, type 0.004.
8
Click  Build All.
Component 1 (comp1)
Free Shape Domain 1
1
In the Physics toolbar, click  Optimization and choose Shape Optimization.
2
In the Settings window for Free Shape Domain, locate the Domain Selection section.
3
From the Selection list, choose Deforming Domain.
Transformation 1
1
In the Shape Optimization toolbar, click  Transformation.
2
In the Settings window for Transformation, locate the Geometric Entity Selection section.
3
From the Selection list, choose Objects to Mirror.
4
Locate the Translation section. In the table, enter the following settings:
Lock
Lower bound (m)
Upper bound (m)
R
 
-dmax
dmax
Z
 
-coilSpace/4
coilSpace/4
5
Locate the Scaling section. From the Scaling type list, choose No scaling.
Definitions
Standard Deviation 1 (std1)
1
In the Definitions toolbar, click  Physics Utilities and choose Standard Deviation.
2
In the Settings window for Standard Deviation, locate the Geometric Entity Selection section.
3
From the Selection list, choose Rectangle 4.
4
Click Replace Expression in the upper-right corner of the Standard Deviation section. From the menu, choose Component 1 (comp1) > Magnetic Fields > Magnetic > comp1.mf.normB - Magnetic flux density norm - T.
5
Locate the Quadrature Settings section. Select the Compute integral in revolved geometry checkbox.
Average outer magnetic field
1
In the Definitions toolbar, click  Probes and choose Domain Probe.
2
In the Settings window for Domain Probe, type Average outer magnetic field in the Label text field.
3
In the Variable name text field, type Bouter.
4
Locate the Source Selection section. From the Selection list, choose Outer Objective Domain.
5
Locate the Expression section. In the Expression text field, type mf.normB.
Infinite Element Domain 1 (ie1)
1
In the Definitions toolbar, click  Infinite Element Domain.
2
In the Settings window for Infinite Element Domain, locate the Domain Selection section.
3
From the Selection list, choose Infinite Domains.
Study 1
Step 1: Frequency Domain
1
In the Model Builder window, under Study 1 click Step 1: Frequency Domain.
2
In the Settings window for Frequency Domain, locate the Study Settings section.
3
In the Frequencies text field, type f0.
General Optimization
1
In the Study toolbar, click  Optimization and choose General Optimization.
2
In the Settings window for General Optimization, locate the Optimization Solver section.
3
From the Method list, choose GCMMA.
4
Click Add Expression in the upper-right corner of the Objective Function section. From the menu, choose Component 1 (comp1) > Definitions > comp1.std1 - Standard deviation.
5
Click Add Expression in the upper-right corner of the Objective Function section. From the menu, choose Component 1 (comp1) > Definitions > comp1.Bouter - Average outer magnetic field - T.
6
Locate the Control Variables and Parameters section. Click  Add.
Initialize the study to generate a plot for use while solving.
7
In the table, enter the following settings:
Parameter
Initial value
Scale
Lower bound
Upper bound
Unit
lastTurns (Outer loop current factor)
0.5
1
0
1
 
8
Click to expand the Solver Settings section. Find the Objective settings subsection. From the Objective scaling list, choose Initial solution based.
9
Click to expand the Output section. From the Keep solutions list, choose First and last.
10
From the Probes list, choose None.
11
In the Model Builder window, click Study 1.
12
In the Settings window for Study, type Shape Optimization in the Label text field.
13
In the Study toolbar, click  Get Initial Value.
Results
Shape Optimization
The plot shows the displacement. Add an Annotation feature to also show the value of the lastTurns parameter.
Annotation 1
1
In the Model Builder window, right-click Shape Optimization and choose Annotation.
2
In the Settings window for Annotation, locate the Annotation section.
3
In the Text text field, type eval(lastTurns).
4
Locate the Coloring and Style section. Clear the Show point checkbox.
5
From the Background color list, choose Gray.
Shape Optimization
General Optimization
1
In the Model Builder window, under Shape Optimization click General Optimization.
2
In the Settings window for General Optimization, locate the Output section.
3
Select the Plot checkbox.
4
In the table, enter the following settings:
Plot group
Plot window
Shape Optimization
Graphics
Enable move limits to reduce the risk of inverted elements.
Solver Configurations
In the Model Builder window, expand the Shape Optimization > Solver Configurations node.
Solution 1 (sol1)
1
In the Model Builder window, expand the Shape Optimization > Solver Configurations > Solution 1 (sol1) node, then click Optimization Solver 1.
2
In the Settings window for Optimization Solver, locate the Optimization Solver section.
3
Select the Move limits checkbox.
4
Select the Maximum number of outer iterations checkbox. In the associated text field, type 50.
5
Click  Run.
Results
Magnetic Flux Density, Revolved Geometry (mf)
1
In the Magnetic Flux Density, Revolved Geometry (mf) toolbar, click  Plot.
2
Click the  Zoom Extents button in the Graphics toolbar.
Field on Axis
1
In the Results toolbar, click  1D Plot Group.
2
In the Settings window for 1D Plot Group, type Field on Axis in the Label text field.
3
Locate the Data section. From the Optimization solution list, choose First.
4
Click to expand the Title section. From the Title type list, choose Label.
Line Graph 1
1
Right-click Field on Axis and choose Line Graph.
2
In the Settings window for Line Graph, locate the Selection section.
3
From the Selection list, choose Whole Axis.
4
Locate the x-Axis Data section. From the Parameter list, choose Expression.
5
In the Expression text field, type z.
6
Click to expand the Legends section. Select the Show legends checkbox.
7
From the Legends list, choose Manual.
8
In the table, enter the following settings:
Legends
Initial Design
Line Graph 2
1
Right-click Line Graph 1 and choose Duplicate.
2
In the Settings window for Line Graph, locate the Data section.
3
From the Dataset list, choose Shape Optimization/Solution 1 (sol1).
4
From the Optimization solution list, choose Last.
5
Locate the Legends section. In the table, enter the following settings:
Legends
Optimized Design
Line Graph 3
1
In the Model Builder window, right-click Field on Axis and choose Line Graph.
2
In the Settings window for Line Graph, locate the Selection section.
3
From the Selection list, choose Inner Axis.
4
Locate the x-Axis Data section. From the Parameter list, choose Expression.
5
In the Expression text field, type z.
6
Click to expand the Coloring and Style section. From the Color list, choose Cycle (reset).
7
From the Width list, choose 3.
Line Graph 4
1
Right-click Line Graph 3 and choose Duplicate.
2
In the Settings window for Line Graph, locate the Data section.
3
From the Dataset list, choose Shape Optimization/Solution 1 (sol1).
4
From the Optimization solution list, choose Last.
5
Locate the Coloring and Style section. From the Color list, choose Cycle.
Line Graph 3, Line Graph 4
1
In the Model Builder window, under Results > Field on Axis, Ctrl-click to select Line Graph 3 and Line Graph 4.
2
Right-click and choose Duplicate.
Line Graph 5
1
In the Settings window for Line Graph, locate the Selection section.
2
From the Selection list, choose Outer Axis.
Line Graph 6
1
In the Model Builder window, click Line Graph 6.
2
In the Settings window for Line Graph, locate the Selection section.
3
From the Selection list, choose Outer Axis.
4
In the Field on Axis toolbar, click  Plot.
5
Click the  Zoom Extents button in the Graphics toolbar.
Compute the value of the objective functions before and after optimization.
Evaluation Group 1
In the Results toolbar, click  Evaluation Group.
Global Evaluation 1
1
Right-click Evaluation Group 1 and choose Global Evaluation.
2
In the Settings window for Global Evaluation, click Add Expression in the upper-right corner of the Expressions section. From the menu, choose Component 1 (comp1) > Definitions > std1 - Standard deviation - T.
3
Click Add Expression in the upper-right corner of the Expressions section. From the menu, choose Component 1 (comp1) > Definitions > Bouter - Average outer magnetic field - T.
4
In the Evaluation Group 1 toolbar, click  Evaluate.
Compute the value of the corners, so that one can construct an interpolation function for 3D verification.
Point Displacements
1
In the Results toolbar, click  Evaluation Group.
2
In the Settings window for Evaluation Group, type Point Displacements in the Label text field.
3
Locate the Data section. From the Optimization solution list, choose Last.
Point Evaluation 1
1
Right-click Point Displacements and choose Point Evaluation.
2
In the Settings window for Point Evaluation, locate the Selection section.
3
From the Selection list, choose Lower left point.
4
Locate the Expressions section. In the table, enter the following settings:
Expression
Unit
Description
r
m
r-coordinate
z
m
z-coordinate
5
In the Point Displacements toolbar, click  Evaluate.
Geometry Modeling Instructions
From the File menu, choose New.
New
In the New window, click  Blank Model.
Add Component
In the Home toolbar, click  Add Component and choose 2D Axisymmetric.
Global Definitions
Parameters 1
1
In the Model Builder window, under Global Definitions click Parameters 1.
2
In the Settings window for Parameters, locate the Parameters section.
3
In the table, enter the following settings:
Name
Expression
Value
Description
R1
45[cm]
0.45 m
Domain radius
infR
10[cm]
0.1 m
Infinite domain radius
coilWidth
1[cm]
0.01 m
Coil width
coilHeight
2[cm]
0.02 m
Coil height
R2
6[cm]
0.06 m
Coil inner radius
nCoil
3
3
Number of coils
coilSpace
1.5[cm]
0.015 m
Coil spacing
objHeight
33[cm]
0.33 m
Objective domain height
objR
2[cm]
0.02 m
Objective domain radius
objOuter
6.5[cm]
0.065 m
Outer objective domain
objSpace
1.5[cm]
0.015 m
Objective domain spacing
deformR
13[cm]
0.13 m
Deforming domain width
deformHeight
40[cm]
0.4 m
Deforming domain height
tTube
2[mm]
0.002 m
Tube thickness
objInner
objHeight-2*objSpace-2*objOuter
0.17 m
Inner objective domain
Geometry 1
Circle 1 (c1)
1
In the Geometry toolbar, click  Circle.
2
In the Settings window for Circle, locate the Size and Shape section.
3
In the Radius text field, type R.
4
In the Sector angle text field, type 180.
5
In the Radius text field, type R1.
6
Locate the Rotation Angle section. In the Rotation text field, type -90.
7
Click to expand the Layers section. In the table, enter the following settings:
Layer name
Thickness (m)
Layer 1
infR
Rectangle 1 (r1)
1
In the Geometry toolbar, click  Rectangle.
2
In the Settings window for Rectangle, locate the Size and Shape section.
3
In the Width text field, type coilWidth.
4
In the Height text field, type coilHeight.
5
Locate the Position section. In the r text field, type R2.
6
In the z text field, type -coilSpace*(nCoil+0.5)-(nCoil+1)*coilHeight.
7
Locate the Selections of Resulting Entities section. Select the Resulting objects selection checkbox.
Rectangle 2 (r2)
1
Right-click Rectangle 1 (r1) and choose Duplicate.
2
In the Settings window for Rectangle, locate the Size and Shape section.
3
In the Width text field, type coilWidth-2*tTube.
4
In the Height text field, type coilHeight-2*tTube.
5
Locate the Position section. In the r text field, type R2+tTube.
6
In the z text field, type -coilSpace*(nCoil+0.5)-(nCoil+1)*coilHeight+tTube.
Difference 1 (dif1)
1
In the Geometry toolbar, click  Booleans and Partitions and choose Difference.
2
In the Settings window for Difference, locate the Difference section.
3
From the Objects to add list, choose Rectangle 1.
4
From the Objects to subtract list, choose Rectangle 2.
5
Locate the Selections of Resulting Entities section. Select the Resulting objects selection checkbox.
6
Click  Build Selected.
Lower left point
1
In the Geometry toolbar, click  Selections and choose Disk Selection.
2
In the Settings window for Disk Selection, locate the Geometric Entity Level section.
3
From the Level list, choose Point.
4
In the Label text field, type Lower left point.
5
Locate the Size and Shape section. In the Outer radius text field, type coilWidth/100.
6
Locate the Disk Center section. In the r text field, type R2.
7
In the z text field, type -coilSpace*(nCoil+0.5)-(nCoil+1)*coilHeight.
Copy 1 (copy1)
1
In the Geometry toolbar, click  Transforms and choose Copy.
2
In the Settings window for Copy, locate the Input section.
3
From the Input objects list, choose Difference 1.
4
Locate the Displacement section. In the z text field, type coilSpace+coilHeight.
5
Locate the Selections of Resulting Entities section. Select the Resulting objects selection checkbox.
Inner Coils
1
Right-click Copy 1 (copy1) and choose Duplicate.
2
In the Settings window for Copy, type Inner Coils in the Label text field.
3
Locate the Input section. Click to select the  Activate Selection toggle button for Input objects.
4
From the Input objects list, choose Copy 1.
5
Click  Build Selected.
Array 1 (arr1)
1
In the Geometry toolbar, click  Transforms and choose Array.
2
In the Settings window for Array, locate the Input section.
3
From the Input objects list, choose Inner Coils.
4
Locate the Size section. In the z size text field, type nCoil-1.
5
Locate the Displacement section. In the z text field, type coilHeight+coilSpace.
Objects to Mirror
1
In the Geometry toolbar, click  Selections and choose Union Selection.
2
In the Settings window for Union Selection, type Objects to Mirror in the Label text field.
3
Locate the Geometric Entity Level section. From the Level list, choose Object.
4
Locate the Input Entities section. Click  Add.
5
In the Add dialog, in the Selections to add list, choose Difference 1, Copy 1, and Inner Coils.
6
Click OK.
Mirror 1 (mir1)
1
In the Geometry toolbar, click  Transforms and choose Mirror.
2
In the Settings window for Mirror, locate the Input section.
3
From the Input objects list, choose Objects to Mirror.
4
Select the Keep input objects checkbox.
5
Locate the Normal Vector to Line of Reflection section. In the r text field, type 0.
6
In the z text field, type 1.
Outer Objective Domain
1
In the Geometry toolbar, click  Rectangle.
2
In the Settings window for Rectangle, type Outer Objective Domain in the Label text field.
3
Locate the Size and Shape section. In the Width text field, type objR.
4
In the Height text field, type objOuter.
5
Locate the Position section. In the z text field, type -objHeight/2.
6
Locate the Selections of Resulting Entities section. Select the Resulting objects selection checkbox.
7
Click  Build Selected.
Outer Axis
1
In the Geometry toolbar, click  Selections and choose Box Selection.
2
In the Settings window for Box Selection, type Outer Axis in the Label text field.
3
Locate the Geometric Entity Level section. From the Level list, choose Boundary.
4
Locate the Box Limits section. In the r maximum text field, type objR*0.1.
5
In the z minimum text field, type -objHeight/2-objOuter*0.01.
6
In the z maximum text field, type -objHeight/2+objOuter*1.01.
7
Locate the Output Entities section. From the Include entity if list, choose Entity inside box.
Mirror 2 (mir2)
1
In the Model Builder window, under Component 1 (comp1) > Geometry 1 right-click Mirror 1 (mir1) and choose Duplicate.
2
In the Settings window for Mirror, locate the Input section.
3
Click to select the  Activate Selection toggle button for Input objects.
4
From the Input objects list, choose Outer Objective Domain.
Rectangle 4 (r4)
1
In the Geometry toolbar, click  Rectangle.
2
In the Settings window for Rectangle, locate the Size and Shape section.
3
In the Width text field, type objR.
4
In the Height text field, type objInner.
5
Locate the Position section. From the Base list, choose Center.
6
In the r text field, type objR/2.
7
Locate the Selections of Resulting Entities section. Select the Resulting objects selection checkbox.
Rectangle 5 (r5)
1
In the Geometry toolbar, click  Rectangle.
2
In the Settings window for Rectangle, locate the Size and Shape section.
3
In the Width text field, type deformR.
4
In the Height text field, type deformHeight.
5
Locate the Position section. In the z text field, type -deformHeight/2.
6
Locate the Selections of Resulting Entities section. Select the Resulting objects selection checkbox.
Form Union (fin)
1
In the Model Builder window, click Form Union (fin).
2
In the Settings window for Form Union/Assembly, click  Build Selected.
Deforming Domain
1
In the Geometry toolbar, click  Selections and choose Difference Selection.
2
In the Settings window for Difference Selection, type Deforming Domain in the Label text field.
3
Locate the Input Entities section. Click the  Add button for Selections to add.
4
In the Add dialog, select Rectangle 5 in the Selections to add list.
5
Click OK.
6
In the Settings window for Difference Selection, locate the Input Entities section.
7
Click the  Add button for Selections to subtract.
8
In the Add dialog, in the Selections to subtract list, choose Rectangle 1, Outer Objective Domain, and Rectangle 4.
9
Click OK.
Infinite Domain Boundaries
1
In the Geometry toolbar, click  Selections and choose Disk Selection.
2
In the Settings window for Disk Selection, locate the Geometric Entity Level section.
3
From the Level list, choose Boundary.
4
In the Label text field, type Infinite Domain Boundaries.
5
Locate the Size and Shape section. In the Outer radius text field, type R1*0.99.
6
In the Inner radius text field, type R1*0.98.
Infinite Domains
1
In the Geometry toolbar, click  Selections and choose Adjacent Selection.
2
In the Settings window for Adjacent Selection, type Infinite Domains in the Label text field.
3
Locate the Input Entities section. From the Geometric entity level list, choose Boundary.
4
Locate the Output Entities section. From the Geometric entity level list, choose Adjacent domains.
5
Locate the Input Entities section. Click  Add.
6
In the Add dialog, select Infinite Domain Boundaries in the Input selections list.
7
Click OK.
Coil Cavities
1
In the Geometry toolbar, click  Selections and choose Box Selection.
2
In the Settings window for Box Selection, type Coil Cavities in the Label text field.
3
Locate the Box Limits section. In the r minimum text field, type R2+tTube*0.5.
4
In the r maximum text field, type R2+coilWidth-0.5*tTube.
5
Locate the Output Entities section. From the Include entity if list, choose Entity inside box.
Outer Coils
1
In the Geometry toolbar, click  Selections and choose Difference Selection.
2
In the Settings window for Difference Selection, type Outer Coils in the Label text field.
3
Locate the Input Entities section. Click the  Add button for Selections to add.
4
In the Add dialog, select Difference 1 in the Selections to add list.
5
Click OK.
6
In the Settings window for Difference Selection, locate the Input Entities section.
7
Click the  Add button for Selections to subtract.
8
In the Add dialog, select Copy 1 in the Selections to subtract list.
9
Click OK.
Outer Coils 2
1
Right-click Outer Coils and choose Duplicate.
2
In the Settings window for Difference Selection, type Outer Coils 2 in the Label text field.
3
Locate the Input Entities section. Click Build Preceding State.
4
In the Selections to subtract list box, select Copy 1.
5
Click the  Delete button for Selections to subtract.
6
Click the  Add button for Selections to subtract.
7
In the Add dialog, in the Selections to subtract list, choose Inner Coils and Outer Coils.
8
Click OK.
Inner Axis
1
In the Geometry toolbar, click  Selections and choose Box Selection.
2
In the Settings window for Box Selection, type Inner Axis in the Label text field.
3
Locate the Geometric Entity Level section. From the Level list, choose Boundary.
4
Locate the Box Limits section. In the r maximum text field, type objR*0.1.
5
In the z minimum text field, type -objInner/1.99.
6
In the z maximum text field, type objInner/1.99.
7
Locate the Output Entities section. From the Include entity if list, choose Entity inside box.
Whole Axis
1
Right-click Inner Axis and choose Duplicate.
2
In the Settings window for Box Selection, type Whole Axis in the Label text field.
3
Locate the Box Limits section. In the z minimum text field, type -objHeight/1.99.
4
In the z maximum text field, type objHeight/1.99.
5
Click  Build Selected.
6
Click the  Zoom Extents button in the Graphics toolbar.
The model geometry is now complete.