Manufacturing constraints in topology optimization

Manufacturing constraints are optional restrictions that you can include in your topology optimization solution to ensure that the suggested design meets your production criteria.

Each manufacturing constraint is a modeling object. You can create multiple manufacturing constraint modeling objects and use one or more for each topology optimization solution. For example, you might create both a planar symmetry constraint and a casting die direction constraint to ensure that the part is both symmetrical and can be molded.

Manufacturing constraints apply only to the optimized elements in the design area, not the frozen ones.

Note:

• If you use the minimum member size or maximum member size manufacturing constraint, you can increase the solving speed by using parallel processing. For more information about the parallel option, see Solver Parameters dialog box (Nastran).

• The following figures illustrate the potential effects of omitting or including particular manufacturing constraints. The effects on your own models might be different.

Planar Symmetry (SYMP)

When any optimization changes are made on one side of the plane, equivalent changes are made to unfrozen elements on the other side as well. The mesh does not have to be identical on both sides of the plane, but if there are differences, the vector direction normal to the plane might affect the optimization results. In the following figures, the plane divides the model into right and left halves.

Without planar symmetry

With planar symmetry

Your solution can include up to three planar symmetry constraints, but the planes must be orthogonal to each other.

Cyclic Symmetry (SYMC)

When any optimization changes are made to one sector of a circular model, equivalent changes are made to unfrozen elements in the other sectors in a rotational manner. The mesh does not have to be identical in all sectors, but differences might affect the optimization results.

Cyclic symmetry can be either repeated or reflected. With repeated symmetry, each sector is similar to every other sector. With reflected symmetry, every other sector is the mirror image of the previous sector. You can use reflected symmetry only with an even number of sectors. The following results use the same model with six sectors.

Without cyclic symmetry
Repeated cyclic symmetry	Reflected cyclic symmetry

Maximum Member Size (MAXS)

Any trusses created by the optimization process are not thicker than the specified size. This might mean that the recommended design has more trusses than it would without this constraint.

In addition, most of the optimized trusses use the specified thickness, so it is usually not necessary to define both a maximum member size and a minimum member size.

Without a maximum member size	With a maximum member size

Minimum Member Size (MINS)

Any trusses created by the optimization process are not thinner than the specified size, although there might be exceptions.

Without a minimum member size	With a minimum member size

Casting Die Direction (CDID)

The optimization process does not create any internal cavities or undercuts that would make it impossible to remove the part from the mold. For molds that have two halves, you can specify the direction in which each half is separated from the part.

Extrusion (EXTC)

The optimization process ensures that the part has material continuity in the extrusion direction. Only extrusions in a straight line are supported.

Without an extrusion constraint

With an extrusion constraint

Checker Boarding Control (CHBC)

By default, Simcenter Nastran automatically averages the material density values of adjacent elements, which prevents the removal of elements in an alternating pattern similar to a checker board.

To allow checker boarding to occur (that is, to disable the checker boarding control in Simcenter Nastran), you can create a checker boarding control manufacturing constraint and set the radius to a negative value.

With checker boarding

Without checker boarding

Additive Manufacturing Overhang Angle (ADDM)

This constraint ensures that there is sufficient structural integrity as you build the model layer by layer using 3D printing technology. You can specify the maximum angle for any trusses, protrusions, or slopes relative to the base plate normal vector, as well as the minimum thickness for any portions of the body.

Without an additive manufacturing constraint	With an additive manufacturing constraint

Working with manufacturing constraints

• You can create a manufacturing constraint either by using the Modeling Objects command or by right-clicking the Manufacturing Constraint container under the solution node in the Simulation Navigator and then choosing New Manufacturing Constraint.Both approaches create a manufacturing constraint modeling object, which appears under the Modeling Objects container in the Simulation Navigator. However, when you create the manufacturing constraint by right-clicking the Manufacturing Constraint container, that modeling object is automatically added to the solution.

• You can add an existing manufacturing constraint to a solution by dragging a manufacturing constraint modeling object from the Modeling Objects container to the Manufacturing Constraint container. You can also right-click a manufacturing constraint modeling object and choose Add to Active Solution or Step.

• When using multiple manufacturing constraints in a single solution, keep the following in mind:If the solution includes both a planar symmetry and a cyclic symmetry manufacturing constraint, the plane of the planar symmetry constraint must be orthogonal to the plane of rotation of the cyclic symmetry constraint.If the solution includes both a cyclic symmetry and an extrusion manufacturing constraint, the vector of the extrusion constraint must be collinear to the plane of rotation of the cyclic symmetry constraint.If the solution includes an extrusion manufacturing constraint and one or two planar symmetry constraints, the planes of the planar constraints must be parallel to the vector of the extrusion constraint and normal to each other.

• To see the information that will be sent to Simcenter Nastran when you solve the model, right-click the manufacturing constraint node and choose Solver Syntax Preview.

• To remove a manufacturing constraint from a solution, right-click the manufacturing constraint node and choose Remove. To remove all manufacturing constraints from a solution, right-click the Manufacturing Constraint container and choose Remove All.

Where do I find it?

Application	Pre/Post
Prerequisite	A Simulation file as the work part and displayed part
Command Finder	Modeling Objects
Simulation Navigator	Right-click the Manufacturing Constraint container under the solution→New Manufacturing Constraint

Learn more

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Manufacturing constraints in topology optimization, Simcenter 3D 2021.1 Series

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