TM Topology Optimization for Designers Siemens AG 2016 Realize innovation.
Topology Optimization for Designers Product Features Uses a different approach than traditional Topology Optimization solutions. Works in the NX CAD Work part in the context of an assembly. Meshless (to the user) Model definition uses the designs Functional Requirements, eg: Keep in/out volumes. Cylindrical holes with offset material around the hole. Counter bore holes with space for screw head, nut, socket wrench etc. Manufacturing constraints. FE loads & constraints. Level of resolution control. Max stiffness objective with a Mass constraint. Quick Topology Optimization solution. Highly smoothed, organic shapes with sharp edges where required.
Downstream 1. Direct to AM printing. 2. Direct use using Convergent models Convergent model is a new Parasolid format introduced in NX 11. Single data format for both/either NURBS and Facet geometry. Existing modeling functionality will work on both in the same CAD body. Start with faceted body add NURBS geometry, fillet between them. Limited support in NX 11. Only Facet Convergent bodies, boolean join, subtract & intersect. 3. Guidance for re-modeling using traditional CAD tools. Holes cut into Convergent Facet model
Topology Optimization in the Assembly Context Works in the NX CAD Work part in the context of an assembly. Enables users to reference the context geometry to: Build the design space shape. Locate connecting holes, pads, plates etc. Define keep-in/out geometry relative to the context geometry. Define load vectors relative to the context geometry.
Design Space The Design Space is the max envelope that the Topology Optimization engine will see. So to be included in the solution, the geometry must lie within the Design Space. Features that cross the boundary will only have the volume that lies within the Design Space, included. The Design Space can be any Solid body (no limit on creation method) or a closed (water tight) Faceted body Design Space
Optimization Features Functional Requirements are described by the use of Optimization Features. Some NX modelling features are automatically recognised and included in the list. These include the following types: Cylinder, Block and Sphere primitives Copy Face Simple Hole Counter Bored Hole These feature directly map to the same Frustum features. Further Solid Bodies (no limit on creation method) can also be added to the Optimization Features list.
Optimization Features These Optimization Features can describe Functional Requirements. For example: M8 Bolt connection that requires a clearance for a socket wrench. CounterBored hole feature with a hole diameter of 8mm and 30mm diameter counter bore diameter. Counter bore length long enough to allow socket wrench access. A boss cylindrical in shape is required. Keep-In cylinder. A block is used to define a Keep-Out area. Keep-Out block with a 10mm offset for safety. A force is only applied to a specific part of a face. The face is split to define the limit of the load applied and a Copy Face feature used to define the optimization feature. Reorder
Optimization Feature Properties Each Optimization Feature will have properties that define it s use in the Topology Optimization. Some Features have fixed properties. Include in Optimization A feature can be excluded from the Topology Optimization, but left in the list. Keep-In/Out A feature can be defined as a Keep-In there must be material in that volume during the Topology Optimization. Keep-Out there must be no material in that volume during the Topology Optimization. Shell this creates a shell around the selected feature Simplified Holes and Counter Bored Holes are always Keep-Out Optimization features.
Keep In Optimization Feature Any CAD body can be used as a Keep In Optimization Feature. This ensures the Keep In feature s space will be included in the final optimized model. Unless it is cut by other optimization features. Used to maintain connections to surrounding components, to limit the optimizers freedom, etc. Keep In Optimization Features These CounterBore Optimization Features cut through the Keep In features
Keep Out Optimization Feature A Keep Out Optimization Feature tells the optimizer that no material can be placed in this space. Any CAD body can be used as a Keep Out Optimization Feature. Some Optimization Features are pre-defined as Keep Out features, these include: SimpleHole CounterBore Hole Keep Out CounterBore Holes Keep Out Block
Shell Optimization Feature A Shell Optimization Feature is similar to the NX CAD Shell command creating a uniformly thick offset of the body. Thickness of the Shell is defined by the Offset Thickness value.
Optimization Feature Properties Offset Thickness To define a hole it must have material around the hole. This is the Offset Thickness on a Hole feature. Offset of a solid Keep-Out body. Offset of Copy Face features (similar to an NX Thicken feature). Offset Thickness on a CopyFace feature Offset Thickness around a solid Keep-Out body Offset Thickness on a Hole feature
Manufacturing Constraints Extrude Along Vector The optimized shape will be a constant cross-section along the specified vector. Void Exclusion No internal empty voids will be created. This is important for parts built using a powder bed additive manufacturing method. Interior voids will be filled with wasted expensive metal powder. Overhang Prevention Prevents overhanging geometry along the specified vector. This is important for parts built using a powder bed additive manufacturing method. Overhanging geometry often requires supports to hold it up during the manufacturing process. Reducing or removing the need for supports reduces time and cost to make the part.
Load Cases Different combination of loads can be applied using Load Cases. For example, front loads, side loads, top loads, etc. The solution will take all these different load cases into account. 4x Load case examples
Load Types Load types available: Force Pressure Torque Global Loads are applied to the whole model independent to Load Cases. Acceleration Most commonly this will be used to add a Gravity effect.
Manufacturing Constraints Planar Symmetry Manufacturing Constraints guide the geometry shape during the optimization. Symmetry about a Plane Only half the Design Space required, Optimization Features and Loads need be created so that the resultant model will be symmetrical about the plane.
Manufacturing Constraints Blend Radii Blend Radii This is the blending between the Optimization Features and the optimized geometry to ensure a smooth resultant part. Auto Blending can be used and the sizes will look good for that part. A single Blend size can be defined for all the blends for members interacting with that Optimization Feature. Each Optimization Feature Blend size can be defined.
Resolution The Resolution chosen by the user is important to the results as it dictates how much detail is carved out of the model. A slider bar is presented to enable the user to choose a Resolution between Fast & Coarse or Slow & Fine. During exploration, leaving the slider towards the Fast/Coarse end will give good indication of what the Topology Optimization is doing. Enabling the user to adjust/change the model setup as required. Once the user is happy with the model setup, then moving the slider more to the right will generate the detail in the model. The Minimum Feature Size value changes with the Resolution setting and gives an indication as to the detail that will be created. The Approximate Run Time gives the user an estimate of how long the Optimization will take.
Optimization Objective & Mass constraint The objective is to maximize the stiffness. The user is required to enter a Target Mass value for the optimization. The original Design Space mass is given to the user as guidance. Running the Topology Optimization During the Topology Optimization a first rough pass is performed to size the problem, followed by a second pass. This better ensures a good result. The Topology Optimization performance is shown in the bar chart diagram. After the Optimization run the Status changes to Meshing. This indicates the Optimization has completed and the result (mesh) models are being created.
Geometry Results After the Optimization has completed the geometry results are displayed along with the Design Space and Optimization Features. Hiding some/all of these reveals the Optimized geometry. This is imported as a Facetted model. To do further modeling this needs to be converted to a Convergent model.
FEA Results The FEA results can be displayed with a Legend Displacement Stress Strain These are Max envelope for all the load cases.
Topology Optimization Results
Courtesy of Oerlikon
Summary New approach to optimizing the topology within the given design space. Designer for CAD users and does not require deep CAE expertise. Focuses on the Functional Requirements of the design. Results are returned quickly. Highly smoothed Convergent model results ready for AM printing, or guidance for re-design.
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