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PTC Express

November 23, 2011
3

In Creo Parametric 5.0 and beyond, there is a new way to pattern geometry that is easier to use, produces models that are more flexible, and it can significantly reduce feature count and also improve model performance. Does this sound too good to be true? Let’s take a deep dive and find out. 

 

Why Did We Need Another Pattern Method?

 

Creo Elements/Pro has always had very powerful patterning capabilities. If you have ever needed to pattern several features together, you are familiar with these challenges:

 

Using Reference Pattern Over and Over

 

The pattern is defined with the first feature that is patterned. After that, you Reference Pattern each additional feature until the final set of geometry has been duplicated, Figure 1.

 

GP-Fig1.gif

Figure 1

 

In some cases, it can be difficult to connect the features together in such a manner that the Reference Pattern will work. Also, Reference Patterns are patterned as General Patterns, which are the slowest to regenerate.

 

Using Groups and Patterns Together

 

The idea here is to Group the features first, and then pattern them all in one action. If the Group is edited to have more features, the pattern has to be recreated. Lastly, Group patterns are always patterned as a General Pattern, which can be slower to regenerate if there are a large number of pattern members.

 

GP-Fig2.gif

Figure 2

 

Geometry Pattern Basics

 

In many cases, the solution to these issues is the Geometry Pattern feature.

 

Selecting Geometry

 

As the name implies, you first need to select the “geometry” you want to duplicate and then initiate the Geometry Pattern feature. Typically, you will use the Seed and Boundary method for selecting the geometry.

 

GP-Fig3.gif

Figure 3

 

This can be done by:

 

  • Setting the Selection Filter to Geometry. This is not necessary, but will make this step easier for many.
  • Selecting the Seed surface. This is a face that is located on the geometry you want to pattern. It is important to select a face on a feature that will not be deleted due to a future change. Choose faces on major Extrude features instead of on Round, Draft or Chamfer features.
  • Press the [Shift] key and select one or more Boundary surfaces.

 

Depending on your model, you may need to select more than one bounding surface to properly surround the geometry.  

 

GP-Fig4.gif

Figure 4

 

Defining the Pattern

 

With the geometry selected, launch the Geometry Pattern function and define the pattern as usual to create a Dimension Pattern, Direction Pattern, Axis Pattern, etc. If the Geometry Pattern command/icon is “grayed out”, it means you have not selected any geometry yet.

 

Useful Settings

 

This is where things get interesting! Be sure to pay attention to these dashboard settings:

 

  • Pattern Type: Patterns in Creo will always default to be a General Pattern. This is the most robust feature type but is also the slowest to regenerate. If regeneration time is an issue, consider changing this to Variable.

 

GP-Fig5.gif

Figure 5

 

  • Solid Feature vs. Surface Feature: By default, you will be creating a pattern of solid geometry. But, you can change this to produce a pattern of quilts instead by clicking References > Geometry References > Options tab. Why would you do this?
    • If your pattern is failing, toggle this to surface and see if that works. This is a great troubleshooting technique and you can determine if the pattern falls off the part or intersects something that would be a problem.

     

GP-Fig6.gif

Figure 6

 

    • The pattern of quilts will regenerate very quickly, allowing you to review pattern member location and quickly make adjustments when working with very large patterns.

 

GP-Fig7.gif

Figure 7

 

  • Solid Creation Method: It is important to understand that the Geometry Pattern feature is using a surfacing copy and solidify technique “under the hood”. What this means to you is that the Geometry Pattern is set to add material by default. This will be appropriate some of the time, but not always so look into this if your Geometry Pattern fails to regenerate. This setting can be changed by clicking References > Geometry References > Options tab. Other choices are:
    • Cut: Change to this setting if your pattern will remove material from the model.

     

GP-Fig8.gif

Figure 8

 

    • Patch: Change to this setting if you will add material and remove material at the same time. The example below compares the results of using Cut vs Patch.

 

GP-Fig9.gif

Figure 9

 

Now that we have described the details of this feature, let’s consider how it behaves in the model.

 

Results & Benefits of Geometry Pattern

Less Is More

 

The desired pattern is created in one action instead of many Reference Pattern features, simplifying the overall process. Also, even though you are patterning the geometry created by many features, the Geometry Pattern function produces one single Copy Geometry feature at each pattern member location. This also simplifies the model and reduces feature count.

 

GP-Fig10.gif

Figure 10

 

Flexibility

 

It is important to understand that the Seed & Boundary technique is used to collect the geometry to pattern and we are not patterning the features themselves. This means that any collected geometry can be patterned using Geometry Pattern without having to build the features in a special way that  will allow a Reference Pattern to be used.

 

Handling Edits To The Driving Features

 

The only connection to those features is the Seed surface. Any other feature can be deleted and when it is regenerated, the change will be reflected in all of the pattern members without failure.

 

Of course, if you delete the feature that contains the Seed surface, the pattern will fail. So, choose a Seed surface wisely and choose one that will not get deleted or consumed by another feature.

 

Deleting The Pattern

 

What is interesting is that the Geometry Pattern exists in the Model Tree outside of the original geometry. Deleting the pattern will not remove the original geometry.

 

Summary

 

The Geometry Pattern is a feature that every designer needs to understand and utilize in his or her models. When you need to pattern several features together, Geometry Pattern will reduce the number of features in your model and improve regeneration speed if there are many pattern members, keeping your models fast. Also, being able to pattern geometry without having to build the features in a special way will keep your designs moving forward and make it easier for others to edit your models.