Pattern Problems Part 1: The benefit of “Keep specifications” and its limitations in CATIA V5

Rand 3D

By Trisha Freeman

 

When creating a pattern with an object feature that has utilized one of the “Up-to” options (Up to Next, Up to Last, Up to Plane or Up to Surface), the “Keep specifications” option will cause all instances of the pattern to also use the same up to reference. In the picture below, a cylindrical pad feature is created to go up to a contoured surface.  

Image 1

Using this same pad feature as the object in a rectangular pattern will initially cause the pattern instances to have the same height profile as the original.

Image 2

Selecting the “Keep specification” option will allow the pattern surfaces to follow the contour of the original 'Up to surface' reference.

Image 3

However, “Keep specifications” does have its limitations in CATIA V5. In the scenario below, a hole is patterned along a spline in a user pattern.

Image 4

 

Note how the circular disk is not a constant thickness. In the picture below, it is evident that the disk has a shallow concentric cutout underneath.

Image 5

The location of the original hole to pattern happens to be at the shallower thickness. The hole was patterned using the 'Up To Last' depth option.

Image 6

Using this hole to create a user pattern will cause three of the holes to also go to that shallower depth.

Image 7

As stated earlier, activating “Keep specifications” will fix this problem. All instances created via the pattern know to have the depth type as “Up To Last.”

Image 8

Now let’s take that same user pattern on the circular disk and duplicate it using a circular pattern. The pattern in this case is the UserPattern.1.  As shown in the image below, the problem we run into is that any time you use a pattern as an object in another pattern feature, the “Keep specification” option isn’t accessible. This will cause the 3 outer most holes in the circular pattern to still have the shallower depth.

Image 9

The solution to fix this problem is to move the location of the original hole to any of the outer three holes. These locations are placed within the disk at the thickest height.

Image 10

Now, all holes are maintained to be designated through holes for both the original user pattern as well as circular pattern.

Image 11

 

This topic is covered Rand 3D's training class, CATIA V5: Advanced Part Design

 

 

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