SolidWorks 2011 Parts Bible - Matt Lombard [134]
To compare the performance of various types of patterns, I made a series of 20-by-20 patterns using circles, squares, and hexagons. The patterns are both sketch patterns and feature patterns, and I created them with both Verification on Rebuild and Geometry Pattern turned on and off. Verification on Rebuild is an error-checking setting that you can access through Tools⇒Options⇒Performance, and Geometry Pattern is a setting that is applicable only to feature patterns that disables the intelligence in patterned features.
Table 9.1 shows the rebuild times (in seconds) of solid geometry created from various types of patterns as measured by Feature Statistics (found at Tools⇒Feature Statistics). Sketch patterns are far slower than feature patterns, by a factor of about ten. The biggest speed reduction occurs when you use sketch patterns in conjunction with the Verification on Rebuild setting, especially as the number of sketch entities being patterned increases.
Generally, the number of faces and sketch relations being patterned has a significant effect on the speed of the pattern. The sketch pattern times are taken for the entire finished model, including the sketch pattern and a single extrude feature, using the sketch with the pattern to do an extruded cut. The sample parts are on the DVD for reference. Look for the filenames beginning with Reference1 through Reference7.
The most shocking data here is the difference between a sketch pattern of a hex when a patterned sketch cuts into a flat plate compared to a feature pattern of a single extruded hex with each using the Verification on Rebuild option — 0.36 seconds compared to 126 seconds.
Always keep this general information about sketch patterns in mind:
• Sketch patterns are bad for rebuild speed.
• The more faces created by any pattern, the longer it takes to rebuild.
• The more sketch relations a sketch pattern has, the longer it takes to rebuild.
• Geometry pattern does not improve rebuild speed (unless a special end condition like Up to Surface has been used).
• Verification on Rebuild dramatically increases rebuild time with the number of faces but is far less affected by feature patterns than extruded sketch patterns.
Figure 9.1 shows one of the parts used for this simple test.
FIGURE 9.1
A pattern part used for the test
One interesting result of this test was that if a patterned extruded feature creates a situation where the end faces of the extruded features have to merge into a single face, the feature could take ten times the amount of time to rebuild as a pattern with unmerged end faces. This was an inadvertent discovery. I'm sure you would make your own discoveries if you were to investigate rebuild speeds for end conditions for cuts such as Through All, Up to Face, Up to Next, and so on, as well as the difference between cuts and boss features. Further, using Instant 3D can be an impediment when you're editing very large sketches simply due to the effects of the preview.
You should also note that the situation this simple test covers is very limited in scope. Because the plate is a constant thickness, the Geometry Pattern option actually works, which it wouldn't if the plate varied in thickness (with the through holes). It also only tests the Through All end condition, and the Geometry Pattern is best used to simply disable intelligent end conditions. I get the impression that many people use it as a random toggle trying to get patterns to work that SolidWorks would otherwise not allow to work.
I discuss the Geometry Pattern option in more detail later in this chapter. I wanted to start the chapter with a discussion that called attention to the misperception that some people have that sketch patterns are somehow