2010 Knit: Worth the Price of Admission

If you are a surface feature user, the 2010 enhanced Knit feature is worth the price of admission all by itself. This is a feature that allows you to get the job done. In 2010, when a 2009 knit would otherwise fail, the Knit feature shows you what the gaps are that cause the knit to fail, and allows you to adjust the tolerance for the gap. Let’s take an example I ran into on the SW forums recently.

Here is a set of sketches a guy on the forum posted. He’s making a puffy box with rounded ends. He’s trying to do it as a solid with a single feature, lofting to points on each end. Not working. Break it up into surfaces with a big boundary and two filled caps, and it works.

Except for one thing. It won’t Knit.

Even with the Minimal Adjustment option on the Knit in 2009, the knit completes without an error, but you can see the blue edges say that there are gaps, and the knit will not solidify.

The Minimal Adjustment option in Knit is supposed to tighten the tolerance, so the gaps have to be smaller to work with Minimal Adjustment on. But in this case, Minimal Adjustment allowed the Knit to work (SW09 sp4.0), which seems backwards.

This is a little off topic, but this is one of those terminology things that SW doesn’t do so well on. “Minimal Adjustment” to me is completely ambiguous. It has different meanings depending on what point of view you are coming from. If you assume that SolidWorks is not adjusting your models at all, then a minimal adjustment means “more adjustment than usual”. If you assume SW changes your models a lot, then minimal adjustment is “less adjustment than usual”. So which is it? You have to look it up in the Help and assume the Help is correct. My experience here is exactly opposite of what the help suggests. Help says:

Select Minimal adjustment to make minimal changes to surfaces during knitting. Clear this option to increase the tolerance used during knitting, which might result in larger adjustments to surfaces.

The first sentence is a throw away. An English major could have told me that much (and probably did). It doesn’t add to my understanding even a little bit. It could still go both ways. Unfortunately, there is a lot of this kind of writing in the SW Help. “Clear” the option is code for “turn it off”. “Increase the tolerance” is something I think some people will misunderstand. You need a better way to say this. Maybe tighten or loosen would be better than increase or decrease. Increase is good, right? No, increase is bad. Increase tolerance means you need to accommodate bigger gaps, and make a bigger adjustment. Anyway.

So here’s the new stuff. Wow, this is powerful, and will bring a new understanding of the software to surface modelers. Information is power. Automated stuff that makes dozens of assumptions and decisions for you is not power, its letting someone else do your work for you. Automation is cool, but it always requires a sacrifice. There are two directions CAD developers can go: automation or modeling power. Gimme power.

Anyway, the plan here is that you can enter a number in the Knitting Tolerance box that is just bigger than the biggest gap. Or just checking the box next to the biggest gap will do that for you automatically. I can see this being used as another analysis tool. It might be useful if the gap information were available separately. You can get similar information from an import diagnosis, but only for imported geometry, not for native feature data.

This one enhancement makes this release worthwhile for me. I can’t tell you how much time this would have saved me if since I started working with surface models in SolidWorks. Every time a knit failed for some unknown reason and you had to try to find a workaround.