History Based Direct Modeling Using IRONCAD – Part 3

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OK, so now that we know the basics of how features are created and modified in IRONCAD, let’s get back to the subject of this series – history based direct modeling. I mentioned in part 1 that IRONCAD is a history based modeler which gives the user the freedom to do direct modeling. I will explain this by means of a simple example. Consider this very simple model consisting of three features – a base block with a hole in it and another block sitting on top of it.

I first created the base block, cut a hole into it and then created the top block last. So the feature tree looks like this.

Now I decide to move the hole from the bottom block to the top block. In a traditional history based parametric modeling system I would need to move the sketch of the hole feature out into empty space and make it cut thin air, which would result in a rebuild error. Now since this is a simple model I know that I could move the hole feature after the top block in the feature tree and solve the rebuild problem. But what if this was a complex part with a mile long feature tree and the hole was at the top of the feature tree and the top block was towards the bottom. In that case, I would normally have to resort to using the hack and whack method and add a Move Face feature to the bottom of the tree.

But in IRONCAD this is what I do. I pick the hole feature and move it to the top block. As simple as that. The model looks like this.

But wait. What about the feature tree? The top block comes after the hole, right? So if IRONCAD is indeed a history based system how can it calculate the hole in a block that does not exist? Take a look at what the feature tree now looks like.

The top block and the hole have switched places. Now the hole comes after the top block, which means that the top block exists when the hole is being calculated and that’s why the feature move operation succeeded. The absolutely wonderful thing is all this is that I didn’t touch the feature tree at all. IRONCAD reordered the features in the tree automatically. And this is precisely the fantastic patented technology that I was talking about. This is also the reason why when this technology surfaced more than a decade ago, people thought that it was direct modeling and nothing else. They simply didn’t realize that the software was smart enough to take care of the history tree all by itself.

As a user, IRONCAD lets me concentrate on what I need to do next. It takes care of the book keeping of features in the history tree. I can’t stress enough how far ahead of its time this technology was when it first came out. And its sad that many people still do not fully appreciate its true power even today.

OK, enough of moving holes in blocks. Lets do some real world direct modeling. Here is a part with 43 features. Click the image for a larger view. I have highlighted two features, a hole and a base extrude.

The hole happens to be the second feature in the tree whereas the base is the ninth feature. One would think that it should be the other way round. But this model was built starting with the features in the middle of the part and then grown outwards. So now, suppose a design change needs me to move the hole somewhere onto the base. Note that the base was created after the hole. So as I explained above, in a traditional history based parametric modeling system, effecting such a change the right way would involve a tremendous amount of time and energy. But in IRONCAD I simply pick the hole and move it wherever I want on the base and the software rearranges the features for me. In the image below the feature tree on the left is the original, whereas the one on the right shows what IRONCAD did to it without me having to lift a finger.

Truly amazing! I think you can now see why many people didn’t (and still don’t) consider IRONCAD a history based modeler. The software is designed in such a way that when the user picks and moves features around the model, he is not required to bother himself with the order in which they appear in the feature. The software does that for him automatically. And by the way, unlike synchronous features in Solid Edge ST3, the order of features in IRONCAD is important. If I manually move the hole feature before the base feature in the tree it disappears from the model, obviously because the base does not exist when the hole is being calculated.

In the next part of this series I will do some direct modeling as most of us know it. I mean, grab a bunch of faces from different features and move them.

Part 4 >>


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