Ordered vs. Synchronous Modeling in Solid Edge – Part 1

Many Solid Edge users ask me if they should be using the synchronous or ordered modeling method for their designs. I always answer, yes. To which they smile and usually ask “No, really, which is better?” To which I respond, why choose? Use both.

This may seem like a political answer, but it’s not. The true power behind Solid Edge is its hybrid approach that integrates both modeling methods. To understand the benefits, we first have to look at the pros and cons of each paradigm.

Pros and Cons of the ordered paradigm
Ordered modeling has been in Solid Edge since day one. It’s like an old friend that many long time users are comfortable with and experienced in. Many of the users I talk to claim that they like the control ordered modeling gives them. Ordered modeling forces the user to build the model in a certain order of steps, which are predefined by the intent of the designer.

For example, the designer starts with the sketch or profile for his/her base feature. He/she draws the profile and constrains it with 2D geometric and dimensional constraints. By doing this, he/she is controlling how the sketch can change. This involves some thinking ahead and predictions of potential future edits.

Once the sketch is complete, it becomes the parent of the base feature. In other words, the sketch drives the base feature. Additional profile base features are then added to the base feature in a similar manner—each becoming a child of the base feature—thus creating an ordered structure that is shown in the Pathfinder. Treatment features are then added, creating more parent-child relationships, until you have a completed model.

The ordered structure appeals to a lot of designers, especially if the design lends itself to a master model approach, where you create a master model and then generate many variations off that model by simply changing a few parameters. This does require intelligent set up of the master model and a good understanding of how the model was constructed.

So, when I ask my customers what they like most about ordered, I get the following list of Pros:

• Very structured approach to modeling.
• Predictability to the designer who created the model.
• Ability to lock down how the model behaves.
• Other users can’t accidentally change my design.
• Easy to set up a family of parts or a family of assemblies with a master model approach.
• Long accepted method of modeling with a proven track record.
• Creating the initial model is just as fast in ordered as it is in synchronous method.
• I am use to ordered design and have lots of ordered legacy data.

From a designer’s point of view, all these are good reasons to stay in the ordered paradigm. However, when I look at the list, I get a feeling of déjà vu. It looks very similar to the list of reasons designers gave for staying in 2D. But, we all know many companies have switched to 3D. Why? Because the industry recognized that switching to 3D design provided many advantages. In other words, there were a lot of Cons in 2D design. So what are the Cons of the ordered method?

It should be noted that some of the Cons or disadvantages that I am about to list come from working with the synchronous technology for almost six years now. Many designers will disagree with some of these because they don’t have a true understanding of how synchronous modeling works.

With that in mind, let me list some of the main problems with ordered designs:

• Forced structured approach to modeling.
• Modeling requires the designer to predict how the model could change in the future.
• Editing the model is slow and cumbersome if the designer incorrectly predicted future changes, or uses the part as a reference part to initiate a new model.
• Making changes requires an in-depth understanding of how the model was originally created. In some situations, it has proven faster to re-model the part then to try and understand all the parent-child relationships.
• On large models, re-compute times can be lengthy due to the structured approach.
• Models are heavy because of all the history saved in the part files. This makes opening and saving times lengthy.
• Working with foreign data can be a challenge without the history/feature tree.

I’m sure my colleagues could list a few others, but I think these are the main ones. The next question then becomes how can synchronous eliminate or minimize the problems we face in ordered, and is it enough of an improvement to start using synchronous modeling? To answer this question, let’s look at the Pros and Cons of the synchronous paradigm.

Pros and Cons of the Synchronous paradigm
If you believe the marketing from Siemens, they claim the following:

“Synchronous technology provides the first history-free, feature-based modeling technology that enables up to 100 times faster design experience.”

Let me clarify this statement. It is not saying that all your designs can be done 100 times faster. In fact, if you start a design from scratch, the initial design process may only be slightly faster in the synchronous paradigm. However, there are aspects of the design process that are up to 100 times faster, if not more.

Synchronous takes advantage of today’s powerful computer processors, and the elimination of Parent-Child relationships, to allow fast flexible modeling. Yet, with tools such as Live Rules, Procedural Features and 3D driving dimensions (PMI), it still provides the designer with control over the design when needed.

So let me give you my list of synchronous Pros:

• Rapid, flexible design tools.
• The designer does not have to predict how the model will change in the future.
• A history-free approach allows for instantaneous model changes while editing the model.
• The sketch does not drive the model. The dimensions are migrated to the model and directly drive the model at the 3D level.
• Rapid edit tools and handles allow the designer to edit the model without having to understand how it was originally modeled.
• Designers can edit a part file or group of parts from the assembly level, without having to edit into each part.
• They can also edit models from any CAD system as easily as editing Solid Edge models.
• Model can be constrained at the 3D level, but it’s not really necessary.
• Models are lighter and, therefore, open and save faster than in the ordered paradigm.
• Legacy ordered models can be converted to synchronous models.
• Although a different approach to modeling, it shares many similarities with the ordered paradigm. Thus, it’s easier to learn for existing Solid Edge users.

Given all the Pros, you may be asking why everyone hasn’t changed to synchronous modeling. I believe there are a few reasons for the hesitance. The first is the way Siemens introduced synchronous technology. It was first launched in the fall of 2007 in Solid Edge ST. It was new, and limited to part modeling with no real tie in to the ordered parts. Many users tried it then, but were left unsatisfied due to the limitations.

The following year, Solid Edge ST2 was released and introduced synchronous sheet metal modeling. Again, there seemed to be two separate paradigms with limited connection between the two. This all changed with the release of ST3, which introduced integrated modeling and allowed users to combine both paradigms within the same part. Unfortunately, many users had already made up their minds based on their less than successful attempts with ST and ST2.

Another reason for resistance is lack of training. Too many companies fail to see the benefit of properly training their users in the synchronous paradigm. They expect the user to pick it up on their own, while maintaining the same level of output. It has been my experience that this approach fails most of the time. Designers may attempt to learn it, but will often revert back to the way they know to meet company deadlines. The user will often resist the change for no other reason than lack of time to properly learn it.

The third reason is that there are some definite limitations in synchronous modeling. Certain features or techniques behave better in ordered because of the nature of synchronous modeling. I list the main Cons of synchronous modeling as follows:

• Certain features have limited editing capabilities and are handled better in the ordered paradigm. Some examples include:
  • Swept and lofted features
  • Certain rounds and blends
  • Surfacing
• Dangling bends are not currently supported in synchronous sheet metal. This limits certain functionality.
• Training – users need proper training to understand the synchronous paradigm.

Some users may believe they have more control in ordered, but that is a myth, based on lack of knowledge of the synchronous modeling tools. I will explain this more in my next article. But let me finish this article by discussing the integrated modeling approach.

Pros and Cons of the integrated modeling approach
Solid Edge allows the user to start the design in the synchronous paradigm and add ordered features if necessary. This approach allows the user to utilize the best of both paradigms. The synchronous portion of the model becomes the parent of the ordered features. This allows the user to change the synchronous parent, which triggers an automatic update of the ordered dependent features. Furthermore, the assembly can be populated with ordered parts, synchronous parts and integrated parts.

The only Con for this approach is that the designer has to be trained properly.

In my next article, I will further discuss the reasons why customers are resistant to changing to synchronous technology and show how these perceived reasons are based on myth or inaccurate information. It is my hope that, after reading both of these articles, you’ll have a better understanding of Synchronous Technology and be willing to take a second look at how it can be integrated into your design process, saving you time and money.

For part 2 of this article and other Solid Edge tips, check out the Design Fusion blog:
www.designfusion.ca/blog.html

John Pearson is a Senior Technical Trainer and Application Specialist at Designfusion. He has over 24 years’ experience in the CAD/CAM industry, is a Certified Adult Trainer and has taught evening CAD courses at colleges in Ontario. He is also a major contributor of articles on the Design Fusion blog.