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Ordered vs. Synchronous – Which should I use? – Part 1

John Pearson - Thursday, October 10, 2013
  1. I’ve been approached by many Solid Edge users who ask me if they should be using the synchronous or the ordered method for the 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 the hybrid approach utilized through integrated modeling. 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 is 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 that 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 family of parts or 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 that designers use to give for staying in 2D. But we all know that 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 6 years now. Many designers will disagree with some of these because they do not have a true understanding of how synchronous modeling works. So 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 the

        future changes, or uses the part as a reference part to initiate a new model.
Making changes requires an in-depth understanding of how 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 that 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, which are up to 100 times faster if not more. Synchronous takes advantage of today’s powerful computer processers, and the elimination of Parent-Child relationships, to allow fast flexible modeling. Yet, with tools such as Live Rules, Procedural Features, 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. 
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.
Can edit a part file or group of parts from the assembly level, without having to edit into each part.
Can edit models from any CAD system as easily as editing solid edge models.
Model can be constrained at the 3D level, but not really necessary.
Models are lighter therefore open and save faster than in the ordered paradigm.
Can convert legacy ordered models into synchronous models.  
Although a different approach to modeling, it shares many similarities with the ordered paradigm. Thus 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 that there are a few reasons for the hesitance to change. 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.  But 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, allowing 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 in 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, in order 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:
o Swept and lofted features 
o Certain rounds and blends
o 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 that 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 blog 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 blog article I will continue this article and further discuss the reasons why  customers are resistant to changing to synchronous technology. I will show how these perceived reasons are based on myth or inaccurate information. It is my hope that after reading both these articles you will 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. 



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