Based on the technology behind direct modeling, large assembly design and management can be fast and easy. As direct modeling does not record the modeling steps used to create the model, memory requirements and file sizes can be considerably smaller than with traditional parametric history-based modeling. With PTC CoCreate Modeling, for example, I have found file sizes to be 60% to 80% smaller than the same model created in most any traditional history-based system. This would indicate that these parts and assemblies will also consume much less memory when loaded.
In a traditional history-based CAD system, an assembly is basically a collection of references and relationships to other individual history trees. These history trees represent individual parts and sub-assemblies The history trees can be large and complex. The assembly references and relationships between these trees can be even more complex. With direct modeling an assembly is simply a collection of solid models that are organized in a hierarchical structure. There is no history tree. There are no hidden references or relationships. What you see is what you get. It’s as simple as that.
I’ve been doing some large assembly testing with several different CAD systems. It has been startling to witness how poor many of the most popular CAD tools perform with large assemblies, even with “dumb solids”. The assembly that I am using in this example is made up of 29,455 part and assembly objects. The STEP file of the entire assembly comes out at just over 302mb. The native CoCreate package file of the entire assembly comes in right at 100mb. This is not a large assembly compared to many of the assemblies I have witnessed CoCreate users working with. Most CoCreate users would consider a large assembly to be somewhere around 100,000 to 250,000 parts. (By the way, the native geometry resolution/accuracy of a model developed in CoCreate Modeling is 1.0E-6 mm by default – about 2500 times higher accuracy than any other CAD system on the market, and yet it is still possible to manage these large assemblies.)
Below is a picture of the assembly I have been working with. It comes from a company in Europe. This is a coagulator used in the cheese making process. CoCreate Modeling was used from beginning to end to support the design process.
For the video below I loaded this assembly in its entirety. All parts are loaded as high accuracy solid models. None of the parts were loaded as lightweight, graphics only or in some suppressed mode. Based on the privileges controlled by the PDM system, every part and/or assembly can be quickly and easily modified. As you will see, in-context design is simple and fast, even in the context of 30,000 other parts.