In CAD circles we often hear CAD/CAM software developers speak about bottom-up or in place design. In fact whether you know it or not when you design a part using a CAD software you will use one of these 2 design methods. So what is bottom-up and in place design and does your CAD system allow you to choose the method which is best adapted to your needs?
Bottom-up design
Bottom-up design is in fact the most widely used design process used in the CAD world. In this case the designer designs one part per file, all parts are completely isolated from their context. After all parts have been designed they are then assembled in one assembly file. There are a few main advantages of the bottom-up design method. The first is that the engineer can easily modify or reuse the part. Another key reason for bottom-up design would be when you have multiple engineers working on one project. With the bottom-up design method, the work load can be shared equally across your engineering department. Also bottom-up designs are very useful for the design of large assemblies that contain thousands of parts. In these large assemblies, the file size is spread out between all of the parts in the assembly, thus making it easier to work with the large assembly. However, a bottom-up design method does not allow close geometric ties to be created between files, which means that building associativity between files is extremely difficult to achieve, if your CAD product even allows it to happen in the first place.
In place design
Following on from the description of bottom-up design a logical question arises: How can an engineer design when close associativity needs to be maintained between parts? The solution is called in place design. Our definition of in place design is: The design of a part in its assembly context. Let's take the example of the design of a machine: most parts can be deigned using the bottom-up program of different components and parts. How can the engineer deal with the linked parts or the chassis? The chassis depends entirely on its environment (i.e. the assembly file with all the parts of the machine) Therefore, it would seem natural to design the chassis in the assembly file which would offer the following advantages:
Important time gains - all design is carried out in 1 file which is completely associated with its environment. Time gains are also achieved by the simple fact of working in 1 file instead of several at the same time
Error reduction - as the file is associative all changes are carried though the entire file. In the case of bottom-up assembly each file would have to be manually changed individually.
In place design enables pre-project work to advance quickly thanks to the use of one single file
Version control - In an in place design, you always have 100% access and control over your parts/assembly. You always know that you are working with the latest version of the part/assembly.
In place design in industry
In place design has been a design program offered by Missler Software since the beginnings of TopSolid. It is in fact one of the cornerstones of TopSolid. In place design is an essential design program in industries such as the toolmaking and wood industries. If we look at the toolmaking industry we know that the design of a mold is often a unitary study. All parts are strongly linked and in place design permits the creation of strong links between parts: a component such as a guiding pin can, for example, provoke a drilling or boring operation on several parts. Each part is very closely linked to the rest of its environment. For this reason TopSolid's in place design offers huge advantages to toolmakers and is one of the very strong points of TopSolid'Mold.
In place and bottom-up design
In fact, both methods of design are very powerful by themselves. However, what makes TopSolid unique is its ability to work with the 2 design methods without limitations. There are definitely certain parts of an assembly that can be designed in their own files and then assembled into the main assembly document. Again, this method is perfect for teams of engineers. However, when designing a mechanical element that includes gears for example, it just makes sense to use the in place method of design. With the in place method you can be sure that your gears are created correctly and that they interact correctly as well. When your assembly of gears is complete, you can insert it into your bottom-up assembly and move on. What makes TopSolid a powerful leading CAD/CAM product is its ability to allow you to work the way you need to work. Your needs can and most likely will change from project to project. It is clear that it only makes sense to work with a product that can support both strategies of design seamlessly and effortlessly.
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