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Assemblies Vs. Multi-Bodies Part 2

Cory Holden

This is a continuation of the Article Assemblies Vs. Multi-bodies Part 1.

Using multi-bodies in SOLIDWORKS can be really useful if you need dimensions to be related to each other. When using multi-bodies it is very quick and easy to convert the inner diameter of a cylindrical opening onto a sketch plane, and then make that the outer diameter of the new cylindrical part that will fit inside using the inner diameter edge (view picture). The inner diameter is the one on the inside of the piston rod, and the outer diameter is that of the brass insert. This makes it very quick and easy to reference dimensions in your design, and get the new body created while ensuring that it fits properly. This is also possible and easy to do in assemblies using component > New Part command. Upon picking a plane, you can quickly convert the cylindrical edge into a circular sketch for the current part you would be designing. From here, you can make a multibody part with the proper dimensioning, where the inner diameter of one body will match the outer diameter of another body perfectly. Using either of the strategies mentioned previously will make design changes easy. Also, anytime you change that inner diameter the outer diameter will change to match the new design accordingly. It is important to mention when using the two methods, the multi-bodies approach in this case is quicker and a bit easier to manage, so I would lean in favor of the multi-bodies approach over assemblies for this design method. That being said, both methods will still work with ease.

Now, if your assembly has dynamic references or moving parts, the rule of thumb is that you should use assemblies and not multi-bodies. The reason behind this is that the assemblies, in SOLIDWORKS, are designed in a manner in which you can see the dynamic motion between individual parts. You can literally see how the parts will interact together mechanically in the SOLIDWORKS assemblies environment. Also, there are special tools when working with SOLIDWORKS assemblies that you may want to take advantage of in order to ensure that your designs are exactly what you intended them to be. So by using assemblies, you have the option to use the clearance detection tool which will show you whether or not any of the components in your assembly are occupying the same space. This tool will help you catch possible dimensioning mistakes that have caused your parts to overlap. Another tool available with the use of assemblies is the interference detection. This tool works similar to the clearance detection by letting the designer know if parts are overlapping, this one however is designed to specifically tell you if parts are colliding on movement. In other words it lets the designer verify if the assembly components are running into each other, or interfering when moving. These tools are very powerful, and a great way to check to make sure that all of the components in your design are going to work together as expected. Overall, the reasons mentioned previously are the big advantages to using assemblies inside SOLIDWORKS.

In summary, the reasons why I would use multi-bodies are:

  1. It’s one file to update when you want to make changes.
  2. You only have one file to deal with which contains all of the necessary information.
  3. Your relations between bodies will be controlled by your sketch relations.

And you may find it necessary to do assembly modeling when:

  1. You have a design which requires moving parts, and you want to test these.
  2. When every part in your assembly has a separate part number, due to design.
  3. If you want to use a part multiple different places in an assembly.
  4. Assemblies will also help you when your projects become too big. Assemblies are organized better in your feature manager design tree and also there are special methods for loading large assemblies to save you time and computing power.

Whereas both methods discussed in this article will work for most situations, hopefully this outlined when the better time to use each of the two methods is. This being said, keep in mind you can use both multi-bodies and assemblies within the same project. This will allow you to really dial it in on your design, save time, and make the work flow quicker and easier on you to make SOLIDWORKS suit your needs the best.

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