As the title describes, you may have often come across a situation where you need to import the motion loads on any one of the component/part and the moment you click on simulation-Import motion loads, you do not see any part mentioned in the “Available Assembly Components”. This might lead you to think whether – did the motion study go through? or is it a bug in the software ? Well the answer is simple. In Simulation, you have to make sure that the components of interest has to be a single part i.e. child of the main assembly rather than being a part of a sub assembly. Any part belonging to a subassembly will not show up in the available components list. In Simulation motion, where you have to often deal with mates, redundancies and so on, it is always better to think about the parts of interest in the beginning cause this might lead you to spend long hours in re-creating the mates while trying to dissolve the subassembly.
There is another work around for the above problem. This can be done by using the command “Dissolve sub assembly”. All you need to do is right click on the sub-assembly and select “Dissolve sub assembly”. This will help you to break the parts under the sub-assembly and make them the children of the main assembly. Again, as mentioned earlier, care has to be taken before proceeding with the motion study as this might leave you with all of errors in mates.
I hope, this will give you a heads up on how to proceed with a motion study and save you some time and focus more on simulation (motion and FEA) rather than re-creating the assembly mates.