Updated: Mar 9, 2020
This occurs because one side of the 3705 Cooling Fan interferes with a catch on the DIY Case's top cover. This can be seen from an idealised assembly simulation, wherein a Khadas VIM3 CAD model was used. The red circle shows the interference region.
Users may experience this issue, or not at all. This is dependent on the unique combination of components you've used, and therefore cannot be said to affect all users. So what can you do if you encounter this situation? Let's continue on to three solutions:
The simplest method is to simply rotate the top cover so that the GPIO window (with the catch), is above the port assembly. There is more space above the ports than there is above the fan, and your problem will be solved immediately.
The second more tedious solution, would be to use a sharp pen-knife to shave off a few millimetres of material from the plastic catch itself. In the photograph below, you'll be able to see the length of material required, and that the result should be flush with the cover.
Once you've shaved-off the appropriate amount, fitting should take little effort. This method is not recommended for users with shaky hands or who aren't comfortable with sharp objects.
The final solution is to install a set of nylon spacers (M2 clearance); they needn't be thicker than a millimetre. Some users on our forum believe this method also improves casing ventilation, and it is also a non-destructive solution.
In the photograph above, you can see that the top cover is raised by a millimetre above the middle cover. Avoid using spacers that are too thick, as you would need to use longer M2 screws to reach the bottom cover.
Whatever your chosen solution is, destructive or non-destructive, the tolerance issue between the 3705 Cooling Fan and DIY Case is easily resolved. Do you have an impressive case-mod you'd like to share? Head over to Khadas Forums to let others know! Warmly, Khadas Team