Hi Michael thank you very much for the responce,
I have attached the file.

Thanks
Josh

Hi Josh, the thing that's probably causing fillet difficult in those areas is that this cutout surface here is not smoothly closed, it comes to a slightly sharp corner where it comes together:





When there's a sharp crease at an edge rather than a smooth closure, it means the fillet surface that is created along that edge also does not close smoothly with itself either and it becomes much more difficult for the filleter to figure out how to deal with that.

Ideally you'd want to have made those surfaces used to cut out those areas smoothly closed and then there would probably not be any problem filleting those things. It can be difficult to go in later on and try to fix stuff like that up, I'll take a look though.

Anyway that's what's likely to be the cause there - filleting especially does not like it when things have sharp creases like that but with it being fairly close to being smooth but not actually smooth. It tends to mean there is a pretty tiny slivery gap between the ends of the fillet surfaces that are generated along those edges.

- Michael

Hi Josh, so probably the best way to get that area filleted is to repair the object so that it is smooth along that whole cutout rather than just slightly sharp at that closing area as shown above.

The way I did that was to use "untrim" to recover the larger cutting surface and to remove the holes in the main object, there is some info on how to do that in this post about untrim here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=444.4

And there's more detailed information on this kind of low level surface repair process in the object repair tutorial here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=446.17

Once I had the original cutting surface extracted, I used Edit > Trim with the "isoparm" option to slice up the surface making some empty space between its ends and then putting in a blend surface between the edges so that it will be a smooth closed shape like this:



Then after repairing a couple of unjoined edges in some other areas of the shape I used boolean difference to cut those now smooth cutting surfaces out from the main object, and now the resulting structure with all smoothly meeting pieces in those areas should fillet ok.

I've attached the repaired 3DM file which you should now be able to fillet, the edges to fillet are now made up of 2 edges instead of just one so make sure to select them as well when you go to do the fillet:




Hope this helps! You want to try and void making slightly sharply meeting pieces like that if you want to fillet them later on, slightly sharp meeting things tend to be particularly difficult to fillet.

- Michael

Thank you very much Michael, that completely makes sense,
This was my first attempt at bringing curves through from Maya and its good to see what to look out for.
Very much appreciated, looking forward to getting more into this program =)