tooling split "cannot knit sheets together"

Hey,

I am trying to create a mold for a part (fan) I imported as a .igs file. I created the parting line, parting surface, but get an error when tring to use the Tooling Split fuction, the error reads: "cannot knit sheets together". Here are some images of the part and the process I have taken so far. I assume the promblem is due to the shape of the parting surface as it moves between the blades, but I can't seem to make the surface and simpler.

Parting Line.

Parting Surface, gives a strange surface that crosses over itself between the blades of the fan.

Note: the resulting Parting Surface between at the top left and bottom right of the image.

This is the error I then recieve when trying to use Tooling Split

I have included the part file.

Any assistance would be greatly appreciated!

Thanks