Toon transparent material question

[bdochia]

I want to show the inner works of a machine in a sketchy way. The toon materials are just right for this job.
I have used a transparent black toon material for the outer case of the machine and all looks good. Now, inside it I have another component that has something inside of it. When I apply the same transparent black toon material to this object, I can not see the small object inside. I get that I should get less and less transparency with each "layer" that I see through, but I can not see the small interior object at all.
How can I fix this?
Is there a way of making the transparency not take in consideration the other layers ?

thank you ! 

[jhiker]

Have you got any intersecting/touching surfaces anywhere?
In this scene I had to scale the circular object inside the outer tube a wee bit to make it show 'transparent'.