The fan which is as a reference. Now i want to change the thickness of the fan including whole structure without changing the diameter of the fan i just want to increase the thickness in one direction. i want to thicken the structure from 8 mm to 25 mm.
If it is a solidworks model, and not an imported body, there should be a feature tree item which controls the thickness. Just change it.
I would not do it this way, but in a pinch you could use the Scale tool to scale the part in only one direction.
Another possible fix is offsetting and thickening the "skin" of what you want to thicken. Its success really depends on the geometry of the model.
Upload the model here and I'm sure there are some better options once the model can be reviewed.
The model is sort of weird. Towards the end a Scale feature was added to make the part 33% smaller.
I'd go back and make the model the correct size to start with, but I guess it can still work with the scale feature, it just requires some simple math.
To thicken the blade, go back to BossExtrude2 and increase the depth of the extrusion. It is now 1.5mm But keep in mind the Scale feature will reduce this by 33% later.