Size optimization

SSD

I have been doing a size optimization tutorial on a bike frame. Optimization objective is to minimize the mass. After following all the step which is given in the pdf, results are not correct. 
After optimization mass is supposed to reduce but it increased.
What am I doing wrong?

Ingeniorator

Which tutorial is it? Most likely, the result is due to your constraints. The solver tries to satisfy the constraints at first, and only then optimises towards the objective even if the minimum found is above the initial value. It is simply the optimum feasible with the given constraints.