what causes warping in my

This demo may help you understand 3D printing and make better designs.

I use electrical tape to show layers of polymer (just like FDM printing) that have internal stresses. Each layer wants to contract and sometimes causes:

-warping
-prints peel from bed
-residual stress

Once you know the behavior of the forces you can improve with action:

-protect your printer from cool drafts
-raise the bed temperature
-adjust designs to relieve stress build-up
-enclose your print and insulate
-avoid sharp changes in cross section in designs (along z-direction)

I hope this helps and you comment with any questions!