The deformation is an excessive change in the shape of the part after it has been ejected from the injection mold. Also known as deformation, a deformed part is bent or bent due to internal stresses in the part caused by irregular shrinkage rates or by some mechanically forced forces such as during the ejection phase.
Removing warp can have huge cost savings and should be part of a lean manufacturing program.
Picture above shown us how warpage detected on plastic parts. Those were heavily deformed as its ejected from mold. In some case you could increase number of rib, if possible to eliminate warpage. Counter mold is the last chance to cure this defect. So you able to get desired plastic part shape.