Vostro 3520 Hinge Issues

We have a total of 4 Vostro 3520 laptops still under warranty, all of which have nearly identical damage; one or both hinges have broken free of the LCD back panel. This damage occurred under normal daily use due to the hinges being too tight. I have requested a warranty repair for what is clearly a manufacturing defect, but I was told those repairs would not be covered. What is the best way to receive service for these failed devices?