Initial calls into OEM's - Industrial Sales

I am a current maintenance/specialty steel supplier and have a vendor number. The challenge is getting into new plants. For example a Ford contact at a facility that I am currently selling just told me that even as a Ford employee he can't get into another stamping facility that I have targeted. Questions asked of higher ups on LinkedIn have gone primarily ignored. The facilities themselves are always automated with no attendants or with security guards that won't grant you access unless you have an appointment and an escort.

Anyone have any successful strategies for breaking into these OEM facilities?