What is the fine-grained topic of the following text: Encouraged by the successful diplomatic negotiations, which began in 1991 between the three NAFTA partner countries, and the subsequent signing of the agreement in December of 1992, Metalfit's ownership decided to invest in a vastly larger foundry and machining center not far from the original Monterrey area site. Only return the topic.
Metalfit's investment in a new foundry and machining center following NAFTA negotiations.