A printer can make individual parts so long as it’s the same kind of molecule. Some assembly would be required.
You could theoretically have a mix of substances printed through a single head, if they’re compatible and they all melt at one reasonable temperature. The mixing would happen during the manufacture of the spool of material.
Additionally, in one printer you could theoretically have an array of heads available which print from different spools of material. Somewhat similar to how industrial CNC machining stations typically have an array of cutting heads available for automatic selection. Once again the various materials would have to be compatible and capable of melting together into a cohesive structure.