How would a Human Resource Manager find manufacturers and a R&D Engineer?

Depends how senior/important the posts are and whether employer claims to be an equal opps employer. Usual methods:

- direct advertising

- using an agency

- using a headhunter

When has HR ever hired a suitable candidates for anything? They can't tell the difference between competence and confidence but their vote holds as much weight as the person who is an expert in the area and has to work with the new employee