Well, design is a noun, so it is okay. Its verb form is the same as its noun form, so that makes it different from manufacture and manufacturing.
In the same way manufacture is as much a verb as it is a noun:
Manufacture 1. noun, The process of manufacturing goods
2. verb, Process or make goods at a large scale using machinery.
(Source Collins English Dictionary and Thesaurus Express Edn.)
So I think it is exactly the same. :) If the gerund was required, CAD would be Computer Aided Designing??? :)
About 'discovery of the'... yeah, I think discovery is a bad word! I think it is almost a cliche even though it is only one word. But I think you should find an alternative to 'attachment'... what do you mean by attachment?
Attachment is a term used to mean a junior position at a firm, think internship, work experience. I think it originates from attaché (The junior member in an ambassadors suite). Would you think internship was more appropriate? Because I really wasn't enrolled as a student, but I was getting instruction in the workshops and laboratories. So summer school doesn't quite explain it.