Excel 2016 Pivot table or Consolidate or ?

Briankf 

If I were doing it, I'd approach it as I'll describe below. One of the lovely things about Excel is that there are always multiple ways to accomplish an objective. Fortunately you've done a pretty good job of describing your objective. I fully expect that somebody is going to come along and give you a Power Query solution. I'm old school enough (which is to say, I learned Excel before Power Query came along, and haven't yet successfully mastered it)....but, with that as the up front disclaimer

I'm a big believer in using a single table (aka database) whenever that can work. Excel is remarkably powerful when we need to extract data from that table. So, in your case, given that each of your 77 sheets is arrayed similarly (I think identically, except for numbers of rows)...

1. I'd make them all one big database, simply adding a column that differentiates which assembly a given row refers to. (Doing this would still allow you to readily create any one of the 77 distinctive lists by using FILTER and simply setting the criterion to the desired assembly descriptor.)
2. And then the Pivot Table would work to do that consolidation you're asking for.

I am assuming, since you've clearly been doing this kind of thing and asked about it, that you're proficient enough with Pivot Tables to know how to use its features to define/filter/display the kinds of results you're looking for.

So that's this man's way to tackle your task. Now I'm going to watch to see what other solutions come forth.