Executive directors Adrian Allen and John Baragwanath and strategic adviser Richard Caborn have retired from the Advanced Manufacturing Research Centre.
Their departure follows the shock resignation of Mr and Mrs Ridgway last month. The five played key roles in launching the site with Boeing in 2001.
As sales director at Sheffield tooling company Technicut, Adrian Allen worked with Prof Ridgway to forge new links between Boeing and the University of Sheffield, culminating in the launch of the AMRC in 2001.
As head of the Government Office for Yorkshire and the Humber Regional Innovation Unit, John Baragwanath played a key role in establishing the AMRC and Advanced Manufacturing Park in Rotherham. He joined the AMRC as projects director in 2005.
Both were awarded OBE for services to industry.
Former Sheffield MP, Richard Caborn, was business minister when in 2000 he organised a dinner with Keith Ridgway and the then Boeing chief executive Phil Condit which led to the firm's initial £6m investment. Mr Caborn has been a well connected and active supporter ever since.
The AMRC pioneered paid-for work by academics for manufacturers including Rolls-Royce, McLaren and Boeing. It was run at arm’s length from the main university.
A governance review and calls for more oversight are believed to have played a part in the departures.
It is understood university bosses wanted to better understand the financial and reputational risks of the rapidly-expanding organisation. Among many projects, it bid for collapsed Sheffield engineer Davy Markham.
Prof Dave Petley, vice-president for innovation, said the university and city region owed Adrian and John “huge thanks” for developing an ecosystem that has “helped transform the UK's manufacturing sector by improving processes, materials and skills.”
The AMRC was now led by an experienced board that had been mentored by Keith, Adrian and John, he added.
"We had a very positive meeting with our industrial partners where we discussed our collective commitment to the next chapter of the AMRC's development.
“Working with major partners such as Boeing, GKN, BAE Systems and Rolls Royce, we have ideas for new and ambitious projects that help to attract investment into Sheffield and other regions, increase productivity and re-shore manufacturing for the UK."
Sheffield Chamber chief Richard Wright said he hoped it would continue to deliver.
He added: “It’s been critical to the last 20 years and will be to the next 20.
“It’s always been different from other parts of the university by engaging in and commercialising applied research. It gained favour with government and lots and lots of businesses. It has a fantastic reputation, it’s the reason Boeing, McLaren and Rolls-Royce have factories in our region.
“I’m grateful to Keith Ridgway and what has happened under his leadership. I hope that continues.”
The AMRC has more than 100 industrial paying partners, employs more than 700 in several hi-tech buildings and has attracted more than 100 companies to the Advanced Manufacturing Park.
It has a successful Training Centre for hundreds of apprentices and satellites in Derby, Preston, Wales, the Wirral and Korea.
Sheffield University took top spot for income for engineering research in the UK this year, earning £124m, some 57 per cent from the AMRC.