It's always a challenge to deal with people and ask them to buy your idea.
As a sourcing professional, my job responsibility is to look for new suppliers to achieve the cost savings for the company. I am always working in the cross-functional team as a project leader to facilitate the project. Of course, engineers or operations have the excuse to delay the project. That's what I do:
1. Set up the goal for the project. Cost saving $ amount, lead time reduction etc.
2. Present to different stakeholders such as finance, engineers, operations and top management.
3. Analyse the cost and benifit, strategically, operationally and financially.
4. Set up a timeline for each milestone.
5. Resources needed, money and man power
6. Check the progress once a week or once every two weeks depending the importance of the projects.
When someone is behind, I talked to him or her first then send an e-mail to write down our conversation to confirm the delivery date for his or her task. I will follow up three times before I talk to my boss and his or her boss.
Hope it helps.