Generating novel ideas is a challenging part of engineering design, especially when the design task has been undertaken for an extended period of time. How can experienced designers develop new ideas for familiar problems? A tool called Design Heuristicsprovides strategies that support engineers in considering more, and more different, concepts during idea generation. Design Heuristics have been shown to help novice engineers create a set of more diverse and creative candidate concepts. In this case study, we extended this approach to a group of professional engineers who had worked on a specific product line for many years. In a workshop format, a small group of engineers worked with the heuristics in two separate sessions and generated ideas collaboratively. Video recordings were analyzed to reveal how the heuristics were used to stimulate new designs for their product line. We found that Design Heuristics bring order in ideas and elaboration on ideas, perhaps through coordinating effort on idea evaluation, increasing capacity to improve the ideas of others, and facilitating interaction between participants. This case study shows using Design Heuristics can assist even expert engineers to increase the variety of concepts generated, resulting in a larger set of ideas to consider.