Introduction of Case

Building momentum through word of mouth, the product development group at Graco has been adding CFD analysis to its early engineering workflows with big results.

Getting engineers to switch tools or change their work habits is never an easy task. Management may mandate a move to a particular piece of software or make modifications to the engineering workflow, but that top-down approach often is met with resistance, jeopardizing the overall product development goals.

Graco, which delivers systems and technology for a wide range of fluid-handling applications, has overhauled its design practices significantly, moving away from a pure trial-and-error design process and embracing simulation—specifically,computational fluid dynamics (CFD)—far earlier in the cycle. Incorporating CFD into the early design stage has helped Graco hit the mark on a number of fronts. The company has been able to optimize its designs and create more repeatable and predicable engineering results. The changes also have led to significant achievements on the product front. Specifically, Graco was able to deliver a state-of-the-art plural component spray gun in two-thirds the time of its traditional cycles despite the fact it was a product design in which the company lacked prior engineering expertise.

The move to treat CFD simulation as an integral part of early design work instead of a late-stage specialty phase did not unfold from the top. There was no formal corporate mandate and no concerted effort by engineering management to enact changes to existing engineering workflows. Instead, the transformation evolved slowly over the course of the last six or seven years, led by the success of a single engineering team that went on to promote the practice and the results to the rest of the organization. What began as a technology experiment and later an informal exchange between a couple of colleagues has blossomed into a grassroots campaign to promote the use of CFD to other Graco divisions and product groups. This gradually introduced compelling changes to the company’sproduct development practices. The upside from this kind of slow and organic approach is that there has been automatic buy-in from the engineering ranks as more individuals and projects groups decide to adopt CFD as part of their processes.

Trial-and-Error Design

Traditionally, CFD did not have a starring role in the product development process. Years back, the company had a single license for a high-end CFD tool that was used by one engineer, who was charged with running simulations for the different groups within the company on an as-needed basis. The complex models would take days, if not weeks, to set up and run—a lag time that discouraged engineers from employing CFD as part of their efforts. When that individual engineer left Graco, the company was left with a void, having no one adequately trained in the specific tool and CFD discipline to pick up the task.

As a result, the bulk of the development projects remained a trial-and-error process that went much like this: An engineer would start with a benchmark that usually was based on scaling up the original design. After building and testing a physical prototype, the team would identify performance problems, take a guess at the reason for the problem, address it with a new design, and start the prototype and test cycle anew. This process would continue through multiple designs and scores of prototypes until a satisfactory but not optimized design was found.

Optimizing designs with the trial-and-error method was typically not practical for a number of reasons. First, it was far too time-consuming and costly to build a prototype of each ensuing design iteration. It also was next to impossible to predict flow patterns, which are an integral part of the plural-component spray gun products. The spray guns are designed to apply materials, such as polyurethane foam insulation and polyurea, that have to be mixed just before spraying. The performance of the spray guns is predicated on how thoroughly the unit mixes the two components that constitute polyurethane foam: the resin and the catalyst. Controlling the motion of the spray is another critical design element since it is key to delivering the desired pattern shape on the surface to which the substance is applied.

When a team was charged in early 2003 with creating a new kind of plural-component spray gun, it became clear that the trial-and-error process was no longer practical. The specifications called for the gun to deliver round spray patterns with a diameter 50% greater than the standard. Simply scaling up the mix chamber from existing designs would not deliver optimal performance because the nature of fluid flow changes substantially when the scale of the design is modified. That problem prompted the team to revisit CFD technology as a means to simulate the fluid flow inside the gun so that the team could experiment with various iterations and optimize a design well before building a costly physical prototype.

Using FloEFD from Mentor Graphics’ Mechanical Analysis Division, the team was able to home in on an optimized design in less than four months, a third of the time it would have taken with the old trial-and-error approach. The resulting product, the Graco Fusion Air Purge Spray Gun, was a resounding success, helping the company garner more than a 30% market share in just two years despite the fact that it was Graco’s first entry in this category.

Lessons Learned

Word of the Fusion team’s success with CFD spread quickly. Engineers throughout the different divisions began to reach out to the Fusion team to learn about the role of CFD and specifically to get a jump on using the Mentor FloEFD tool. The technology became an agenda item at interdivisional engineering meetings, in which the divisions regularly share information and provide updates on project status. The word-of-mouth campaign continued over the last few years, and as a result, CFD is now deployed in Graco’s three divisions by multiple engineers and designers, not just one or two fluid dynamics experts.

The choice of tool was critical to CFD’s expanded use. Mentor FloEFD works within commonly used computer-aided design systems so that engineers can access the functionality without having to master a new discipline or learn another complex design program. The Fusion team also played a key role in introducing the technology to others. As word spread, the team did its part to acquaint engineers with CFD technology and provide basic training on the FloEFD product. Because of the grassroots culture, the responsibility for serving as the CFD champion did not last long. As individual engineers and groups came up to speed on CFD, they took on that role, creating a broader base of proponents to provide mentoring and support and underscore the value of infusing CFD into the early design phase.

There is still work to be done to promote CFD, and eventually engineeringmanagement may opt to take a more active role. Nevertheless, there is no denying that CFD has made consistent inroads in the Graco engineering culture and significantly altered the way the firm designs and builds products.