By Bruce Jenkins, Ora Research

Prairiefire Consulting is a provider of engineering consulting, application and training services based in Urbana-Champaign, IL whose differentiating expertise is sensitivity-based design. This approach to new product development focuses on product and process quality, with the goal of ensuring that product functional requirements and supplier capabilities are surfaced, quantified and managed in every phase from concept engineering through manufacturing execution.

Prairiefire describes its core value as helping clients in product development “map complex system-level problems and solve them down to the details on the drawings. We make it work at every level: concept, design, manufacturing, in the field, and even remanufacturing. Our experience has especially helped the medical and industrial fields, where getting it right the first time really pays off. From simple tolerance stacks all the way to performance and risk optimization, Prairiefire can help you develop a stable solution.”

Before the comparatively recent advent of practical software technologies that automate the various tasks involved in sensitivity-based design, this approach to product development required volumes of tedious, time-consuming, labor- and expertise-intensive manual calculation. Consequently, engineering organizations applied it sparingly, only able to justify its use on their most mission-critical projects. But today, through 20 years’ investment in building and refining the requisite knowledge and skills, Prairiefire reports it has put in place a combination of methodologies and expertise in relevant software tools that make sensitivity-based design an economical, cost-effective solution for virtually any product development project.

What is sensitivity-based design?

Sensitivity-based design finds, defines and manipulates system sensitivities. Sensitivities act like levers, the company explains—different design inputs have differing amounts of leverage on various outputs.

Conventional practice in product development and manufacturing, Prairiefire observes, is to attempt to control the system by tightening tolerances—simple to say, but expensive to apply. Without insight as to what extent tightening tolerances will improve the product’s quality, tightening tolerances may not even control the system.

By contrast, sensitivity-based design focuses on understanding the multiple relations between input variations and quality outputs of the system designed. Sensitivity is leverage, Prairiefire explains, and sensitivity-based design is positioning the “fulcrum” in a design to the engineer’s greatest advantage. Structuring the engineering design process to achieve visibility into, and control over, system sensitivities is more effective, more sustainable and lower-cost than the conventional practice of simply tightening tolerances.

What sensitivity-based design helps engineering and manufacturing organizations do:

• Control manufacturing risk—Minimize scrap, rework, and fit-up problems by quantitatively understanding and controlling risk before and during production.
• Design quality in—Guarantee performance and sustainably reduce warranty costs.
• Avoid design problems—Understand design concept quality during the selection stage.
• Understand the design drawings—Capture functional requirements clearly and accurately. Tolerances are correlated to physical requirements.
• Eliminate firefighting from design and production—Prevent the scramble to control warranty problems. Spend time on engineering instead of reactionary firefighting.

Examples of project success reported by Prairiefire:

• Serpentine belts—Belt life sensitivity to mounting strategy and design guidelines for FEAD (front engine accessory drive).
• Bearings, seals and gears—Root cause analyses and lifespan improvements.
• Planetary gears—Alignment analysis to find root cause of failures.
• Fit-up and assemblability—Cast, forged, machined, molded, weldments, non-metallics, sheet metal and more.
• Knee implants—Interfacing manufactured components with unique bone geometry and quantifying robotic precision.

Supporting software tools

Key software tools employed in Prairiefire’s work processes:

• Enventive Engineering’s Enventive mechanical design and tolerance analysis tools for modeling geometric and multi-physics system variation in two dimensions, to identify and optimize critical parameters early in the design process.
• Sigmetrix’s CETOL 6σ tolerance analysis software for streamlined, deterministic modeling of fully 3D systems, which provides product development teams the insight required to confidently release designs to manufacturing.
• Noesis Solutions’ Optimus multi-parameter design space exploration and design optimization system. Prairiefire uses Optimus in conjunction with other variation analysis tools when multiple multi-physics parameters need to be solved for a stable design point simultaneously.
• 3D geometry modeling, with import capabilities for multiple CAD data formats.

Prairiefire also creates processes for solving complex, specific variation problems, then encapsulates those processes in custom software tools that let customers quickly solve recurring design tasks.

Seeking manufacturing industry partners for new software development project

In the course of its engineering consulting work, Prairiefire has developed a series of multi-physics equations that make it possible to design more durable and lower-cost taper joints. Taper joints are typically designed and tested empirically, requiring a custom thickness shim in each joint. Existing methods that do not use shimming, such as a castle nut or thread locker, compromise the integrity of the joint and increase the probability of sudden catastrophic failure modes.

Through careful control of system sensitivities and knowledge of the variations likely to be present in taper joints, the company reports it now possesses the know-how to eliminate the need for shimming during their assembly process, without reducing long-term structural integrity of the joint. Its method allows automated optimization of dimensions, tolerances, torque, load, stress and other attributes.

Prairiefire is currently seeking one or more partners to fund development of software code to automate the methods it has developed, and a graphical user interface for the code. Contact the company at:

Prairiefire Consulting, Inc.
www.pfcae.com