7.4 Integration of Design Considerations

During the creation of a design, the primary objective is to satisfy the specific functional and physical objectives established in the requirement documents. Coordination between design engineering and manufacturing engineering has proven to be effective in providing for flexibility in producing the product at the lowest cost without sacrificing performance or quality. The development of a successful producibility program is dependent upon the ability of the PMO to integrate the producibility task into the acquisition program.

The requirement documents establish what the system must accomplish in terms of performance objectives for the system. Subsequent statements in the requirements document describe the physical, functional, and support framework for the system. These statements operate as constraints on the design. The relationships between the performance objectives and the constraints establish the potential standards of producibility for the design. If the statements of constraints rigidly specify the system, subsystem, components, materials, and manufacturing processes, the producibility of the design is essentially determined (even though it may not have been a primary consideration in establishing the specification). The issue of design producibility and capabilities of the production system should be specifically considered when the PMO is tailoring the system specification and ether contractual requirements for the development contract.

Figure 7-4 Spider Diagram

Figure 7-4 is a design spider diagram used to identify trade-off criteria. The diagram is a tool used to identify the relative importance of various factors that need to be considered during the design process (conceptual and detailed). The further away from the center of the diagram a factor is the more important that factor is. So as you can see from this diagram "safety and affordability" appear to be the two most important factors. In addition, the further away from the center a factor is indicates that the program may be willing to assign more resources (time and money) against achieving those factors.

Physical and functional characteristics place constraints upon the level of producibility that can be attained. By changing some of the requirements or constraints, the system might be more simply designed and more easily fabricated if the weight limitations could be increased by 5 percent. The objective of a balanced design is to create an item that will satisfy all of the specified performance and physical objectives and concurrently maximize producibility. Producibility engineering can make a substantial contribution to achieving program goals. Below are several design best practices:

1. Simplicity of Design: Eliminate components of an assembly by building their function into other components or into integral components through application of unique manufacturing processes. In one case, the objective may involve working with the design engineer to identify and eliminate excess components. In another case, the focus may be on working with a manufacturing engineer to combine components.
2. Standardization of Materials and Components: A wide variety of off-the-shelf materials and components are available. When those items are incorporated in the design, cost is generally reduced and parts availability greatly increased.
3. Manufacturing Process Capability Analysis: Determinations of the available manufacturing capacity, and its capability to produce the desired end item without special controls, is a critical activity in the producibility analysis. This normally includes analysis of the degree of process variability, the causes of variability and the definition of methods to reduce it.
4. Design Flexibility: The design should offer a number of alternative materials and manufacturing processes to produce an acceptable end item. Unwarranted limitations of materials or processes seriously constrain the producibility analysis.
5. Modular Open Systems Approach (Figure 7-5): The design should utilize standardized units or dimensions, for easy assembly and repair or flexible arrangement and use. A modular design organizes a complex system (tank, aircraft, ship, electronic box) as a set of distinct components that can be developed independently and then plugged together.

Figure 7-5 Modular Open Systems Approach

Modular designs are characterized by the following:

• Functionally partitioned into discrete scalable, reusable modules consisting of isolated, self-contained functional elements,
• Rigorous use of disciplined definition of modular interfaces, to include object oriented descriptions of module functionality, and
• Designed for ease of change to achieve technology transparency and makes use of commonly used industry standards for key interfaces.

The key systems' producibility activity during conceptual design is the development of a producibility plan. System producibility design efforts generally are concerned with system-level tradeoffs. Alternative design approaches and concepts were analyzed for projected impact on manufacturability and affordability downstream in production. Customer interface and review of the producibility plans are also performed.

Emphasis on producibility can have a direct impact on RMS as well as life cycle cost. Many techniques are available to address manufacturability during design. Ease of manufacturing and repeatability in the process, along with concepts like process control and Six Sigma approaches, application of variability reduction analysis using Taguchi and Design for Experiments (DoE) techniques, as well as material characterization analysis and statistical process control, are essential elements to realizing affordable, reliable, and supportable design.

The Navy's Best Manufacturing Practices Center of Excellence (BMPCOE) conducted a benchmarking review of Northrop Grumman Electronic Systems (NGES) in Baltimore, MD and identified their Producibility Guidelines as a best practice. NGES personnel developed Producibility Guidelines that provide detailed manufacturing and production considerations to design teams. This process-specific information supports trade studies and preliminary design and establishes rules for validating manufacturability objectives during the detailed design phase. Northrop Grumman Electronic Systems has realized significant improvements in first-time-through-test yield, cycle times, touch labor requirements, and standardized part selection with the implementation of these guidelines.

Northrop Grumman Electronic Systems (NGES) defines producibility as "the capability to effectively produce a product at the target cost without additional process development beyond the release of a design to production." This approach uses simple, standardized manufacturing processes while providing the optimum compromise between cost and performance. The objective is achieved only when manufacturability factors such as material selection, yield, and process technology are considered during the design process and are included in alternative trade analyses.

NGES began a program in 2001 that has improved performance in this critical area through the development and distribution of Producibility Guidelines. These guidelines are established by manufacturing engineering for use by design engineering and exist for every manufacturing area within NGES. These documents contain key information impacting design choices that include:

• Material selection rules and implications;
• Detailed process capabilities and limitations;
• Established mechanisms for checking and verifying compliance with the guidelines; and
• Impact of design choices on manufacturing characteristics such as yield, cost, and non-recurring expenses.

Guidelines are used throughout the design and development cycle. During concept design, the guidelines support trade studies of competing designs and consider material selection, process technology, production cost, yield, and manufacturing cycle time. The preliminary design review is supported by information detailing parts selection, process capability/variation that impacts engineering analyses, and identification of cost drivers that support production cost estimation. During the detailed design phase, the guidelines provide "rules checking" to ensure that established production and manufacturing objectives are met by the final design.

Producibility Guidelines have been successful in positively impacting several manufacturing areas. In the manufacture of electronic modules, first-time-through-test yield (FTTTY) increased nominally by 2.1 percent, while touch labor was reduced by 15 percent. Standardization of part selection across electronic component assemblies reduced the number of line items needed to support production, improving kitting cycle time, throughput, setup time, and part restocking and changeout time. In the Surface Mount Technology (SMT) area, FTTTY has improved, with NGES achieving 100 percent yield in July 2005 for the first time. Cycle times are also consistently meeting or exceeding industrial engineering time standards, with this area seeing no design revision notices (RNs) in the past several years for parts influenced by the Producibility Guidelines.

Producibility must be addressed during every aspect of the design and development of a product in order to achieve the desired outcome of affordable products that meet the needs of the customer. During detailed design, it is crucial that the Integrated Product Team (IPT) responsible for the product continue to include a representative of manufacturing. As the product transitions to a final detailed design, the IPT must ensure that every aspect of producibility has been addressed. During this stage of the process, the IPT must continue to focus on the needs of the customer as stated in the product goals and on the product's key characteristics. As part of detailed design, product and process data are definitized through prototyping and testing of hardware and processes. The manufacturing plan gets fully developed during detailed design.

In this section, the three elements to address producibility during detailed design are presented. The three producibility system elements include the following:

1. Conduct Producibility Engineering Review;
2. Error-Proof the Design; and
3. Optimize Manufacturing.

Engineering reviews using personnel who have not been involved in the product development are a traditional method for assessing the maturity of a design. In most cases, these reviews are conducted periodically during the design phases. With respect to producibility, a specific producibility engineering review (4.1) focused on the maturity of manufacturing processes is an essential step in achieving affordable products. Such a review should be accompanied by efforts to error-proof the design (4.2) and to optimize manufacturing (4.3). As described in this section, these three activities are inter-related. Although presented here as three separate elements, it is common practice to execute all three elements together, since they complement each other, to result in a final detailed design of a product that can be affordably manufactured.

The intent of a Producibility Engineering Review is to focus on manufacturability and not on the product's functionality. The goal is to identify manufacturing and assembly difficulties and potential problem areas. New process capabilities can then be traded off if the requirements exceed present capabilities.

As part of the Producibility Engineering Review, detailed attributes of the product under design are compared with documented process capabilities. This review is used as a checking mechanism to ensure that the product, as designed, can be produced with available manufacturing capabilities. This systematic, thorough evaluation is a necessary step in achieving enhanced producibility. The review can be conducted at one time or it can be done either continually or at pre-defined points in the design process.

The producibility engineering review is conducted in addition to normal and necessary design reviews. These latter reviews are conducted by the IPT throughout the design process and should be used to assess progress against the goals and metrics for the product. Since it is imperative that the IPT maintain a focus on producibility, the regular design reviews address many producibility issues. However, they are typically focused on individual processes and components and normally include tool, production, and facilities planning for those processes.

In contrast, the focus of the producibility engineering review expands to an evaluation of whether the entire product can be manufactured in the intended facility within the given schedule and budget. Internal experts who are not part of the product IPT nor involved in the product development are normally brought in to conduct this review.

Another key element to achieve enhancements in producibility is to error-proof the design. This oft-overlooked activity can have a remarkably big payoff in the reduction of manufacturing errors that can result in the need for rework and/or the production of scrap. The goal is to eliminate the causes for error, minimize the possibilities of error, and make errors that do occur more readily detectable. In simple terms, this goal is accomplished by designing products so that they can only be assembled the correct way and by using manufacturing processes that can only be implemented correctly. In reality, this goal may be unattainable for every product. However, by striving to identify opportunities to meet the goal, producibility will be enhanced.

An error-proof design is one in which the design team has considered ways to eliminate or reduce the occurrence of mistakes during manufacturing, assembly, and maintenance processes. A Failure Mode and Effects Analysis (FMEA) can assist in the identification of potential failure modes and in understanding the manufacturing process implications.

An example of eliminating an opportunity for errors is shown in Figure 7-6. In this redesign, a small lip was added to prevent installation of the bracket on the wrong side of the flange.

Figure 7-6 Error-Proofing Bracket Design

This element involves the final tradeoffs of design details and manufacturing capabilities to arrive at a final detailed design configuration that will enable on-time, error-free, affordable production. As in error-proofing the design, optimizing manufacturing is a goal. The objective is to continuously improve both product design and process capabilities. During the detailed design phase, trade studies can assist in arriving at an optimum balance of quality, functionality, cost, performance, and producibility. Most of the techniques used to trade conceptual designs can now be used to assess detailed designs.

In this step, prototypes are manufactured or purchased, testing is conducted, and simulations of the planned manufacturing processes are evaluated. Virtual prototypes and the use of simulations can reveal changes required prior to any actual manufacturing. Physical prototypes can be tested extensively to provide data to support the achievement of the design goals as well as for process control variables. Process maturity, ease of assembly, and manufacturing risk continue to be key elements considered during these final trade studies. Prior to final design release, it is appropriate to review the manufacturing plan for the design to attempt to identify improvements. Prototyping of product and process, using either real mock-ups or computer simulations, can assist in identifying opportunities for improvement.

Factory floor, assembly, and process simulation tools can provide a cost-effective evaluation of the manufacturing plan before any product is manufactured. Manufacturing system simulation may be used to model the overall production process, material flow, and schedules, while process simulations help predict the outcome between individual processes and the product's characteristics.

Advances in solid modeling and improvements in computer performance make it possible to perform a comprehensive analysis of virtual parts and to assess the capability of processes before actual manufacturing begins. Tolerance analysis tools allow users to simulate different tolerance stack-up conditions that are likely to occur during a manufacturing process. Modeling software also allows designers to model the behavior of mechanical systems under real-world conditions.

The classic systems engineering process is a top-down comprehensive, iterative and recursive problem solving process, applied sequentially through all stages of development. The SE process (Figure 7-7) is used to:

• Transform needs and requirements into a set of system product and process descriptions;
• Generate information for decision makers; and
• Provide input for the next level of development.

Figure 7-7  Systems Engineering Process Model (New)

The transformation process includes top-down design, design considerations and trade studies. Bottom-up realization includes the build of product for testing (validation and verification).

Manufacturing and production are one of the primary functions and manufacturing considerations should be included in the top-down design considerations and trade studies, and bottom-up realization for the fabrication of engineering test models and "brass boards," low rate initial production, full-rate production of systems and end items, or the construction of large or unique systems or subsystems.

The importance of addressing producibility early is illustrated in Figure 7-8. As a product concept matures, the ability to influence producibility and resulting product costs decreases. In contrast to the typical producibility activity profile shown on the figure, the goal is to reduce producibility activity during the production phase of a product and increase that activity during the initial concept and design phases. The producibility guidelines and tools presented in this document are focused on the consideration of manufacturing issues throughout the design and development of a product.

Figure 7-8 Producibility Impact

NAVSO P-3687, the Navy's Producibility System Guidelines, has identified several tools and techniques that can be used to support producibility efforts. Many of these tools are available as software tools, thus making the process that much easier to implement. Some of these tools, such as "benchmarking," can be used during all five of the Producibility Steps and Elements. Others, such as "statistical quality control," are applicable during only one of the steps (measurement). The following list identifies the tool and where in the Producibility Step and Element it is applicable. Those tools identified with an asterisk (*) have been discussed in other chapters of this guide. Most are in Chapter 5 on Continuous Process Improvement.

Table 7-1 Producibility Tools and Techniques

Benchmarking is the process of measuring one product or process against another similar product or process to identify best practices. It is a starting point for initiating change within a company or organization. The most common reasons an organization will benchmark are to determine where they stand amongst the competition and whether value can be added by incorporating the practices of others. Benchmarking can be used by organizations for comparison of internal operations, competitor-to-competitor products, industry standing, and generic business functions or processes. The goal of benchmarking is to identify the best practices of industry and to adapt and/or incorporate those practices that are beneficial to the organization.

A database management system is a computer application used to create, maintain, and provide controlled access to a database. A database is a shared collection of logically related data pertinent to an area of endeavor. A database management system is used to facilitate the collection, organization, and retrieval of data needed by the community of individuals involved in the endeavor. The system is used through the facilities of a "user interface" which provides the computer aided functions of data storage, retrieval, and modification.

Decision support tools permit people to efficiently analyze and process large amounts of data required for decision making. Modern tools are computer based with interactive access to large database systems and allow for extracting, analyzing and presenting information from the databases in a useful format. Decision support tools are used as an aid to the decision makers by extending their intuitive capabilities; the tools are not meant to replace the decision-makers judgment or expertise.

DFMA is a systematic analysis of the design of an assembly or subassembly to reduce product cost by simplifying its design, assembly, and manufacturing without impacting performance. The analysis allows you to determine the theoretical minimum number of parts that must be in the design for the product to function as required. As you identify and eliminate unnecessary parts, you eliminate unnecessary manufacturing and assembly costs.

Figure 7-9 below is for an F-18 Oxygen Tank Bottle Holder. The original design was too complex, had too many parts, too many manufacturing operations and took too long to assemble. In addition, the complexity of the design provided more opportunities for parts failures and lower reliability. The improved design, as a result of producibility engineering, had 33 percent fewer parts, 38 percent fewer fasteners, 31 percent fewer operations and took 20 percent less time to assemble. The design was made more efficient and producible by using Design for Manufacturing and Assemble (DFMA).

Figure 7-9 F-18 Oxygen Tank Bottle Holder

A technique developed by Boothroyd-Dewhurst measures a design's efficiency and has developed rules to assess a design to identify opportunities to improve the design, that is make the current design more producible, more efficient. Ask the following questions of the design on the right:

• During operation, does this part move relative to the part to which it is attached?
• Does this part need to be made of a different material than the part to which it is attached?
• Does this part need to be removable?

If the answer to all three questions is "no," then the part is a candidate for elimination or combination with other part(s). The redesigned oxygen tank bottle holder on the right is a result of producibility engineering.

FMEA is a structured methodology for identifying failures, errors, and defects before they occur and prioritizing them for corrective action. There are two types of FMEA. Design Failure Mode and Effects Analysis (DFMEA) is a means of analyzing the part design for potential failures, errors, and defects prior to the first production run. Process Failure Mode and Effects Analysis (PFMEA) helps to analyze the parts manufacturing processes prior to production to identify possible process failures that can induce defects into the part. Both methodologies have the same goal, early identification of and reduction and/or elimination of failure mechanisms.

World-class companies have begun using integrated design and development concepts to improve their manufacturing processes, improve producibility and maintaining global competitiveness. Integrated Product and Process Development (IPPD) emerged from earlier integrated design practices, such as concurrent engineering. IPPD, also referred to as integrated product development, expands upon this concept by involving appropriate, multi-disciplinary teams in all phases of a product's development life-cycle. IPPD activities primarily focus on meeting the customer's needs, while simultaneously reducing costs, decreasing development times, and improving product performance and quality.

Knowledge-based systems are computer-based programs that incorporate human expertise and other documented knowledge with the facilities for applying that knowledge to real-world circumstances. Knowledge-based systems provide the benefit of and satisfy the requirement for documenting, developing, and dissemination rules, processes, and/or guidance related to a specific domain or problem area. Knowledge-based systems may be automated in embedded systems or employed through a user interface where questions can be presented in a manner similar to how they would be asked of a human consultant or expert.

Prototyping is a tool used for assessing form-fit-and-function of a product and for visualizing aesthetic quality. Prototyping techniques can also be used to create molds for full-scale production. Through use of a prototype, a designer can get feedback on design information and initial part acceptance for further use in optimizing the design and/or the manufacturing processes. Prototyping is used to check design features and complexity and is helpful in tradeoff studies. The use of prototyping begins in the preliminary design step and continues into the early stages of the final design step. The ability to quickly transform a design into a three-dimensional solid model or prototype can significantly streamline the design and product development process, while substantially reducing costs.

Product prototyping is an essential part of the product design cycle. It is a technique for design functionality and aesthetic quality assessment. Through use of a prototype, a designer can get feedback on design information and initial part acceptance for further use in the manufacturing process. Prototyping is used to check design features and identify complexity issues and is helpful in tradeoff studies. The use of prototyping begins in the preliminary design phase and can continue throughout the early stages of the detailed design. Prototyping can also be performed in production to test whether a new process can be used to produce a product that meets the customer's quality requirements. The ability to quickly transform a design into a three-dimensional solid model or prototype can significantly streamline the design and product development process, while substantially reducing costs.

Risk is common to any product development effort. A risk is the potential inability of achieving product goals and is quantified by the probability of a failure and the consequences of that failure. Risk management includes risk identification and assessment, tracking of risks to determine how risks have changed, and mitigation/reduction of risk impact on the product.

Risk management activities begin at the outset of any product development effort and continue through all phases. They are important elements in achieving a producible design. Although the scope and method of implementation will vary with product scope and complexity, among other things, common threads of any risk reduction effort are:

• Risk identification: What process improvements are needed to ensure that producibility will be achieved? Do design analysis processes include a producibility assessment? Do trade study activities include producibility as a tradeoff criterion?
• Risk assessment: What consequences will result if identified areas of risk are not dealt with or are only partially addressed? Will the impact affect performance, cost, and/or schedule, and to what degree?
• Risk tracking: Is an unmitigated risk growing? By when must the risk be mitigated?
• Risk mitigation/reduction: What can be done to eliminate the source of the risk or reduce it to an acceptable level? Are funds available to develop and conduct the necessary risk mitigation efforts?

Root Cause Analysis (RCA) is a method or series of actions taken to identify the reasons why a particular failure or problem exists and to highlight alternative solutions to eliminate the sources of those problems. An analysis of the comparative benefits and cost-effectiveness of the alternative solutions aids the decision maker in implementing the most beneficial course of action. RCA goes beyond identifying resolutions for the symptoms of a problem. It aims to provide solutions to eliminate the root cause of the problem to ensure that the problem can never occur or recur.

Enterprises are placing a greater emphasis on improving the quality of products provided to the consumer as a means of improving and maintaining competitiveness within the global market. Many world-class organizations have adopted Statistical Quality Control (SQC) which involves using statistical tools and techniques, such as acceptance sampling, process capability analysis, and Statistical Process Control (SPC), to analyze, monitor, and control the efficiency and quality of its manufacturing processes. By improving the quality of the manufacturing processes used in production, the quality of the end-product increases, as does productivity and customer satisfaction.