Design for Manufacture and Assembly

Design for Manufacture and Assembly

 

INTRODUCTION

Globalization of both the economy and the society has confronted the world over the past decade ( 2000,  1990;  1990). Among the important contributors to world confederacy and the global economy are the advances in computerization, telecommunications, and other forms of information technology. A shift of focus and interest from the local market to the international setting has demanded innovation not just in corporate leadership but also to product development as new information, forms of communication, and high technologies are intervening to the mainstream mechanism that business organizations used to implement during the past decades. These are being offered to be utilized in encouraging and reinforcing interaction among individuals and the operating enterprise. In the dawn of various processes such as globalization, industrialization and technological advancement, the international marketplace including the particular areas and systems is overly affected. Among the observable impacts of such emerging conditions in the business world is competition. Competition among the various industries in every given economy is rapid and stiff. It is as if ‘survival of the fittest, extinction of the weakest’ phenomenon. Today, as various industries are aiming for competitive advantage and sustainable development along with its management and operations, there are numerous actions that are being implemented and are directed to the eventual success and growth of the company’s assets. In competition, there is motivation in every business to improve and develop their objectives. For an enterprise to succeed in global competition, hence, there is a continuous plan to develop marketing techniques such as innovation of new products with higher quality than its competitors.

Today, as business organizations aims for market dominance coupled with the ability to sustain products and services, there is a need to resolve the issues of product management, development, and other related aspects of production. In order to cope up with the changing and varying demands of the consumers, every profit-oriented establishment should concentrate not only to management and marketing segments of the business but also to the design fort manufacturability and assembly of products they offer. Thus, this paper aims to provide pertinent body of knowledge in relation to Design for Manufacture and Assembly (DFMA). Specifically, definitions and related principles are discussed as to determine existing theories and practices in DFMA. 

 

DESIGN FOR MANUFACTURE AND ASSEMBLY (DFMA)

            According to  (1998), the manufacturing industry – regardless of its type, is facing several major pressures that originated from the customers and the business environment as well. With the aims of becoming world class, global standards on manufacturing are directed to integrated engineering and manufacturing systems that address shorter product development cycles, increased product quality, and reduced production cost. Traditionally, it has been assumed that low price, high quality, and short lead time cannot be achieved simultaneously. Recent innovations in manufacturing practices, however, indicate that the manufacturing process can be managed so that a trade-off between these goals may not be necessary.

            Effective management of product and process design offers yet another potential source of simultaneous improvement in cost, quality, lead time, and performance (1992). These improvements result from a better fit between product and process design and from greater simultaneity in the design of the product and process. Both of these efforts require a significant change in the relationship between the design and manufacturing functions.

 

DEFINITION

            Design for Manufacturability (DFM) pertains to the general engineering and art of designing products in ways that will offer the easiest way to manufacture them ( 1989). According to  (2004), it is the process of proactively designing products to optimize all the manufacturing functions such as fabrication, assembly, test, procurement, shipping, delivery, service, and repair. He added that DFM also assures the best cost, quality, reliability, regulatory compliance, safety, time-to-market, and customer satisfaction.  (1998) stated that the application of DFM must consider the overall design economics. It must balance the effort and cost associated with development and refinement of the design to the cost and quality leverage that can be achieved. In other words, greater effort to optimize a products design can be justified with higher value or higher volume products.

On the other hand, Design for Assembly (DFA) refers to the systematic analysis process primarily intended to reduce the assembly costs of a product by simplifying the product design (1992). It is also characterized by first reducing the number of parts in the product design and then by ensuring that remaining parts are easily to assemble (1987). This close analysis of the design is typically conducted by a team of design and manufacturing engineers, although other functional expertise such as field service and purchasing may also be included. DFA is used for discrete manufacturing products, and primarily for durable goods, but occasionally for consumer products. Since it is used to optimize assemblies, it is often used for smaller and medium-sized products, or for many sub-elements of larger systems. DFA does not specifically support system level applications and is usually applied to subassemblies ( 1988).

 

CONCURRENT ENGINEERING

            Concurrent engineering (CE) is the practice of simultaneously developing products and their manufacturing processes ( 2004). It implies interaction between organizational functions, several personnel and other members, and specific departments. In application, concurrent engineering may be approached using existing processes and new processes. According to (2004), if existing processes are to be utilized, then the product must be design for these processes. On the other hand, if new processes are to be used, then the product and the process must be developed concurrently.

 and colleagues (1998) provided complementary systems to implement concurrent engineering such as:

1.    integration and optimization of product and process design

2.    organizational changes to promote parallel product and production planning

3.    the adoption of a team approach to product development

4.    technological approaches to improvement of communications and data sharing facilities.

Further, CE is used by companies and individuals by employing variety of methodologies that is applicable in multidisciplinary product development acted upon by teams or individuals. Such methodologies range from standard systems like DFMA guidelines, Failure Modes and Effects Analysis (FMEA) and Quality Function Deployment (QFD) to specific corporate strategies and tools.

 

DESIGN FOR MANUFACTURE AND ASSEMBLY (DFMA) PRINCIPLES

With the definition of DFM and DFA discussed, both techniques provide a framework for collecting and integrating multiple sources of information. Similarly, design reviews by groups composed of diverse technical and other specializations provide either formal or informal occasions for focused information assembly. Such practices serve to aggregate varied and innovative perspectives on many aspects of design, tooling, and service. Manufacturing systems simulation requires collection and integration of detailed product and process information as this technique can provide valuable feedback for the improvement of both product and process designs (1992).

Pressures from the competitive marketplace are forcing manufacturers to continuously reduce product development cycle times (Hansen et al. 2000).  (2001) believes that the primary objective of a designer is to design a functioning product within given economic and schedule constraints. Using the information gathered from relevant literatures, here are the underlying principles of DFM/A.

 

Design for Manufacturability (DFM)

            Simplification and Standardization. With the evolution of multidisciplinary design and manufacturing systems, the need to standardize procedures to develop discrete products is increasing (2006). Standardization is the process of establishing certain technical standards among competing entities in a market. It considers the bringing up of benefits without hurting competition. In DFA, standardization is applied on trusted and proven design standards. According to  (2001), Group technology (GT) and Component Supplier Management (CS) systems can facilitate standardization. As designers work into several mechanisms, it is fundamental to remain loyal to the communally accepted and globally prescribed standards. Standards are classified as de facto and de jure. De facto means followed for convenience while de jure means used due to legally binding contracts or documents. National governments often follow standards prescribed by officially recognized standardization organizations. From here, doing business on particular market and type of industry is rooted on such.  Standardization increases purchasing leverage, simplify supply chain management, reduce part and overhead cost, and enhance flexibility ( 2004). In addition to standardization,  (2001) recognized simplification of part and product designs as it offers significant opportunities to reduce costs and improve quality. Designers need to evaluate if there is an easier way to accomplish the part function. DFM tools and principles provide a structured approach to seeking simplified designs. Product complexity can be further reduced by utilizing a modular building block approach to assembling products. Through standard product modules, a wide variety of products can be assembled from a more limited number of modules, thereby simplifying the design and manufacturing process. By simplifying and standardizing designs, establishing design retrieval mechanisms, and embedding preferred manufacturing processes in the preferred part list, design and production efficiencies are enhanced.

 

            Product Design. In product design, it has been customary that products should achieve higher quality, lower cost, improved applications of automation, and better maintainability. Aside from the general guideline given by  (1998),  (2004) identified the importance of good product development as follows:

      Good product development is a potent competitive advantage.

 

      Product design establishes the feature set, how well the features work, and, hence, the marketability of the product.

 

      The design determines 80% of the cost and has significant influence on quality, reliability and serviceability.

 

      The product development process determines how quickly a new product can be introduced into the market place.

 

      The product design determines how easily the product is manufactured and how easy it will be to introduce manufacturing improvements like just-in-time and flexible manufacturing.

 

      The immense cost saving potential of good product design is even becoming a viable alternative to automation and off-shore manufacturing.

 

      True concurrent engineering of versatile product families and flexible processes determines how well companies will handle product variety and benefit from Build-to-Order and Mass Customization.

 

 

Evaluation of Design Alternatives. In DFM, there are several alternative ways that can be used in designing a product. Among these is are design tools like computer-aided design (CAD), computer-aided engineering (CAE), solids modeling, finite element analysis, group technology (GT) and computer-aided process planning (CAPP). The designer must decide on what tools is the most practical and applicable. Adopting the guidelines specified by  (2001), design alternatives are evaluated under the following principles:

      Identify design alternatives and develop these alternatives economically

 

      Evaluate these alternatives against DFM objectives

 

      Establish standardized designs based on DFM principles which can be readily retrieved for new products

 

      Utilize design reviews and include participation of Manufacturing in the design process to evolve the producibility guidelines.

 

 

            Improved Manufacturing. Companies that embrace the ideals of globalization will benefit from improved manufacturing processes particularly those that capitalize on computer-assisted engineering, JIT, and advanced information technology (1995). They will design more cleverly, design for manufacturability, and do it in a more timely and cost-efficient manner. Designs will assure error-free assembly and ensure high quality and reliability, felicitously meeting customer needs. Additionally, they can benefit from strategic networking with suppliers around the world, optimizing distribution and reducing time and distance barriers. The approach of (1992) suggests that by integrating nationally disparate operations into securely connected, distributed production systems, companies can harvest manufacturing scale advantages. With quality and delivery in place, and focus on manufacturing flexibility, companies can incorporate rapid design changes and allow for the speedy introduction of new products at low costs.

           
Design for Assembly (DFA)

            Assembly may be classified as manual or automated ( 2003). (1992) identified the primary objective of DFA – to minimize parts counts, thereby having fewer parts to be manufactured and assembled, fewer parts that can fail, and fewer interfaces between parts. The following are given applications, advantages, and practicability of DFA:

-       provides a quantitative method for evaluating the cost and manufacturability of the design during the design stage itself;

 

-       served as a tool for supplier selection and involvement. This aspect is highlighted as large firms continue to move design and assembly functions to suppliers. DFA provided leverage over suppliers since firms can estimate product costs better;

 

-       facilitates translation from product design configuration to assembly cost, exact parts, and resultant equipment and personnel needs;

 

-       provides important analytical enhancement because the DFA algorithms enable new kinds of subassembly design analysis that precede the development of physical prototypes and generate early findings that might otherwise not arise;

 

-       serves other information-processing functions in a more secondary manner. Its relationship to focused information assembly is that the practice of DFA requires the bringing together of particular product configurations, general assembly costs and times, design axioms, and manufacturing systems principles, all to support a design choice;

 

-       When used in early design or prototype analysis, DFA provides early information to manufacturing and production, planning, and control regarding needed equipment, labor skills, and parts. In this fashion, DFA supports the firm’s communication acceleration function.

 

-       Another contribution of DFA is in the realm of management control –  this practice enforces desired reductions in parts count, provides a basis for resolving issues of manufacturability, strengthens supplier management, focuses engineering efforts, and provides a relative evaluation score for alternative designs.

 

-       requires that design and manufacturing engineers coordinate activities but does not specifically require the involvement of others. Its actual value in serving the information focus function may thus be less than is ideally achievable.

 

In evaluating DFA, Chan and Salitri (2003) said that it is important to quantify the improvements and goals of DFA. There are two methods for DFA quantification: Boothroyd-Dewhurst method and the Lucas method. Boothroyd-Dewhurst method is based on two principles: a) the application of criteria to each part to determine if it should be separate from all other parts; and b) estimation of the handling and assembly costs for each part using the appropriate assembly process. The latter is extensively detailed and requires separate description.

 

Table 1

Assembly Links Unit Manufacturing Processes to Business processes

Source: Whitney 2004

 

DOMAIN

CONTEXT

EXAMPLE APPLICATION

 

Assembly in the Large

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Assembly in the Small

Business Level

 

 

 

 

 

 

 

System Level

 

 

 

 

 

 

 

 

Technical Level

Market size and production  

     volume

Model mix

Upgrade/update

Reuse/carryover

Outsourcing and supply

     chain

 

Data management and

     control

Quality management

Subassemblies

Assembly sequences

Involvement of people

Automation

Line layout

 

Individual part quality

Individual part joining

Part logistics, preparation,

     and feeding

Manual vs. automatic

Economics

Ergonomics

 

 The given previous discussion encompasses the attributes and principles present in DFA. All in all, it coincides with DFM have its unique inherent characteristics and applications. Meanwhile, the figure below illustrates the processes involved in manufacture. As seen in the figure, assembly falls under the umbrella of activities.

 

Figure 1

Process Involved in Manufacture

Source:  (1998)

 

 

DESIGN FOR MANUFACTURE AND ASSEMBLY (DFMA) RULES

Design for manufacturability and assembly is very essential to production. Requiring design and manufacturing engineers to consider carefully each part for manufacturability, and manufacturing sign-offs on product designs to guarantee manufacturing’s willingness to accept responsibility for producing the product are also imperative to use. Thus, rules are used to regulate the DFMA processes. There are numerous authors that provided rules in DFMA ( 2004;  1998; 1992).   (1998) provided a comprehensive list of DFMA guidelines. Here are as follows:

      Simplify the design and reduce the number of parts because each part, there is an opportunity for a defective part and an assembly error.

      Standardize and use common parts and materials to facilitate design activities, to minimize the amount of inventory in the system, and to standardize handling and assembly operations.

       Design for ease of fabrication.

      Design within process capabilities and avoid unneeded surface finish requirements.

      Mistake-proof product design and assembly (poka-yoke) so that the assembly process us unambiguous.

      Design for parts orientation and handling to minimize non-value-added manual effort and ambiguity in orienting and merging parts.

      Minimize flexible parts and interconnections.

      Design for ease of assembly by utilizing simple patterns of movement and minimizing the axes of assembly.

      Design for efficient joining and fastening.

      Design modular products to facilitate assembly with building block components and subassemblies.

      Design for automated production.

      Design printed circuit boards for assembly.

 

THE DESIGN PROCESS

            The design process is a series of steps followed by all designers, architects, and some system designers. According to Molloy and co-authors (1998), its typical phases is divided into:
            1. analysis and requirements definition

            2. functional design

            3. conceptual design consisting of:

a) product structure design – determination of main components and subassemblies

b) design sizing – specifying component relationships and main parameters

c) identification of appropriate available production technologies

            4. detailed design resulting in the product’s total form.

 

            In general, the design process is considered to be the most elementary yet complex stage in product development. As such, designers are facing numerous considerations that will cater to the welfare of the business organization as well as the customers. The design process also includes the product life – cycle. In business, product life – cycle (PLC) is the sequence of stages a product goes through (1981). It falls under the principle of PLC management that delves has more to do with managing descriptions and properties of a product through its development and useful life, mainly from a business/engineering point of view.

           

 

Figure 2

The Product Life – Cycle

Source:  (1998)

 

 

SIX SIGMA OVERVIEW

            Six Sigma is a business-driven, multi faceted approach to process improvement, reduced costs and increased profits (2000). With a fundamental principle to improve customer satisfaction by reducing defects, its ultimate performance target is virtually defect-free processes and products. The Six Sigma methodology consisting of the following steps: define, measure, analyze, improve and control. Within this improvement framework, it is the responsibility of the improvement team to identify the process, the definition of defect, and the corresponding measurements. This degree of flexibility enables the Six Sigma method, along with its toolkit, to easily integrate with existing models of software process implementation.   

According to  (2005), Six Sigma is a well-liked method to make changeability from developments by means of prevailing statistical instruments and skills. Although originally introduced by Motorola in 1986 as a quality performance measurement, six sigma has evolved into a statistically oriented approach to process and product quality improvement. Many organizations have reported significant benefits as a result of six sigma project implementation, though not all are yet success stories.

The relationship of Six Sigma and DFMA is crucial. The interconnected mechanisms and similar objectives are the main factors that are indispensable to the accomplishment of the execution of any excellence development inventiveness. The identification of such factors will encourage their consideration when companies are developing an appropriate implementation plan such as identifying the key components of successful Six Sigma implementation, such as upper management support, organizational infrastructure, training, application of statistical tools and link to human resources-based actions such as bonuses and promotions.

 

CONCLUSION

            In conclusion, the discussion herewith is based on relevant literatures adopted from published sources. The concepts of Design for Manufacture and Assembly (DFMA) are bounded on the principles of product design, development, and management. All in all, there are similar attributes as well as unique characteristics that differentiate the one from the other. However, in cases of applications and practicability, it is still the role of the designer to choose among the highly effective and efficient mechanisms. The aims must be achieved, the guidelines must be followed, and the related factors must be considered. With this fact, product design process is directed towards success and guaranteed profitability.

 

 

 

 

 

 

 

 

 

 

 

 

 

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