Chapter 1

Chapter 1Introduction1Dr. Mohammad AbuhaibaWHAT IS DESIGN FOR MANUFACTURE AND ASSEMBLY?Design for Manufacture(DFM): Design for ease of manufacture of the collection of parts that will form the product after assembly Design for Assembly (DFA): Design of the product for ease of assembly. Design for manufacture and Assembly" (DFMA): combination of DFA and DFM.The word design has different meanings2Dr. Mohammad AbuhaibaWHAT IS DESIGN FOR MANUFACTURE AND ASSEMBLY?The word "design: detailing of the materials, shapes, and tolerance of the individual parts of a product.This is the aspect of product design mainly considered in this class.It is an activity that:starts with sketches of parts and assemblies;progresses to the CAD workstation, where assembly drawings and detailed part drawings are produced.These drawings are then passed to the manufacturing and assembly engineers whose job it is to optimize the processes used to produce the final product.3Dr. Mohammad AbuhaibaWHAT IS DESIGN FOR MANUFACTURE AND ASSEMBLY?Conceptual design without DFMAConceptual design with DFMADetailed designPrototype & design changesTimeFig. 1.1: extra time spent early in the design process is more than compensated for by savings in time when prototyping takes place.4Dr. Mohammad AbuhaibaWHAT IS DESIGN FOR MANUFACTURE AND ASSEMBLY?DFMA shortens the time to bring the product to marketDFMA reduces product costsExample: Ingersoll-Rand CompanySlash product development time from two years to oneReduce No of parts in a portable compressor radiator and oil-cooler assembly from 80 to 29Decreased No of fasteners from 38 to 20Trimmed No of assembly operations from 159 to 40Reduced assembly time from 18.5 to 6.5min5Dr. Mohammad AbuhaibaWHAT IS DESIGN FOR MANUFACTURE AND ASSEMBLY?Over 70% of final product costs are determined during design. (Fig 1.2)Over-the-wall approach: "we design it, you build it.Consult the manufacturing engineers at the design stage.The resulting teamwork (simultaneous engineering) teams avoids many problems.6Dr. Mohammad AbuhaibaHOW DOES DFMA WORK?Figure 1.7: motor drive assembly that is required to sense & control its position on two steel guide rails.

7Dr. Mohammad AbuhaibaHOW DOES DFMA WORK?Motor must be fully enclosed for aesthetic reasonsHave a removable cover to provide access to adjustment of the position sensor.Principal requirements: A rigid base designed to slide up and down with guide rails that will both support the motor and locate the sensor.The motor and sensor have wires connecting to a power supply and control unit.8Dr. Mohammad AbuhaibaHOW DOES DFMA WORK?DFA provides three criteria against which each part must be examined:During operation of the product, does the part move relative to all other parts already assembled?Must the part be of a different material than or be isolated from all other parts already assembled? Only fundamental reasons concerned with material properties are acceptable.Must the part be separate from all other parts already assembled because otherwise necessary assembly or disassembly of other separate parts would be impossible.9Dr. Mohammad AbuhaibaHOW DOES DFMA WORK?

10Dr. Mohammad AbuhaibaHOW DOES DFMA WORK?Base: 1st part to be assembled, it is a theoretically necessary part.Bushings (2): Base and bushings could be of same material.Motor: standard subassembly of parts.Motor screws (2): separate fasteners do not meet the criteria because an integral fastening arrangement is always theoretically possible.Sensor: Standard subassembly.Set screw: Theoretically not necessary.Standoffs (2): They could be incorporated into the base.End plate: Must be separate for reasons of assembly of necessary items.End plate screws (2): Theoretically not necessary.Plastic bushing: Could be of the same material as the end plate.Cover: Could be combined with the end plate.Cover screws (4): Theoretically not necessary.11Dr. Mohammad AbuhaibaHOW DOES DFMA WORK?Motor and sensor subassemblies could be arranged to snap or screw into the base and a plastic cover designed to snap on.Only four separate items would be needed instead of 19.These four items represent the theoretical min number needed to satisfy the requirements of the product design without considering practical limitations.Two screws are needed to secure the motor.One set screw is needed to hold the sensor.The design of these screws could be improved by providing them with pilot points to facilitate assembly.The two powder metal bushings are unnecessary.It is difficult to justify the separate standoffs, end plate, cover, plastic bushing, and six screws.12Dr. Mohammad AbuhaibaHOW DOES DFMA WORK?TABLE 1.1: Results of DFA Analysis for Motor Drive Assembly Proposed Design

13Dr. Mohammad AbuhaibaHOW DOES DFMA WORK?Parts that did not meet criteria for min part count involved a total assembly time of 120.6 s.Total assembly time for all 19 parts = 160s.Parts with screw-fastening operations resulted in largest assembly times.Elimination of remaining parts not meeting the criteria would result in the design concept shown in Fig. 1.6:bushings are combined with the basestandoffs, end plate, cover, plastic bushing, and six screws are replaced by one snap-on plastic coverThe eliminated items involved an assembly time of 97.4 s.The new cover would take only 4s to assembleScrews with pilot points would be usedBase redesigned so that the motor was self-aligning. and would avoid the need for a reorientation. 14Dr. Mohammad AbuhaibaHOW DOES DFMA WORK?

15Dr. Mohammad AbuhaibaHOW DOES DFMA WORK?TABLE 1.2: Results of DFA Analysis for the Motor Drive Assembly RedesignAssembly cost*Assembly time (s)Theoretical part countNo.

2.93.511Base3.84.511Motor Sub.10.012.002Motor Screw7.18.511Sensor sub.7.18.501Set screw4.25.0--Thread leads3.34.011Plastic cover38.44646TotalDesign Efficiency = (4x3)/46.0 = 26%16Dr. Mohammad AbuhaibaHOW DOES DFMA WORK?TABLE 1.3: Parts Cost for Motor Drive Assembly Proposed Design and RedesignRedesignProposed designCost ($)ItemCost ($)Item13.43Base (nylon)12.91Base (Aluminum)0.20Motor screw (2)2.40Bushing (2)0.10Set screw0.20Motor screw (2)8.00Plastic cover(Includes tooling)0.10Set screw5.19Stand off (2)21.73Total5.89End plate0.20End plate screw (2)Tooling cost for plastic cover = $5k0.10Plastic bushing8.05Cover0.40Cover screw (4)35.44Total17Dr. Mohammad AbuhaibaHOW DOES DFMA WORK?The outcome of this study is a second design concept representing a total savings of $15.95, of which only 95 cents represents the savings in assembly time.In addition, the design index has been improved by about 250%.18Dr. Mohammad AbuhaibaHOW DOES DFMA WORK?FIG. 1.10: Typical steps taken in a DFMA study using DFMA software

19Dr. Mohammad AbuhaibaREASONS FOR NOT IMPLEMENTING DFMA1. No TimeDesigners are not allowed sufficient time to carry out their work.Designers are usually constrained by the urgent need to minimize the design-to-manufacture time for a new product.More time spent in the initial stages of design will reap benefits later in terms of reduced engineering changes after the design has been released to manufacturing.Company executives and managers must be made to realize that the early stages of design are critical in determining not only manufacturing costs, but also the overall design-to-manufacturing cycle time.20Dr. Mohammad AbuhaibaREASONS FOR NOT IMPLEMENTING DFMA2. Not Invented HereResistance when new techniques are proposed to designers.Any proposal to implement DFMA should come from the designers themselves.It is the managers or executives who have heard of the successes resulting from DFMA and who wish their own designers to implement the philosophy.Under these circumstances, great care must be taken to involve the designers in the decision to implement these new techniques.21Dr. Mohammad AbuhaibaREASONS FOR NOT IMPLEMENTING DFMA3. The Ugly Baby SyndromeTelling a designer that their designs could be improved is much like telling a mother that her baby is ugly.Involve the designers in the analysis and provide them with the incentive to produce better designs.If they perform the analysis, they are less likely to take as criticism any problems that may be highlighted.22Dr. Mohammad AbuhaibaREASONS FOR NOT IMPLEMENTING DFMA4. Low Assembly CostsThe application of DFMA showed that the first step is a DFA analysis of the product or subassembly.It will be suggested that since assembly costs for a particular product form only a small proportion of the total mfg costs, there is no point in performing a DFA analysis.Figure 1.12 shows the results of an analysis where the assembly costs were extremely small compared with material and mfg costs.DFA would suggest replacement of the complete assembly with, say, a machined casting. This would reduce total manufacturing costs by at least 50%.23Dr. Mohammad AbuhaibaREASONS FOR NOT IMPLEMENTING DFMA5. Low VolumeDFMA is worthwhile only when the product is manufactured in large quantities.The use of the DFMA is even more important when the production quantities are small.Reconsideration of an initial design is usually not carried out for low-volume production.Figure 1.12 is an example of this where the assembly was designed to be built from items machined from stock as if the product were one-of-a-kind. The prototype then became the production model.Do it right the first time: becomes even more important when production quantities are small.In fact, the opportunities for parts consolidation are usually greater under these circumstances because it is not usually a consideration during design.24Dr. Mohammad AbuhaibaREASONS FOR NOT IMPLEMENTING DFMA6. The Database Doesn't Apply to Our ProductsEveryone seems to think that their own company is unique.When one design is rated better than another using the DFA database it would almost certainly be rated in the same way using a customized database.DFMA should be applied at the early design stage before detailed design has taken place, there is a need for a generalized database for this purpose.Later, when more accurate estimates are desired, then the user can employ a customized database if necessary.25Dr. Mohammad AbuhaibaREASONS FOR NOT IMPLEMENTING DFMA7. We've Been Doing It for YearsSome procedure for "design for producibility" has been in use in the company.Design for producibility means detailed design of individual parts for ease of mfg.26Dr. Mohammad AbuhaibaREASONS FOR NOT IMPLEMENTING DFMA8. It's Only Value AnalysisThe objectives of DFMA and value analysis are the same.DFMA is meant to be applied early in the design cycle and that value analysis does not give proper attention to the structure of the product and its possible simplification.DFMA is a systematic step-by-step procedure that can be applied at all stages of design and that challenges the designer to justify the existence of all the parts and to consider alternative designs.DFMA makes significant improvements of existing products even after value analysis has been carried out.27Dr. Mohammad AbuhaibaREASONS FOR NOT IMPLEMENTING DFMA9. DFMA Is Only One Among Many TechniquesSince the introduction of DFMA, many other techniques have been proposed:design for quality (DFQ)design for competitiveness (DFC)design for reliabilityDFMA is the subject that has been neglected over the years, while adequate consideration has always been given to the design of products for performance, appearance, etc.28Dr. Mohammad AbuhaibaREASONS FOR NOT IMPLEMENTING DFMA9. DFMA Is Only One Among Many Techniques

29Dr. Mohammad AbuhaibaREASONS FOR NOT IMPLEMENTING DFMA10. DFMA Leads to Products That Are More Difficult to ServiceA product that is easy to assemble is usually easier to disassemble and reassemble.In fact, products that need continual service involving the removal of inspection covers and the replacement of various items should have DFMA applied even more rigorously during the design stage.30Dr. Mohammad AbuhaibaREASONS FOR NOT IMPLEMENTING DFMA11. I Prefer Design RulesGenerally, rules attempt to force the designer to think of simpler shaped parts that are easier to manufacture.This can lead to more complicated product structures and a resulting increase in total product costs.Systematic procedures used in DFMA that guide the designer to simpler product structures and provide quantitative data on the effect of any design changes or suggestions are found to be the best approach.31Dr. Mohammad AbuhaibaREASONS FOR NOT IMPLEMENTING DFMA12. I Refuse to Use DFMAIf the individual does not have the incentive to adopt this philosophy and use the tools available, then no matter how useful the tools or how simple they are to apply, the individual will see to it that they do not work.The designer should be given the incentive and the necessary facilities to incorporate considerations of assembly and manufacture during design.32Dr. Mohammad AbuhaibaWHAT ARE THE ADVANTAGES OF APPLYING DFMA DURING PRODUCT DESIGN?Reduction in product manufacturing cost is not necessarily considered to be the most desired outcome of redesign efforts.The example in Fig. 1.14 shows that reduced time to market and improved quality were thought to be more important than cost reduction.DFMA provides a systematic procedure for analyzing a proposed design from the point of view of assembly and manufacture.33Dr. Mohammad AbuhaibaWHAT ARE THE ADVANTAGES OF APPLYING DFMA DURING PRODUCT DESIGN?Simpler and more reliable products that are less expensive to assemble and manufacture.Any reduction in the No. of parts in an assembly produces a snowball effect on cost reduction because of:Drawings and specifications that are no longer neededVendors that are no longer neededThe inventory that is eliminated.All of these factors have an important effect on overheads, which, in many cases, form the largest proportion of the total cost of the product.DFMA tools encourage dialogue between designers and the manufacturing engineers and any other individuals who play a part in determining final product costs during the early stages of design.This means that teamwork is encouraged and the benefits of simultaneous engineering can be achieved.34Dr. Mohammad AbuhaibaWHAT ARE THE ADVANTAGES OF APPLYING DFMA DURING PRODUCT DESIGN?The savings in manufacturing costs. Ford Motor Company: savings in billions of dollars as a result of applying DFMA to the original Ford Taurus line of automobiles.NCR: savings in millions of dollars as a result of applying DFMA to their new point-of-sales terminals.Brown & Sharpe were able, through DFMA, to introduce their CMM, MicroVal, at half the cost of their competitors, resulting in a multi-million dollar business for the company.35Dr. Mohammad AbuhaibaTYPICAL DFMA CASE STUDIESDefense IndustryFigure 1.15: original design of a reticle assembly for a thermal gun sight used in a ground-based armored vehicle.Used to track and sight targets at night, under adverse battlefield conditions, and to align the video portion of the system with the trajectory path of the vehicle's weapon to ensure accurate remote controlled aiming.

36Dr. Mohammad AbuhaibaTYPICAL DFMA CASE STUDIESDefense IndustryIt makes steady, precise adjustments of a critical optical element, while handling ballistic shock from the vehicle's weapon systems and mechanical vibrations generated by the vehicle's engine and rough terrain.It must also be lightweight.The results of a DFA analysis showed that fasteners and reorientations of the assembly were the two main contributors to the assembly time.Special operations for drilling and pinning couplers and applying adhesive to screws were also major contributors.Redesign to reduce hardware, eliminate unnecessary parts, standardize the remainder, and reduce or eliminate reorientations.37Dr. Mohammad AbuhaibaTYPICAL DFMA CASE STUDIESDefense IndustryThe new design was analyzed using DFATable 1.5: results for original design and for redesign.In the original design there were 24 different parts and in the new design only eight.The documentation, acquisition, and inventory of 16 part types has been eliminated.

38Dr. Mohammad AbuhaibaTYPICAL DFMA CASE STUDIESDefense Industry

39Dr. Mohammad AbuhaibaOVERALL IMPACT OF DFMA ON U.S. INDUSTRYA summary of results of case studies from various companies shows that the average part reduction is around 50% with some studies resulting in reductions in the range of 81 to 90%Table 1.7 shows other improvements due to DFMA applications.12 studies reported an average 37% reduction in product cost.40Dr. Mohammad AbuhaibaOVERALL IMPACT OF DFMA ON U.S. INDUSTRY

41Dr. Mohammad AbuhaibaOVERALL IMPACT OF DFMA ON U.S. INDUSTRYThe incentive to implement DFMA or concurrent engineering often arises because a company is under pressure to reduce manufacturing costs, improve time to market, etc., because of competitive pressures. 42Dr. Mohammad AbuhaibaOVERALL IMPACT OF DFMA ON U.S. INDUSTRYDFMA is not only a procedure, it is knowledge - so much knowledge that it cannot be satisfactorily presented in handbook form.Those who decided that they could manage with a handbook and thought they did not need the more sophisticated assistance offered by computer software have generally not succeeded.43Dr. Mohammad AbuhaibaCONCLUSIONSThe use of DFMA software has a tremendous impact where properly applied in a concurrent engineering environment.Significant ideas for design improvements can invariably be made in the space of only a few hours.Unfortunately, small manufacturers have not been able to take advantage of the huge potential of DFMA; they do not have the manpower or the necessary experience.Even with large companies, proven successes in one division do not necessarily spread to other divisions without management support and commitment.44Dr. Mohammad AbuhaibaCONCLUSIONSIt is still claimed by some that design rules or guidelines by themselves can give similar results.Guidelines or qualitative procedures can lead to increased product complexity because they are usually aimed at simplifying the individual component parts, resulting in a design that has a large number of parts and poor quality and involves greater overheads due to larger inventory, more suppliers, and more record keeping.The objective should be to utilize the capabilities of the individual manufacturing processes to the fullest extent in order to keep the product structure as simple as possible.45Dr. Mohammad AbuhaibaCONCLUSIONSThe major barrier to DFMA implementation continues to be human nature.People resist new ideas and unfamiliar tools, or claim that they have always taken manufacturing into consideration during design.The DFMA methodology challenges conventional product design hierarchy. Designers are traditionally under great pressure to produce results as quickly as possible and often perceive DFMA as yet another time delay.46Dr. Mohammad AbuhaibaCONCLUSIONSThe overall design development cycle is shortened through use of early manufacturing analysis tools, because designers can receive rapid feedback on the consequences of their design decisions where it countsat the conceptual stage.47Dr. Mohammad AbuhaibaCONCLUSIONSIn some people's minds, simultaneous engineering means gathering together designers, manufacturing engineers, process monitors, marketing personnel, and the outside "X factor" person.But unless one can provide a basis for discussion grounded in quantified cost data and systematic design evaluation, directions will often be dictated by the most forceful individual in the group, rather than being guided by a knowledge of the downstream results.48Dr. Mohammad AbuhaibaCONCLUSIONSIn order to remain competitive in the future, almost every manufacturing organization will have to adopt DFMA philosophy and apply cost quantification tools at the early stages of product design.49Dr. Mohammad Abuhaiba