Archive for the ‘Uncategorized’ Category
Monday, October 31st, 2011
Six Steps is all it takes to ensure product success.
- Statement of Requirement for Fit, Form & Function
- Design Failure Modes & Effects Analysis (DFMEA)
- Design Validation for Performance, Value & Reliability
- Design for Assembly, Manufacture, Service, Safety and Cost
- Tolerance Specification based on Process Capability
- Estimating Product Quality & PPM at Design Stage
1. Statement of Requirement (SOR) for Fit, Form & Function:
Attention paid at the beginning of a product design, towards enumerating the product requirements in terms of Fit, Form and Function goes a long way in ensuring product acceptance, performance and delivery. Time well spent in documenting the capabilities and limitations of the proposed product, would ensure that the Voice of Customer, Marketing Strategies, Unique Selling Points, Performance Specifications and Acceptance Criteria are known and accepted by the cross-functional team comprising of Design, Manufacturing, Marketing, Sales, Finance, Quality and After-Sales-Service members. Sign off on the SOR indicates the acceptance and endorsement of the proposed design by all team members with their input given the priority as required. SOR is a live working document that is updated during the life of the product. Without this document and its acceptance by concurrent engineering team members, the product would go thro’ many design changes in the initial stages of the product development process that the goals could get compromised. In fact, prioritization of design objectives in consultation with the cross-functional team members assures timely development of the product with little scope for unpleasant surprises towards the end of the development cycle.
Structure of the Statement of Requirement could consist of Objectives, Fit Requirements, Form Specification and establishment of Functional criteria for product performance and acceptance. Additionally, Functional Test Criteria, Quality Acceptance Criteria, Voice of Customer, Scope of Product Usage, Limitations of Product proposed, Life & Reliability expectancy, Safety parameters, Sustainability Goals should form a part of the SOR.
2. Design Failure Modes & Effects Analysis (DFMEA)
Design criticality is captured by incorporating the DFMEA as a part of the product design process. This document forms the IPR of the organization. The design assumptions, verification, criticality assessment and considerations included in understanding and preventing failure modes in addition to the calculation of the Risk Priority Number (RPN) help ensure that all aspects of the product are considered and addressed. This reflects the strength of the design process and the ability to address potential threats to the product during and after launch. Needless to say, successful and careful assessement of the DFMEA assures the management on the product viability, reliability and life-time performance. This homework needs to be done by the design team in charge of the product design early in the design process leaving ample scope for improvement and update.
3. Design Validation for Performance, Value & Reliability
Validation of the Design at every stage of the product evolution is a necessity driven by competition, predatory pricing and enhanced customer satisfaction. Technologies such as Finite Element Analysis (FEA) and Computational Fluid Dynamics (CFD) have matured for practical application to real-world problems. Post-processing of FE Stresses, Strains and computing Fatigue Life for analyses performed on the basis of the DFMEA document ensures that the objectives of Performance and Reliability are met. Design for Cost is an added responsibility of the Design Team to ensure that the product cost parameters are met. Targets for Cost Reduction, Value Addition & Value Engineering (VAVE) goals should be provided to the Design Team, and monitored, to achieve assured profitability.
4. Design for Assembly, Manufacture, Service, Safety and Cost
Design for Assembly (DFA) is a criteria that is sometimes overlooked or given lesser priority. However, it is a single important assessment that will influence product cost in terms of manufacturing stages, inspection time, assembly time and fitment issues that lead to wastage and re-work. Method of assembly, Interference check at extremes of tolerance variation, Sequence prioritization for efficiency and cycle time reduction, wrongful assembly check (including Poka Yoke) are some of the considerations that need to be addressed early on in the design process.
Design for Manufacture (DFM) considerations regarding tooling (such as Drill Depth to Diameter Ratio, Undercut, Draft among others). Design for Serviceablity, Safety and Cost are as important as product reliability for improved Customer Satisfaction.
5. Tolerance Specification based on Process Capability
Tolerancing of part features is an important part of the design process that usually is given least importance, until product sign-off. Design Engineers need to understand the process capability of the manufacturing processes (Cp, Cpk) and reflect the same in the selection of tolerances. If the process capability does not meet the tolerance criteria required, in addition to specifying the process capability required, it is the responsibility of the design team to justify the selection of tolerances. Least cost tolerancing should be the guiding principle in selection of tolerances without affecting Fit, Form and Functional specifications.
6. Estimating Product Quality & PPM at Design Stage
Tolerance Stack Up Analysis is a part of the Dimensional Management process that needs special emphasis before design drawing sign-off. By incorporating GD&T (Geometric Dimensioning & Tolerancing) and ensuring the correctness and compleness of the Drawing Specification, the pre-requisite to perform Tolerance Stack Up Analysis is ensured. 1-D, 2-D, or sometimes, 3D Tolerance Stack Up Analysis can be performed using CAD based tools by either manually or automatically selecting the Vector Loop. The process capability of the various processes can be attributed to the feature dimensions and their tolerances to perform what-if analysis of tolerance variations. Additionally, by specifying the assembly build criteria, the PPM based on control limits as against specification limits are known a priori, even before the first product build is completed. This ensures the identification of critical features and their required tolerance deviations that would permit achievement of PPM based on Sigma Levels. This provides the management a profitability dashboard to evaluate the pros and cons of making investments in new manufacturing lines and tooling depending on ROI calculations. Additionally, the Quality personnel can monitor critical processes based on these assessments and ensure that the SPC stays within limits as stipulated by design.
Now that we have completed the enumeration of the Six Steps in Product Design for Success, the design engineers have to ask themselves the following questions for continuous improvement in processes and products:
- Is this the best design that is possible to achieve for the cost provided?
- Is the design reliable?
- Have I given the best to the Company, Customer and Society?
- If I were to go about re-designing the product all over again, where would I start the correction process?
- Am I a good Corporate Citizen in delivering Sustainable Products and Technologies?
Friday, March 11th, 2011
Design Engineering Community is faced with many challenges in terms of Reliability, Performance, Cost and Time. Simple Questions, when asked and answered, help Designs get better. Here are a few simple steps that help Design Engineers achieve Superior results and products. As a part of the Design Process if the Engineering Team incorporates the checklist it saves the Organization, Time and Money, resulting in enhanced Profit and Success.
What is my Design’s Real Factor of Safety?
More often than not, actual answers are not known. A simple Simulation validates the Design and gives the Designer a Factor of Safety Plot that gives true insight. This helps identify critical regions where inspection dimensions can be used to protect component boundaries.
Illustration 1: Factor of Safety Plot for Geneva Mechanism using SolidWorks Simulation
When will My Product Fail?
Warranty period for products can be provided without risk of cost escalation if product life can be estimated in advance. Fatigue life prediction helps estimate Minimum Life Guarantee for developing fail-safe design and peace of mind. As a part of the Design Process if life is computed, it helps in the designer specifying right choice of material after evaluating different material options and their impending costs. This results in a win-win situation in terms of product cost and warranty resulting in greater customer satisfaction. Assured performance during warranty period also provides for considerable savings in terms of replacement costs, time and travel to customer place and above all trust.
Illustration 2: Life Estimation using SolidWorks Fatigue Solver
How Sustainable is my Design?
Raw-material selection, methods of manufacture and assembly, material re-cycling, consumption of energy, water and air are influenced by Green Design Principles. Sustainable Designs are important for market acceptability, profitability and above all, eco-friendly development of products for long term growth and success. Air Acidification, Water Eutrophication, Energy Consumption and Carbon Footprint assessments can be done at the Design Stage.
Illustration 3: Alternative Material Evaluation for Sustainable Design
Is my Design Cost-effective?
Material optimization, Weight Optimization and Functional optimization help reduce cost of the product. Finite Element Analysis helps in reducing weight, number of parts and selection of alternate materials for lower cost. This has a cascading effect in terms of power required, in addition to handling and manufacturing costs resulting in substantial savings in overall product cost.
Illustration 4: Product Development Cycle for Optimization
Would I face Assembly Build & Quality Issues?
Allocation of tolerances at the part level, based on Process Capability and Functional requirements eliminates re-work and performance issues. Effect of part tolerances on assembly build quality is required to be studied using Tolerance Stack Up Analysis. This approach leads to maximizing tolerance for assembly build requirements and performance criteria while lowering cost of power quality. Estimation of rejections in terms of PPM provides for a power process of evaluating alternatives at the design stage before Job 1. For companies looking ahead to becoming innovators and technological leaders this is a crucial and mandatory step in product development process.
Illustration 5: Predicting Assembly Build and PPM using SigmundWorks
Checklist for Perfecting Designs
A more generalized approach would be to incorporate the following checklist to arrive at Superior designs to ensure higher customer satisfaction, enhanced profitability and greater success.
- Design for Sustainability
Friday, July 16th, 2010
Engineers have always had a passion for writing programs (since the advent of Fortran) that would perform calculations based on design parameters provided, to arrive at sizing dimensions. Be they calculations involving Heat Transfer, Fluid Flow, Strength or Deflection, engineering community has evolved many standards including TEMA, EJMA, ASME, API or Material Handling codes, for specific engineering requirements.
Going a step ahead, let us pose some questions for the benefit of organizations:
How to ensure that knowledge possessed by the Engineering Team is always available and put to effective re-use for Benefit of the company?
How can error-free drawings be produced there-by eliminating re-work and revisions while reducing time?
How to increase the productivity of a Designer, who generates Drawings, without compromising on accuracy?
Can lead time required to produce drawings, even at RFQ Stage, be reduced so that the product development cycle time can be compressed?
Effectively, the answers to these questions lead directly to the profitability, efficiency and IPR of the organisation. Essentially all of the above relate to design engineering functions, either directly or indirectly.
Rule Based Engineering Design:
Knowledge, when put to re-use, with automated decision making, results in higher productivity and reduced errors. Rule based engineering design created within a framework of knowledge driven design process helps in developing fool-proof designs of products that could have variants as well.
Benefits of this approach is manifold:
Knowledge available with various members, across different levels, in an organisation is given a form for effective re-use
Decisions made are logical and driven by finite set of parameters
Specification of a product design gets refined and well-defined
Range and limitations of the knowledge, ability to re-use and the Company’s IPR gets documented
Modern day 3D CAD Systems, such as SolidWorks, have built-in/ add-on products functionalities that help capture knowledge based on rules defined by users as shown in Fig. 1. Part features and their dimensions are captured to create rules with facility for decision making.
- Fig. 1: DriveWorksXpress – Rule Based Engineering Framework inside SolidWorks
Additionally, spreadsheet calculations driven dimensional mapping enables design engineers to develop 3D models of their designs faster. Microsoft Excel driven Design Table, as shown in Fig.2 enhances the power of design engineers to embed their calculations to drive design dimensions.
- Fig. 2: Embedding Design Table inside SolidWorks with Microsoft Excel
In these approaches, not a single line of programming code needs to be written to develop designs ! Integrating such spreadsheet based calculations with configuration of parts/ assemblies (product variants) gives powerful alternatives to designers for automating designs.
- Fig. 3: SolidWorks Configuration manager exploiting Microsoft Excel for Family of Parts and Assemblies to create product variants
For example, the automobile brake rotor model shown in Fig. 4 facilitates design and drawing automation for a family of rotors at a fraction of the time required to produce the same manually. Configuration Manager ensures that the casting and machining drawings come out of one integrated design database, thereby reducing time, errors and increasing productivity.
- Fig. 4: Automating Designs and Drawings with Rule Based approach
Drawing Automation – Recipe for higher productivity
With design automation enabled, drawing generation is the next step that extends the benefits further. Visual Basic, .NET Framework and Macros (enabling VBA) are common programming approaches adopted by CAD Design Automation experts to create user-input forms (Fig. 5), manipulation of design data and update of template-based 3D CAD Geometries resulting in picture-perfect drawings (Fig. 6). Intrinsically the design knowledge, product representation, adherence to standards, if any, are automatically complied with, resulting in gains for the organization.
- Fig. 5: Sample Input Form that drives 3D Design and associated 2D Drawing
- Fig. 6: Sample Drawing Output using SolidWorks API
With Open architecture and user-friendly programming approach offered by mid-range 3D CAD software such as SolidWorks, high level Design and Drawing Automation is now within the reach of Engineering Organisation at a fraction of the cost of investment in ‘high-end’ CAD software of yore.
Customers, for example, in the power sector, have derived huge benefits in time savings and cost savings by employing design automation, even at the RFQ Stage. Boiler assemblies, Pressure parts, pressure vessels, steel structural supports, plant engineering functions, material handling equipment design are some of the areas that have already witnessed rapid deployment of design automation as a framework for reducing development cycle time.
Imagine a Crane manufacturer getting the customer requirement via Web, and then triggering the automation process of assembling the crane in 3D, developing the General Arrange Drawing of the assembly and individual part drawings of required components, exporting the Bill of Materials for cost estimation and providing a proposal to the customer in a few minutes! Add to that, the manufacturing process drawing automation, running weld length estimation and stage wise drawings provided to the manufacturing team, once the order is obtained, and we have a winning combination of higher productivity, error-free process and above all capturing all essential data available across the organization for better re-use.
3D CAD has matured with high levels of technology integration, enabling engineering corporations to adopt a risk free approach to product development in the fastest manner possible. Only the challenges of assimilating the knowledge and securing the same remain. 3D CAD Design and Drawing Automation has come of age for large-scale adoption for higher productivity. It comes with no strings attached !
Tuesday, June 15th, 2010
Of late CAD software developers have started looking at providing tools and technologies to assist designers in developing sustainable designs. This is definitely a positive development as a Corporate Social Responsibility initiative that could have far reaching consequences for the evolving globally connected societies. If the issues relating to waste generation, energy conservation and efficient resource utilization are addressed at the design stage, downstream issues involving environmental, social and economic considerations are more effectively manageable. But will this lead to profitability?
Before we get into the aspects of mechanical engineering design for sustainable development, let us look at what the implications of small actions towards sustainability mean to this planet. Setting the computer to sleep mode instead of the screen saver mode would
significantly reduce electricity consumption for every user. Imagine the implication when there are millions of users on this planet having their computers go into sleep mode, after say 5 minutes of inactivity! The savings when computed would be astronomical. A default setting of ‘sleep mode in 5 minutes’ by the Operating System designer would save more trees, fossil fuel among other resources in one stroke. The implications are larger than what the mind can perceive.
Returning to our subject of discussion, let us take a look at a simple toggle lever design as shown in the figure. If the design intent is to provide for location and path traversal alone with not much load coming on it, then the designer would be driven in terms of cost
focusing on material selected. If the designer chose Carbon Steel Sheet, for example, a simple analysis of sustainability in terms of environmental impact would be as shown. The component would weight around 1.9 kilograms. If stamping process for sheet metal is employed in manufacturing, the environmental impact assessment (using SustainabilityXpress inside SolidWorks) would be as shown in the figure.
Based on design considerations, if the designer chose alternate material, say plastics, what would the environmental impact be? Now the situation becomes more interesting since cost and sustainability are getting attention at the design stage.
Finding Alternate Plastics for Injection Moulding process
We find that in terms of Environmental impact, Energy Consumption, Product Manufacturing, Water Eutrophication, the indicators are definitely better for the chosen plastic material except for End of Life Considerations under Water Eutrophication. A few more iterations, and we would have all the sustainability considerations addressed and a green design is bound to emerge. Now where does this stand vis-a-vis profitability.
If we look closer at the toggle mechanism its mass has been reduced. Hence its inertia is lesser, pointing to a smaller energy required to move it – a smaller motor required for actuation. Now, that is going to lead to a lower initial cost as well as a lower running cost. That again, is sustainability and profitability without any ambiguity.
Sustainability checklist as given below could be incorporated in the design process:
Raw Materials – Sustainable, Damage Free, Eco- Friendly?
Manufacturing – Energy Intensive, Polluting, Un-healthy?
Packaging – Uses Minimum Materials, Re-cyclable, Eco-friendly ?
Transport – Energy or Resource Intensive?
Use – Uses less water, electricity, consumables and is safe?
Disposal – Re-processible, Recyclable, Bio-degradable, non-polluting?
Finally,let us look at the Goals of Sustainability and its benefits as follows:
|Least amount of material used
|Least amount of energy consumed
(in manufacturing and in use)
|Least amount of resources used to
produce the design
||Increased Value / USP
|Smallest Carbon Footprint
The benefits overwhelmingly point to increased market share and increased profitability, while addressing Corporate Social Responsibility. Consciousness about Sustainability, with focus on design, could not have come a day sooner.