11. Concurrent Engineering

11.1 Overview

• Concurrent engineering is a common sense approach to product design.

• Originally (hundreds of years ago) the designer was also the person who produced the design. So during the design phase they considered production problems.

• As designs, and manufacturing methods became more complex, it became necessary to break down design and manufacture to more specific tasks.

• These areas of specialization caused different functions to arise in an enterprise. So it became common for the designer to have little, or nothing to do with production.

• For many years designs tended to be thrown over-the-wall. This was effective in big companies, but some problems arose as a result,

The designer did not always understand the results of his decisions

More time was spent trying to get a design to work right

• But, now with the aid of computers, and other information tools, we are able to close the gap between the designer, and production. Hence, concurrent engineering.

• Reasons for using the traditional design methods,

Product development is traditionally its own organization and is physically and organizationally isolated.

Process development and production operations are located together in a different organization labeled manufacturing.

Most emphasis is on manufacturing operations, that is, shipping product out the door.

• Problems with current design methods,

The design is driven by scheduled deliverable data items. There is pressure for drawings and specifications, which leads to a depth-first design search. Design alternatives are quickly eliminated in the interest of time, and one particular idea is pursued.

The definition of design detail is costly in labor hours. Even with CAD/CAM tools, much manual effort is needed. It would be better to delay this task until the design is somewhat optimized.

The design process is characterized by a rigid sequence of design decisions. The ultimate goal is usually lower cost, when the goals should include optimal performance and ease of manufacture.

Producability and supportability issues are not considered until relatively late in the process, when a design change may be very costly.

Production planning, support analysis, maintenance, and reliability are considered separately from the design process. The designers are left on their own to select the particular set of utilities considered in the first design iteration.

Design data is fragmented. Documentation includes CAD files, dimensioned component drawings, sketches, process drawings, 3-D solid models, etc. It is difficult, if not impossible to maintain consistency at all times across these representations.

Information is lost as the design progresses. The design intent may be lost by the time the documentation gets to the producability experts. They then must rely on experience and luck in guessing what changes can be made to make the item producible and also functional. Ideally, the reasons for the design features would be included in the design documentation.

Designers are usually not aware of cost information, so they cannot intelligently set cost reduction as a realistic goal. Companies do not release cost information routinely. There are no tools for estimating costs as there are for other design domains, and when the costs are calculated, it is often too late to make major design changes.

• Some of the goals of concurrent engineering are,

Avoiding component features that are unnecessarily expensive to produce. This often happens because when a decision is made about a manufacturing feature, there is often a lack of information about the effect of the decision.

Minimizing Material Costs, and selecting better materials.

• Concurrent Engineering means that during design, we consider more than just the design, we also consider how to make it, how to package it, and all of the other functions that were previously left-for-later.

• The development of Concurrent engineering can be traced to 1979 Xerox, HP & Ford look at design practices, and foreign competition. Many small developments since then.

• Important tasks for a concurrent engineering team are,

1. Define the design concept as behavior: The design team must define exactly how a product must perform, and rank the options. This will tend to focus the multidisciplinary team.

2. Define error recovery procedures: In effect the team must now define the challenges which the product will face. For example, if we are designing a transmission, what are the possible failure modes the transmission may face, or stacking for shipping.

3. Define how components interact: As components are defined, and detailed, their interdependence must be considered. At this stage the power of the multidisciplinary team becomes important. If all team members participate, most problems can be eliminated before they become problems.

4. Define product integration and testing procedures: The group as a whole define how the product will be brought together, and tested. This ensures that original design intent is present in the final product, and also the final product should be manufacturable with very little backtracking.

11.2 The Practice of Concurrent Engineering

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1. From the start, include all domains of expertise as active participants in the design effort.

2. Resist making irreversible decision before they must be made.

3. Perform continuous optimization of product and process.

4. Identify product concepts that are inherently easy to manufacture.

5. Focus on component design for manufacture and assembly.

6. Integrate the manufacturing process design and product design that best match needs and requirements.

7. Convert concept to manufacturable, salable, usable design by stating all constraints.

8. Anticipate fabrication and assembly methods and problems.

9. Reduce number of parts.

10. Increase interchangeability between models.

11. Define subassemblies to allow models to differ by the subassemblies.

12. Standardize fastener types and sizes; use low-cost, irreversible fasteners only where a skilled service person would work.

13. Improve robustness of product and process.

14. Identify difficult process steps for which costs and process times cannot be predicted.

15. Use existing processes and facilities so that product yield is high.

16. Break down products and processes into self-contained modules and assembly lines.

17. Adjust tolerances to eliminate failures during assembly.

18. Identify testable areas.

19. Make assembly easier by minimizing setups and reorientations.

20. Design parts for feeding and insertion.

21. Determine character of product; what design and production methods are appropriate.

22. Subject the product to a product function analysis to ensure rational design.

23. Carry out design for producability and usability study; can these two be improved without impairing function ?

24. Design fabrication and assembly process

25. Design assembly sequence

26. Identify subassemblies

27. Integrate quality control strategy with assembly.

28. Design each part so that tolerances are compatible with assembly method and fabrication costs are compatible with cost goals.

29. Design factory system to fully involve production workers in the production strategy, operate on minimum inventory, and integrate with vendor capabilities.

11.3 Future Tool for Concurrent Engineering

• More computer tools are becoming available for breaking down the barriers between the ‘Islands’ of automation.

• Some tasks have been defined for evolving software to support concurrent engineering. [ get source]

1. Interoperable tools and tasks: Develop standards for file transfer, so that software may pass information freely between various engineering systems.

2. Interoperable computing environment: The differences between different computers, from different vendors should be eliminated, or at least made to be insignificant. This will overcome the need for separated systems which occurs now. This also extends to other aspects of computing technology, such as User interfaces, Database interfaces, Files management systems.

3.Data management: Basically integrate all information into a single framework, so that transferring information is no longer an issue. An example of this is a single database which would serve all software in a facility, so that there is no need for transferring designs, and other information.

4. Process management: At present human judgement is still required to initiate any, and all processes in an automated environment. If the computers could be made to automatically review designs, or forward information the interested parties, then the computer would create an automated framework for concurrent engineering.

5. Decision support: While most of the other 4 developments are concerned with the design information. We would eventually require tools that examine the work done by the group, and determine which aspects of the design still need to be performed, or are insufficient. In effect, the computer takes on some of the management tasks.

• As the 5 stages above develop the focus changes from data to knowledge, and from simple storage of files, to shared collaboration of data.

11.4 Software for Concurrent Engineering

• A number of software tools have been developed which make it possible to consider later stages of a product life during the design stage.

• There are some standard tools like FEA for failure analysis, but there are also tools which use knowledge about a problem domain to suggest design changes.

11.5 Methods

• Some methods have already been identified for supporting concurrent engineering,

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Axiomatic Design: This topic applies methods such a Nam Suh’s theories so that production costs, and problems can be eliminated in the design stage by following the rules. An example of an axiom would be “Everything being equal, conserve materials”.

Design For Manufacturing (DFM) guidelines: Methods which focus on rules for simplifying manufacturing in general. An example of one of these rules is “Use known and proven vendors and suppliers”.

Design For Assembly (DFA): A method for evaluating whether designs may be assembled quickly, and effectively. An example is “Use tapers to align parts which must be mated”.

Taguchi Methods: Experimental methods for determining sensitivity of design factors to change. This allows designs to be made less sensitive to variations in the production process.

Group Technology: A number is given to a part. The number tends to identify what the part is. Similar parts will have similar numbers. As a result it becomes easy to use similar designs, and process plans. The use of standards allows problems discovered before to be considered.

Failure-Mode and Effects Analysis (FMEA): Estimates of failures, and possible outcomes can be examined before the part ever reaches production, and provisions may be made in the design phase.

Value Engineering: During the design stage, an attempt is made to evaluate all of the parts in a design, and decide what their value to the customer is. Financial costs are also considered. This allows a picture of how good the design is before the customer gets it.

Simulation: Simulation is an important aspect of product evaluation. If a production facility does not exist, or a new technology is being used, simulation allows evaluation of production times, costs, efficiencies, and problems, before any equipment is purchased, or designs are finalized. This overlaps with some elements of CAE. For example a simulation of cooling of plastics in an injection mold allow consideration of production problems.

• The advantages of the various tools can be any of the following,

Optimize design satisfaction of customer requirements

Simplify designs

Ensure manufacturability

Optimize production ease and cost.

11.6 References

11.1 Ullman, D.G., The Mechanical Design Process, McGraw-Hill, 1997.

 

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