Week 6 – MSE508/L

Costea, Ph.D.

Computer Aided Engineering

(CAE)

Computer Aided Engineering

• CAE design stages• CAE production engineering stages

CAE fits into the design process at:• Synthesis level – DFMA• Analysis level• Evaluation level

CAE provides productivity tools to aid the production engineering as well.

CAE

• Definition: The analysis and evaluation of engineering design using computer-based techniques to calculate product operational, functional, and manufacturing parameters too complex for classical methods

• CAE is part of the design process in Synthesis, Analysis, and Evaluation level.

• CAE also includes:• Group Technology (GT)• Computer-Aided Process Planning (CAPP)• Computer-Aided Manufacturing (CAM)

Synthesis Stage

• Synthesis Stage: Enriches the product by adding basic geometric detail and reshapes the product by applying DFMA.

• Design for Manufacturing Assembly (DFMA). Any procedure or design process that considers the production factors from the beginning of the product design.

• DFMA aims to:• Answer the question: Is the design optimum for manufacturing and

assembly?• Analyze the manufacture and the assembly of the finished product

to result in lower product cost

Synthesis Stage

• DFMA is manual or computer-based:

– Manual: Provides a step-by-step procedure to query the designer about part function, material limitations, and part access during assembly

– Computer: The designer enters the specifications for the part design and the software provides a quantitative analysis of the alternative designs.

Analysis Stage

• Analysis Stage: Testing the product with two main categories, Finite-Element Analysis (FEA), and Mass Property Analysis (MPA)

– FEA: A numerical program technique for analyzing and studying the functional performance of a structure or circuit by dividing the object into a number of small building blocks, called finite elements.

– Mass Property Analysis: Calculates and returns numerical values that describe properties of the drawing geometry selected

Analysis Stage

• FEA Includes:

– Static Analysis: Deflections, strains, and stresses in structures– Transient Dynamic Analysis: Deflections and stress under load– Natural Frequency Analysis: Stresses during resonant frequency

which can be destructive– Heat Transfer Analysis: Temperature distribution, steady state,

and transient heat transfer in a structure– Motion Analysis (Kinematics): Computes geometric properties to

determine needs of a required motion– Fluid Analysis: Flow, diffusion, dispersion, and consolidation

characteristics of a fluid under varying controlled conditions

Analysis Stage

• Mass Property Analysis includes:

• Mass• Bounding box• Centroid• Moments of inertia• Products of inertia• Radii of gyration• Principal moments with X-Y-Z directions about

centroid

Evaluation Stage

• Evaluation Stage: Examination of data to determine the degree of match between the actual design and the initial design goals and specifications

• Evaluation Stage includes:– Prototyping– RP, SLA, SGC, SLS, 3DP, FDM, LOM– Various software programs

For acronyms see next slide…

RP- ACRONYMS

• Laminated Object Manufacturing (LOM)

pp. 563 – 564 text Chang

• Fused Deposition Modeling (FDM)

• Selective Laser Sintering (SLS)

• Sterolithography (SLA) • Solid Ground Curing

http://www.efunda.com/processes/rapid_prototyping/sgc.cfm ( good, but you must pay after a brief use of efunda a subscription fee)

• http://www.societyofrobots.com/mechanics_FEA.shtmlFEA Tutorial – emphasis on robots but very good

• http://www.andrew.cmu.edu/user/sowen/softsurv.htmlA Survey of Unstructured Mesh Generation Technology

• http://en.wikipedia.org/wiki/Finite_Element_Analysis

CAE Software

• ANSYS (in AutoCAD)http://www.ansys.com/solutions/meshing.asp

• COSMOS (in SolidWorks)• CATIA

http://www.journeyed.com/itemDetail.asp?itmNo=74464939N

• MSC Nastran Patram Adamshttp://www.mscsoftware.com/products/mdpatran.cfm?Q=457&Z=430

• Others• http://www.esi-group.com/products/Fluid-Dynamics

Group Technology

• Group Technology: A manufacturing philosophy that justifies small and medium-size batch production by capitalizing on design and/or manufacturing similarities among component parts

• GT is the beginning stage of Computer-Aided Process Planning

• (Will expand upon this later)

Computer-Aided Process Planning (CAPP)

• CAPP: A system designed to improve the process planning in the integrated environment

• CAPP includes two techniques:– Variant: Uses a library of manually prepared process

plans in a database and a retrieval system to match components on new parts to existing process plans of similar components

– Generative: Creates plans for new components without referring to existing plans or with the assistance of a human planner

Computer-Aided Process Planning (CAPP)

• Variant (Figure 5-24, 5-25):• A new production component is given a family code• The part is passed to a part-family search to determine the

family code• The standard plan for that family is retrieved• A human adjuster makes the needed changes to the plan

• Advantage: A reduction in process planning time by almost 50%

Computer-Aided Process Planning (CAPP)

• Generative (Figure 5-26):

• Convert the design specifications into a format compatible with CAPP software which typically include:

• Code• Descriptive Language• CAD

• The decision logic portion of CAPP creates an operational plan based on the following:

• Production machine capability• Tooling• Fixtures• Time standards• Design specifications

Computer-Aided Process Planning (CAPP)

• Generative advantages:

• Process plans are created rapidly and consistently• New plans are created as fast as those plans

similar to existing components• Serves as an interface from the designer to the

shop floor (Figure 5-27)

Source: Computer Integrated Manufacturing, 2nd Edition, James A. Rehg, and Henry W. Kraebber, Prentice-Hall 2001, pp. 138-171