OMU-307 Chapter I

8/8/2019 OMU-307 Chapter I

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OMU-307Machine Design

CHAPTER 1

Fundamentals of Machine Design

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Mechanical Engineering Design

Phases of design

A Design Process:

• Identification of need

• Background research

• Goal statement

• Task specifications

• Synthesis

• Analysis

• Selection

• Detailed design• Prototyping and testing

• Production

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Design Considerations

• Marketability

• Functionality

• Reliability

• Wear

• Strength/stress

• Distortion/deflection/stiffness

• Corrosion

• Shape

• Styling

• Noise

•

Safety• Control

• Size

• Lubrication

• Surface

• Lubrication

• Maintenance

• Manufacturability

• Friction

• Volume

• Remanufacturing/resourcerecovery …

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Standards and Codes• American National Standards Institute (ANSI)

•

American Society of Mechanical Engineers (ASME)• American Society of Testing and Materials (ASTM)

• International Standards Organization (ISO)

• Society of Automotive Engineers (SAE)

• Turkish Standarts Institution (TSE)

•Deutsches Institut für Normung (DIN)

• Conformité Européenne (CE)

• American Welding Society (AWS)

• ASM International

• Aluminum Association (AA)

• American Gear Manufacturers Association (AGMA)• American Bearing Manufacturers Association (ABMA)7

• Institution of Mechanical Engineers (I. Mech. E.)

• National Institute for Standards and Technology (NIST)8

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Sample Standards

TS61 – DIN 103 Design Requirements

for trapezoidal screws

DIN 4766 Surface Roughness Values for

Different Manufacturing Process

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Case Study: A Disposable Bioreactor

Design (by Senstec and Hemosoft)

• A bioreactor is the general term applied to a closed culture

environment, that is usually mixed, that enables control of one or

more environmental or operating variables that affect biological

processes such as reproducible cell, tissue and organ proliferation.

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Design Steps

1. Recognition of need (or market brief ) : A company (Hemosoft) hasidentified a potential market (national and international) for a newdisposable bioreactor and wants a design from Senstec group.

2. Definition of problem :

• What type of bioreactor is needed for the tissue and organ grow?

• Who will use this product (laboratory, hospital, special institutesetc.)?

• How many units can the market sustain?

• What are the manufacturing-related issues of the cell-basedengineering products?

•

What size of disposable bioreactor is needed for tissue and organgrow?

• Is the device to be fully automatic or semi-manned?

• How many times (cycles) will this device be used (life-time of theproduct)?

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• Standards and Safety : ISO,CE, ASTM,ANSI,CE…

– CE MDD 93/42/EEC - Medical Device Directive

–CE IVDD 98/79/EC - In-Vitro Diagnostic Device Directive

– ISO 10993:2003 Biological Evaluation of Medical Devices

– ANSI/ASME BPE- Bioprocessing Equipment Standards

– ASTM F2027-08 Guide for Characterization and Testing of Raw orStarting Biomaterials for Tissue-Engineered Medical Products

–ASTM F2150-07 Guide for Characterization and Testing of Biomaterial Scaffolds Used in Tissue-Engineered Medical Products…

• Further considerations: Allowable operation resolution for thesensors (temperature, oxygen, pH etc.), type of pump be used for thefluid flow, type of controller (PID, adaptive PID, neural etc.), fluid flowcharacteristics (laminar or turbulent), sterilization type, scaffold type,type of valves and pipes, production in an European country, targetselling price 9000 Euros, 12 units per year, automatic use, design toISO standards and target countries national standards …

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S th i Th f ti d ti t f d i S i iti l id t b



Synthesis: The formative and creative stage of design. Some initial ideas must beproposed. Examples for our case : – Disposable reservoir bag,

– Limit size with 1 lt,

– Controlling the 10 reservoir with one controller,

– Design according to the diffusion limitation, sheer forces, and mass transfer …

Analysis and Optimization To determine whether constituent components canmeet the demands placed on them in terms of performance, manufacture, costand any other specified criteria. Conflicts between requirements: Cost, ease of use, stability and speed etc.: Cost minimization.

– Basic design (CFD analysis, mathematical models for cell growth, simulations forcontroller…),

– Process analyses,

– Mechanical design (CAD drawing, geometry and tolerances of the components …),

– User requirement identifications,

– Detailed Design (Selection of sensors and actuators, assembly drawing, controllerdesign, …)

Manufacturing, Evaluation and Validation : Once a concept has been proposedand selected and the details of component sizes, materials, manufacture, costsand performance worked out, it is then necessary to manufacture a prototype.Some tests should be performed to evaluate the device (ex. Controllerperformance tests, fluid flow effect on cell grow, sensor calibration tests, waste

product test etc.). Also need to be validating the reliability of the productaccording to the standards.

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Final Design Schematic: Iterative!

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Uncertainty• Uncertainties:

– Composition of material and the effect of variation on properties.

– Variations in properties from place to place within a bar of stock.

– Effect of processing locally, or nearby, on properties.

– Effect of nearby assemblies such as weldments and shrink fits onstress conditions.

– Effect of thermomechanical treatment on properties.

– Intensity and distribution of loading.

– Validity of mathematical models used to represent reality.

– Intensity of stress concentrations.

– Influence of time on strength and geometry.

– Effect of corrosion.

– Effect of wear.

– Effect of noise and vibration …

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Factor of Safety

• Factor of Safety (nd≥1):

• Ratio of two quantities of same units:

– Strength/stress

–

Critical Load/Applied Load – Maximum cycles/Applied cycles

– Maximum safe speed/Operating speed …

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OMU-307 Chapter I

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