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Environmentally Conscious Process Planning

Georgia Institute of TechnologySystems Realization Laboratory

Prepared by Felipe Román

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Last Week… Today

• Last lectures– Some ECDM assessment tools…

• For processes: process mapping I/O assessment• For facilities & regions: EnviroFacts & TRI Explorer

• Today– Begin considering environmental concerns

during the product development process… particularly in the process planning stage

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Learning Objectives

1. Know what is process planning and how it fits in the product development process

2. Understand how to carry out environmentally conscious process planning

3. Learn how to quantitatively assess manufacturing environmental loads

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Focus: Manufacturing Life Cycle Stage

MaterialProcessing

DisposalMaterial

Demanufacture

ProductManufacture

Distribution

ProductDemanufacture

Use &Service

Mining /Extraction

Environment:air, sea, land

ProductTakeback

Recycling/ Reuse

Remanufacture

Demanufacture

Raw materialgeneration

Energy recovery

MaterialProcessing

DisposalMaterial

Demanufacture

ProductManufacture

Distribution

ProductDemanufacture

Use &Service

Mining /Extraction

Environment:air, sea, land

ProductTakeback

Recycling/ Reuse

Remanufacture

Demanufacture

Raw materialgeneration

Energy recovery

Why manufacturing?...

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Product Development

Component n.1Process Planning

Subsystem 1 AssemblyProcess Planning

...

System Design

Componentn.1 Component n.n

Process Planning

SubsystemDesign 1

Componentn.n

Subsystem n AssemblyProcess Planning

System AssemblyProcess Planning

Product Design Process Planning

SubsystemDesign n

...

...

...

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Environmentally Conscious Manufacturing Strategies

• Good housekeeping• Training and supervision • Waste handling • Material substitution /

elimination / addition• In-process recycling• Process modification • Process Planning• Part / product

modification Source: http://www.fotosearch.com/ICL154/bim_139/

Adapted from (Sutherland and Gunter, 2001) and (Skerlos 2005).

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Process Planning

• Also known as…– Process engineering– Manufacturing engineering– Process design– Process routing

• Resources– Machines– Auxiliary equipments– Cutting tools– Cutting fluids

Figure from Feng and Song, 2000

Process planning is the set of product development activities that determines how a part will be manufactured given product and production specifications.

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Manufacturing Processes• Metal Casting• Bulk Deformation / Forming• Sheet Metal Forming• Material Removal

– Traditional Machining– Precision Machining– Deburring– Advanced Machining

• Surface Preparation– Cleaning– Hardening– Electro-plating– Painting

• Joining and Fastening / Assembly

• Polymer Processing• Rapid Prototyping

Source: http://divisions.asme.org/med/enewsletter/2003july/meTCreportWeb_files/image002.gif. More information can be found at http://erc.engin.umich.edu/.

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Some Auxiliary Equipment (Supporting)

• Air compressors• Coolant systems• Water softeners• Water Recirculation• Material/waste

handling• Chillers• Boilers• Piping system

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Some Auxiliary Equipment (Pollution Control)

• Oil/dust mist collectors• Incinerators / oxidizers• Wastewater treatment• Gondolas & roll offs• Chip centrifuges / Chip wringers• Briquetting machines

Source: http://www.nationalconveyors.com/metal_chip_only/metal_chip_processing/chipwringers6.html

Source: http://www.ars-inc.com/industrial.htm

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Environmentally Conscious Process Planning

• For traditional machining (turning)…– Process selection– Resource selection

• Machine selection• Auxiliary equipment selection• Cutting fluid selection• Cutting tool selection

– Process parameter, operational sequence selection

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Turning Process - Lathe

Source: http://www.efunda.com/processes/machining/turn.cfm

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Turning Categories

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Mass & Energy Balances

* Mass & energy balances are your friend…

CV

1m2m

3m

4m

5m

outincv mmdt

dm

Mass balance equation for an open system:

Energy balance equation for an open system:

o

o

outouti

i

inincv gz

Vhmgz

VhmWQ

dt

dE

22

22

2W

2Q

1W1Q

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Machine-Level Assessment

1. Identify process-related environmental Inputs/Outputs (I/Os)

2. Quantify I/Os• Electricity (kWh)• Coolant (gals)• Wet chips (lbs)• Used coolant (gals)• Oil mist (mg/m3)

3. Identify mathematical relationship / function for I/Os

Elec. = f (x1,x2,x3)

Mist = f (y1,y2,y3,…)

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Some Machine-Level Models

• Electricity (kWh/yr)

• Coolant (gals/yr)

• Wet chips (lbs/yr)

• Used coolant (gals/yr)

• Oil mist (mg/m3)

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Straight TurningOperation

cylindricalpart

wetmachined

part

Cuttingenergy

filteredcoolant

coolant& chips

oil mist

CVheat

Operational-Level Assessment

Energy = f (z1,z2,…)

Coolant = f (w1,w2,…)

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Some Operational-Level Models

For straight turning operations…• Cutting energy (kWh)

– Cutting force– Machining time

• Coolant lost from machined part (gals)– Density of cutting fluid– Surface tension of cutting fluid– Cross-sectional area of workpiece

• Oil mist generated from straight turning (mg/m3)

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Different Cleaning ProcessesMechanical Chemical

Wire Acidic Brushing Fiber Neutral

Steam-Jet Cleaning

Aqueous

Alkaline Sand Spray Metal shot Immersion Silicon carbide

Solvent

Vapor-degreasing

Plastic Ultrasonic Corncobs Biological Nut shells Liquid CO2 pellets

CO2 Supercritical

Abrasive blasting

Ice pellets Pickling Tumbling Salt-Bath Vacuum de-oiling Burn-off Scrubbing / wiping

Thermal Plasma

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Aqueous Cleaning Processes

• Direct consumption • Closed-loop consumption

Source: http://www.karcher.ca/CCE/HD%20-%20HDS%20Web%20Pages/Features/PowerNozzle%20Spray%20Others.jpg

Source: http://www.acme-fab.com/html_640/PROD_Monorail-washer.html

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Aqueous Cleaning Inputs/Outputs

• Can you think of mathematical models for estimating these inputs/outputs for a closed-loop system?

Cleaning System

On-site and in-site air emissions

Wastewater

Water

Dirty Part(s)

Non-electricEnergy

Sludge

Cleaning Agent(s)& Chemicals

Electric Energy Off-site airemissions

Recoveredoil

Basket / Fixture

Cleaned Part(s)

Basket / Fixture

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Generic Process Map of an Aqueous System

Cleaning Machine(s)

WaterRecirculation

WastewaterTreatment

Wastewater

DirtyWater

Clean Water

Cleaned Part(s)

RecoveredOil

On-site AirEmissions

Elec. and/or Gas

CleaningSystem

MachiningProcess

MachiningProcess

CleaningSystem

DirtyPart(s)

DirtyPart(s)

CleanedPart(s)

CleanedPart(s)

Dirty Basket/Fixture

Dirty Part(s)

Boiler

Mist / VentilationExhaust

Sludge

Elec.

Elec.

Natural Gas /Coal

Steam

Compressor

Elec.

Pressurized Air

TreatedWastewater

Sludge

WaterSoftener

Elec.

HardWater

Chemicals

SoftWater

Cleaned Basket/Fixture

Air

CleaningAgent

Methane

Fugitive emissions / mist

Incinerator

Elec.

Recovered Oil

Add chemicals and electricity to wastewater treatment

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Summary Main Points

• Showed how to estimate environmental loads of straight turning operation

• Similar approach should be applicable to other manufacturing processes (e.g., milling, cleaning, etc.)

• By estimating environmental loads & impacts a process engineer can (quantitatively) tradeoff cost, quality and productivity objectives and make better process planning decisions

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References

1. Sutherland, J.W. and Gunter, K.L., 2001, "Environmental Attributes of Manufacturing Processes," in Handbook of Environmentally Conscious Manufacturing, C.N. Madu, Kluwer Academic Publishers, pp. 293-316.

2. Skerlos, S.J., 2005, "Prevention of Metalworking Fluid Pollution: Environmentally Conscious Manufacturing at the Machine Tool, under peer review for textbook," in Handbook of Environmentally Conscious Mechanical Design - Volume 2: Environmentally Conscious Manufacturing, John Wiley & Sons.