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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.