Environmentally Conscious Process Planning Prepared by Felipe Román Georgia Institute of Technology Systems Realization Laboratory 1 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 2 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 3 Focus: Manufacturing Life Cycle Stage Why manufacturing?... Mining / Extraction Environment: air, sea, land Disposal Material Processing Product Manufacture Demanufacture Raw material generation Remanufacture Material Demanufacture Product Demanufacture Energy recovery Distribution Recycling / Reuse Use & Service Product Takeback 4 Product Development Product Design System Design ... Subsystem Subsystem Design 1 Design n Component n.1 Component n.n ... Process Planning System Assembly Process Planning Subsystem 1 Assembly Subsystem n Assembly Process Planning Process Planning ... ... Component n.1 Component n.n Process Planning Process Planning 5 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 Adapted from (Sutherland and Gunter, 2001) and (Skerlos 2005). Source: http://www.fotosearch.com/ICL154/bim_139/ 6 Process Planning Process planning is the set of product development activities that determines how a part will be manufactured given product and production specifications. • 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 7 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/meT CreportWeb_files/image002.gif. More information can 8 be found at http://erc.engin.umich.edu/. Some Auxiliary Equipment (Supporting) • • • • • Air compressors Coolant systems Water softeners Water Recirculation Material/waste handling • Chillers • Boilers • Piping system 9 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_onl y/metal_chip_processing/chipwringers6.html 10 Source: http://www.ars-inc.com/industrial.htm 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 11 Turning Process - Lathe Source: http://www.efunda.com/processes/machining/turn.cfm 12 Turning Categories 13 Mass & Energy Balances * Mass & energy balances are your friend… m 2 Mass balance equation for an open system: dmcv m in m out dt W 2 m 1 m 4 W1 Q 1 CV m 3 Energy balance equation for an open system: Q 2 2 2 dEcv V V i o Q W min hin gz i mout hout gz o dt 2 2 m 5 14 Machine-Level Assessment Elec. = f (x1,x2,x3) 1. Identify processrelated environmental Inputs/Outputs (I/Os) Quantify I/Os 2. • • • • • 3. Electricity (kWh) Coolant (gals) Wet chips (lbs) Used coolant (gals) Oil mist (mg/m3) Identify mathematical relationship / function for I/Os electricity used coolant cylindrical part coolant (c) wet chips Coolant System filtered coolant coolant & chips Turning Machine A heat wet machined part CV electricity oil mist Mist = f (y1,y2,y3,…) 15 Some Machine-Level Models • Electricity (kWh/yr) • Coolant (gals/yr) • Wet chips (lbs/yr) • Used coolant (gals/yr) • Oil mist (mg/m3) 16 Operational-Level Assessment Coolant = f (w1,w2,…) filtered coolant cylindrical part coolant & chips Straight Turning Operation heat Energy = f (z1,z2,…) wet machined part CV Cutting energy oil mist 17 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) 18 Different Cleaning Processes Mechanical Brushing Wire Fiber Steam-Jet Cleaning Abrasive Sand blasting Metal shot Silicon carbide Plastic Corncobs Nut shells CO2 pellets Ice pellets Tumbling Vacuum de-oiling Scrubbing / wiping Chemical Aqueous Solvent Ultrasonic Biological CO2 Pickling Salt-Bath Thermal Acidic Neutral Alkaline Spray Immersion Vapordegreasing Liquid Supercritical Burn-off Plasma 19 Aqueous Cleaning Processes • Direct consumption Source: http://www.karcher.ca/CCE/HD%20%20HDS%20Web%20Pages/Features/Powe rNozzle%20Spray%20Others.jpg • Closed-loop consumption Source: http://www.acmefab.com/html_640/PROD_Monorail-washer.html 20 Aqueous Cleaning Inputs/Outputs • Can you think of mathematical models for estimating these inputs/outputs for a closed-loop system? Off-site air emissions Electric Energy Water Non-electric Energy Cleaning Agent(s) & Chemicals Cleaned Part(s) Dirty Part(s) Basket / Fixture Wastewater Cleaning System Recovered oil Sludge Basket / Fixture On-site and insite air emissions 21 Generic Process Map of an Aqueous System Dirty Part(s) Machining Process Cleaned Part(s) Cleaning System Dirty Part(s) Machining Process Cleaning Agent Natural Gas / Coal Elec. Air Compressor Pressurized Air Elec. and/ or Gas Elec. Steam Cleaning Machine(s) Wastewater Wastewater Treatment Treated Wastewater Elec. Soft Water Dirty Water Dirty Part(s) Recovered Oil Chemicals Water Softener Sludge Recovered Oil Cleaned Part(s) Cleaned Basket/ Fixture Fugitive emissions / mist Incinerator Elec. Hard Water Clean Water Sludge Methane Cleaning System Water Recirculation Boiler Dirty Basket/ Fixture Cleaned Part(s) Mist / Ventilation Exhaust On-site Air Emissions Elec. Add chemicals and electricity to wastewater treatment 22 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 23 References 1. 2. 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. 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. 24