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Materials Handling

Materials Handling

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Materials Handling

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  1. Materials Handling

  2. Objectives • To review modern technologies for material handling: - Part handling - AGV’s - AS/RS - conveyors • To consider application conditions (student presentations) • To introduce assessment criteria • To test understanding of the material presented

  3. Material handling principles ( from Groover ) Principle 1 - PLANNING PRINCIPLE:All material handling should be the result of a deliberate plan where the needs,performance objectives, and functional specification of the proposed methods are completely defined at theoutset. • The plan should be developed in consultation between the planner(s) and all who will use and benefit fromthe equipment to be employed. • Success in planning large-scale material handling projects generally requires a team approach involvingsuppliers, consultants when appropriate, and end user specialists from management, engineering,computer and information systems, finance, and operations. • The plan should promote concurrent engineering of product, process design, process layout, and materialhandling methods as opposed to independent and sequential design practices. • The plan should reflect the strategic objectives of the organization as well as the more immediate needs.

  4. Material handling principles ( from Groover ) Principle 2 - STANDARDIZATlONPRINCIPLE:Material handling methods, equipment, controls, and software shouldbe standardized within the limits of achieving overall performance objectives and without sacrificing neededflexibility modularity, and throughput. • Standardization means less variety and customization in the methods and equipment employed. • Standardization applies to sizes of containers and other load forming components as well as operatingprocedures and equipment. • The planner should select methods and equipment that can perform a variety of tasks under a variety ofoperating conditions and in anticipation of changing future requirements. • Standardization, flexibility, and modularity must not be incompatible.

  5. Material handling principles ( from Groover ) Principle 3 - WORK PRINCIPLE:Material handling work should be minimized without sacrificing productivity orthe level of service required of the operation. • The measure of material handling work is flow rate (volume, weight, or count per unit of time) multiplied bydistance moved. • Consider each pickup and set-down, or placing material in and out of storage, as distinct moves andcomponents of the distance moved. • Simplifying processes by reducing, combining, shortening, or eliminating unnecessary moves will reducework. • Where possible, gravity should be used to move materials or to assist in their movement while respectingconsideration of safety and the potential for product damage.

  6. Material handling principles ( from Groover ) Principle 3 - WORK PRINCIPLE:Material handling work should be minimized without sacrificing productivity orthe level of service required of the operation. • The Work Principle applies universally, from mechanized material handling in a factory to over-the-roadtrucking. • The Work Principle is implemented best by appropriate layout planning: locating the production equipmentinto a physical arrangement corresponding to the flow of work. This arrangement tends to minimize thedistances that must be traveled by the materials being processed.

  7. Material handling principles ( from Groover ) Principle 4 - ERGONOMIC PRINCIPLE:Human capabilities and limitations must be recognized and respected in thedesign of material handling tasks and equipment to ensure safe and effective operations. • Ergonomics is the science that seeks to adapt work or working conditions to suit the abilities of the worker. • The material handling workplace and the equipment must be designed so they are safe for people. • The ergonomic principle embraces both physical and mental tasks. • Equipment should be selected that eliminates repetitive and strenuous manuallabor and that effectivelyinteracts with human operators and users.

  8. Material handling principles ( from Groover ) Principle 5 - UNIT LOAD PRINCIPLE:Unit loads shall be appropriately sized and configured in a way whichachieves the material flow and inventory objectives at each stage in the supply chain. • A unit load is one that can be stored or moved as a single entity at one time, such as a pallet, container, ortote, regardless of the number of individual items that make up the load. • Less effort and work are required to collect and move many individual items as a singleload than to movemany items one at a time. • Large unit loads are common in both pre- and post-manufacturing in the form of raw materials and finishedgoods. • Smaller unit loads are consistent with manufacturing strategies that embrace operating objectives such asflexibility, continuous flow and just-in-time delivery. Smaller unit loads (as few as one item) yield less in-process inventory and shorter item throughput times.

  9. Material handling principles ( from Groover ) Principle 6 - SPACE UTILIZATION PRINCIPLE:Effective and efficient use must be made of all available space. • Space in material handling is three-dimensional and therefore is counted as cubic space. • In storage areas, the objective of maximizing storage density must be balanced against accessibility andselectivity. • When transporting loads within a facility, the use of overhead space should be considered as an option. Useof overhead material handling systems saves valuable floor space for productive purposes.

  10. Material handling principles ( from Groover ) Principle 7 - SYSTEM PRINCIPLE:Material movement and storage activities should be fully integrated to form acoordinated, operational system that spans receiving, inspection, storage, production, assembly, packaging,unitizing, order selection, shipping, transportation, and the handling of returns. • Systems integration should encompass the entire supply chain, including reverse logistics. It should includesuppliers, manufacturers, distributors, and customers. • Inventory levels should be minimized at all stages of production and distribution while respectingconsiderations of process variability and customer service. • Information flow and physical material flow should be integrated and treated as concurrent activities. • Methods should be provided for easily identifying materials and products, for determining their locationand status within facilities and within the supply chain, and for controlling their movement.

  11. Material handling principles ( from Groover ) Principle 8 - AUTOMATION PRINCIPLE:Material handling operations should be mechanized and/or automatedwhere feasible to improve operational efficiency, increase responsiveness, improve consistency andpredictability, decrease operating costs, and eliminate repetitive or potentially unsafe manual labor. • In any project in which automation is being considered, pre-existing processes and methods should besimplified and/or re-engineered before any efforts to install mechanized or automated systems. Suchanalysis may lead to elimination of unnecessary steps in the method. If the method can be sufficientlysimplified, it may not be necessary to automate the process. • Items that are expected to be handled automatically must have standard shapes and/or features that permitmechanized and/or automated handling. • Interface issues are critical to successful automation, including equipment-to-equipment, equipment-to-load, equipment-to-operator, and in-control communications. • Computerized material handling systems should be considered where appropriate for effective integrationof material flow and information management.

  12. Material handling principles ( from Groover ) Principle 9 - ENVIRONMENTAL PRINCIPLE:Environmental impact and energy consumption should be considered ascriteria when designing or selecting alternative equipment and material handling systems. • Environmental consciousness stems from a desire not to waste natural resources and to predict andeliminate the possible negative effects of our daily actions on the environment. • Containers, pallets, and other products used to form and protect unit loads should be designed forreusability when possible and/or biodegradability after disposal. • Materials specified as hazardous have special needs with regard to spill protection, combustibility, andother risks.

  13. Material handling principles ( from Groover ) Principle 10 - LIFE CYCLE COST PRINCIPLE:A thorough economic analysis should account for the entire life cycle ofall material handling equipment and resulting systems. • Life cycle costs include all cash flows that occur between the time the first dollar is spent to plan a newmaterial handling method or piece of equipment until that method and/or equipment is totally replaced. • Life cycle costs include capital investment, installation, setup and equipment programming, training,system testing and acceptance, operating (labor, utilities, etc.), maintenance and repair, reuse value, andultimate disposal. • A plan for preventive and predictive maintenance should be prepared for the equipment, and the estimatedcost of maintenance and spare parts should be included in the economic analysis.

  14. Material handling principles ( from Groover ) Principle 10 - LIFE CYCLE COST PRINCIPLE:A thorough economic analysis should account for the entire life cycle ofall material handling equipment and resulting systems. • A long-range plan for replacement of the equipment when it becomes obsolete should be prepared. • Although measurable cost is a primary factor, it is certainly not the only factor in selecting amongalternatives. Other factors of a strategic nature to the organization and that form the basis for competitionin the market place should be considered and quantified whenever possible.

  15. Automated Guided Vehicle (AGV) Definition- An AGV is an independently operated vehicle that moves material along defined paths between defined delivery points or stations. Typically the paths are defined by either using wires embedded in the floor or reflecting paint strips on the floor. Some of the more advanced technologies use laser triangulation or inertial guidance systems on-board the vehicles, with distributed calibration stations for position updating.

  16. AGV classification Driverless trains - AGV is a towing vehicle used to tow one or more trailers forming a train between stations. Pallet trucks - Used to move palletized loads along predetermined routes. Typically, personnel will steer the AGV to the pallet, acquire the pallet, then steer it to the guide-path where the automated guidance system will then move it to its destination. In a sense, it can be thought of as an automated forklift. Unit load carriers - Move unit loads from from one station to another station. A unit load is a collection of items that is delivered repetitively as a unit.

  17. AGV applications Driverless train operations - Movement of large material quantity over large distances (between buildings, warehouses). Storage/distribution systems - Uses unit load carriers and pallet trucks to transfer material between stations, sometimes interfacing with other automated systems such as an AS/RS (Automated Storage and Retrieval System). Works well in assembly operations where the unit loads (or kits) can be transferred from a central storage area to assembly sites. Assembly line operations - AGV’s become part of the assembly operation by transferring material along an assembly line (such as moving an engine block between operational stations) Flexible manufacturing systems (FMS) - AGV’s are used to transfer parts, materials and tooling between the FMS process stations. Miscellaneous applications - Non-manufacturing applications include the handling of sensitive waste, transportation of material at hospitals, mail transportation.

  18. AGV guidance and control Guidance and control functions: Vehicle guidance- on-board control system to move the vehicle along pre-defined paths by a feedback loop between the control system and the guide wire (or paint). More modern systems use inertial guidance to move the AGV between calibration stations. In situations where the guide wire or paint is discontinuous, the control system uses dead reckoning to transition these points. Traffic control- collision avoidance between multiple AGV’s. The control system is designed with blocking algorithms that use a combination of on-board vehicle sensing and zone control. Systems management- programming interfaces and algorithms for moving AGV’s between stations, and for scheduling the movement of multiple AGV’s.

  19. AGV material handling analysis Terms: vc - AGV average speed (c = conveyor, carrier, cart, etc.) ve - AGV empty speed Th - load handling time Ld - destination distance Le - empty move distance Tf - traffic factor (<= 1) Eh - handling system efficiency A - proportion of time vehicle is operational AT- available time in min/hr/veh E - worker efficiency Rdv - rate of deliveries per vehicle nc - number of carriers required Rf - specified flow rate of system (del/hr) Tc - delivery cycle time (min/del) TL - time to load at load station (min) TU - time to unload at load station (min) WL - workload (total work in min per hour)

  20. AGV material handling analysis Equations: del cycle time Tc = TL + TU + Ld / vc + Le / ve(min) available time AT = 60 A Tf E (min/hr/veh) rate of del per vehicle Rdv = AT / Tc(num del/hr/veh) work by handling system per hr WL = Rf Tc (min/hr) num of vehicles for workload nc = WL/AT = Rf / Rdv(num of veh for work load)

  21. AGV example (from text) Given the AGV layout in the figure and the info listed, determine the number of vehicles required for a delivery (flow) rate of 40 del/hr. Info: Loading time = 0.75 min Unloading time = 0.5 min Vehicle speed = 50 m/min Availability = 0.95 Traffic factor = 0.9 (from fig) =>Ld = 110 m ; Le = 80 m E = 1 Solution: Ideal cycle time/del/veh = Tc = 0.75+ 0.5+ 110/50 + 80/50 = 5.05 min Compute workload = WL = (40) (5.05) = 202 min/hr Available time = AT = (60) (0.95) (0.90) (1.0) = 51.3 min/hr/veh Num of vehicles = nc = 202/51.3 = 3.94 veh => 4 vehicles!

  22. AGV questions • Who are major vendors of AGV’s? • Describe their components (power source, transmission system, communication system, etc.)? • What are typical costs? • What type of interfaces do they have? How are they programmed? • How fast do they move? • What are load to weight ratios? • Unusual maintenance requirements? • How do they avoid collisions? • How are they scheduled?

  23. Automated Storage and Retrieval System (AS/RS) Definition- An AS/RS is a combination of equipment and controls which handles, stores, and retrieves materials with precision, accuracy, and speed under a defined degree of automation. (Materials Handling Institute)

  24. AS/RS classification Unit load AS/RS - Large automated system designed to use S/R machines to move unit loads on pallets into and out of storage racks. Mini-load AS/RS - Smaller automated system designed to move smaller loads into and out of storage bins or drawers. Man-on-board AS/RS - Uses personnel to pick items from racks or bins, reducing transaction time. Automated item retrieval system - Items to be moved are stored in single file lanes, rather than in bins or drawers.

  25. AS/RS applications Unit load storage and handling - Warehousing for finished goods/products. Order picking - Used to store and retrieve materials in less than full unit load quantities, such as man-on-board or mini-load applications. Work-in-process - Support just-in-time production activities, buffer storage, and as integral part of assembly systems.

  26. AS/RS control The S/R is a large Cartesian type robot that integrates modern control technology, I/O, and sensors (compartment identification) to move between storage compartments. AS/RS control is integrated with modern material management software for real-time inventory control, storage transactions, and material delivery.

  27. AS/RS material handling analysis Terms: C – capacity per aisle x - width of unit load y - length of unit load (in horizontal direction) z - height of unit load (in vertical direction) nz - number of vertical compartments ny - number of horizontal compartments U - system utilization per hr W - width of AS/RS rack H - height of AS/RS rack L - length of AS/RS rack vz - vertical speed (m/min, ft/min) vy - horizontal speed (m/min, ft/min) tz - vertical travel time (min) ty - horizontal travel time (min) Tcs - single command cycle time (min/cycle) Tcd - dual command cycle time (min/cycle) Tpd – pickup and deposit time (min) Rcs - num of single commands per hr Rcd - num of dual commands per hr Rc - total cycle rate in cycles/hr Rt - num transactions per/hr

  28. AS/RS material handling analysis Equations: AS/RS dimensions W = 3 (x + a) a = 6 in L = ny (y + b) b = 8 in H = nz (z + c) c = 10 in capacity per aisle C = 2 ny nz single command cycle Tcs = Max {L/vy , H/vz } + 2 Tpd “uniform racks, random storage” dual command cycle Tcd = Max {1.5 L/vy , 1.5 H/vz } + 4 Tpd utilization 60 U = Rcs Tcs + Rcd Tcd hourly cycle rate Rc = Rcs + Rcd num transactions per hr Rt = Rcs + 2 Rcd

  29. AS/RS example (from text) Given a 4 aisle AS/RS layout, each aisle contains 60 horizontal racks and 12 vertical racks. Unit load dimensions are x = 42 in, y = 48 in, and z = 36 in. The S/R machine has a horizontal speed of 200 ft/min and vertical speed of 75 ft/min. It takes 20 s for a P&D operation. Find • Num of unit loads that can be stored • Total dimensions of AS/RS • Single and dual command cycle times • Throughput per aisle assuming utilization = 90% and num of single command cycles equals the num of dual command cycles Solution: Total capacity = 4C = (4) 2 ny nz = (4)(2)(60) (12) = 5760 unit loads Width = 3 (42 + 6) = 144 in => 12 ft/aisle Length = 60 (48 + 8) = 3360 in = 280 ft Height = 12 (36 + 10) = 552 in = 46 ft

  30. AS/RS example (cont) Solution: Single command cycle time = Tcs = Max{280/200,46/75} + 2(20/60) = 2.066 min/cycle Dual command cycle time = Tcd = Max{(1.5)(280/200), (1.5)(46/75)} + 4(20/60) = 3.432 min/cycle Utilization = 0.9: 2.066 Rcs + 3.432 Rcd = 60 (0.9) = 54 min, but Rcs = Rcd Thus, solve and get Rcs = Rcd = 9.822 command cycles/hr System throughput is the total number of S/R transactions per hour = 4 Rt Throughput = 4 Rt = 4(Rcs + 2 Rcd) = 4(29.46) = 117.84 transactions/hr

  31. AS/RS questions Who are major vendors of AS/RS? Describe their components (power source, transmission system, communication system, etc.)? What are typical costs? What type of interfaces do they have? How are they programmed? How fast do they move? What are load capabilities? Unusual maintenance requirements? What type of S/R control is used? PID? Who are primary users?

  32. Conveyors Definition - A conveyor is a mechanized device to move materials in relatively large quantities between specific locations over a fixed path.

  33. Conveyors Roller conveyors - Series of tube rollers perpendicular to motion direction, which can be powered or use gravity for motion. Skate-wheel conveyors - Similar to rollers but use skate wheels parallel to motion direction. Belt conveyors - Drives move flat or belts shaped into a trough. Belt Skatewheel

  34. Conveyors Trolley Chain conveyors - Uses loops of chain that are typically moved by sprockets as driven by motors. Overhead trolley conveyors - Items are moved in discrete loads by hooks or baskets suspended from overhead rails.

  35. Conveyors In-floor towline conveyors - Similar to overhead trolley but carts are pulled by hook to in-floor conveyor. Cart on track conveyors - Items are moved by a cart attached to a rail system, which uses a rotating tube to move the cart along the rail. Towline

  36. Conveyor material handling Terms: vc – carrier average speed (c = conveyor, carrier, cart, etc.) sc – material spacing on conveyor TL – loading time (min) TU – unloading time (min) Rf – material flow rate (parts/min) Ld – distance between load and unload Le –distance of return loop (empty) L – length of conveyor loop Td – delivery time np – number of parts per carrier nc – number of carriers RL – loading rate (parts/min) RU – unloading rate (parts/min) Tc – total cycle time (min) Np – total number of parts in system Note: If one part per carrier, then part flow rate is carrier flow rate.

  37. Conveyor handling analysis Equations – single direction: time from load to unload Td = Ld /vc (min) “delivery time = delivery distance divided by carrier speed” material flow rate (np = 1)Rf = RL = vc /sc1/ TL(num carriers/min) “system flow rate = loading rate = flow rate of carriers on conveyor” material flow rate (np > 1) Rf = np vc /sc1/ TL (num parts per min) “system flow rate = loading rate of parts = flow rate of parts on conveyor” unloading constraint TU TL(min) “unloading time must be less than loading time or else pile up carriers”

  38. Conveyor handling analysis Equations – continuous loop: time to complete loop Tc = L/vc(min) “full loop carrier time = loop distance divided by carrier speed” time in delivery Td = Ld/vc(min) “delivery time = delivery distance divided by carrier speed” number of carriers nc = L/sc “num of carriers = loop distance divided by carrier spacing” total parts in system Np = np nc Ld/ L “parts in system = num of parts per carrier times num carriers with parts” material flow rate Rf = np vc /sc (num carriers per min) “material flow rate = num parts per carrier times carrier flow rate”

  39. Conveyor handling analysis Equations – recirculating: Speed rule – operating conveyor speed must fall within a certain range from load/unload rates Rf = np vc /scMax{RL , RU} “flow rate of parts on conveyor must exceed the max load or unload part rate to maintain part spacing” from time to load/unload carriersvc /scMin{1/TL,1/TU} “flow rate of carriers on conveyor must exceed the max load or unload carrier rate to maintain part spacing” Capacity constraint –conveyor capability (np vc /sc ) must exceed desired/specified flow rate Rf conveyor speed and carrier parts np vc /scRf Uniformity principle –loads should be distributed uniformly over the conveyor

  40. Conveyor questions Who are major vendors of conveyors? Describe their components (power source, transmission system, I/O subsystem, etc.)? What are typical costs? How are they programmed and controlled? How fast do they move? What are load capabilities? Unusual maintenance requirements? Who are primary users?

  41. Material handling What have we learned?