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This article discusses the symptoms and causes of inefficient material flows in a facility and presents the benefits and principles of using Production Flow Analysis (PFA) for facility layout design. It also highlights the reasons for implementing the project at Company X and compares different layout options.
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Production Flow Analysis: A Foundation for Design of a “Lean” Facility Layout
Large travel distances in the material flow diagram • Perceived shortage of floor-space for facility expansion • High WIP inventory levels • Large inter-machine transfer batch sizes • High levels of finished product inventories • Bottleneck resources with large queues • Large cycle times for order fulfillment • Significant queuing and material handling delays • Significant forklift truck activity • Poor order tracking capability • Highly unpatterned material flow network • Absence of a network of material handling aisles • Inefficient communications between workcenters • Low machine and labor utilization • Frequent machine setups • Absence of pull scheduling based on resource constraints • Inflexibility to handle demand and/or part mix changes Symptoms of Inefficient Material Flows in a Facility
Causes of Poor Material Flows in a Facility • Building architecture • Locations of manufacturing departments • Locations of support services and utilities • Design of the network of material handling aisles • Locations of input/output points of departments • Shortage of space for facility expansion • Process plans for making parts and products • Variety of routings in the part mix • Current manufacturing technology • Current material handling equipment in use • Current material handling scheduling policies • Choice of subcontracted operations and/or parts
Benefits of Using PFA for Facility Layout • Verification and updating of operational and planning documents • Verification and updating of current equipment inventory • Review and improvement of business and manufacturing processes • Redesign of product designs • Redesign of process plans • Strategic reallocation of equipment between departments • Strategic duplication of equipment between departments • Strategic consolidation of departments • Strategic investment in flexible multi-function equipment • Planning for flexibility - machine, process, routing, volume, etc. • Implementation of capacity-constrained scheduling techniques • Implementation of efficient machine loading rules • Implementation of efficient job sequencing rules • Implementation of setup reduction practices • Revision of the product routings to eliminate redundant variety • Revision of the product routings to eliminate "outlier" routings
Reasons for the Project at Company X • Machines not located in close proximity • Machines not arranged according to the process flow • Backtracking in the process flow • A new layout would save floorspace • Lack of streamlined material and operator flows • The area and layout of several machine footprints are not optimized • WIP quantities at different machines differ significantly • Material is moved in large batches between machines • Significant delays in order throughput • Quality problems due to absence of feedback* between machines * due to large distances of separation
Reasons for the Project at Company X (cont’d) • No production planning, finite capacity scheduling system or shopfloor control systems to track and progress orders • Lack of prompt communications between the shopfloor and the production planner • Production lot sizes are not based on any systematically planned master production schedule • Difficulty in synchronizing production with the supply schedule for forgings
“Design For Flow” Principles for Effective Layout Design Maximize: • Directed flow • One piece flow • Ergonomics of material handling in every workcell • Visual scheduling and material flow control • Flexibility to accommodate variations in product mix and /or volume Minimize: • Backtracking • Transfer batches • Travel distance in every workcell • Travel distances between consecutive workcells • WIP storage space between consecutive workcells* * design of a standard storage cart (“Kanbin”)
Design of a Standard Storage Cart (“Kanbin”) Original Design: Proposed Design:
Comparison of Routings for 6-cylinder and 4-cylinder Products
Flow Diagram for 6-cylinder Products START FINISH
Flow Diagram for 4-cylinder Products START FINISH
Preliminary Layouts Presented to Company X Layout #1 Dock • Company X feedback on Layout #1*: • Allows direct line of sight between the Oven and the Wheelabrator • Does not require relocation of the Borringer • Keeps the Oven close to the dock — In the summer, heat can escape easily through the dock * This layout was chosen by the company
Preliminary Layouts Presented to Company X Layout #2 Dock • Company X feedback on Layout #2: • Oven cannot be moved into the position shown because the Borringer cannot be relocated • Prevents direct line of sight between the Oven and the Wheelabrator
Preliminary Layouts Presented to Company X Layout #3 Dock • Company X feedback on Layout #3: • Oven cannot be moved into this position
Flow Diagram showing “Lean” Flow in an Initial Layout that was Proposed Flow of both 6-cylinder and 4-cylinder products Flow of 6-cylinder products only Flow of 4-cylinder products only
Constraints on Layout Design • Borringer cannot be relocated. • Final Inspection Area cannot be located near the Dock because winter cold would affect parts and gauges. • M/Cs 757 and 1025 need 17' clearance on one side where their chip conveyors (17' in length) may need to be pulled out for machine maintenance. • M/C 567 (Mori Seiki) needs 13' clearance on one side where its chip conveyor (13' in length) may need to be pulled out for machine maintenance. • All M/Cs need to be accessed from at least one aisle for machine maintenance. • An inspection area (10' by 20') must be located centrally in the flowline. • The aisles could be used to accommodate large machines projecting out of a bay. • The 5th bay should be kept clear to implement new product lines. (See “Initial Layout of Company X Shopfloor” shown earlier)
Needs to be Dust Free Creates Dust Creates Dust Creates Dust Wet Maggie Balancer Needs to be Protected from Cold and Dust Constraints on Layout Design (Cont’d) • Final Inspection Area constraints: M/Cs 776 and 736 (Grinders) and M/C 590 (Snag Grinder) create too much dust that could “corrupt” the Maggie. Therefore Maggie cannot be located adjacent to the Grinders. * M/Cs in the Finish Grinding area were removed by Lycoming during the project period. • M/Cs #510 and #738 (Okuma & Howa) were taken out of the machining line. • M/C #109 (Bridgeport) was replaced by M/C #778. • M/Cs #795 ( Cincinnati Drill Press) and #759 (G&L Drill Press) were to be replaced by a new machine.
Incoming Cart Dock Operator’s Standing Point Final Layout based on “Lean” Flow N
Detailed Layout of Workcells (M/Cs #380, #568 and #569) N Note: All measurements are in feet.
Detailed Layout ofWorkcells (M/C #768 and GFMs) N Spacing Bench can be easily shared by two GFM operators *The constraint of 17' clearance is satisfied for both GFMs in this layout. Note: All measurements are in feet.
Detailed Layout ofWorkcells (M/Cs #777 and #735) N Leave 5' between the two M/Cs to minimize the operator’s travel distance Note: All measurements are in feet.
AISLE AISLE Detailed Layout ofWorkcells (M/Cs #567 and #724) N Note: All measurements are in feet.
Detailed Layout ofWorkcells (M/Cs #763 and #843) N AISLE AISLE Note: All measurements are in feet.
Detailed Layout ofWorkcells (From M/C #756) N Locate the vending machines in this way in order not to block the line of sight between consecutive workcells Incoming “Kanbin” Cart Operator’s Standing Point Note: All measurements are in feet.
Detailed Layout ofWorkcells (Operation #180 to Operation #235) N
Detailed Layout of Workcells (Final Inspection Area) N Note: All measurements are in feet.
Key Benefits of the “Lean” Layout • Pure flowline layout • Smooth workflow within every workcell • Space was “freed” to accommodate a new product line • Standardization of containers for WIP storage and transfer (“Kanbin”) • Decrease in transfer batch sizes • Reduction in floorspace due to proximity of cells • Optimization of several machine footprints • Improved communications between consecutive operations • Layout designed for and with full cooperation of Company X operators, supervisors and managers
Conclusion “…..Thank you for the excellent work that you and your students did on the project. While it was a learning experience for us, I’m sure your students gained much more by seeing the classroom applied to the shop floor. It is rare to find an academician that is as comfortable on the shop floor as you are. This attribute helps not only the client using the service, but also the student, as it shows the student how it should be done in the “real world”. I believe the partnership between a public university and private industry is extremely important as it enables the businesses in the State of Ohio to enjoy the fruits of a great institution of higher learning. The way to make manufacturing in Ohio competitive into the future is to do just what we did, apply academic principles to the practical world on the shop floor. We are on our way to becoming more profitable and competitive thanks to the work your team did at Company X…...” • Chief Financial Officer (Company X)