Lean Operations and Maintenance & Reliability
Lean Operations
Lean operations focus on providing customers with exactly what they want, precisely when they need it, eliminating waste through continuous improvement, driven by customer demand. This includes just-in-time (JIT) methods for problem-solving and the Toyota Production System (TPS), which emphasizes continuous improvement, respect for people, and standardized work practices. Addressing fundamental issues of waste elimination, variability reduction, and throughput improvement sustains competitive advantage and increases stakeholder returns.
Eliminate Waste
Waste, anything not adding customer value, includes storage, inspection, delays, waiting, and defective products. Ohno's seven wastes are overproduction, queues, transportation, inventory, motion, overprocessing, and defective products, alongside wasted resources like energy and water. Efficient, sustainable production minimizes inputs using the 5Ss: sort/segregate, simplify/straighten, shine/sweep, standardize, and sustain/self-discipline, with safety and support/maintenance added for good practices and reliability.
Remove Variability
Variability, any deviation from the optimum process, is reduced in lean systems to minimize waste. Sources include poor processes, inadequate maintenance, changing demands, and inaccurate documentation. Both JIT and inventory reduction effectively identify variability causes.
Improve Throughput
Throughput, the rate at which units move through a process, is increased by pull systems that remove inventory cushions, exposing problems and improving manufacturing cycle time. Push systems, conversely, dump orders without regard to need.
Lean and Just-In-Time
Lean and JIT strategies improve operations by delivering materials when needed, identifying problems, and reducing waste, costs, and variability, enhancing throughput through buyer-supplier relationships, asset liberation, quality improvement, pricing flexibility, and rework reduction.
Supplier Partnerships
Supplier partnerships aim to remove waste and reduce costs through eliminating unnecessary activities, in-plant and in-transit inventory, and improving quality and reliability. Supplier concerns include diversification risks, scheduling difficulties, lead time issues, quality limitations, and cost transfers due to small lot sizes.
Lean Layout
Lean layouts minimize movement waste by building work cells for product families, incorporating many operations in small areas, reducing distances, limiting inventory space, improving communication, using poka-yoke devices, and employing flexible equipment and cross-trained workers.
Distance Reduction
Replacing large lots and long production lines with flexible cells, often U-shaped, shortens paths and improves communication using group technology.
Increased Flexibility
Flexible cells adapt to volume or design changes applicable in both production and office environments, facilitating product and process improvements.
Impact on Employees
Cross-trained employees and improved communications enhance process information flow, with poka-yoke functions and inventory reduction making first-time quality critical.
Reduced Space and Inventory
Reduced space necessitates small inventory lots and continuous movement.
Lean Inventory
Lean inventory maintains minimal levels necessary for operation through pull systems, reduced lot sizes, JIT delivery, point-of-use delivery, schedule adherence, setup time reduction, and group technology.
Reduce Variability
Reducing variability in inventory, downtime, scrap, setup time, deliveries, and quality exposes problems, ideally leading to near-zero inventory and issues, as Shingo notes, "Inventory is evil."
Reduce Lot Sizes
Ideally, lot sizes of one are pulled through processes, using EOQ analysis to optimize setup time, improving material handling, and reducing setup time.
Setup Time Example
Example: With annual demand of 400,000 units, daily demand of 1,600 units, a production rate of 4,000 units, desired EOQ of 400, and holding cost of $20 per unit, the setup time calculates to 4.8 minutes.
Reduce Setup Costs
Reducing setup costs lowers lot sizes and average inventory through preparation before shutdown and changeover.
Lower Setup Costs
Lower setup costs are achieved by separating setup tasks, improving material handling, standardizing tooling, using one-touch systems, and training operators until subminute setups are reached.
Lean Scheduling
Lean scheduling communicates schedules, levels production, processes frequent small batches, and freezes schedules for stability, using kanban signals as a pull system.
Lean Scheduling Tactics
Tactics include level schedules, kanbans, supplier communication, schedule freezing, adherence, one-piece flow, waste elimination, small lots, and perfect part production.
Level Schedules
Processing frequent small batches makes level schedules economical, with performance improved by freezing schedules near due dates.
Kanban
Kanban, Japanese for card, authorizes the production of the next material container, pulling material through the process with signals for production starts.
Kanban Visual Contact
Visual signals authorize replenishment, with producing departments making optimal lot sizes.
Kanban Cards
Cards are used when visual contact is lacking, controlling part quantities and limiting work-in-process between cells, complicated by manufacturing time needs.
The Number of Kanban Cards or Containers
The number of kanban cards/containers is determined by demand during lead time plus safety stock, divided by container size.
Number of Kanbans Example
Example: With a daily demand of 500 cakes, 2-day lead time, 0.5-day safety stock, and container size of 250 cakes, the number of kanbans is 5.
Advantages of Kanban
Kanban advantages include tight schedules, smooth operations, immediate impact from shortages, emphasis on schedules, lead time and setup reduction, economic handling, and standardized containers reducing waste.
Lean Quality
Lean quality is enhanced by exposing poor quality through shorter lead times, reducing the need for buffers and simplifying systems.
Lean Quality Tactics
Tactics include statistical process control, employee empowerment, fail-safe methods (poka-yoke, checklists), small lots, and immediate feedback.
Toyota Production System
The Toyota Production System focuses on continuous improvement (kaizen) as everyone’s job and respects people by engaging their mental and physical capabilities and empowering employees.
Toyota Production System: Processes and standard work practice
Processes and standard work practices specify work content, sequence, timing, and outcomes, with direct customer-supplier connections, simple material and service flows, and scientific process improvement at the lowest level.
Processes and standard work practice
Stopping production due to defects (jidoka) and focusing on employee education and system responsiveness leads to continuous improvement.
Lean Organizations
Lean organizations understand and meet customer expectations through functional communication and Lean tool implementation.
Building a Lean Organization
Transitioning to Lean involves building a culture of continual improvement, open communication, respect, and Gemba walks.
Lean systems tend to have the following attributes
Lean systems respect and develop employees, empower workers, develop flexibility, foster supplier partnerships, and eliminate non-value-added activities.
Lean Sustainability
Lean sustainability maximizes resource use and economic efficiency, focusing on issues outside the firm, with waste reduction as common ground.
Lean in Services
Lean techniques from manufacturing are applied to services, including managing suppliers, layouts, inventory, and scheduling.
Maintenance and Reliability
The objective of maintenance and reliability is to maintain system capability, addressing failure's effects on operations, reputation, idle time, investment protection, safety, profitability, and satisfaction.
Maintenance and Reliability
Maintenance keeps equipment working, while reliability ensures proper function over time.
Important Tactics
Tactics include improving components, providing redundancy, implementing preventive maintenance, and increasing repair speed.
Maintenance Management
Maintenance management involves employee involvement through autonomous maintenance, skill training, rewards, empowerment, and continuous improvement.
Maintenance and Reliability Procedures
Procedures include cleaning, lubrication, monitoring, adjustments, minor repairs, and record-keeping.
Results
This leads to reduced variability and inventory, improved quality and capacity, and protected investments.
Reliability
System reliability is the product of individual component reliabilities:
Product Failure Rate (FR)
Failure rate is measured as: and , with mean time between failures
Failure Rate Example
Example: 20 AC units tested for 1,000 hours with two failures results in , , , and failure rate per trip FR = .0153 failure/trip.
Providing Redundancy
Redundancy increases reliability:
Maintenance
Maintenance includes preventive (routine servicing) and breakdown (emergency repairs) activities.
Implementing Preventive Maintenance
Preventive maintenance is informed by understanding system service needs and failure likelihood, addressing infant mortality and using MTBF data.
Maintenance Costs
Traditional views on balancing preventive and breakdown costs often ignore full breakdown costs like inventory and morale impacts.
Maintenance Cost Example
Example: Comparing breakdown costs of $480 per month to a service contract costing $450 per month (including some expected breakdowns), hiring the service firm is more economical.
Increasing Repair Capabilities
Increasing repair capabilities involves well-trained personnel, adequate resources, repair plans, material planning, identifying breakdown causes, and extending MTBF.
Autonomous Maintenance
Autonomous maintenance engages employees in observing, checking, adjusting, cleaning, and notifying to predict failures and prolong equipment life.
Total Productive Maintenance (TPM)
TPM involves designing reliable, easy-to-operate machines, emphasizing total cost of ownership, developing best-practice preventive plans, and training operators for autonomous maintenance.
Predictive maintenance
Predictive maintenance uses technology to monitor equipment and predict failures via visual inspection, vibration, temperature, and oil/water quality measurements.
Predictive Maintenance Tools
Tools include vibration analysis, infrared thermography, and oil/water analysis.
Vibration Analysis
Vibration analysis uses transducers and instruments to detect vibration patterns and pinpoint defects in equipment.
Predictive Maintenance Infrared (IR) Thermography
IR thermography uses cameras to detect temperature variations indicating equipment problems.
Predictive Maintenance Oil and Water Analysis
Oil and water analysis involves sampling fluids to detect wear and contaminants.
Predictive Maintenance Other Tools and Techniques
Other tools include ultrasonic and dye testing for stress cracks and shock-pulse testing for bearing flaws.
Maintenance Strategy Comparison
Maintenance strategies include breakdown, preventive, and predictive approaches, each with distinct advantages, disadvantages, and technology requirements.
Is Predictive Maintenance Cost Effective?
Predictive maintenance typically yields a 7:1 to 35:1 return, avoiding downtime, especially in JIT environments.
Predictive Maintenance and Effective Reliability
Effective Reliability (Reff) extends reliability by considering the probability of failure and detection, enhancing maintenance planning and avoiding unplanned breakdowns:
How Predictive Maintenance Improves Effective Reliability
Example: Vibration monitoring increases a gearbox's effective reliability from .90 to .97 by detecting potential