TOM 301 Midterm PDF

Preview

Summary

Midterm study guide...

Description

2 TERMS Process: Set of activities that takes a collection of inputs, performs some work or activities with those inputs, and then yields (produces) a set of outputs // Example- a hospital accepts patients as inputs, performs procedures, and then sends patients home as outputs // Process Flow Diagram: Provides graphical representation of the process // Resources: Group of people and/or equipment that transforms inputs into outputs // Flow Unit: Basic unit that moves through a process, generally associated w/the output of a process // Process Scope: Set of activities included in the process // Process Metric: Something we can measure that informs us about the performance and capability of a process // 3 KEY METRICS: Inventory: The number of flow units within a process (how much stuff is in the process) //Flow Rate: The rate at which flow units travel through a process (people per month, dollars per hour, etc.) Flow Time: The time a flow unit spends in a process, from start to finish (days, weeks, etc.) Little's Law: Inventory = Flow rate x Flow time or I = R x T; Tells us that if we know any 2 processes, we can derive the third Also tells us that if we change on process and keep another constant, we can determine how the third one changes. From the perspective of process analysis, number of customers would be the appropriate flow units for a hardware store. Over the course of a month, the number of patients is most likely to describe the flow unit for a hospital’s process analysis. A computer server experiences large fluctuations in the amount of data requests it receives throughout the day. Because of this, Little’s Law does not apply. (FALSE) PROBLEMS FLOW UNIT What is an appropriate flow unit for a roller coaster; seats, riders, employees, mph, operating time? Ans: Riders. || FLOW RATE Over an 8 hour day, a dentist’s office treats 24 patients. What is the flow rate of patients in this dentist’s office per hour? // Flow Rate = Total Inventory/Total Time  Total Inventory = 24  Total Time = 8 hours  24/8 = 3 patients || During a typical Friday, the West End Donut Shop serves 2400 customers during the 10 hours it is open. A customer spends, on average, 5 minutes in the shop. On average, how many customers are in the shop simultaneously? 2400 customers = Total Inventory  10 operating hours a day = Total Time  Flow Rate = 2400/10  Flow Rate = 240 customers During the course of an 8-hour day, there are, on average, 5 students in an undergraduate advising office, and each student spends, on average, 10 minutes with an advisor. At what rate do students go to the advising office (in students per hour)? Flow Rate = R  Flow Time = 10 minutes (1/6 hours)  Avg. Inventory = 5 students  I = R x T  R = I/T  R = 5/(1/6) = 30 AVG FLOW TIME From 5 a.m. to 6 a.m., four callers contact a help desk. The callers spend 2, 5, 3, and 10 minutes on their calls. What is the average flow time of a caller at this help desk?  Average Flow Time = (2 + 5 + 3 + 10)/4 = 5 minutes AVG INV AT ANY POINT Patients take a drug for severe acne for 5 months and there are 100,000 new patients every month. How many patients are taking an acne drug at any given time? (5 months x 100,000 new patients = 500,000 patients) FORMULAS Flow Rate = Total Inventory/Total Time // Little's Law: Inventory = Flow rate x Flow time or I = R x T; // Flow Time = Inventory / Flow Rate ------------------------------------------------------------------------------------------------------------------------------------------------------------3 TERMS Process Analysis: Provides a rigorous framework for understanding the detailed operations of a business Identifies and analyzes all activities involved in serving one unit of demand, or providing one unit of supply, Can be used for everyone running a business // Process Flow Diagram: Graphical way of describing the process Buffer Inventory - flow units waiting to be worked on, drawn as a triangle Resources - help the flow units move from being a unit of input to a unit of output, shown as rectangular boxes Activity - Action that is being performed in the process, drawn as a rectangle Flow - The direction of the process, drawn as an arrow // Upstream - Beginning of the flow // Downstream - End of the flow Processing Time: How long a particular resource takes to complete one flow unit Capacity: How much of our single resource can be processed in a certain timespan Capacity-Constrained: Demand exceeds supply and the flow rate is equal to process capacity Demand-Constrained: Process capacity exceeds demand, and the flow rate equals the demand rate Throughput: Another term for flow rate // Utilization: The ratio between the flow rate (how fast the process is currently operating) and the process capacity (how fast the process could be operating if there was sufficient demand) Cycle Time: Measures the time between the previous cycle ending and the new cycle beginning Lead Time: The time between a customer placing their order and the order being filled Demand Rate: Number of flow units that customers want per unit of time // In a multistep process, each sub-process has its own processing time // Process capacity in a multistep process can be found by identifying the weakest link, or the bottleneck // Bottleneck: The resource with the lowest capacity // Non-bottleneck resources have slack capacity, utilization levels // Bottleneck resources have 100% utilization // Worker-Paced Line: Each worker is free to work at his or her own pace Machine-Paced Line: All steps are connected through a conveyor belt

PROBLEMS CAPACITY It takes a color printer 10 seconds to print a large poster. What is the capacity of the printer expressed in posters per hour?  1 poster/10 seconds = x posters/3600 seconds  1*3600/10 = 360 FLOW RATE A primary care doctor has the capacity to see 16 patients a day. The demand rate is only 12 patients a day. What is the flow rate?  Flow Rate = Minimum {Demand, Process Capacity}  Flow Rate = Min {16, 12}  Flow Rate = 12 UTILIZATION What is the utilization of the doctor?  Utilization = Flow Rate/Capacity  Utilization = 12/16 = 0.75 = 75% CYCLE TIME What is a the cycle time, assuming a 10-hour work day?  Cycle Time = 1/Flow Rate Cycle Time = (1 day/12 patients) * (10 hours/1day) = 10 hours/12 patients // time to make 20 units = Cycle time * 20 customers  46 seconds/customer * 20 customers = 920 seconds FORMULAS WORKER PACED Capacity = 1/Processing Time Flow Rate = Minimum {Demand, Process capacity} Utilization of a Process = Flow Rate/Process Capacity Utilization of a Resource = Flow Rate/Capacity of Resource Cycle Time = 1/Flow Rate Process Capacity = Min{Capacity(i)} that are strictly less than 100% Time to make Q units (full system) = Cycle time * Q WORKER PACED Time to make Q Units: Cycle Time * Q WP Time through process = Sum of all processing times WP Time to Finish X units starting w/empty system = Time through an empty process + [(x-1) * Cycle Time] MACHINE PACED Time Through Empty System: # of stations * Cycle Time MP Time to Finish X units starting w/empty system = Time through an empty process + [(x-1) * Cycle Time] MACHINE PACED The process is empty at 7am when 30 passengers arrive. Step 1 takes 30 seconds, Step 2 takes 10 seconds, Step 3 takes 60 seconds. How long will it take?  time to finish 30 passengers w/empty system = 1.5 mins + [29 * 1 min] = 30.5 mins ------------------------------------------------------------------------------------------------------------------------------------------------------------8 TERMS Waste of Time @ Resource: Workforce or production equipment, idle time, non-value-adding work like remaking a product. Reduces the capacity of the resource.Waste of Time @ Flow Unit: Longer flow time than necessary for that product to be produced. // Waste (Muda): needless waste of time and worker movements that ought to be eliminated immediately Non-Value Added Work: Work that needs to happen given the way the process is designed, but is not valued by the customer Value-Added Work: Work valued by the customer b/c they are required to turn a flow unit from its inputs to desirable outputs Overall Equipment Effectiveness: Measures the percentage of the available time at a resource that is used for value-added work TPS: Roof (main goal) – waste reduction; Pillars – Just in Time, Built-In Quality; Foundation – Process Improvement 7 Sources of Production Waste: Waiting, overproduction, inventory, transport, over-processing, rework, unnecessary motions Pull System: Resource closest to the market is paced by market demand; production only happens when demand happens Kanban: Production & delivery are triggered by the consumption of parts downstream // Make-to-Order: Product is made when a specific order arrives // Jidoka: Shutting down the machine to force human intervention // Kaizen: Making small changes to the process with the goal of eliminating waste // Poka- yoke: Fool-proofing an operating to avoid the recurrence of defects // Genchi Genbutsu: Observing situation yourself, collecting & analyzing data // Andon: Employee pulls cord to stop the line In a service operation, we can NOT compute the value add time by looking at labor content. ABABAB layout is better. If takt time increases, the operation requires fewer workers. If demand rate increases, takt time decreases PROBLEMS OEE # of Jobs: 89, Time/job: 3 mins, Value-Add Time: (3*89= 267 mins) , Total Available Time: (24hrs * 60mins = 1440 mins)  267/1440 = 18.5% // VALUE-ADD % Flow Time: (16.65 hrs * 60mins =100.4 mins); Value-Add Time: 1.4mins (not waiting)  1.4mins / (1000.4 mins * 100) = 0.1399% // # KANBAN Demand during Lead Time: 3 days; Daily demand: 2100 units/day, 3*2100 = 6300 units  1 day safety stock: 2100 units/day * 1 day = 2100 units  Total needed: 8400 units, 400 units/container (given)  (Demand during lead time + Safety stock) / Container size = (6300 + 2100) = 8400 / 400 = 21 containers TAKT TIME Total Available Time: 8 hours * 5 days = 40hours  Demand: Total # of units A & B = 180 units  40/180 = 0.222hrs/unit FORMULAS OEE = Value-Added Time / Total Available Time // Value-Added Percentage = Value-Added Time of a Flow Unit / Flow Time # of Kanban Cards = Demand during replenishment time + Safety stock / Container size // Takt Time = Available Time / Demand Rate // Target Manpower = Labor Content / Takt Time...