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Chapter 5:. Process Analysis. Process Analysis. Process Analysis Terms. Process capacity - of the process is its maximum output rate, measured in units produced per unit of time. The capacity of a series of tasks is determined by the lowest capacity task in the string.
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Chapter 5: Process Analysis
Process Analysis Terms • Process capacity - of the process is its maximum output rate, measured in units produced per unit of time. The capacity of a series of tasks is determined by the lowest capacity task in the string. • Capacity utilization - the percentage of the process capacity that actually is being used. • Cycle time - the time between successive units as they are output from the process. • Idle time - time when no activity is being performed.
Process Analysis Process analysis generally involves the fol tasks: • Define the process boundaries • Construct a process flow diagram • Determine the capacity of each step • Identify the bottleneck • Evaluate further limitations • Analyze, make decisions and to improve process. Process Flowcharting • Process flowcharting is the use of a diagram to present the major elements of a process
Other Types of Processes • Make-to-order -Only activated in response to an actual order. Here both work-in-process and finished goods inventory kept to a minimum • Make-to-stock-Process activated to meet expected or forecast demand, Here, customer orders are served from target stocking level • Hybrid-Combines the feature of both make-to-order and make-to-stock.
Types of Processes • Single-stage Process – • Multi-stage Process– • Blocking - occurs when an activity becomes idle because the next downstream activity is not ready to take it. • Starvation - occurs when a downstream activity is idle with no inputs to process because of upstream delays. • Both starvation and blocking can be reduced by adding buffers that hold inventory between activities. • Buffer- refers to a storage area between stages where the output of a stage is placed prior to being used in a downstream stage • Bottleneck -occurs when the limited capacity of a process causes work to pile up or become unevenly distributed in the flow of a process
Measuring Process Performance • Setup time: The time required to prepare the equipment to perform an activity on a batch of units. Set-up time can be reduced on a per unit basis by increasing the batch size. • Run time: Time require to produce a batch of parts. • Operation time = Setup time + Run time • Throughput time ( or Flow time or lead time) - the average time that a unit requires to flow through the process from the entry point to the exit point. The flow time is the length of the longest path through the process. • Throughput rate (also known as flow rate ) - the average rate at which units flow past a specific point in the process. The maximum throughput rate is the process capacity.
Measuring Process Performance • Throughput rate = 1 / cycle time • Pacing -Refers to the fixed timing of the movement of items through the process • Value-added time – The time in which useful work is actually being done on the unit. • Process Velocity or Throughput Ratio = Throughput time / Value-added time
Measuring Process Performance Little’s Law • Throughput time = WIP / Throughput Rate • Estimates a mathematical relationship between Throughput rate, Throughput time and amount of work in process (WIP) inventory. • Assumption : process is operating at steady rate. • Usefulness : help to diagnosis the performance of process.
Process Improvement Improvements in cost, quality, flexibility, and speed are commonly sought. • Add additional resources to increase capacity of the bottleneck. • Improve the efficiency of the bottleneck activity • Minimize non-value adding activities - decreases cost, reduces lead time. • Change the sequence of activities. • Redesign the product for better manufacturability - can improve several or all process performance measures. • Flexibility can be improved by outsourcing certain activities.
