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Chapter 7 - Process Interruptions

Terms in this set (26)

Setup
A set of activities that are required to produce units but for which the time to complete these activities does not depend directly on the number of units produced.
stays the same no matter how many units you are producing
Changeover Time
A setup time to change production from one type of product to another
(a.k.a. Switch-over Time)
Production Cycle
A repeating sequence of produced units that can include setup time, production time, and idle time.
Batch
Collection of units
Batch Process
Type of production in which units are produced in batches.
Capacity of Resource with 1 Worker (Equation)
= 1/Processing Time
Capacity of a Process (Equation)
= Units Produced/Time to Produce Units
Capacity of a Process with Batches & Setup Times
= Batch Size/[Total Setup Time + (Processing Time x Batch Size)]
Idle Time
Time not producing or performing a setup
Utilization of Resource without Setup Time (Equation)
= Flow Rate/Capacity
Utilization of Process with Setups (Equation)
= Flow Rate/Output Rate when Producing
Output Rate when Producing (Equation)
= 1/Processing Time
Utilization (Equation)
= Flow Rate x Processing Time
maximize by matching the capacities of the resources
Maximum Inventory (Equation)
= Batch Size x Processing Time [(1/Processing Time) - Flow Rate]
~OR~
= Batch Size x [1 - (Flow Rate x Processing Time)
Inventory in a Process with Setups
~When inventory follows a saw-toothed pattern, the average inventory is half of the maximum inventory.
~Smaller batch size = smaller maximum & average inventory.
Drawback of High Inventory
it is costly to hold and increased the Flow Time through the process.
Target Capacity
~The target capacity for a resource is the smallest capacity that does not reduce the Flow Rate of the process.
~If process is demand-constrained, then it is the demand rate.
~If process is supply-constrained, then it is the capacity of the bottleneck.
Target Capacity (Equation)
= Batch Size/[Total Setup Time + (Batch Size x Processing Time)]
Batch Size (Equation)
= (Target Capacity x Total Setup Time)/[1 - (Target Capacity x Processing Time)]
Setup Times vs Product Variety
~these things do NOT mix well
~increased inventory, higher flow rate, longer production cycles/larger batches.
Advantage of Resource with a Setup
they generally have a short processing time.
Single-Minute Exchange of Die (SMED)
~A goal to reduce the setup time to a single-digit number of minutes. (i.e. max of 9 minutes)
~Associated with Toyota
Internal Setups
Activities that can only be done during the actual setup, for example, when the machine is not producing.
External Setups
Activities that can be done while production continues to occur.
Steps to Reduce Setup Time
1. Once internal & external setups are identified, make sure that all external tasks are done outside of the setup.
2. Attempt to change internal setups into external setups.
3. Consider how each remaining internal activity can either be reduced, simplified, or eliminated.
Heijunka (a.k.a Mixed Model Assembly)
~An assembly process in which production resembles the true rate of demand, even over a short time horizon. (Toyota)
~Absolutely necessary to reduce setup times to the point where they are essentially inconsequential.
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