MGT302 Chapter 6
Continuous Process
Assembly line only the flow is continuous such as with liquids
Project
Product remains in a fixed location and equipment is moved to the product High degree of task ordering is common Arrange materials according to their assembly priority
First of the three steps in high-level view of manufacturing
Sourcing the parts we need
The Avis Company is a car rental company and is located 3 miles from LAX.Avis dispatches a bus from its offices to the airport every 2 minutes and the average round trip travel time is 20 minutes. How many Avis buses are traveling to and from the airport?
30 buses per hour(60/2) Throughput Time = 20/60 = 1/3 hours Inventory = Throghput X Flowtime = 30 X 1/3 = 10 buses travel to and from the airport at any one time
Flexible
A "" line layout can increase opportunities for work sharing among workstations in an assembly line
Dissimilar
A Mfg. Cell is made up of "" machines
Manufacturing Cell
A dedicated area where products that are similar in processing requirements are produced Put dissimilar machines to cells - designed to work on similar products Family of items is produced containing needed machinery to process the item through several stages - identified by operation
Production Process Map
A map showing the flow of materials through a manufacturing system
Lean Manufacturing
A means of achieving high levels of customer service with minimal investment in inventory
Job Shop
AKA Work Center
Na
Actual Number of work stations
Difference in bottlenecks as you go from a workcenter to an assembly line environment
Bottlenecks decrease in an assembly line
Workstation Cycle Time
C = Production Time Per Day/ Required Output Per Day (Units)
CODP
Customer Order Decoupling Point
Difference in capial/labor intensity as you go from a workcenter to an assembly line environment
Capital intensity increasees as you move to an assembly line because you need more machinery. Labor intensity increases as well.
Assemble to Order
Combine a number of preassembled modules to meet a customer's specifications Wide variety of finished goods combinations can be build from a set of components Move the customer order decoupling point from finished goods to components
Manufacturing Cell
Company groups dissimilar machines to work on products that have similar processing requirements
Inventory Turn
Compares COGS to Avg. Inventory
Precedence Relationship
Describes the order in which tasks must be completed
Producing one type of operation
Focus of workcenters
Tracking flow of material through the system
How a production process map is built
Days of supply measures...
How long a firm's inventory can support sales
Customer order decoupling point determines the position of what in the supply chain
Inventory
A firm has redesigned its production process so that it now takes 10 hours for a unit to be made. Using old process, it took 15 hours to make a unit. If the process makes one unit each hour on average and each unit is worth $1,500, what is the reduction in work-in-process value
Inventory = Throughput X Flowtime Before Change: Inventory = 1 X 15 X 1,500 = $22,500 After Change Inventory = 1 X 10 X 1,500 = $15,000 Reduction in WIP = 22,500 - 15,000 = 7,500
Minimum Number of Workstations
Nt = Sum of Task Times (T)/Cycle Time (C)
Customer Order Decoupling Point
Inventory is positioned to allow entities in the supply chain to operate independently The point at which the product is linked to a specific customer
Workcenter
Job shop - similar equipment or functions are grouped together Arrange workcenters in a way that optimizes the movement of material - place workcenters high levels of interdepartmental traffic adjacent to each other Similar types of machines or equipment are located (drills, grinders, heat treatment, etc.)
Term used to define lean manufacturing designed to achieve high customer satisfaction with minimum levels of inventory investment
Lean Manufacturing
Throughput
Long term average rate of flow through the process
Workcenter
Machines are grouped together according to type or function and parts travel to the appropriate location for processing
Make to Order
Make the customer' product from raw materials, parts, and components Ex. Boeing makes a commercial aircraft
Inventory
Materials held by the firm for future use
Manufacturing Area
Not a common layout
Product-Process Matrix
Product Standardization vs. Product Volume Low and High
Make to Stock
Serve customers "on demand" from finished goods inventory Issue: balancing level of inventory against level of customer service because inventory is expensive -- make a trade-off, use lean manufacturing
Steps associated with making a product
Source, Make, Deliver
Assembly Line Balancing
Specify sequential relationship among tasks using a precedence diagram Determine the required workstation cycle time (C) Determine the theoretical minimum number of workstations (Nt) Select primary rule to assign tasks to workstations and a secondary rule to break ties Assign tasks one at a time to the first workstation until no more tasks can be added. Repeat until all tasks are assigned Evaluate the efficiency
How to reduce task time requirements
Split the task, share the task, use parallel workstations, use a more skilled worker, work overtime, redesign
Efficiency
Sum of Task Times (T)/ Actual Number of Work Stations (Na) X Workstation Cycle Time (C)
T
Sum of task times
Safety regulations require that the time between airplane takeoffs will be at least three minutes. When taking off, the run time of a plane is 45 seconds. Planes are on average waiting 4.15 minutes for take-off and on average, there are 15 planes taking off per hour. How many planes are either on the runway or waiting to take off?
TR = 15 planes an hour TT = (.75 + 4.25)/60 = 1/12 of an hour WIP = TT X TR = 15 X 1/12 = 1.25 planes in line or taking off
Little's Law
The flow of items through a production process Inventory = Throughput Rate X Flow Rate
Little's Law
The long-term relationship bewteen inventory, throughput, and flow time
Inventory is positioned at the customer order decoupling point to allow...
The supply chain to operate independently
Nt
Theoretical minimum number of work stations T/C
Difference in throughput time as you go from a workcenter to an assembly line environment
Throughput time decreases as you more from a work center to assembly line environment due to a reduction in non-value-added movement time plus time waiting in que in a workcenter set up
Flow Time
Time for a single unit to traverse the entire process
Lead Time
Time needed to respond to a customer order
You are in line at the bank drive-through and 10 cars are in front of you. The clerk takes 5 minutes per car to serve. How long do you expect to wait in line?
Wait = 10 X 5 = 50 minutes
Assembly Line
Work processes are arranged according to the progressive steps by which the product is made
Engineer to Order
Work with the customer to design and make the product May even be possible to pre-order parts
When parts are moved on a conveyor that passese a series of workstations in a uniform interval, this is called a
workstation cycle time
Assembly Line Design
•Workstation cycle time - a uniform time interval in which a moving conveyor passes a series of workstations •Also the time between successive units coming off the line •Assembly-line balancing - assigning tasks to a series of workstations so that the required cycle time is met and idle time is minimized •Precedence relationship - the order in which tasks must be performed in an assembly process
