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Terms in this set (82)
Gnatt charts can be used to:
monitor the program of jobs and sequence work on each time
a measure for evaluating service performance of waiting lines
average number of customers waiting in line, percentage of capacity utilized, and the probability that an arrival will have to wait for service
The arrival rate is described by a Poisson distribution
an assumption in common single server queuing models
Johnson's rule for two machines
It minimizes idle time and makespan
the total time needed to complete a group of jobs
earliest due date first (EDD) rule
local scheduling rules tends to minimize the average lateness
Not local scheduling rules that tends to minimize idle time are
first come first serve, shortest processing time first, earliest due date first, and longest processing time first
first come, first served
local scheduling rules is most likely to be utilized in a service setting
In a one-machine scheduling problem, the following are local scheduling rules which will minimize makespan.
first come first serve, shortest processing time, earliest due date, longest processing time
A materials requirements plan contains information with regard to
quantities and required delivery dates of all sub-assemblies
Bill of Materials
The information on the materials, components, and assemblies required to produce the product
Inputs are not required by a MRP system
detailed customer demand data
Lot sizing rules
the EOQ provides the optimum lot size when the demand is constant.
Accurate inventory records
One of the key requirements in using MRP system
Following are part of MRP
Are: Bill of Materials, Netting requirements, and time phasing
Are Not: Stock out costs
A _____ is a timetable that specifies what is to be made and when.
Master Production Schedule or MPS
Necessary input to an MRP system are
Inventory records for each item in the Bill of Materials, Master Production Schedule for the end item, and Bill of Materials
When netting requirements under MRP, the difference between a company's gross requirements and their net requirements is
When releasing a planned order under MRP, if the company is operating under EOQ and the net requirement is less than EOQ, then the company should order
When releasing a planned order under MRP, if the company is operating under EOQ and the net requirement is more than the EOQ, then the company should order
Products and services are 'standard'. They are made in anticipation of demand and stocked in inventory. Customers choose among the products that are available for purchase.
Assemble-to order (ATO)
Products and services are produced in standard modules. Production of modules starts in anticipation of customer demand. Then, as customer orders are recieved, options are added according to customer specifications.
Products and services are designed, produced and delivered to customer specifications. Production starts after the customer order is received.
the choice of inputs, operations, workflows, and methods for producing goods and services.
high volume commodity products that are very standard. Hardly any flexibility exists in products variety or volume. Production is highly automated, with little labor content.
Assembly lines for high volume production of standard products with model variation only(in most cases); little flexibility (but more than continuous production) in product variety or volume.
can include a batch flow system or a job shop
production of a moderate (but fixed) variety of products in moderate volumes.
production of a high variety of products in small to moderate volumes. Products/services are totally customized.
Functional Focus vs. Product Focus
manufacturing operations can be product-focused, and sometimes the shop is referred to as either flow shop (for product-focused manufacturing) or job shop (for functionally-focused manufacturing).
The processes that are designed to produce a large variety of products where similar machines are grouped in work centers (or departments) and where the material is routed from one department to others as needed.
the processes that are designed to mass produce standard products (continuous and assembly lines) where operations are laid out in the order that the material should flow
manufacturing operations generate high production volumes, while providing customers with customized features.
the production process is driven by an actual customer order, instead by a company forecast(push-strategy)...Allows a company to build-to-order.
Just In Time
an integrated set of activities directed at achieving high volume production using minimal inventories of raw materials, work in process, and finished goods. AKA get the right products to the right customer at the right time.
Central core belief of JIT
elimination of waste. BUT also includes A broad view of operations and simplicity
Elimination of Waste
anything that is non value added such as, excess inventory, excess (under-utilized) equipment, poorly maintained equipment etc.
Broad view of operations
everyone should have a broad view of the company. Each employee should understand how their functional area fits into the whole company and how their individual tasks contribute to the success of the company.
Simple solutions are easier and less costly to implement. Too often people are tempted to develop and implement an elegant (and costly) solution which only adds time and costs to the company.
called Kaizen in japan. This is one of the core elements of the JIT philosophy. It applies to every aspect of the business and is never ending.
make all waste visible. If it is visible then someone will eliminate it.
In order to eliminate waste it is imperative to be flexible.
Just-In-Time is Simply to Produce and Deliver
Finished goods JIT to be sold, subassemblies JIT to be assembled into finished goods, fabricated parts JIT to go into subassemblies, and purchased materials JIT to be fabricated
3 basic Elements of JIT system
JIT manufacturing, Total Quality Management, and Respect for People
Implies flexible multi-functional workers and flexible machines.
Small Lot Sizes
Effect on material handling, storage, quality, responsiveness
essential for producing small lots, contributes to the reduction in production lead time, and thus contributes to flexibility and responsiveness
Flow vs. Clustered (job shop)
good plant layout and bad plant layout
What JIT achieves
Eliminates waste, exposes problems, and Lean Production
The Requirements of JIT
Flexible resources, small lot sizes, Quick set ups, "good" layout, and Quality Control
What JIT assumes?
Stable operating environment
the process of predicting a future event
important in determining how much product, inventory to keep, and material to purchase.
Executive Judgement, Sales Force Composite, Market Research/Survey, Delphi Method (new products)
Time Series Analysis and Regression Analysis
Opinion of a group of high level experts or managers is pooled
Sales Force Composite
Each regional salesperson provides his/her sales estimates. Those forecasts are then reviewed to make sure they are realistic.
Solicits input from customers pertaining to their future purchasing plans. It involves the use of questionaires, consumer panels and tests of new products and services. Gathering data to determine what demand will be like.
Panels where the individuals involved are in direct communication, this method eliminates the effects of group potential dominance of the most vocal members. Range of value break talk through and the hope
Time Series Forecast
uses past values of a variable to predict future values of that same variable.
accomplishes the weighted moving average rationale without the need for determining n and corresponding W's
measured as the difference between actual demand and forecasted demand....error= (actual demand for period t) - (forecast for period t).
forecast+ (alpha between 0 and 1)X (error made)
Exponential Smoothing Formula
alpha(actual) + (1 - actual) X forecast
Running Sum of Forecast Errors
should be around zero (indicating that the negative and positive errors nullify each other). Its adjusted by its MAD. Thus, a popular measure called tracking signal.
often used to measure "bias" which combines the RSFE and MAD information as TS= RSFE/ MAD
determines the quantity and timing of production for the intermediate future (generally 6-18 months)
Characteristics of Sales and Operation Planning (APP)
Service Sector, Most services cant be inventoried, Demand for services is difficult to predict, capacity is also difficult to predict, service capacity must be provided at the appropriate place and time, Labor is usually the most constraining resource for services. Also an immediate term.
S&OP(Product lines or product families) >>Master Production Schedule(individual products) >> Material Requirements Plan(components) >> Shop Floor Schedule(short term) [Manufacturing Operations]
Inventories are used to absorb changes in demand. During periods of low demand, inventory is built to be used in period of high demand. (cost of holding, inventory is associated with the strategy without having to layoff workers.
Workers can be hired and laid-off, so that the production rate matches the level of demand.
Subcontracting (outsourcing) work to other companies can be an effective strategy, if a supplier can reliably meet cost, quality and delivery time requirements.
Inventory Holding/Carrying Costs
Goods can be produced in one period and held or carried over to the next period to meet the future demand. The major cost component associated with holding inventory is the cost of capital tied up in inventory.
represents, for example, meeting period 1's demand with production in period 2. It include expiditing, loss of customer goodwill and loss of sales revenues.
Purpose of scheduling (sequencing)
to decide in what order to perform the jobs so that certain desired objectives are met.
Objectives of Scheduling (sequencing)
to meet the due dates to the "customers", to minimize lead time, to minimize setup time or costs, to minimize work in process inventory, to maximize or labor utilization, to improve customer service, and to increase market share and most importantly to improve the bottom line; namely, profitability
Processing time + Wait Time + setup time + Travel time
total time it takes to process ALL the accepted jobs.
Minimize Average Flow Time
Sum of Flow Times/ Number of Jobs
Minimize average number of jobs in the system
sume of Flow times/ Total processing time
Minimize average job lateness
Total days late/ number of jobs
Recommended textbook explanations
Signals and Systems
Alan S. Willsky, Alan V. Oppenheim, S. Hamid
Fundamentals of Electric Circuits
Charles Alexander, Matthew Sadiku
Mechanics of Materials
Mechanics of Materials
David Mazurek, E. Russell Johnston, Ferdinand Beer, John T. DeWolf
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