[completed] 6과 Production Activity Control

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Introduction

Production Activity Control(PAC) is responsible for executing the master production schedule(MPS). At the same time, it must make good use of labor and machines, minimize work-in process inventory, and maintain customer service.

Material Requirements Plan authorize PAC:

• to release work orders toe the shop for manufacturing
• to manage work orders and make sure they  are  completed on time
• to be responsibel for the immediate detailed planning of the flow of orders through manufacturing, carrying out the plan and controlling the work as it progresses to completion.
• to manage day to day activity and provide the necessary support

Planning: the flow of work through each of work centers must be planned to meet delivery date, which means PAC must do the followings:

• ensure that required materials, tooling, personnel, and information are available to manufacture the components when needed.
• schedule start and completion dates for each shop order at each work center so the scheduled completion date of the order can be met. 

Implementation:once the plans are made, production activity control must put them into action by advising the shop floor what must be done. instruction can be given by issuing a shop order with the relevant information. 

• gather the information needed by the shop floor to make the product
• release orders to the shop floor as authorized by the material requirements plan. this is called dispatching

Control: the process must be montored to learn what is actually happening. the results are compared to the plan to devide whether corrective action is necessary.

• rank the shop orders in desired priority sequecnce by work center and establish a dispatch list based on this information.
• track the actual performance of work orders and compare it to planned schedules. where necessary, PAC must take corrective action by replanning, rescheduling or adjusting capacity to meet final delivery requirements.
• monitor and conrtol wrok-in process, lead times, and work center queues.
• report wrok center efficiency, oepration tiems, order uqnatities, and scrap.

Manufacturing Systems : the relative importance of these functions will depend on the type of manufacturing process. manufactuirng process can be follwing;

• flow manufacturing : is concerned with the production of high volume standard products. the process is usually called ' repetitive manufacturing'.  and if the goods are made in a continuous flow(e.g. gasoline), the process is called 'continuous manufactuing'.
  • routing are fixed
  • work center are dedicated to producing a limited range of similar products. machinery and tooling are especially designed to make the specific products.
  • material flow from one workstation to another using some form of mechanical transfer.
  • capacity is fixed by the line
• Intermittent manufacturing: is characterized by many variations in product design, process requirements, and order quantities. 
  • flow of work through the shop is varied
  • machinery and worker must be flexible enough to do the variety of work involved in intermittent manufacturing.
  • throughput times are generally lone.
  • the capacity required depends on the particular mix of products being built and is sometimes difficult to predict.
• Project manufacturing : usually involves the creating of one unit or a small number of unit. project manufactuinrg or management uses many of the same techniques as production activity control, but also has some unique characteristics.
  • initiating the project
  • planning the project, including the scope, schedule and tasks.
  • executing the project by carrying out the tasks.
  • monitoring and controlling the project tasks and reources and communication the status of the project to stackholders.
  • closing the project, which includes documenting the results, as well as anu variance in time and costs.
  •  

Data requitements

to plan the processing of material throught manufacturing, PAC(production activity control) must have the following information. the informationn contained in the databases related Production Acitivity Control) are of two types: planning and control.

• what and how much to produce
• when parts are needed so the completion date can be met
• what operations are required to make the product ans how long the operations will take.
• what the available capacities of the various work center are. 

Planning information : four types of palnning information are needed: item master, product structure, routing, and workcenter master. 

• item master : containing all of the pertinent data related to the part.
  • part number
  • part description
  • manufacturing lead time
  • lot-size quantity : the quantity normally ordered at one time.
• product structure(bill of material) : the product structure(bill of material) contains a list of the single - level components and quantities needed to assemble a parent. it forms a basis for a pick list to be used by storeroom personnel to collect the parts required to make the assembly.
• routing: contains a record for each part manufacutred. the routing consist of a series of operations required to make the item. it gives details of the following;
  •  the operation required to make the product and the sequence in which those operation are performed.
  • a brief description of each operation.
  • equipment, tools, and accessories needed for each operation.
  • setup times, the standard time required for setting up the equipment for each operation.
  • run times, the standard time required to process one unit throught each operation.
  • lead times for each operations
• work center master : collects all of the relevant data on a work center. for each work center, it gives details on the following;
  • work center number
  • capapcity
  • number of shift worked per week
  • number of machine hours per shift
  • number of labor hours per shift
  • efficienfy
  • utilization
  • queue time, the average tiem that a job wait at the work center before work is begum.
  • alternative work centers.

Control information

control in intermittent manufacturing is exercised through shop orders and the data contained on these orders.

• shop order master: each active manufactuing order has a record in the shop order master. the purpose is to provide summarized data on each shop order, such as the following information;
  • shop order number, a unique number identifying the shop order.
  • order quantity
  • quantity completed
  • quantity scrapped
  • quantity of material issued to the order
  • due date, the date the order is expected to be finished
  • priority
  • balance due
  • cost informatio
• the detailed records containingeach shoporder
  • operation number
  • setup hours
  • run hours
  • quantity reported complte at that operation
  • quantity reported scarraped at that operation
  • due date or lead tiem remaining

order preparation

once authorization to process an order has been recieved, production activity control is responsible for planning and preparing its release to the shop floor. the order should be reviewed to be sure that the necessary tooling, material, and capapcity are available. if not, the order cannot be completed and should not be released.

checking capacity availability is a two-step process. first, the order must be scheduled to see when the capacity is needed, and second, the load on work centers must be checked in that period.

 

scheduling

the objectivity of scheduling is to meet delivery dates and to make the best use of manufacturing resources. it involves establishing start and finish dates for each operaion required to complete an item. to develp a reliavle schedul, the planner must have information on the routing, requried and available capacity, completing jobs and manufacturing lead times at each work center involved. t

• manufactuing lead time : is time normally required to produce an item in a typical lot quantity. PAC must manage both the input of orders to the production process and the available capacity to control queue and work in time process. a term that is closely related to manufacturing lead time is cycle time defines as ' the length of time from when material enters a production facility until it exits'. typically it contains of five elements;
  • queue time - the largest of the five elements.
  • set up time
  • run time
  • wait time
  • move time
• scheduling techniques : there are many techniques used to schedule shop orders through a plant, but all of them requires an understanding of forward and backward scheduling as well as finite and infinite loading.
  • forward scheduling
  • backward scheduling
  • infinite scheduling
  • finite scheduling
• operation overlapping : in operation overlapping, the next operation is allowed to begin before the entire lot is completed on the previous operation. this reduces the total manufactuing lead times. a concept used in operation overlapping is the difference between a process batch and a transfer batch. to perform oepration overlapping, an order is divided into at least two lots. operation overlapping is a method of expediting an order, but ther are some costs involved. - 1) increasing move costs 2)increasing queue and lead time for other orders.3) increasing waiting time for parts from the first operation.
  • process batch : is the total size that has been released to production. 
  • transfer batch : is that quantity that moves from workcenter to workcenter.
• operation splitting : is second method of  requcing manufacturing lead time. the order is split into two or more lots or transfer batches and run on two or more machines smultaneously. operation splitting is practical when;
  • setup time is low compared to run time
  • a suitable work center is idle.
  • it is possible for an operator to run more than one macine at time.
  • duplicate tooling or equipment is available.

load leveling 

load leveling for a work center is constructed by calculating the standard hours of operation for each order in each time period and adding then together by time period.

scheduling in a nonmanufactuing setting

all industries deal with the issues of scheduling resources, and balancing demand and supply as well as available versus required capacity.

scheduling bottenecks

the overloaded workstations are called bottelnecks and by definition, are those workstation where the required capacity  is greater than the available capacity. APICS defines as ' a facility, function, department or resources whose capacity is less than the demand planced upon it'.

• throughput 
  •  is the total volume of producition passing through a facility. bottlenecks control the throughput of all products processed by them as total throughput cannot be more then can be processed through the bottleneck. if work center feeding bottlenecks product more than the bottleneck can process, excess work-in process inventory is built up. threfore, work should be scheduled through the bottleneck at the rate it can process the work. 
• bottlencek principles : since bottlenecks control the throughput of a facility, some important principle should be noted; - 아래 건은 예시 통해서 다시 이해해보자..
  • utilization of a nonbottleneck resources is not determined by its potential but by another constraint in the process.
  • using a nonbottleneck resource 100% of the time does not produce 100% utilization.
  • the capacity of the facility depends on the capacity of the bottleneck
  • time saved at a nonbottleneck does not save capacity elesewhere
  • capacity and priority must be considered together
  • loads can, and should be split
  • focus should be on balancing the flow throug the shop
• managing bottlenecks
  • establish a time buffer before each bottleneck
  • control the rate of material feeding the bottleneck
  • do everything to provide the needed bottleneck capacity
  • change the schedule

theory of constraints and drum-buffer-rope

the fundamental concep behind the work is tha tevery operation producing a product or dervice is a series of linked processes. each process has a specific capapcity to produce the given defined output for the operation. identifying the constraint in a process can actually be fairly simple. there is always a set of defined actions(processed) that are needed to create a finished product. when one process is discovered that is working to full capacity, while inventory is growing behind the process waiting for the process and processes downstream from that one process tend to have idle tiem with respect to their need to process the inventory, then the constraints has been identified.

manage the constraint

these principles of balancing the overall flow and maintaining steady work at the constraint are critical to the theory of constraints.

improve the process

• identify the constraint
• exploit the constraint : find methods to maximize the utilization of the constraint toward productive throughput.
• subordinate everything to the constraint : everything else but constraints is secondary
• elevate the constraint
• once the constraint is no longer a constraint, find a new one and repeat the steps

scheduling with the theory of constraints

the scheduling system developed for the theory of constraints has its own specific approach.  it is often described as drum-buffer-rope.

• drum
  • refers to the drumbeat or pace of production. note that once the pace of the constraint has been defined, it does no good to schedule more production that the constraingt can handle.
• buffer
  • assembly buffer
  • shipping buffer
  • processing (constraint buffer)
• rope
  • is that the rope pulls production to the constraint for necessary processing.

implementation

implementaion is performed by issuing a shop order or schdule to manufacturing, which is the authorization for them to proceed with making the item. a shop packet that contains the shop order and whatever other information that is needed by manufacturing can be complied.

control

once work orders have been issued to manufacturing, their progress has to be controlled. to control progress, performance has to be measured and compared to what is planned.  if what is actually ahppenign caries significantly from what was planned, either the plans have to be changed or corrective action must be taken to bring perfomance back to plan.

theobjective of production activity control are to meet delivery dates and to make the best use of company resources. to meet delivery dates, a company must control the progress of orders on the shop floor , which means controlling the lead time for orders. the largest component of lead time is queue. it queue can be controlled, delivery date can usually be met.

to control queue and meet delivery commitments, production activity control must;

-control the work going into and comming out of a work center. this is generally called input/out control

-set the correct priority of orders to run at each work center, which is referred to as dispatching.

• input/output control
  • input/output report
• operation sequencing : defines as ' a technique for short term planning of actual jobs to be run in each work center based on capacity and priorities. priority , in this case, is the sequence in which jobs at a work center should be wroked on. control of priorities is exercised through dispatching.
  • dispatching: is function of selecting and sequecing available jobs to be run at individual work center. the dispatch list is the instrument of priority control. it is a listing by oepration of all the jobs availalbe to be run at a work center with the job list in priority sequence. it normally the following information and is updated and published at least daily.
    • plant, department, work center
    • par number, shop order number, operation number
    • standard hours
    • priority information
    • jobs comming to the work center.
  • dispatching rules -> 이것도 다시...
    • the ranking of jobs for the dispatch list is created through the application of dispatching or priority rules.
      • first come,first served
      • earliest job due date
      • earliest operation due date
      • shortest process tiem
    • critical ratio

production reporting

production reporting provides feedvack of what is actually happening on the plant floor. it allows PAC to maintain valid records of on-hand and on-order balances, job status, shortages, scrap, material shortage, and so son.

once the data is collected and recorded, appropriate reports are produced. types of information needed for the various reports include: 1) order status 2) weekly input/output by department or workcenter 3) exception report on such things as scrap, rework, late shop orders 4) inventory status 5) performance summaries on order status, work center and department efficiencies and so on.

 

product tracking : this is the process of tracking parts and materials back to their origins.

measuremnet systmes

the primary purpose of these measurements is to provide an objective means of evaluating performance, and to take corrective action if necessary. it is also important to make sure whatever type of measurement is used, it is aligned with the overall performacne measurement of the organization.

• actual vs planned lead time
• percent orders completed on time
• performance to schedule

summary

key terms

backward scheduling

bill of material

bottlenecks

continuous manufacturing

critical ratio(CR)

cumulative variance

cycle time

dispatching

drum-buffer-rope

earliest job due date

earliest operation due date

finite loading

first come, first served

flow manufactuing

forward scheduling

gateway operation

infinite loading

input/output control

input/out report

intermittent manufactuing

item master

load profile

manufacturing lead time

move time

operation overlapping

operation splitting

process batch

product etructure

product tracking

project manufactuing

queue time

repetitibe manufacturing

routing

run time

setup time

shop order master

shortest process time

slack per operaton

slack time

throughput

throughput time

transger batch

wait time

work center master