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Definition
| producing only what is needed |
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| good quality parts with zero defects |
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| more frequently stated as a lot size of one, the goal is to replenish stock as taken, from one lot. Not always possible bc different parts from different lots are needed |
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| by using large batch sizes, reduces setups. ie, changing paint on an assembly line |
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| can have no unplanned failures |
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| not to be handled more than necessary, no extra moves, feed material directly from workstation to workstation |
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| very close to the core of the zero inventory objective, a downstream workstation request parts and they are provided immediately |
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| tasks that take place when machine is stopped |
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| tasks that can be completed while the machine is running |
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| includes use of statistical process control (SPC) charts and other statistical methods, but also involved simply giving workers responsibility for quality and the authority to make changes when needed |
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| display boards, gauges, meters, plaques, and awards; poka-yoke:design the system so that the worker cannot make a mistake |
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| 3)Insistance on compliance |
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Definition
| if materials from a supplier did not measure up, they were sent back. Quality comes first and output second |
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Definition
| stoppling the line to correct quality problems; ie, using lights to display status' of different areas of the plant |
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| 5)Correcting one's own errors |
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Definition
| no rework lines as seen in the US, fix problems as seen/found |
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| inspect every part, not just a random sample. If not possible use N=2 method |
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| by aimming for zero defects, there is always room for more quality improvements |
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Term
Workstation Layout:
Cellular Layout |
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Definition
1)one worker for all machines
2)flexible in # of workers, allows to respond to changes in production req.
3)single workers monitors all work entering and leaving, ensuring it remains constant, results in JIT flow
4)Workers work together to fix problems |
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Definition
| work releases are scheduled |
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| work releases are authorized |
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Definition
| a collection of one or more machines or manual stations that perform, essentially, identical functions |
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| workstations are physically organized according to the operations they perform |
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| workstations are organized in lines making specific products |
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| a piece of raw material, a component, a subassembly, or an assembly that is worked on at the workstations in the plant |
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| refers to parts purchased outside the plant |
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| individual pieces that are assembled into more complex products |
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| or final assemblies, are fully assembled products or end items |
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| a part that is sold directly to a customer, whether or not it is an assembly |
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| materials such as lubricants, bits, and chemicals that are used but do not become part of the product that is sold |
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| describes the sequence of workstations passed through by a part |
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| a request from a customer for a particular part #, in a particular quantity, to be delivered on a particular date. aka: an order |
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| refers to a set of physical materials that traverses a routing, along with the associated logical information |
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Definition
| average output of a production process per unit time, or average quantity of good (non-defective) parts produced per unit time |
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Definition
| an upper limit on the (TH) of a production process |
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Term
| raw material inventory (RMI) |
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Definition
| the physical inputs at the start of a production process |
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Term
| Finished goods inventory (FGI) |
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Definition
| stock point at the end of a routing |
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Term
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Definition
| inventory between the start and end points of a product routing |
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Term
| inventory turns (turnover ratio) |
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Definition
| commonly used measure of the efficiency with which inventory is used |
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Definition
| average time from release of a job at the beginning of the routing until it reaches an inventory point at the end of the routing |
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Definition
| time alloted for production of a part on that routing or line |
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Definition
| the fraction of orders that are filled from stock |
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| the fraction of time a workstation is not idle for lack of parts |
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Definition
| the rate of the workstation having the highest long-term utilization |
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Definition
| the sum of the long-term average process times of each workstation in the line |
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Definition
| the WIP level for which a line with given values of rb and To but having no variability achieves max. throughpout (rb, that is) with min. cycle time (To) |
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Definition
| the quality of nonuniformity of a class of entities |
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Definition
| occurs as a direct result of decisions |
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Definition
| a consequence of events beyond our immediate control |
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| the total time "seen" by a job at a station |
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Term
| coefficient of variation (CV) |
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Definition
| standard deviation divided by the mean (t) |
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Definition
1)Natural variability
2)Random outages
3)Setups
4)Operator availability
5)Rework |
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Term
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Definition
| includes minor fluctuations in process time due to differences in operators, machines, and material |
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Definition
| breakdowns that occur whether or not we want themn to. ie, power outages, operators being called away on emergencies, and running out of consumables |
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Term
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Definition
| represent downtimes that will inevitably occur but for which we have some control as to exactly when. ie, when a tool starts to become dull |
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Term
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Definition
| rework due to quality problems. Decreases capacity and increases variability of teh effective process time. Equivalent to nonpreemptive outages |
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Term
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Definition
| adding variability may increase revenue by more than the additional cost |
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Definition
| an undesired side effect of a poor operating policy |
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Definition
| what can you manipulate to make the objective happen |
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Definition
| how do you evaluate your performance |
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Definition
| way to characterize performance measures. For each efficiency, 1-perfect performance has a value of 1. 2-worst possilbe performance has value of 0. |
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Term
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Definition
rate of parts produced by the line that are used.
if TH >= D, then TH eff. is equal to 1.
Any shortage, not able to meet demand, then TH eff. < 1 |
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Term
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Definition
fraction of time a station is busy.
Ideally all workstations at 100% utilization |
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Term
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Definition
Includes WIP, FGI, and RMI
Ideally RMI=FGI=0 and critical WIP |
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Term
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Definition
Ratio of best possible CT to actual CT.
Independent measure because of FGI and RMI |
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Term
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Definition
Time quoted to the customer.
Ideally lead time is zero:1-possible in make-to-stock. 2-as close to raw processing time as possible for make-to-order |
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Term
| Customer Service Efficiency |
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Definition
Fraction of demands that are satisfied on time.
Make-to-stock = fraction of demand filled from stock (not backordered).
Make-to-order = fraction of orders filled within lead time |
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Term
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Definition
Complex interaction of product, process, and customer.
For operational purposes, EQ= fraction of jobs that go through the line with no defects on first pass |
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Term
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Definition
increasing variability always degrades the performance of the production system, at least one eff. is degraded.
3 general dimensions effected are: 1-inventory, 2- capacity, 3-time |
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Term
| Variability Buffering Law |
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Definition
Variability in a production system will be buffered by some combination of: Inventory, capacity, time.
The appropriate buffering strategy depends on the production enviroment and business strategy |
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Term
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Definition
| flexibiliy reduces the amount of variability buffering required in a production system |
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Term
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Definition
| output had to be greater than input |
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Term
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Definition
| In steady state, all plants will release work at an average rate that is strictly less than the average capacity |
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Term
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Definition
| if a station increases utilization without making any other changes, average WIP and cycle time will increase in a highly nonlinear fashion |
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Definition
| In a line where releases are independent of completions (push system), variability early in routing increases cycle time more than equivalent variability later in the routing |
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Term
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Definition
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Definition
| each part in batch processed one at a time |
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Definition
| entire batch processed at once |
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Definition
| parts are transferre3d in batches; tradeoff between waiting for a batch to form and material handling |
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Term
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Definition
| In stations with batch operations or significant changeover times. 1-the min. process batch size that yields a stable system may be greater than one. 2-as process batch size becomes large, cycle time grows proportionally with batch size. 3-cycle time at the station wil be min. for some process batch size, which may be greater than one. |
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Term
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Definition
| Cycle times over a segment of a routing are roughly proportional to the transfer batch sizes used over that segment, provided there is no waiting for the conveyance device. Cellular manufacturing |
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Term
| Cycle Time is made up of... |
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Definition
1-Move time
2-Queue time
3-Setup time
4-Process time
5-Wait-to-batch time
6-Wati-to-batch time
7-Wait-to-match time |
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Term
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Definition
The performance of an assembly station is degraded by increasing any of the following:
1-# of components being assembled
2-Variability of component arrivals
3-Lack of coordination between component arrivals |
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Term
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Definition
| The average cycle time in a line is equal to the sum of the cycle times at the individual stations less any time that overlaps 2 or more stations |
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Term
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Definition
1-Keep process batches large and transfer batches small
2-Useful where there are long setup times but short processing times |
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Term
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Definition
| The manufacturing lead time for a routing that yields a given service level is an increasing function of both the mean and standard deviation of the cycle time of the routing |
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Term
| Lead time law (in own words) |
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Definition
| keeping service level constant, raising your CT or standard dev. of CT, you will be increasing your lead time |
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