Cheat Sheet

Topics: Time, Chemical engineering, Inventory Pages: 5 (1557 words) Published: October 11, 2011
Cycle time: Bottleneck| Cycle time = 1/Capacity rate | | Inventory = Throughput Rate x Flow Time | Little’s Law: I = R x T | Inventory Turns (IT) = 1 / Flow time (T) = R / I |
BCWS = Budgeted Cost of Work Scheduled BCWC = Budgeted Cost of Work Complete |ACWC = Actual Cost of Work Complete
| Cost Variance CV = BCWC – ACWC | Schedule variance SV = BCWC – BCWS |
Utilization=Demand /CAPACITY| Inventory Buildup rate IBR|No IBR if no stations limits Throughput rate| Capacity rate = 1 / Cycle time = 1/55 /second | Convert to hourly base: 3600 seconds/hr * Capacity Rate |

Business strategy should by compatible with operational structure that is with the Order Winners=Cost/ price, Quality, response time (delivery lead time)-speed, flexibility/variety.| Slack time = late start – late finish, duration = total length of critical path longest time.| Expected Time = Optimistic Time + 4(Likely Time) +

LD score (i, j) = Load (i, j) x Distance (i, j)
Flow Time Analysis
Cycle time: Bottleneck
Total operation time
Operation time = Labor time associated with one product
Flow time
Flow time (item) = Operation Time + Delay
Delay = Aging + WIP + Other possible delays (Rework)
Flow time efficiency
Theoretical flow time / Actual flow time
Recall the other efficiencies
Class 06 – Basic Tools of Process Design
Efficiency = Sum of tasks time / (Actual # of stations  Required cycle time)
Class 07 – Samsung International
Labor efficiency = Average working time / Bottleneck cycle time
Inventory Turns (IT) = 1 / Flow time (T)
Little’s Law:
Average I = R x Average T
Average Inventory Turns = R / Average I
Last Class:
Variability: Customer demand for finished goods, availability of raw materials, processing capacity.
Predictability /stochastic are the two types of variability.
Average service rate, customer served in a particular time, an arriving part that is prevented from entering the system because the line is full has been blocked / a work station that is ready but has nothing to work on has been starved / a buffer is any accumulation of material between two systems that decouples them and increases their ability to operate independently. Parts will not accumulate without bounds. There is an upper limit to the inventory held that limit size is the buffer size. Safety stock is to protect against stochastic variability. Seasonal inventories result from predictable seasonal variations in the production or demand process. Cycle stocks are inventories driven by periodic production cycles. Any amount of unit in the transit line is known as pipeline inventories in the delivery system. If a manager anticipates a price hike and stock piles to avoid premium later these are known as speculative inventories.

Demand Rate: Rate at which materials or orders enter the system
Capacity Rate: Maximum rate that system allows materials or orders to flow through
Throughput Rate: Minimum of capacity rate and demand rate
(Theoretical) Utilization: Demand rate / Capacity rate
Utilization profile: Utilizations calculated for all activities / stations
Flow time efficiency: Theoretical flow time / Actual flow time
Actual flow time: all the time unit spends in the stage or system (includes waiting)
Theoretical flow time: exclude the waiting time
Inventory Build-up Diagram
Demand Rate < Capacity Rate : no inventory build-up
Demand Rate > Capacity Rate : Inventory Build-up
At rate of ( Demand Rate - Capacity Rate )Little’s Law
Inventory = Throughput rate  Flow time

Consider the following six tasks that must be assigned to 4 workers on a conveyor-paced assembly line (i.e., a machine-paced line flow). Each worker must perform at least one task.Time to complete taskTask 1: 30 secondsTask 2: 25 secondsTask 3: 35 secondsTask 4: 40 secondsTask 5: 15 secondsTask 6: 30 seconds| The current conveyor-paced assembly line configuration assigns...
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