Chapter 6

little law

flow of items through production process inventory = throughput rate x flow rate

Customer order decoupling point

inventory is positioned to allow entities in the supply chain to operate independently

throughput rate

long term average rate of flow through process

manufacturing cell

dedicated area where a group of similar products are produced

Every 2 minutes a bus departs from AVIS. Flow time is 20 minutes. How many buses are in the system at a time?

(1 bus / 2 minutes) x 20 minutes = 10 buses

organization of product processes

- project - workcenter (jobshop) - manufacturing cell - assembly line - continuous process

Using the assembly-line balancing procedure, which of the following is the required cycle time if the production time in minutes per day is 1440 and the required output per day in units is 2000? - 1.388 - 500 - 0.72 - Cannot be determined from the information above - 250

0.72

You have just determined the actual number of workstations that will be used on an assembly line to be 6 using the assembly-line balancing procedure. The cycle time of the line is 5 minutes and the sum of all that tasks required on the line is 25 minutes. Which of the following is the correct value for the resulting line's efficiency? - 0.833 - None of these - 0.973 - 0.500 - 0.990

0.833 Using equation 6.5, [25 / (6 x 5)] = 0.833.

250 people/hour 15 min average time in a store how many customers in the store at any given time?

250 ppl/hour x (15/60 mins) - 62.5 customers

Which of the following basic types of process structures is one which equipment or work processes are arranged according to the progressive steps by which the product is made? - Manufacturing cell - Assembly line - Project - Workcenter - Continuous process

Assembly line

work station cycle time formula

C = total production time/ total units needed per day

inventory turn

COGS / avg. inventory value

assemble to order

Combine a number of preassembled modules to meet a customer's specifications

The placement of which of the following is not determined by production process organization decisions? - Emergency exits - Machines - Workstations - Departments - `Workgroups

Emergency exits

Which of the following is not considered a major work flow structure? - Work Center - Project - Fabrication - Assembly line - Continuous Flow

Fabrication

number of work stations needed formula

Nt = sum of task time (t) / cycle time

make to stock

Serve customers "on demand" from finished goods inventory

When balancing an assembly line, which of the following is not a way to reduce the longest task time below the required workstation cycle time? - Split the task between two workstations - Use a more skilled worker - Speed up the assembly line transfer mechanism - Upgrade the equipment - Assign a roaming helper to support the line

Speed up the assembly line transfer mechanism

Efficiency formula

T (sum of time) / NaC (# workstations x cycle time)

According to Little's Law, which of the following can be used to estimate work-in-process inventory? - Process velocity/Flow time - Value added time/Process velocity - Process time/Cycle time - Throughput rate times Flow time - Set up time/Throughput rate

Throughput rate times Flow time

inventory measures

Total average value of inventory Inventory turns Days of supply

days of supply

the inverse of inventory turns scaled to days

Total average value of inventory

the sum of the value (at cost) of the raw material, work-in process, and finished goods inventory

lead time

the time needed to respond to a customer order

time between plane takeoffs can be at least 3 minutes. after take off, run time is 45 seconds. planes wait an average of 4 minutes and 15 seconds. on average there are 15 planes taking of per hours. How many planes are on the runway at once?

throughput rate: 15 planes/hour flow time: 4 min 15 sec + 45 sec -> 5 minutes inventory: 15 planes/hour x (5 min/60) = 1.25 planes

Using the assembly-line balancing procedure, which of the following is the theoretical minimum number of workstations if the task times for the six tasks that make up the job are 4, 6, 7, 2, 6, and 5 minutes, and the cycle time is 10 minutes? - 8 - 5 - None of these - 6 - 3

3 (4 + 6 + 7 + 2 + 6 + 5) / 10 = 3.

Using the assembly-line balancing procedure, which of the following is the required cycle time in minutes per unit if the daily production time is 480 minutes and the required daily output is 50 units? - 480 - 0.104 - Cannot be determined from the information above - 50 - 9.6

9.6 daily production time (480) / daily output (50)

engineer to order

Work with the customer to design and then make the product

Which of the following is a basic type of process structure? - Process matrix - Manual assembly - Process flow diagram - Product matrix - Workcenter

Workcenter

lean manufacturing

a means of achieving high levels of customer service with minimal inventory investment

Problem 6-17 Some tasks and the order in which they must be performed according to their assembly requirements are shown in the following table. These are to be combined into workstations to create an assembly line. The assembly line operates 13 hours per day. The output requirement is 1,800 units per day. (TASK) (b/4) (TIME) A — 20 G C 13 B A 7 H D 8 C A 14 I E 7 D B 16 J F, G 9 E B 15 K H, I 6 F C 14 L J, K 4 a. What is the workstation cycle time? b. balance the line using the longest task time based on the 1,800-unit forecast, stating which tasks would be done in each workstation. c. What is the efficiency of your line balance? (Round your answer to 1 decimal place.) d. After production was started, Marketing realized that they understated demand and must increase output to 1,900 units. There are two options: reduce cycle time or work overtime. Please identify the following:

a. 26 seconds per unit b. c. 85.3 d. reduce cycle time to 25 (13 x 3600)/1900 = 25 overtime 43 minutes ((1900-1800) x 26 sec) = 2600 sec / 60 sec = 43 minutes

continuous process

assembly line only the flow is continuous such as with liquids

An assembly line is to operate eight hours per day with a desired output of 300 units per day. The following table contains information on this product's task times and precedence relationships: TASK TIME b/4 A 50 — B 40 A C 45 A D 25 A E 60 B, C F 35 C, D G 25 E, F H 50 G b. What is the required workstation cycle time to meet the desired output rate? (Round your answer to the nearest whole number.) c. Balance this line using the longest task time. (Leave no cells blank - be certain to enter "0" wherever required.) d. What is the efficiency of your line balance, assuming it is running at the cycle time determined in part b? (Round your answer to 1 decimal place.)

b. Workstation cycle time 96 correct seconds per unit c. Work Station Task Idle Time I A-C 1 II B-D 31 III E-F 1 IV G-H 21 d. Efficiency 85.9 %

make to order

make a customer's order from raw material

inventory

material held by arm for future use

project

remain in a fixed location, equipment is moved to the product

Workcenter (job shop)

similar equipment or functions are grouped together

Production process

source, make, deliver

flow time

time for one unit to get through a process

production process mapping

useful to understand how material flow and inventory is held

assembly line

work processes are arranged according to the progressive steps by which the product is made