6310 S2 20 Tutorial 6 Answers PDF

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Discussion Explain the difference between cycle time and Takt time? Cycle time is the maximum time allowed to accomplish a task or process step. A completed product may require multiple process steps.Takt time is the speed at which completed units must be produced to satisfy customer demand.We use c...

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QBUS6310 – Business Operations Analysis

Tutorial 6, Week 6

Discussion 1. Explain the difference between

and

?

Cycle time is the completed product

. A .

Takt time is th We use cycle time to balance assembly lines while we use takt time to balance work cells 2. Outline the major difference between a process oriented layout and a product oriented layout? Process Oriented Layout

Product Oriented Layout

Suitable: The

Suitable:

Advantages: • It can

Advantages: • because of

•

or

, especially in terms of “batches” or “job lots.” It has

and

• because

of

task

specialisation. • Disadvantages: •

Disadvantages: •

. –

because of •

B

. drive labour

•

/ stoppages because

are

•

costs. •

.

Challenges:

Challenges

that minimises material handling costs given the variety in process flows and activities

. Line balancing is achieved using different heuristics

3. What is a

? What

?

A heuristic is a “

” . Heuristics . so it may be Line balancing heuristics include: longest task time, most following tasks, ranked positional weights, shortest task time, and least number of following tasks.

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QBUS6310 – Business Operations Analysis

Tutorial 6, Week 6

Problems 9.4 Roy Creasey Enterprises, a machine shop, is planning to move to a new, larger location. The new building will be 60 feet long by 40 feet wide. Creasey envisions the building as having six distinct production areas, roughly equal in size. He feels strongly about safety and intends to have marked pathways throughout the building to facilitate the movement of people and materials. See the following building schematic.

His foreman has completed a month-long study of the number of loads of material that have moved from one process to another in the current building. This information is contained in the following flow matrix.

Finally, Creasey has developed the following matrix to indicate distances between the work areas shown in the building schematic.

ERS BENDERS What is the appropriate layout of the new building?

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QBUS6310 – Business Operations Analysis

Tutorial 6, Week 6

Solution This matrix includes movements in both directions:

M W D L G B

M —

W 125 —

D 75 0 —

L 0 75 0 —

G B 50 60 0 0 150 20 20 0 — 0 —

Here are two optimal layouts:

Movement–Distance Calculations M → W: M → D: M → G: M → B: W → L: D → G: D → B: L → G:

125 × 20 = 75 × 40 = 50 × 20 = 60 × 20 = 75 × 20 = 150 × 20 = 20 × 20 = 20 × 20 =

2,500 3,000 1,000 1,200 1,500 3,000 400 400 13,000

13,000 is the minimum distance movement for both (symmetrical) layouts

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QBUS6310 – Business Operations Analysis

Tutorial 6, Week 6

9.11 After an extensive product analysis using group technology, Leon Bazil has identified a product he believes should be pulled out of his process facility and handled in a work cell. Leon has identified the following operations as necessary for the work cell. The customer expects delivery of 250 units per day, and the workday is 420 minutes. a) What is the takt time? b) How many employees should be cross-trained for the cell? c) Which operations may warrant special consideration? OPERATION STANDARD TIME (min)

Answer (a) Takt time = Minutes available per day/Units demanded per day = 420/250 = 1.68 minutes (b) Number of cross-trained employees = (1.1 + 1.1 + 1.7 + 3.1 + 1.0)/1.68 = 8.0/1.68 = 4.76 » 5 (c) The cleaning operation is substantially longer than the others so it warrants special consideration to ensure that a smooth flow can be maintained. A machine constrained task or lack of cross-training may suggest that more traditional assembly line balancing techniques be used.

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QBUS6310 – Business Operations Analysis

Tutorial 6, Week 6

9.13 Illinois Furniture, Inc., produces all types of office furniture. The “Executive Secretary” is a chair that has been designed with ergonomics to provide comfort during long work hours. The chair sells for $130. There are 480 minutes available during the day, and the average daily demand has been 50 chairs. There are eight tasks on the assembly line: ED BELOW

a) Draw a precedence diagram of this operation. b) What is the cycle time for this operation? c) What is the theoretical minimum number of workstations? d) Assign tasks to workstations. e) What is the idle time per cycle? Why is it high? f) How much total idle time is present in an 8-hour shift? g) What is the efficiency of the assembly line, given your answer in (d)? Solution (a, d)

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QBUS6310 – Business Operations Analysis

Tutorial 6, Week 6

It takes 49 mins to assemble the chair. We have 480 mins of production time available and we need 50 chairs.

480 minutes = 9.6 minutes 50 units ∑ ti 49 (c) Theoretical minimum = = = 5.1 = 6 stations cycle time 9.6 number of stations

(b) Cycle time =

(d) Using the longest task heuristic we need 8 work stations (see diagram above), so the theoretical minimum could not be achieved. Using another heuristic wont help in this case because the task times aren’t very balanced.

(e) Total idle time/cycle = 4 + 1 + 2 + 3 + 2 + 1 + 2 = 15 min. per cycle. Idle is time high because we needed to extra work stations due to the unbalanced nature of the line. (f) Total idle time/day: Since there are 480 minutes, and each chair takes 8 minutes (which is the longest operation time), there are 480/8 = 60 cycles/day. Total idle time = 15 minutes / cycle × 60 cycles = 15 hours

(g) Efficiency 49 mins / (8 stations x 8.0 mins*) = 0.766. Efficiency = 76.6%, which again is quite low.

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