978-0128012420 Chapter 11 Part 2

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Kosky, Balmer, Keat and Wise: Exploring Engineering, Fourth Edition, Solution Manual, Chapter 11

11-14) If you have a MTBF of 160. days it doesn‘t mean you can expect an individual device to

operate for 160. days before failing. MTBF is a statistical measure, and can’t predict anything

for a single unit. However, if you have 1,000 devices with this same MTBF operating

continuously in a factory, a) how often would you expect one to fail, and b) how long would it

take for 20 failures to occur?

Solution:

Need: a) how often would one fail, and b) how long would it take for 20 failures to occur.

11-15) Using a Design of Experiments process, how many experiments do you need to perform

if you have:

a) 2 variables and want to test them over 2 levels of each variable

b) 2 variables and want to test them over 3 levels of each variable

c) 3 variables and want to test them over 3 levels of each variable

d) 5 variables and want to test them over 4 levels of each variable

Solution:

Need: the number of experiments needed to perform the tests.

11-16) List the five stages in methods engineering.

Solution:

Need: the five stages in methods engineering.

11-17) Determine the maximum feasible profit in Example 11.8 if the drilling time for part B

was 10 minutes instead of 8 minutes. Assume all the remaining conditions are unchanged.

Solution:

Need: the maximum feasible profit in Example 11.8 if the drilling time for part B was 10

minutes instead of 8 minutes with all the remaining conditions are unchanged.

11-18) Determine the maximum feasible profit in Example 11.8 if the lathe time for part A was

reduced from 25 minutes to 10 minutes. Assume all the remaining conditions are unchanged.

Solution:

Need: the maximum feasible profit in Example 11.8 if the lathe time for part A was reduced

from 25 minutes to 10 minutes with all the remaining conditions are unchanged.

Know: the data in Example 11.8.

11-19) Freddy works on an assembly line and uses a handheld pneumatic impact wrench. The

assembly line makes up to 1400 products a day and it takes about 3 seconds for Freddy to

tighten each of seven different components. Freddy often has to use poor posture to attach

some of the parts. After a few weeks Freddy found that he was leaving work with shoulder and

neck pain. Using ergonomic principles assess Freddy’s working conditions and suggest at least

four workplace modifications that will reduce Freddy’s problems.

Solution:

Need: at least four workplace modifications that will reduce Freddy’s problems.

11-20) Janet is a sales engineer at your company. Much of her work involves using a telephone

and a computer to make appointments, call customers, and respond to emails. Janet would

often hold the telephone between her shoulder and ear while talking on the phone and typing on

the computer. Also, Janet’s computer screen was difficult to read because of glare and

reflections from light through the window in her office. After working for eight months, Janet

found she was leaving work with an aching shoulder, sore eyes, and a headache. Using

ergonomic principles assess Janet’s working conditions and suggest at least three workplace

modifications that will reduce Janet’s problems.

Solution:

Need: at least three workplace modifications that will reduce Janet’s problems.

11-21) A worker’s hand was seriously injured while trying to clear a reoccurring blockage in

a computer controlled machining station. Access to the machining station is through a door in

its enclosure and all machining operations are stopped when this door is opened. The worker

had obtained an override key so he could open the door and enter the enclosure without

stopping production. Using ergonomic principles identify at least three steps that can be taken

to help prevent a recurrence.

Solution:

Need: identify at least three steps that can be taken to help prevent a recurrence.

11-22) A company uses reusable wooden boxes 36″ square and 48” long to ship their product.

Recently the cost of a new shipping box has increased from $32.50 to $81.00. The box

maintenance has also increased from $15 per year to $21 per year. Also, extra truck runs and

outside trucking services are required to return the wooden boxes. As a material handling

engineer, how would you improve this system by suggestion new methods for shipping the

product?

Some example solutions are:

11-23) The storage area at your company is presently filled to capacity with 20,000 cases of

product. Your company recently increased its manufacturing capability by 100% and the finished

goods inventory storage area is expected to increase by the same amount. The present storeroom

is 250‘ by 375‘ with a 30′ ceiling height. The product is packaged in cases 15″ long, 24″ high,

and 32″ wide and you cannot stack these cases more than 6 high without damage. As a material

handling engineer, suggest methods for increasing the storage area to accommodate the

contemplated increase in finished goods inventory.

Solution:

Need: methods for increasing the storage area to accommodate the contemplated increase in

finished goods inventory.

11-24) One of your first assignments when you graduate with an engineering degree and accept

a well-paying position at a prominent company is working in the product testing laboratory.

Your manager wants you to do a one-variable-at-a-time (OVAT) experiment on the products

reliability. You know that a design of experiments (DOE) testing method would save the

company time and money and produce more accurate results. Your manager has never heard of

DOE and insists you proceed with a long and expensive OVAT experiment. What do you do?

(Use the Engineering Ethics Matrix.)

a) Go over your manager’s head and talk to his boss.

b) Ignore your manager’s orders and carry out a DOE without his knowledge.

c) Ask a colleague for help in convincing your manager to your point of view.

d) Confront your manager in writing (with a cc to his/her boss) saying that he/she doesn’t

understand modern engineering testing methods and should listen to you.

Solution: There are no unique solutions to these scenarios. The student’s responses can be

talking points in class.

11-25) You now have an entry level position as an engineer at a hand tool manufacturing

company. You are put on a team of engineers that is about to release the design of a new battery

powered screw driver to manufacturing. By handling the prototype you notice that the screw

driver has a heavy battery and that the direction that the shaft turns is activated by the user

twisting his/her wrist at a severe angle. You point this out at a team meeting and suggest that the

design may have serious ergonomic problems that could result in user wrist injury during long

term use. The team quietly listens to your comment and replies that profit, not user ergonomics,

is their goal. What do you do? (Use the Engineering Ethics Matrix.)

a) Reassert your position by suggesting that customer satisfaction will also lead to profits.

b) Contact the company lawyer as a whistle blower about a possible dangerous product.

c) Talk to the team leader in private and suggest an ergonomics expert be added to the team.

d) Send an anonymous email to the company president warning him/her about possible law

suits.

Solution: There are no unique solutions to these scenarios. The student’s responses can be talking points

in class.