TECHNICAL NOTE 5 JOB DESIGN AND WORK MEASUREMENT
CHAPTER 6 MANUFACTURING PROCESS SELECTION AND DESIGN
Review and Discussion Questions
1. What does the product-process matrix tell us? Where would you place a Chinese restaurant on the matrix?
Products and processes are closely interrelated and both go through life-cycle stages. The stage in the lifecycle of the product will determine the process. The advantages of cost and flexibility can be combined through the adoption of Flexible Manufacturing Systems technology. The Chinese restaurant case might be debatable since it involves both high volume and high variety.
2. It has been noted that during World War II Germany made a critical mistake by having its formidable Tiger tanks produced by locomotive manufacturers, while American car manufacturers produced the less formidable U.S. Sherman tank. Use the product-process matrix to explain that mistake and its likely result.
The locomotive manufacturers likely used project technology and processes. This is low volume, high cost production. On the other hand, mass-producing automakers had the technology to make high volume at low per unit cost.
3. How does the production volume affect break-even analysis?
A break-even analysis takes into account the production volume and the relevant cost of producing the volume by the available alternative processes. It calculates the relative profit or loss of the alternative processes, thus helping to decide which alternative to choose for a certain volume of production.
4. What is meant by a process? Describe its important features.
A process means a set of tasks that transform input into useful outputs. The important features of process are (a) tasks, (b) flow (of material and information), and (c) storage (of material and information).
Manufacturing Process Selection and Design
Problems
Problem
Type of Problem
Difficulty New Problem
Modified Problem
Check Figure in
Appendi x A Assembly
Chart
Flow Process
Chart Break-even
1 Yes Yes Moderate
2 Yes Yes Difficult
3 Yes Moderate Yes
4 Yes Easy
5 Yes Easy
6 Yes Moderate
7 Yes Easy Yes
8 Yes Difficult
9 Easy
10 Easy
11 Easy
12 Easy
13 Easy
1.
a. Assembly chart (answers may vary).
Chapter 6
b. Flow process chart (answers may vary.)
Manufacturing Process Selection and Design
2. This can be a fairly extensive assignment depending upon the amount of research students do into paddle manufacturing. Without doing any library or field study on the production process, students should be able to come up with a solution approximating the one given below.
a. obtain paddle for model b. equipment and materials
equipment: bandsaw, hand saws, circular saw, sanding machine, lathe, glue press, handtruck materials: wood, plywood, rubber for paddle surface, glue, lacquer, plastic bags for wrapping, shipping boxes, and tape.
(1) Assembly drawing
Chapter 6
(2) Assembly chart
Manufacturing Process Selection and Design
(3) Flow Process Chart
Receive rubber Receive plywood
for main piece
Receive wood for handle
Inspect
Inspect Inspect
To saw
Cut to size
Wait for main piece
To hand saws
Cut from plywood
To glue
To Circular Saws
Cut handle
Cut into two pieces
To glue
Wait for main piece Glue
Inspect
Lacquer
Dry
Glue rubber surfaces
Inspect
To packing
Put in plastic bags
Box for shipment To finished
goods
Chapter 6
(4) Process route sheets
Part Name: Main Piece
Operation number
Operation description Dept. Setup time
Pieces per hour
Tools
10 Cut to size Saw 1.0 100 Band saw
20 Glue handle facing Glue 0.5 50 Clamps
21 Lacquer Glue 0.3 100 Paint brush
22 Glue rubber surface Glue 0.1 100 Paint brush
Part Name: Handle Facing
Operation number
Operation description Dept. Setup time
Pieces per hour
Tools
15 Cut to size Saw 0.25 400 Circular saw
16 Cross cut diameter Saw 0.25 100 Circular saw
20 Glue handle facing Glue 0.5 50 Clamps
Part Name: Rubber Surface
Operation number
Operation description Dept. Setup time
Pieces per hour
Tools
16 Cut to size in batches of 24 Saw 0.3 300 Band saw
22 Glue rubber surface Glue 0.1 100 Paint brush
Manufacturing Process Selection and Design
3. .
a. Process Flow Diagram
Capacity of assembly line 1 = 140 units/hour X 8 hours/day X 5 days/week
= 5,600 units/week.
Capacity of drill machines = 3 drill machines X 50 parts/hour X 8 hours/day X 5 days/week
= 6,000 units/week.
Capacity of final assembly line = 160 units/hour X 8 hours/day X 5 days/week
= 6,400 units/week.
The capacity of the entire process is 5,600 units per week, with assembly line 1 limiting the overall capacity.
b.
Capacity of assembly line 1 = 140 units/hour X 16 hours/day X 5 days/week = 11,200 units/week.
Capacity of drill machines = 4 drilling machines X 50 parts/hour X 8 hours/day X 5 days/week
= 8,000 units/week.
Capacity of final assembly line = 160 units/hour X 16 hours/day X 5 days/week
= 12,800 units/week.
Chapter 6
The capacity of the entire process is 8,000 units per week, with drilling machines limiting the overall capacity.
c.
Capacity of assembly line 1 = 140 units/hour X 16 hours/day X 5 days/week
= 11,200 units/week.
Capacity of drill machines = 5 drilling machines X 50 parts/hour X 8 hours/day X 5 days/week
= 10,000 units/week.
Capacity of final assembly line = 160 units/hour X 12 hours/day X 5 days/week
= 9,600 units/week.
The capacity of the entire process is 9,600 units per week, with final assembly machines limiting the overall capacity.
d. Cost per unit when output = 8,000 units.
Item Calculation Cost
Cost of part A $.40 X 8,000 $3,200 Cost of part B $.35 X 8,000 2,800 Cost of part C $.15 X 8,000 1,200
Electricity $.01 X 8,000 80
Assembly 1 labor $.30 X 8,000 2,400 Final assembly labor $.30 X 8,000 2,400 Drilling labor $.15 X 8,000 1,200
Overhead $1,200 per week 1,200
Depreciation $30 per week 30
Total $14,510
Cost per unit = Total cost per week/Number of units produced per week
= $14,510/8,000
= $1.81
Cost per unit when output = 9,600 units.
Item Calculation Cost
Cost of part A $.40 X 9,600 $3,840 Cost of part B $.35 X 9,600 3,360 Cost of part C $.15 X 9,600 1,440
Electricity $.01 X 9,600 96
Assembly 1 labor $.30 X 9,600 2,880 Final assembly labor $.30 X 9,600 2,880 Drilling labor $.15 X 9,600 1,440
Overhead $1,200 per week 1,200
Depreciation $30 per week 30
Total $17,166
Cost per unit = Total cost per week/Number of units produced per week
= $17,166/9,600
= $1.79
Manufacturing Process Selection and Design
Let X = the number of units that each option will produce.
When the company buys the units, the cost is $3.00 per unit (3X). When it manufactures the units, they incur a fixed cost of $120,000 (4 drilling machines at $30,000 a piece) and a per unit cost of
$1.81. Therefore, 120,000 + 1.81X is the cost of this option. Set them equal to each other and solve for X to determine the breakeven point.
3X = 120,000 + 1.81X X = 100,840 units.
Therefore, it is better to buy the units when you produce less than 100,840, and better to produce them when demand is greater than 100,840 units.
4. .
a. FC = (P - VC) * Break-even (where FC = fixed cost, P = price, and VC = variable cost)
$300,000 = ($23.00 - $8.00) * Break-even Break-even = 20,000 books
b. Higher c. Lower
5.
FC = (P - VC) * Break-even (where FC = fixed cost, P = price, and VC = variable cost)
$150,000 = ($90 - $70) * Break-even Break-even = 7,500 units.
6.
a.
FC = (P - VC) * Break-even (where FC = fixed cost, P = price, and VC = variable cost).
$900 = ($5.50 - $4.50) * Break-even Break-even = 900 units.
b.
FC + profit = (P - VC) * V
(where FC = fixed cost, P = price, and VC = variable cost, and V = Volume)
$900 + $500 = ($5.50 - $4.50) * V V = 1400 units.
c.
Profit per unit = (P-VC)*V - FC)/V
$.25 = (($5.50 - $4.50)*V - $900)/V .25V = V - 900
75V = 900 V = 1,200 units.
Profit per unit = ((P-VC)*V - FC)/V
$.50 = (($5.50 -$4.50)*V - $900)/V .50V = V - $900
.50V = 900 V = 1,800 units.
Chapter 6
Profit per unit = ((P-VC)*V - FC)/V
$1.50 = (($5.50 -$4.50)*V - $900)/V 1.5V = V - 900
.50V = -900
V = -1,800 units. Not possible.
7. FC = (P - VC) * Break-even (where FC = fixed cost, P = price, and VC = variable cost).
$2052 = ($.36 - $.144) * Break-even Break-even = 9,500 miles.
8.
a. FC = (Pc - VCc) * Vc + (Pb -VCb) * Vb where
FC = fixed cost Pi = price for product i
VCi = variable cost for product i Vi = volume for product i where i is
c = chair b = bar stool V = Vc = Vb
$20,000 = ($50 - $25) * V + ($50 - $20) * V 20,000 = 25V + 30 V
20,000 = 55V
V = 364 units of chairs and bar stools.
Break-even in dollars = $50(364 + 364) = $36,400.
b. FC = (Pc - VCc) * Vc + (Pb -VCb) * Vb where
FC = fixed cost Pi = price for product i
VCi = variable cost for product i Vi = volume for product i where i is
c = chair b = bar stool V = Vc = 4Vb
$20,000 = ($50 - $25) * V + ($50 - $20) *4V 20,000 = 25V + 120 V
20,000 = 145V
V = 138 units of chairs and (4 * 138) = 552 bar stools.
Break-even in dollars = $50(138 + 552) = $34,500.
Manufacturing Process Selection and Design
Issue Job Shop Flow Shop
Number of Changeovers Many Few
Labor content of product High Low
Flexibility High Low
9.