UNIVERSITY OF SUNDERLAND
FACULTY OF ENGINEERING AND ADVANCED MANUFACTURING
MODULE CODE: EAT104
MODULE TITLE: Materials & Manufacturing
MODULE ASSESSOR: Alan Wheatley
ASSESSMENT: Two of Two
TITLE OF ASSESSMENT: Manufacturing Systems and Quality
PLEASE READ ALL INSTRUCTIONS AND INFORMATION CAREFULLY.
This assignment contributes 50% to your final module mark.
Please ensure that you retain a duplicate of your assignment. We are required to
send samples of student work to the external examiners for moderation purposes. It
will also safeguard in the unlikely event of your work going astray.
THE FOLLOWING LEARNING OUTCOMES WILL BE ASSESSED:
an understanding of:
3. Modern manufacturing economics, systems and organisation
and the ability to:
5. Undertake a costing analysis for a range of product types.
6. Apply the basic principles of quality control
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Submission Date and Time 4
Submission Location Online
EAT104: Coursework 2: 2016/2017 Session
Manufacturing: Economics, Quality and Organisation
This work contributes 50% of the marks allocated to the module.
This work covers Learning Outcomes 3, 5 and 6. Learning Outcomes 1, 2 and 4 were
covered by the elements within “Coursework 1”.
The tasks comprising this assessment are given below. Part A comprises a series of
quantitative questions relating to manufacturing economics and quality control. Part B
comprises CES exercises which relate to manufacturing economics and some environmental
impacts associated with manufacturing.
PART A: Quantitative Analysis
A1. A company wishes to introduce a new product. In order to do this, it must invest in
some new manufacturing equipment. The choice is between Machine A and Machine B.
Costs and income associated with each machine are as follows.
Costs / Income Machine A Machine B
Fixed Costs £75,000 £87,000
Variable Cost per Product Produced £13 £10.50
Selling Price for each Product £25 £25
Plot separate break-even graphs (Costs/Income -v- No of Products) for Machine A and
Machine B. Which machine would you recommend for purchase? Why?
A2. A batch of 2500 components is manufactured by an operator. Each of these components
takes 4 minutes to make. The direct materials costs are £2 per component. The operator is
paid £15 per hour (direct labour costs). If the total overheads in this company are calculated
at 350% of direct labour costs, what is the true cost of manufacturing each component?
A3. (a) A potential 6-year manufacturing project requires the purchase of a new piece of
machinery. You are the project manager and you must choose between two potential
machines (Machine A and Machine B), either of which would be suitable. The cost of each
machine is identical at £80,000. However, they differ in performance such that the projected
future cash flows are different for each machine. Projected cash flows over the 6 years of the
project are as follows in Table QA3:
Table QA3: Six year cash flow figures for Machine A and Machine B.
Year Cash Flow: Machine A Cash Flow: Machine B
0 -£80,000 -£80,000
1 £5,000 £35,000
2 £8,000 £25,000
3 £12,000 £18,000
4 £20,000 £10,000
5 £25,000 £7,000
6 £30,000 £5,000
(i) By simple inspection of the cash flow figures, estimate the payback period for each
machine and thereby state which machine you would choose and justify your choice.
(ii) Your colleague disagrees with your choice. Suggest one valid reason why your
colleague’s choice may be justified?
(b) Calculate the total NPV for each machine after 6 years assuming a discount (inflation)
rate of 7% for each year of the project. Table B3b provides a list of discount factors for a
range of discount/inflation rates.
(c) Calculate the total NPV for Machine A only assuming a discount (inflation) rate of 4% for
each year of the project. Hence calculate the Internal Rate of Return (IRR) for Machine A
over the 6 year period by a graphical method.
Table B3b. Discount Factors over 6 years for various inflation/discount rates.
A4. A PVC pipe for water transport is manufactured by Company A. This extruded pipe has
a nominal outer diameter of 25 cm and the drawing specifications state that this diameter
should be 25cm ± 0.4cm. As part of a Quality Control regime, the pipe is regularly inspected
for compliance to this requirement. Inspections involve diameter measurements on sample
batches of 10 pipes. For each sample batch, the average diameter and range of diameters
are to be found.
Table QA4 gives details of the measurements for 8 successive sample batches.
Batch 10 x DIAMETER (cm)
1 24.7 25 24.7 24.9 24.9 24.8 24.9 24.9 24.6 24.9
2 25 24.9 24.9 25 25 25.1 25 24.9 24.8 24.7
3 24.6 24.6 24.7 25 24.9 24.9 25 24.7 25 25.1
4 25 24.6 24.8 25 25 24.7 24.8 25 25 24.9
5 25.4 25.5 25.4 25.5 25.6 25.5 25.7 25.7 25.6 25.4
6 25.3 25.4 25.5 25.6 25.6 25.5 25.6 25.6 25.4 25.4
7 25.6 25.7 25.6 25.7 25.6 25.6 25.4 25.3 25.2 25.6
8 25.5 25.6 25.3 25.5 25.5 25.5 25.4 25.5 25.6 25.6
Table QA4. QC data for extruded pipe.
Discount Factors for given discount (inflation) rates over a 6-year project
Years 1% 2% 3% 4% 5% 6% 7% 8% 9% 10%
1 0.9901 0.9804 0.9709 0.9615 0.9524 0.9434 0.9346 0.9259 0.9174 0.9091
2 0.9803 0.9612 0.9426 0.9246 0.9070 0.8900 0.8734 0.8573 0.8417 0.8264
3 0.9706 0.9423 0.9151 0.8890 0.8638 0.8396 0.8163 0.7938 0.7722 0.7513
4 0.9610 0.9238 0.8885 0.8548 0.8227 0.7921 0.7629 0.7350 0.7084 0.6830
5 0.9515 0.9057 0.8626 0.8219 0.7835 0.7473 0.7130 0.6806 0.6499 0.6209
6 0.9420 0.8880 0.8375 0.7903 0.7462 0.7050 0.6663 0.6302 0.5963 0.5645
For the “Average Control Chart”, the Control Limits are 25cm ± 0.2cm and the Drawing Limits
are 25cm ± 0.4cm.
For the “Range Control Chart”, the Control Limit is 5mm and the Action Limit is 8mm.
(a) Calculate (i) the average and (ii) the range for each sample batch.
(b) Plot the average and range control charts showing the appropriate limits on each.
(c) Comment on the Quality implications of the data you have analysed.
A5 The “Economies of Scale” equation may be written as:
C2 = C1 x (Q
2 / Q
where C1 is the known cost of a previous project, C2 is the cost of a new (larger) project, Q1 is
the SIZE of the first project and Q2 is the SIZE of the new project. The index, n, is a term
which governs how economies of scale apply.
If your original manufacturing project cost £1,034,564, how much would a new manufacturing
project 3 times the size cost if n = 0.6?
PART B: CES Exercises on Manufacturing
B1. Compare the manufacturing processes of (i) manual green sand casting and (ii)
gravity die casting in terms of their respective economics. The component to be
manufactured is 20cm in length and possesses a mass of 500g. It is to be manufactured from
a cast aluminium alloy of price £1.75 per kg.
Use CES (Edu Level 3) to generate plots of Cost per Unit (£) – v- Batch size (No of units
produced) for each process similar to that shown below:
Use the UPPER
bound as your line for
the basis of
helps avoid ambiguity
in data analysis and
The full set of assumptions on which you should base your plots is as follows:
Economic Factor Value
Capital Write-Off Time (yr) 5
Component Length (m) 0.2
Component Mass (kg) 0.5
Discount Rate (%) 5
Load Factor 0.5
Materials Price (£/kg) 1.75
Overhead Rate (£/hr) 75
(i) Manually extract sufficient data points from your CES-generated plots (remember to use
the UPPER line of each plot for your own data set to avoid ambiguity).
(ii) Enter the data into Excel in the following format, or similar:
Batch Size Cost per Unit (£)
Die Casting Sand Casting
1 ? ?
10 ? ?
100 ? ?
1000 ? ?
10000 ? ?
100000 ? ?
1000000 ? ?
10000000 ? ?
(iii) Using Excel, plot Cost per Unit (y-axis) -v- Batch Size (x-axis) showing both die casting
and sand casting on the same graph. Use LOG scales for both sets of axes. Label and title
all graphs appropriately.
(iv) Report on your results. Discuss the comparative economics of the two competing
processes in terms of:
(a) the SHAPE of the graph (i.e. why is it this shape?)
(b) Determine the batch size at which the cost per unit is identical for both
(c) Explain why the unit component cost is cheaper for one process at low batch
sizes while cheaper for the other process at larger batch sizes. Use as many of
the economic factors used (in the assumption table above) as necessary to help
B2. Two alternative methods of producing shafts for automotive applications are (i) hot metal
extrusion (for metal shafts) and (ii) filament winding (for fibre composite shafts).
Hot Metal Extrusion
In HOT EXTRUSION, a compressive force is applied to a metal billet to force it to flow
through a shaped die.
There are two methods: direct extrusion, in which the die is stationary and the metal is forced
through it by a moving ram. In indirect extrusion, the die itself compresses the stationary billet.
The advantage of indirect extrusion is the lower friction between the billet and the container,
resulting in lower extrusion forces, but the equipment is more complex and the product length
Hot extrusion is limited to ductile metals with room temperature hardness below 6 GPa and
melting points below 2000K. A variant of the process – hydrostatic extrusion – may be used
with brittle materials. The process is frequently subject to lower tolerances due to effects of
heat and die wear.
Better tolerances can be achieved by cold drawing as a secondary process. Steels usually
require a molten glass lubricant (Sejournet process).
Rolling is frequently more economical for suitable, simple shapes and large production runs.
In FILAMENT WINDING, axisymmetric parts are produced by winding the resin-impregnated
reinforcement (rovings or tape) on a rotating mandrel. The winding pattern could be helical,
hoop or polar depending on the application.
A multi-axis winding spindle could be used for winding more complex shapes. Winding is
continued until the desired material thickness has been achieved.
The component is pulled off the mandrel as soon as it has hardened. The high reinforcement
content of the process results in products with high strengths. The mandrel is made of either
steel or plaster.
Two candidate materials for the shaft are competing here. The metal shaft will be made using
a wrought aluminium alloy. The composite shaft will be prepared using a glass fibre /
polyester resin combination. The choice of material will determine the manufacturing process
employed (i.e. one of the above two processes).
(i) The process economics for hot metal extrusion and filament winding have been calculated
Batch Size (n) Unit Cost (£) Unit Cost (£)
Hot Metal Extrusion Filament Winding
1 10021.6 1021.7
10 1021.6 121.7
100 121.6 31.7
1000 31.6 22.7
10000 22.6 21.8
100000 21.7 21.7
1000000 21.6 21.7
10000000 21.6 21.7
Plot these data on a single set of axes (use log axes) of Unit Cost (y-axis) -v- Batch size (xaxis).
Which process would you choose for small (<1000 shafts) production runs? Which process would you choose for large (>10,000 shafts) production runs? Comment on your choices.
(ii) Your planned production run is ≥ 10,000 shafts. You have been instructed to take
environmental impact issues of your choice into account as well as the process economics.
Use the “Eco-Audit” tool in CES to compare the energy and CO
2 impacts of the 2 possible
material / process choices.
Base your environmental impact assessments on the following data.
i) A wrought aluminium alloy (Al 6061 in T4 condition). Find the alloy in CES via the
“Material Universe” route, Metals and Alloys / Non-ferrous / Aluminium / Wrought / 6000
series / 6061 / T4)
ii) A glass fibre / polyester resin composite of 75/25 w/w respective composition (find in
CES via the “Material Universe” route, Hybrids…../ Composites / Polymer Matrix / Polyester /
Unidirectional fibre / Filament wound ± 60⁰).
Use inputs to the eco-audit tool as per the following screenshots:
Generate plots of energy and CO2 impacts for each stage of the shaft life cycle.
Which shaft material/process would you select if you were seeking to minimise overall
environmental impact (HINT: look at the environmental impact situation both with and
without consideration of “End-of-Life Potential”)?
Justify your answers.