Module DMV20173

8.0 POWDER PROCESSING


9.2.3 SINTERING

1. The last process is sintering, the process after pressing, the purpose of this process

in improve strength and hardness of green compact.
2. This green compact is easily crumbled under low stress.
3. Sintering is a hear treatment operation performed on the compact to bond its metallic
particles, thereby increasing strength and hardness.

4. Since powder metallurgy application is usually involve medium to high production,
most sintering furnace are designed with mechanized flow-through capability for the
work part.
5. The process of heat treatment consists of three steps where the furnace is
segregated into three chambers according to respective process:

a. Preheat, in which the lubricants and binders are burned off.
b. Sinter.
c. Cool down.


Typical sintering temperatures and times are given for the selected metals in Table 8.1.

Table 8.1 Typical sintering temperature and times for selected powder metals.
Metal °C Time (min)

Brass 850 25
Bronze 820 15
Copper 850 25

Iron 1100 30
Stainless steel 1200 45
Tungsten 2300 480


6. In modern sintering process, the atmosphere in the furnace is controlled. The
purposes of requiring controlled atmosphere:
a. Protection from oxidation.
b. Providing a reducing atmosphere to remove existing oxides.

c. Providing a carburizing atmosphere.
d. Assisting in removing lubricants and binders used is pressing.

7. Common sintering atmosphere are inert gas, nitrogen-based, dissociated ammonia,
hydrogen, and natural gas based.

8. Vacuum atmosphere are used for certain metals, such as stainless steel and
tungsten.

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8.2.4 SECONDARY OPERATION


1. In order to further improve the properties of sintered powder metallurgy products, or

to impart special characteristic, several additional operations may be carried out after
sintering.
2. The function of secondary operation are varied, they include densification, sizing,
impregnation, infiltration, heat treatment and finishing.



Example 8.1
Describe the stages to produce compacted product using powder metallurgy

technique in a form of flow chart.



Metal Powder Blending Compaction



Example 8.2

What hazards are involved in powder metallurgy processing? Explain their causes.

Answer.

Because of their high surface area to volume ratio, metal powders can be explosive,
particularly aluminum, magnesium, titanium, zirconium and thorium. Great care must

be exercised both during blending and in storage and handling. Precautions include
(a) grounding equipment, (b) preventing sparks (by using non-sparking tools) and
avoiding friction as a source of heat, and (c) avoiding dust clouds, open flames, and

chemical reactions.


EXERCISE 8.1


1. Describe briefly the production steps involved in making powder

metallurgy parts.

2. Why blending the metal powder is essential in powder metallurgy

processing.







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9.3 PROCESSING OF CERAMIC POWDERS



1. Ceramics are compounds of metallic and nonmetallic elements.
2. Ceramics can be divided into two general categories:

(a) Traditional ceramics—ceramic materials that obtained naturally in minerals
such as clay, bauxite, shales.
(b) Industrial ceramics (also called engineering, high-tech, or fine ceramics) -
cermic materilas that obtained in chemical processing such as nitride,

carbide, alumina, zirconia, silicon.

Example 8.3:
State some applications of the traditional ceramics and engineering
ceramics?


Solution:
Traditional ceramics : Pottery, brick, tiles.
Engineering ceramics : cutting tool, automotive parts, electronic parts.


9.3.1 RAW MATERIALS


1. Raw materials for ceramics mostly are found in nature such as flint (a rock
composed of very fine-grained silica) and feldspar (a group of crystalline minerals
consisting of aluminum silicates plus potassium, calcium, or sodium).

2. Traditional raw materials used for making ceramics is clay, which has a fine-
grained sheet-like structure.
3. Categories of ceramic raw materials include:
a) From natural deposits (clay, bauxite, shales)
b) Refined industrial mineral (feldspar, kyanite, zircon)

c) Industrial chemical processing (alumina, magnesia, nitride)


Think
Some of the ceramic resources mineral in Malaysia.


9.3.2 MANUFACTURING PROCESSES OF CERAMIC MATERIALS

1. Several techniques are available for processing ceramics into useful products
depending on the type of ceramics involved and their shapes.
2. The procedure to produce ceramic product involves the following steps:

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3. Crushing or grinding the raw materials into very fine particles.

4. Mixing them with additives to impart certain desirable characteristics.
5. Shaping, drying, and firing the material.
6. Figure 8.3 shows the processing steps involved in making ceramic parts.





















Figure 8.3 Processing steps in making ceramic parts.

8.3.3 CRUSHING AND MILLING


1. Crushing and milling are the processes used to reduce the ceramic particle size
from coarse to fine particle distribution.
2. It is important because as fine particle distribution obtained, the properties of

ceramic compaction is improve in term of the density, hardness and fracture
toughness etc.
3. Common equipments to perform crushing and milling activities include jaw

crusher, rotary crusher, hammermill, crushing roller etc.(Figure 8.4).

















Figure 8.4 (a)Jaw crusher. ( b) Hammermill.










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8.3.4 ADDITIVIES


The ground particles are then mixed with additives—the functions of which are one or
more of the following:

a) Binder : for holding ceramic particles together.
b) Lubricant : to reduce internal friction between particles during moulding
and to help remove the part from the mould.
c) Wetting agent : to improve mixing.

d) Plasticizer : to make the mix more plastic and formable.
e) Agents : to control foaming and sintering.

8.3.5 FORMING AND SHAPING


1. Forming and shape processes transform the ceramic powders into a green
product.
2. Both processes involve with controlled size, surface quality, density and

microstructure.
3. Some of the major manufacturing methods to produce ceramic parts are slip
casting, extrusion, jiggering, pressing and injection moulding.
4. Table 8.2 shows he advantages and limitations of each process.


I) SLIP CASTING

1. The basic process of slip casting involves the suspension of a powder

material in a solution.
2. The powder and solution mixture (slip) are then cast into a mould .
3. The liquid then removes from the powder by capillary action or drain, leaving
the powder in the form of the mould.

4. This powder shape (green part) can then be removed from the mould and
sintered in an oven to give it strength.
5. Figure 8.5 shows the sequence of operations in slip-casting a ceramic part.


EXERCISE 8.2

State the similarities and differences between slip casting and metal casting.








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(a) (b)














(d) (c)
Figure 8.5 Sequence of operations in slip-casting (a)(b)(c)(d).


II) EXTRUSION


1. The processing of ceramic also same as the processing of powders where
it can be compacted using extrusion technique.

III) JIGGERING


1. A combination of processes is used to make ceramic plates.
2. In this process, clay slugs first are extruded and formed into a bat over a
plaster mould.
3. They then are jiggered on a rotating mould.

4. Jiggering is a motion in which the clay bat is formed by means of templates
or rollers. The part then is dried and fired.
5. The jiggering process is confined to axisymmetric parts and has limited
dimensional accuracy.
6. The operation is automated for improved productivity.Extrusion

7. Fig 8.6 (a) shows Extruding and (b) jiggering operations.









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Figure 8.6 (a) Extruding and (b) jiggering operations.


Example 8.4

What is jiggering? What shape does it produce?


Solution:
Fine size particles Jiggering is a proses of shaping with rotating mould rolls
on the surface of ceramic compacts.


IV) PRESSING

Pressing is a process where ceramic compacts may be subjected to a

pressure in order to achieve uniform compaction and density. Some of the
pressing processes in ceramic manufacturing are dry pressing, hot pressing,
wet pressing and isostatic pressing.


a) Dry Pressing
i. Dry pressing is used for relatively simple shapes, such as whiteware,
refractories for furnaces, and abrasive products.

ii. Density can vary significantly in dry-pressed ceramics (as in P/M
compaction) because of friction among the particles and at the mould walls.

b) Hot pressing
i. In this process (also called pressure sintering), the pressure and the heat

are applied simultaneously.
ii. This method reduces porosity and, thus, makes the part denser and

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stronger.

iii. Graphite commonly is used as a punch and die material, and protective
atmospheres usually are employed during pressing.


c) Wet Pressing
i. In wet pressing, the part is formed in a mould while under high pressure in a
hydraulic or mechanical press.
ii. This process generally is used to make intricate shapes. Moisture content
usually ranges from 10 to 15%.

iii. Production rates are high; however, (a) part size is limited, (b) dimensional
control is difficult to achieve because of shrinkage during drying, and (c)
tooling costs can be high.


d) Isotatic Pressing
i. Isostatic pressing also is used for ceramics in order to obtain uniform
density distribution throughout the part during compaction.
ii. Used extensively in powder metallurgy.


EXERCISE 8.3

Explain the characteristics of particle powders which produce a high density
product.



V) INJECTION MOULDING


1. Injection moulding is used extensively for the precision forming of ceramics
in high-technology applications, such as for rocket-engine components.
2. The raw material is mixed with a binder, such as a thermoplastic polymer
(polypropylene, polyethylene or ethylene vinyl acetate) or wax.

3. The binder usually is removed by pyrolysis (inducing chemical changes by
heat).
4. The part then is sintered by firing.








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Table 8.2 Advantages and limitations of each process

Process Advantages Limitations
Slip casting Large parts Low production rate
Complex shapes Limited dimensional accuracy

Low equipment cost
Extrusion Hollow shapes and small diameters Parts have constant cross-section
High production rate Limited thickness
Dry pressing Close tolerances Density variation in parts with high

High production rates [with length-to-diameter ratios
automation) Dies require abrasive-wear
resistance
Equipment can be costly

Wet Complex shapes Limited part size and dimensional
pressing High production rate accuracy
Tooling costs can be high
Hot Strong Protective atmospheres

pressing High-density parts required
Short die life
Isostatic Uniform density distribution Equipment can be costly
pressing

Jiggering High production rate with Limited to antisymmetric parts
automation Llimited dimensional accuracy
Low tooling cost
Injection Complex shapes Tooling can be costly

moulding High production rate


8.3.6 DRYING


I) GREEN MACHINING

1. The final shape of ceramic product cannot always be achieved by the

original shaping processes.
2. It is often obtained by secondary operations before the sintering process
that is Green machining process.
3. Green machining refers to shaping operations of the dried unfired ceramic
product. Due to the lower strength in green ceramic product, refinement of




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ceramic shapes are applicable where higher rates of material removal can

be achieved.
4. Some of the operations involve in Green machining are machining, milling,
sanding, grinding and jiggering.


II) FIRING AND SINTERING OF CERAMICS

1. Drying is a critical stage because of the tendency for the part to warp or

crack from variations in the moisture content and in the thickness of the
part.
2. Control of atmospheric humidity and of ambient temperature is important in
order to reduce warping and cracking.

3. Firing (also called sintering) involves heating the part to an elevated
temperature in a controlled environment.
4. Some shrinkage occurs during firing.
5. Firing gives the ceramic part its strength and hardness. This improvement
in properties results from:

a) the development of a strong bond between particles in the ceramic;
b) reduced porosity.
6. Figure 8.7 shows the mechanism of shrinkage of wet clay caused by the
removal of water during drying.

7. Figure 8.8 shows shrinkage of ceramic product from green body to
sintered body.














Figure 8.7 Shrinkage of wet clay caused by the removal of water during

drying.











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(a) (b)
Figure 8.8 Shrinkage of ceramic product from (a) green body to (b) sintered body


Example 8.5:
What is the disadvantage of shaping operations after sintering process.
Solution:
Ceramic product becomes refractory after sintering process. Thus, it is very hard to
reshape the product.



8.3.7 FINISHING OPERATIONS


1. In order to produce near net shape product and enhance material
properties, post processing operations is employed to eliminate
unnecessary voids.
2. Process selection is an important consideration because of the brittle

nature of most ceramics and the additional costs involved in some of these
processes.
3. The finishing processes employed can be one or more of the following
operations:
a) Grinding (using a diamond wheel)

b) Lapping and honing
c) Ultrasonic machining
d) Drilling (by using a diamond-coated drill)
e) Electrical-discharge machining

f) Laser-beam machining
g) Abrasive water-jet cutting
h) Tumbling (to remove sharp edges and grinding marks)








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SUMMARY



In this chapter we have studied that :


1. powder processes is a net-shape forming process consisting of producing metal
powders, blending them, compacting them in dies, and sintering them to impart
strength, hardness, and toughness;
2. the powder processes is capable of producing relatively complex parts

economically, in net-shape form, to close dimensional tolerances, and from a wide
variety of metal and alloy powders;
3. secondary and finishing operations may be performed on powder processes parts
to improve their dimensional accuracy, surface finish, mechanical and physical
properties, and appearance;

4. ceramics are particularly attractive for applications such as heat-engine
components, cutting tools, and components requiring resistance against wear and
corrosion;
5. ceramic processing generally started with crushing and milling of raw materials

and mixed with additive materials to enhance powder characteristics;
6. the next important processes are shaping and forming which involve with slip
casting, extrusion, pressing and injection moulding;
7. after drying, green machining applied to form desired ceramic shape before

sintered at elevated temperature;
8. ceramic processing subsequently may be subjected to further processing to
produce the final desired shapes.


REFERENCES



1. S. Kalpakjian, S.R. Schmid, Manufacturing Engineering and Technology 5 edition,
th
Prentice Hall, 2005.
2. Reed James, Principles of Ceramic Processing











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ANSWERS


EXERCISE 2.1


A 200-mm-long, 20-mm-diameter 304 cast irons rod is being reduced in diameter to
15.00 mm by turning on a lathe. The spindle rotates at N = 500 rpm, and the tool is
traveling at an axial speed of 100 mm/min. Calculate the cutting speed, material-
removal rate, cutting time, power dissipated, and cutting force.


Cutting speed:
V= πDN = π (20/1000)(500) = 31.42 m/min
Material Removal Rate:
d = (20-15)/2 = 2.5 mm

f = 100/500 = 0.2 mm/rev
3
MRR = π (17.5)(2.5)(0.2)(500) = 13744.47 m /min
Cutting Time:
t = 200/[(0.2)(500)] = 2 s
Power dissipated:

p = (5.4)(1924)/60 = 173W [Table 2.1, cast iron 5.4 Ws/mm ]
3
Cutting Force:
Torque, T = 173 x 60/[(500)(2)( π)] = 3.3 Nm
Force, F = 3.3 (1000)/(17.5/2) = 377 N


EXERCISE 2.2

Name two basic categories of cutting tools in machining.
Give two examples of machining operations that use each of the tooling types.


Answer: The two categories are:
(1) single-point tools, used in operations such as turning and boring;

(2) multiple-edge cutting tools, used in operations such as milling and drilling.

EXERCISE 2.3


Identify five principal parameters of a grinding wheel?


Answer: The parameters are (1) abrasive material, (2) grit size, (3) bonding material,
(4) wheel structure, which refers to the relative spacing of grains, and (5) wheel
grade, which refers to the bond strength of the wheel in retaining abrasive grains.

EXERCISE 2.4


List four abrasive materials used in grinding wheels?

Answer: The principal abrasive grit materials include:

(1) aluminum oxide;
(2) silicon carbide;
(3) cubic boron nitride;
(4) diamond.


EXERCISE 2.5

Identify three basic categories of material removal processes.


Three basic categories of material removal processes are:
(1) conventional machining;
(2) abrasive processes;
(3) nontraditional processes.


EXERCISE 3.1

Describe the process of sand casting.
1. Preparation of sand mould.
2. Melting of metal at elevated temperature.

3. Molten metal poured into a mould.
4. Solidification and Cooling in a mould.
5. Removal of mould to obtain casting product.
6. Cleaning and finishing.

EXERCISE 3.2


If you need only a few units of a particular casting, which process would you
use? Why?


More than one answers:
Sand casting: almost any metal cast, no limit to size, shape, weight and low tooling
cost.
Investment casting: Intricate part shape, excellent surface finish and accuracy, almost

any metal cast.

EXERCISE 4.1


Describe the cutting process that takes place when a pair of scissors cuts through
aluminium foil.

Solution:
Scissors cut by a shearing process. The material is subjected to shear stresses at

the intersection of the two blades of the scissors. Because shearing takes place in a
small localized region, low forces are required to cut with scissors. The shearing
process involves surface cracks propagating through the material until separation
occurs.


EXERCISE 4.2

Explain why cupping tests may not predict well the formability of sheet metals in
actual forming processes.


Solution:
The difficulty with cupping tests is that deformations are axisymmetric, that is, they

are the same in all directions. Sheet-metal forming operations, on the other hand,
rarely take place in an axisymmetric state of strain. However, cupping tests are easy
to perform on the shop floor and will give some approximate indication of formability.

EXERCISE 4.3


Identify the factors that influence the deep-drawing force, F, in Figure 4, and explain
why they do.
















Figure 4: Deep drawing

Solution:
The blank diameter because the larger the diameter, the greater the circumference,
and therefore the greater the volume of material to be deformed. The clearance, c,

between the punch and die directly affects the force because at smaller clearances,
ironing begins to take place, thus increasing the force. Blank thickness also
increases the area of the volume deformed. The blank holder force and friction affect

the punch force because they restrict the flow of the material into the die.



EXERCISE 4.4


Please explain why the drawability of a material is higher in the hydroform process
than in the deep-drawing process?


Solution:
The hydroform process the inner surface of the cup being formed is pressed against
the cylindrical surface of the punch by the pressure in the forming chamber. This
situation allows the cup to move with the punch, whereby the tensile stresses (that
could eventually lead to cup tearing) are reduced due to the friction between the cup

and the punch.

EXERCISE 4.5


Many axisymmetric missile bodies are made by spinning. What other methods could
you use if spinning processes were not available?


Solution:
Missile components which are spun usually have large cross-sections. Some of
these parts could be made by explosive forming or welding of a number of smaller
rolled and stamped pieces. Smaller components could possibly be forged or formed

by stretch forming.

EXERCISE 5.1


Namely four typical defects in flat rolling.

Solution:
i) Wavy edges.
ii) Zipper cracks.

iii) Edge cracks.
iv) Alligatoring.

EXERCISE 5.2


In impression-die forging, during deformation, some of the material flows outward
and forms a flash. Explain the functions of flash in impression-die forging.

Solution:

Functions of flash in impression die forging:
1. High pressure and high frictional resistance in the flash, present a severe
constraint to the material in the die for outward flow.

2. Based on the plastic deformation principle, material flow in direction of
least resistance.
3. Therefore the material begins to flow into the die cavity and filling it
completely.

EXERCISE 5.3


Identify the factors that control the efficiency of metal extrusion.


1. The type of extrusion.
2. The extrusion ratio.
3. The working temperature.
4. The speed of deformation.
5. The frictional condition.


EXERCISE 6.1

Describe the characteristics of Gas Tungsten Arc Welding (GTAW).

Process characteristic:
 Uses non-consumable tungsten electrode.
 Used shielding gases (Ar, He or CO2).
 Produce very high quality welds.

 No slag or spatter.
 Applicable to thin material.


EXERCISE 6.2

Brazing is widely used in industries because of its many advantages.
Describe any five (5) advantages.


Solution:
1. Dissimilar metals, such as stainless steel to cast iron can be joined by
brazing.
2. Because of lower temperature used, there is less distortion in brazed joint.

3. Because of the simplicity of the process, the joint can be quickly finished
without much skill.
4. The braze joint are reasonable stronger, depending on the strength of the
filler metal used.

5. Since the filler metal reached the joint by capillary action, it is important that
the joint is designed properly; the clearance between two parts should be
critically controlled.

6. The surface to be joint also must be cleaned. Any grease or oil present in the

joint prevents the flow of filler metal.

EXERCISE 6.3


List six (6) advantages of welding process compare to riveting.

Solution:

a) Welding is usually a cheaper process than riveting for any particular joint, and
the joint can often be made much more quickly.
b) Weld seams are normally pressure tight, and do not need caulking as do
riveted joints. Joints are smooth, which is important in many applications. For

example, painting is much easier on welded joints, and turbulence in pipes is
reduced.
c) Designs not practicable for riveting may be constructed by welding.
d) Plate preparation for welding is generally cheaper than for riveting.

e) Labour necessary can often be cut to less than one- third of that necessary
for riveting.
f) Welding is not as noisy as riveting, and permits building and alterations to
proceed with the least disturbance to occupants.


EXERCISE 7.1

An injection-molding machine is divided into two principal components; identify them.
Answer: The components of an injection-molding machine are (1) the injection unit

and (2) the clamping unit.

What are the two basic types of clamping units?
Answer: The clamping units are: (1) mechanical toggle clamp and (2) hydraulic. In

addition, there are hydromechanical units which combine hydraulic and mechanical
actuations.

EXERCISE 7.2


What are the functions of gates in injection molds?


Answer: The functions of gates in an injection mold are (1) to increase shear rate to
increase viscosity and temperature of the polymer melt, (2) the thinner cross section
of the gate freezes more rapidly to seal off the cavity; and (3) parts can be more
easily broken off the runner at the gate.


EXERCISE 7.3

A. _A granular form of plastic powder (polystyrene, nylon, _polypropylene/pvc/etc_
and polythene) are poured or fed into a hopper which stores it until it is needed.

B. The heater is turned on. This warms up and melts the granular plastic. A _motor__
turns a screw thread which pushes the granules along the heater section causing it to
change to a plastic liquid.
C. The liquid plastic is forced into a mould by _screw __.
D. _Pressured_ air is ‘blown’ into the mould. This forces the liquid plastic against the

sides of the _mould_. In this example it forms the shape of a plastic _bottle_.
E. The plastic is allowed to _cooled / solidify_ and the mould is ‘opened_’ and the
plastic bottle removed. The entire process is _repeating_ hundreds or thousands of
times.


EXERCISE 8.1

A typical alloy whose melting point = 500 °C is to be machined using EDM process.
3
If the MRR is 574.709 mm /min, what is the approximate value for the discharged
current used in the process?

4 -1.23
MRR = 4 x 10 ITw

574.709 mm /min = 4 x 10 x I x 500 -1.23
4
3

I = 574.709 mm /min / (4 x 10 4 x 500 -1.23 )
3


I = 30 amps

Describe some advantages of electrical-discharge machining.


With increasing strength and toughness and various other properties of advanced
engineering materials, there was a need to develop processes that were not sensitive

to these properties.

Because EDM basically involves electrical properties and is capable of removing
material in a variety of configurations, it was one of the most important developments
and continues to do so. As in all other processes, it has its advantages as well as

limitations, regarding particularly the material-removal rate and possible surface
damage which could significantly reduce fatigue life.

EXERCISE 8.2


A wire EDM operation is used to cut out die components from 25 mm thick tool steel
plates. However, initial cut give the poor surface finish on the cut edge. What
changes in discharge current and frequency of discharges should be made to
improve the finish?


 Increased Current.
 Increased Frequency.


EXERCISE 8.3

Describe two (2) advantages to use of Laser Beam Machining as compared to
conventional machining.


i. The laser beam is easy to manipulate with computer-controlled machinery,
allowing intricate patterns to be easily programmed.
ii. The laser beam can be focused precisely and it restricts material removal to

sub millimetre depth.
iii. The marking process does not require hard tooling, or any preparation and
subsequent cleaning.
iv. Since marking only requires a very shallow depth of cut, low-powered lasers
are capable of marking most materials, making this approach very cost-

effective.

EXERCISE 8.4


Explain clearly the working principles of Abrasive Jet Machining.


The working principles of Abrasive Jet Machining (AJM);
- In abrasive-jet machining (AJM), a high-velocity jet of dry air, nitrogen,
or carbon dioxide containing abrasive particles is aimed at the
workpiece surface under controlled conditions.
- The material removal takes places due to the important of the fine

abrasive particles.
- These particles move with a high speed air stream.

EXERCISE 8.5


Explain clearly the working principles of Ultrasonic Machining. Use sketches to
support your answer.


Principle of Ultrasonic Machining:


 Tool is hammering the abrasive particles.
 The impact of the abrasive particles which move freely.
 Cavitation Erosion of abrasive slurry.
 Chemical Erosion.

EXERCISE 9.1


1. Describe briefly the production steps involved in making powder metallurgy parts.


Answer:
The powder metallurgy process consists of the following operations in sequence,
which begins with the powder production, blending, compaction, sintering and
finishing operations.
Pressing

Isostatic pressing
Atomization Rolling Atmosphere

Reduction Extrusion

Electrolytic deposition

Carbonyls Cold Sintering
compaction

Metal Blending Secondary

powders and finishing
Hot
compaction
Additive Coining
Lubricant
Isostatic pressing Forging
Machining
Heat treating
Impregnation


2. Why blending the metal powder is essential in powder metallurgy processing?

Answer:
Blending the metal powder is essential in powder metallurgy processing in order to

impart special physical and mechanical properties and characteristics to the powder
metallurgy product. Proper mixing is essential to ensure the uniformity of mechanical
properties throughout the part.

EXERCISE 9.2


State the similarities in slip casting and metal casting and differences between slip
casting and metal casting.


Solution:
Similarities:
Materials poured into a mould.
Influence by fluidity properties of materials.

Differences:
Metal casting used in high temperature.
In metal casting, product can be used as the molten metal solidified.


EXERCISE 9.3

What are the powders characteristics which produce a high density product


Solution:

 Fine size particles.

 Uniform particle size distribution.
 Homogenity particles distribution.



EXERCISE 10.1


A 100 mild steel parts fabricated with RM 160 cost of materials and RM 200 cost of
direct labor. The overhead cost of the production is 35% of the total amount of
materials cost and direct labor cost. The fixed costs is 20% from overall cost. From

the information given, calculate:
a) overall cost;
b) if the management increased 10% of the total cost as a price per unit product,
calculate the overall costs.


Solution:

a) Overall cost = (Cost of Materials + Cost of direct labor + 35% of over head cost) +

20 % of (overall cost)

: 160 + 200 + 35/100(160 + 200) = RM 486.00
: 486 + 20/100 (486) = RM 583.20


b) If 10% increment of sale per unit:

10/100(583.20) + 583.20 = RM 641.52


EXERCISE 10.2


300 mild steel parts fabricated with RM 3000 cost of materials and RM 800 cost of
direct labor. The overhead cost of the production is 45% of the total amount of
materials cost and direct labor cost. The fixed costs is 40% from overall cost. From
the information given, calculate:
a) overall cost;

b) if the management increased 5% of the total cost as a price per unit product,
calculate the overall costs.

Solution:


a) Overall cost = (Cost of Materials + Cost of direct labor + 45% of over head cost) +
40 % of (overall cost)


: 3000 + 800 + 45/100(3000 + 800) = RM 5510
: 5510 + 40/100 (5510) = RM 7714

b) If 5% increment of sale per unit:


5/100(7714) + 7714 = RM 8099.70

EXERCISE 10.3


The ANW Company produces metal plates and fasteners. Lists below showed their
costs of business.

Type Amount (RM)
Building rent 10,000 / month

Machineries 100,000
Raw Materials - steel 5000 / month

Raw Materials - copper 5000 / month
Raw Materials - aluminum 5000 / month
Raw Materials - copper 5000 / month
Salary of administration staff 20,000 / month

Management expenses 5000 / month
Salary of technical staff 15,000 / month
Water bill 1000 / month

Telephone bill 1000 / month

From the information given, find:
a) Labour cost.

b) Materials cost.
c) Overhead cost.
d) Manufacturing cost.

e) Overall cost.

Solution:

a) Labour cost = Salary of administration staff + Salary of technical staff

= 20000 + 15000 = RM 35,000.

b) Materials cost = Raw Materials (steel) + Raw Materials (copper) + Raw
Materials(Aluminum) + Raw Materials (copper)

= 5000 + 5000 + 5000 + 5000 = RM 20,000

c) Overhead cost = Water bill + Telephone

= RM1000 + RM 1000
= RM 2000


d) Manufacturing cost = Materials cost + Labour cost
= RM 35,000 + RM 20,000
= RM 55,000

e) Overall cost = Labour cost + Materials cost + Overhead cost


= RM 35,000 + RM 20,000 + RM 2000
= RM 57,000