Improving BSO Services and
SME Performance Through
Cleaner Production
[SPEAKERS NAMES]
[DATE]
Module 3:
A closer look at the
Cleaner Production process
CASE
STUDY
“Midland Metals”
Enterprise Profile:
country
sector
ownership
Zimbabwe
Foundry
Family-owned
established 1998
employees 16
revenue
US $65,000
Based on case study created by the United National Environment
Program, Division of Technology, Industry and Economics
Improving MSME Performance through Cleaner Production.
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4
Background: What is a Foundry?
Midland Metals
CASE STUDY
A foundry is:
a factory that pours molten metal into
molds, producing cast metal objects.
 Casting is one of the oldest industrial processes
 There are different casting processes.
The focus here is: “GREEN SAND” CASTING
Some
typical
cast metal
objects:
Aluminum
pots
“low tech”
Improving MSME Performance through Cleaner Production.
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Engine blocks,
axles
Turbine blades
in jet engines
“high tech”
5
Background: SAND-CASTING
Midland Metals
CASE STUDY
Basic materials & equipment for green sand-casting
Pattern
(a copy of the shape
you want to produce,
made of wood, plastic
or metal)
Sand,
mixed with clay binder &
water (so it will hold its
shape) plus coal dust to
improve surface finish
Container of molten
(filled from furnace)
metal
Top and bottom mold forms
(made of metal, open at top and bottom)
Rammer (tool to compact the sand;
often a pressing machine is used)
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6
Background: SAND-CASTING
Midland Metals
CASE STUDY
A very basic summary of the sand casting process. . .
First of all,
mix the sand.
THEN
1
MOLDING:
Sand placed
into bottom
mold form &
compacted
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2 MOLDING:
Pattern placed into mold
7
Background: SAND-CASTING
MOLDING:
Midland Metals
CASE STUDY
A tube or pipe
provides a path to
pour the metal in
3 Add the top
mold form
Pattern is still inside!
4
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MOLDING: Fill top form
with compacted sand.
8
Background: SAND-CASTING
5
In the middle of the
sand is a cavity
shaped like the
pattern!
MOLDING:
Take the top
mold off and
remove pattern
& pipe or post
Pouring
hole
6
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Midland Metals
CASE STUDY
MOLDING: Replace the
top mold and fasten
securely!
9
 Background: SAND-CASTING
8
7
CASTING:
Pour the metal (container is
filled from furnace immediately
before you are ready to pour)
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Midland Metals
CASE STUDY
Wait for the metal to cool
(minutes to days,
depending on the size of
the casting)
10
Midland Metals
CASE STUDY
Background: SAND-CASTING
A copy of the
pattern has now
been made in metal
9
CLEANING. Sand is
cleaned off the part, the
“tab” where metal flowed
in must be removed.
8
SHAKE OUT: Break apart the two
halves of the mold & take out the
part—usually requires vibrating or
striking the mold to break apart
the sand
Improving MSME Performance through Cleaner Production.
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10 Mold forms are reused
Sand is broken up,
11 screened to remove
debris and clumps, and
sent for remixing
11
Background: SAND-CASTING
Midland Metals
CASE STUDY
Sand-casting is
simple in concept, but
demanding in
execution. It is a
process essential to
making basic and
advanced products. . .
it is also hazardous
and energy-intensive!
Improving MSME Performance through Cleaner Production.
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12
Midland Metals
Enterprise Profile, cont’d:
products
Production
volume
Markets
Midland Metals
CASE STUDY
Iron mill balls &
crushing hammers
(used for crushing ore)
25 tons/month
(planning 10-fold expansion)
Mining sector
3-15cm
(mill balls)
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13
Midland Metals
CASE STUDY
Foundry process map
Sand (new/old),
bentonite*, coal dust,
water, energy
Sand mixing
area
Dust, gases, noise,
reject mixed sand,
surplus sand
Patterns, mold forms,
sand filling, coatings,
energy
Molding
Molding Section
section
Dust, gases, surplus
sand, noise, rejected
molds
liquid metal
Casting area
Energy
Shake-out &
Cleaning area
INPUTS
Improving MSME Performance through Cleaner Production.
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Finished
products
Gases, organic fumes
Dust, gases, mold
forms, used sand
Non-Product
OUTPUTS
*Bentonite is a mineral clay. It
forms a binding agent when
mixed with water.
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Initial CP assessment findings
Midland Metals
CASE STUDY
1. Sand contains significant amount of dust
2. Wind blows sand and dust from stock piles
3. Workers estimate quantities for sand binder and hardener
4. Energy consumption of furnaces higher than normal for
similar operations
5. Furnace tap-hole not well sealed after use
6. Liquid metal spills during filling of molds
7. Large number of rejects
8. Sand is lost in each cycle
9. Sand mixing and reclamation very labor intensive
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15
Material balance for sand mixing
INPUTS
OUTPUTS
Energy
- Electricity = 6 MWh
Raw materials
- New sand = 135 t
- Old sand = 540 t
- Coal dust = 55 t
- Bentonite = 55 t
- Water = 40,320 litres
!
only 75% reclamation
efficiency (25% of
sand in each batch is
lost.)
Midland Metals
CASE STUDY
Emissions to the
atmosphere
- Dust = 30 t
SAND
MIXING
PROCESS
(mostly
manual)
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Waste
- Used sand = 105 t
Products
- Moulds and cores
= 672 tonnes
Annual
figures
16
Sand Mixing: Raw materials costs
Input
Midland Metals
CASE STUDY
Quantity
per 50 kg
batch (kg)
Annual quantity*
(kg)
New Sand
10
134,400
0.02
2,677
Old Sand
40
537,600
-
-
Bentonite
4
53,760
0.17
9,027
Coal Dust
4
53,760
0.07
3,673
3 litres
40,320 litres
0.02
840
Total
16,217
Water
Unit cost
(US$/kg)
Annual
Total cost
(US$)
(*56 batches/day x 240 days/yr)
!
New sand = 17% of
raw material costs
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17
Biggest CP opportunities
 Waste of raw material (sand)
 During mixing stage
 Spillage
 Dust
Midland Metals
CASE STUDY
loss = 2000 kg
! 25%
sand per ton product
 Inefficient use of labor
 Manual sand mixing
 Manual screening for sand
reclamation
 RESULT:
4 man-hours required
to mix 1 batch
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18
Rapid payback CP opportunities
Midland Metals
CASE STUDY
Annual savings
(US$)

Good
housekeeping
Cover the new sand
Implement more thorough
inspection, segregation of incoming scrap
278
116

Input
substitution
Use sand with low dust content
232

Better process
control
Optimize furnace-melting conditions
Train workers to properly handle
and measure sand binder & hardner
139

Equipment
modification
Improvise proper closing mechanism
for furnace taphole
Install goods spouts on melting pots
Total annual savings:
Improving MSME Performance through Cleaner Production.
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185
28
28
$1005
19
Capital investment CP opportunity:
Mechanical sand reclamation/mixing
Midland Metals
CASE STUDY
Old system:
Manual sand
reclamation & mixing
Molds
shaken out
Shaker table
with Screen
Conveyor
Belt
New system:
Mechanical
sand
reclamation
plant
Hopper
(Removes
lumps)
(Transports
sand)
(Feeds sand
to mixer)
Mechanical
Sand Mixer
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Roller sand mixer +
accessories + shipment
$8,106
Sand shaker
$3,706
Sand screen below the shaker
$347
2 x 5 kW motor
$926
10 m conveyor belt
$694
Other construction material
$463
Sand storage hopper
$1,158
Installation costs
$810
Contingencies
$1,621
TOTAL INVESTMENT COST
$17,833
20
NEW sand mixing
material balance
Midland Metals
CASE STUDY
INPUTS
OUTPUTS
Energy
- Electricity=24MWh
Increase from
6 MWh
Raw materials
- New sand = 65 t
was - Old sand = 610 t
135 t - Coal dust = 55 t
- Bentonite = 55 t
- Water = 40,320 litres
Emissions to the
atmosphere
- Dust = 15 t
SAND
MIXING
process
Waste
- Used sand = 50 t
was 30 t
was
105 t
(mechanized)
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Products
- Moulds and cores
= 672 tonnes
21
Profitability analysis:
Mechanical sand reclamation/mixing
INVESTMENT COST
Vs.
$17,833
Midland Metals
CASE STUDY
SAVINGS (annual)
31.25% saving on labor
$3,543
24% saving on raw
materials
$8,351
Lower overall
operating costs*
$2,630
*even with increase in electricity costs
Total net savings (per year)
ANALYSIS
Payback Period
Net Present Value (@20%, 5 years)
Internal Rate of Return
Improving MSME Performance through Cleaner Production.
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$14,525
<2 years
$25,606
77%
22
Benefits of Cleaner Production
Midland Metals
CASE STUDY
1. Improved Profitability
•
Raw material saving of 25%
•
Labour costs cut by 30%
•
Reduced plant and equipment maintenance costs
2. Improved product quality
3. 5 to 7 fold increase in production levels
(pieces/per day), so total profits increase 5 to 7
fold as well
4. Reduced environmental impact
Improving MSME Performance through Cleaner Production.
Module 3: A Closer Look at CP. Visit www.encapafrica.org.
23