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Technologies
Making the most of modern casting technology
Modern casting technology offers a wealth of possibilities. Keeping these in mind right from the design stage makes it possible to achieve the full benefits that casting offers. In principle, any details can be cast, but you can achieve great savings by using a design that is geared to casting. That’s why it is at the design stage, before the details have been finalized, that we have the greatest opportunities to influence the production costs relating to these details. Sperre Støperi AS has its own design division, which can help you work out optimal details for the design. It can also recommend the casting method that will result in the most competitive price. The table below shows the possibilities and limitations of the various casting methods. The tolerance requirement is the key factor for determining the casting method.
The standard specifying tolerances for castings is NS ISO 8062.
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Casting in sand mould |
Ceramic mould |
Permanent mould |
| Method |
Hand moulding |
Machine
moulding |
Shell
moulding |
Evaporative
moulding |
Lost-wax method |
Gravity die
casting |
Pressure die
casting |
Green
sand |
Chemically
bounded
sand |
Casting
alloy |
All |
All |
All |
All |
All |
All |
All |
Al, Mg, Zn and Cu alloys |
Pattern
material |
Wood, plastic, metal |
Wood, plastic, metal |
Plastic, metal |
Metal |
Expanded
polystyrene |
Wax |
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Mould
material |
Clay-bounded sand |
Chemically
bounded sand |
Clay-bounded sand |
Resin and Sand |
Bounded or unbounded sand |
Ceramic mould |
Cast iron, steel |
Special steel for tools |
| Size range |
No limit |
No limit |
Depends on moulding maschine |
Up to 75 kg |
No limit |
Up to 100 kg |
Up to 100 kg |
Usually 5 kg |
| Batch size |
Individual pieces,
small batches |
Individual pieces,
small batches |
Medium to large batches |
Large batches |
Individual pieces,
small batches |
Large batches |
Large batches |
Very large batches |
Tolerance
[% of nominal
dimension] |
Approx. 1.5% |
Approx. 1% |
Approx. 1% |
Approx. 0.5% |
Approx. 1-1.5% |
Approx. 0.5% |
Approx. 0.5% |
Approx. 0.3% |
| Surface roughness Ra- [m] |
12 - 125 |
12 - 125 |
12 - 125 |
3 - 125 |
12 - 120 |
2 - 6 |
3 - 80 |
1 - 30 |
| Labour costs |
Average |
Average |
Low |
Low |
Average |
High |
Low |
Very low |
| Mould costs |
Low |
Average |
Low |
Average |
Low |
High |
Average |
High |
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Casting methods at Sperre Støperi AS
| Alloys |
| Moulding method |
Grey cast iron |
Ductile iron |
Aluminium |
Copper |
Machine moulding
Hand moulding
Gravity die casting
Low-pressure die casting |
x
x
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x
x |
x
x
x
x |
x |
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Casting in sand moulds
We focus on casting using sand moulds, but we also offer gravity die casting and low-pressure casting. Casting in sand moulds is still the most common method that foundries use. Sand-mould casting has many applications, and can be used for casting both small and large details, individual items or large batches. Sand casting uses a number of moulding methods: hand moulding, machine moulding, shell moulding and vacuum moulding.
Sperre Støperi AS offers machine and hand moulding of iron, aluminium, and copper alloys. Both of our machine moulding lines are based on green-sand moulding, while our hand-moulding divisions are based on chemically bonded sand - furan in the ferrous foundry and alphaset in the non-ferrous foundry.
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Gravity die casting
Sperre Støperi AS has its own gravity die-casting foundry. The main product is aluminium pistons for Sperre's reciprocating compressors. Die casting uses permanent moulds, usually made of grey cast iron. The cores may be made of sand (coldbox), iron or steel.
In light-metal casting, the lifetime of a mould may be 50,000 castings.
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Low-pressure casting
Low-pressure casting is a variant of die casting, where the metal is pressed with a slight overpressure (0.2-1 bar) from a sealed crucible through a riser and up into the mould. Sperre Støperi has equipment for low-pressure casting of light metals, and produces details for high-precision products such as reels for sea angling and pumps.
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Ferrous foundry
We have a highly rationalized machine moulding line (GF Impact Moulding) and a mechanized line for hand moulding (furan).
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Box size |
Weight of casting |
Batch size |
Capacity/year |
| Machine moulding |
600x700x300/300 |
1-150 kg |
10-10 000 |
8 000 tonnes |
| Hand moulding |
Various sizes |
100-2000 kg |
1-500 |
4 000 tonnes |
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Non-ferrous foundry
As well as die casting (gravity and low-pressure) we have two moulding lines - a machine-moulding line (GF Impact Moulding) and a hand-moulding line (alphaset).
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Box size |
Weight of casting |
Batch size |
Capacity/year |
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Aluminium |
Copper |
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| Machine moulding |
650x850x250/250 |
1-50 kg |
1-150 kg |
10-10 000 |
1 500 tonnes |
| Hand moulding |
Various sizes |
1-250 kg |
1-500 kg |
1-500 |
500 tonnes |
| Gravity die casting |
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1-30 kg |
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1-10 000 |
100 tonnes |
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Other divisions
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Core production
We have a well-equipped core-making plant with 11 core-shooting machines, both manual and automatic, in sizes from 2.5 L to 40 L. The cores are manufactured using a coldbox process and furan sand. This is one of our most important business areas.
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Smelting
Our smelting facilities consist of two 5-tonne induction furnaces of low frequency and a new 4-tonne medium-frequency furnace. The melting capacity is about 12,000 tonnes per year. Metal is melted in oil-fired furnaces as well as electrical resistance and induction furnaces with a smelting capacity of 2,000 tonnes per year.
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Finishing and machining
The company has two highly effective finishing divisions, with modern equipment for steel shotblasting, grinding, deburring, machining and heat treatment. Our facilities are new and modern, and we focus on optimal production flow, a good working environment and ergonomically designed workplaces. The finishing division includes sections for shotblasting, grinding, machining, heat treatment, surface treatment including dip coating and two-part coating, quality assurance and packing. In addition to the machining of cast components that we do ourselves, we also have a number of external business partners.
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Laboratory
Sperre Støperi AS has its own operating laboratory for process and product quality assurance, with equipment for chemical and physical tests: tensile-strength testing machine, spectrometers, penetrant, Sonatest, ultrasound, and Brinell hardness testing, as well as dimension checking.
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Casting tolerances
The accuracy of the measurements for a cast part depends on various production factors. The tolerances that can be achieved using various casting methods are specified in the NS_ISO 8065 standard. The standard is divided up into tables for
a) large batches and mass production in which development, adjustment and maintenance of casting equipment make it possible to achieve close tolerances.
b) small batches and individual castings.
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Table1 Tolerances for castings
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Basic dimensions of casting |
Total tolerance for castings |
| over |
up to and including |
CT tolerance for castings |
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1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
11 |
12 |
13 |
14 |
15 |
16 |
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-
10 |
10
16 |
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0.18
0.20 |
0.25
0.26 |
0.36
0.38 |
0.52
0.54 |
0.74
0.78 |
1.0
1.1 |
1.5
1.6 |
2.0
2.2 |
2.8
3.0 |
4,2
4,4 |
-
- |
-
- |
-
- |
-
- |
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16
25
40 |
25
40
63 |
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0.22
0,24
0,26 |
0,30
0,32
0,36 |
0,42
0,46
0,50 |
0,58
0,64
0,70 |
0,82
0,90
1,0 |
1,2
1,3
1,4 |
1,7
1,8
2,0 |
2,4
2,6
2,8 |
3,2
3,6
4,0 |
4,6
5,0
5,6 |
6
7
8 |
8
9
10 |
10
11
12 |
12
14
16 |
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63
100
160 |
100
160
250 |
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0,28
0,30
0,34 |
0,40
0,44
0,50 |
0,56
0,62
0,70 |
0,78
0,88
1,0 |
1,1
1,2
1,4 |
1,6
1,8
2,0 |
2,2
2,5
2,8 |
3,2
3,6
4,0 |
4,4
5,0
5,6 |
6
7
8 |
9
10
11 |
11
12
14 |
14
16
18 |
18
20
22 |
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250
400
630 |
400
630
1000 |
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0,40 |
0,56
0,64 |
0,78
0,90
1,0 |
1,1
1,2
1,4 |
1,6
1,8
2,0 |
2,2
2,6
2,8 |
3,2
3,6
4,0 |
4,4
5
6 |
6,2
7
8 |
9
10
11 |
12
14
16 |
16
18
20 |
20
22
25 |
25
28
32 |
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1000
1600
2500 |
1600
2500
4000 |
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1,6 |
2,2
2,6 |
3,2
3,8
4,4 |
4,6
5,4
6,2 |
7
8
9 |
9
10
12 |
13
15
17 |
18
21
24 |
23
26
30 |
29
33
38 |
37
42
49 |
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4000
6300 |
6300
10000 |
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7,0 |
10
11 |
14
16 |
20
23 |
28
32 |
35
40 |
44
50 |
56
64 |
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Table 2 Tolerances for castings in large batches
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CT tolerance |
| Method |
Steel |
Grey cast iron |
Spheroidal graphite iron |
Malleable cast iron |
Copper alloys |
Zinc alloys |
Light-metal alloys |
Nickel-based alloys |
Cobalt-based alloys |
| Sand casting, hand-moulded |
11 to 13 |
11 to 13 |
11 to 13 |
11 to 13 |
10 to 12 |
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9 to 11 |
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| Sand casting, machine-moulded, shell-moulded |
8 til10 |
8 to 10 |
8 to 10 |
8 to 10 |
8 to 10 |
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7 to 9 |
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| Gravity die casting |
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7 to 9 |
7 to 9 |
7 to 9 |
7 to 9 |
7 to 9 |
6 to 8 |
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| Pressure die casting |
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6 to 8 |
4 to 6 |
5 to 7 |
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| Wax mould |
4 to 6 |
4 to 6 |
4 to 6 |
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4 to 6 |
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4 to 6 |
4 to 6 |
4 to 6 |
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Table 3 Tolerances for small batches or individual items
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CT tolerance |
| Mould material |
Steel |
Grey cast iron |
Spheroidal graphite iron |
Malleable cast iron |
Copper alloys |
Light-metal alloys |
| Green sand |
13 to 15 |
13 to 15 |
13 to 15 |
13 to 15 |
13 to 15 |
11 to 13 |
| Self-curing materials |
12 to 14 |
11 to 13 |
11 to 13 |
11 to 13 |
10 to 12 |
10 to 12 |
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Binder system
Both of our machine moulding lines, in both the ferrous and the non-ferrous foundry, are based on green-sand moulding using bentonite as a binder.
In our hand-moulding divisions, the ferrous foundry uses furan as the binder, and the non-ferrous foundry uses alphaset. Our core production is primarily based on cold-box processing. We also use a number of larger cores in the hand-moulding divisions in furan and alphaset.
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Ferrous foundry |
Non-ferrous foundry |
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Machine moulding |
Hand moulding |
Machine moulding |
Hand moulding |
| Binder system |
Bentonite bonded |
Chemically bonded |
Bentonite bonded |
Chemically bonded |
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sand |
sand (furan) |
sand |
sand (alphaset) |
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;)
;)
