DIAMOND WIRE CUTTING
Within the road and transport sector, diamond wire
cutting can be utilised in the demolition, modification
and extension of bridge structures. The process has
many advantages including low noise, flexibility,
minimal vibration or damage to any retrained structural
elements, large depth of cuts and high accuracy of cuts.
Introduction
Shane McCarthy
Tyrolit Industrial Equipment Sales
Abstract
Drilling and cutting with diamonds has been known
to mankind for thousands of years. The current
prolific use of diamond tools can be attributed to the
manufacture of synthetic diamonds on an industrial
scale.
A diamond wire saw consists of a tension element
made from a loop of high tensile wire joined with a
mechanical joiner. Fitted over this tension wire are
steel carrier rings separated from each other by helical
compression springs. Onto the outside of the carrier
rings, diamonds are either sintered or retained by an
electroplated layer.
Diamond is chemically pure carbon with a
body-centred, cubic crystalline structure. The
crystalline form corresponds, more or less perfectly
developed in shape, to a cube, an octahedron or
a dodecahedron. It is either mined as a naturally
occurring diamond or manufactured synthetically.
Diamond is the hardest known naturally occurring
substance and therefore is exceptionally suitable for
grinding or cutting of very hard materials such as hard
metals, glass, natural stone and concrete.
This article traces the industrial use of diamonds as
an introduction to diamond wire cutting. The aim of
the article is to describe the mechanics and benefits
of diamond wire cutting. As will be explained later,
diamond wire cutting can perform deep cuts in hard
materials that were previously not feasible.
History
Drilling and cutting with diamond tools is now a
commonplace work technique but it is not a new
invention. In Egypt, this process was already being
applied as early as 2500 BC, and diamond tools had
also been used in the ancient world. Amongst the
Greeks, circa 400 BC, Plato mentioned the name
Adamas, the "invincible", from which the word
diamond was later derived. In India, a country with
an immeasurable abundance of diamond fields, and
in China, diamond tools were used at this time for the
working of hard jade (1).
QUEENSLAND ROADS Edition No 10 March 2011
29
While stone can be cut by utilising the great hardness
of diamonds other methods should be acknowledged.
The principle behind any form of cutting is to remove
material from the desired object be it stone, metal,
wood and so on, without incurring excessive wear
to the cutting tool. An alternate method employed
to cut stone is to use a flat metal blade mounted and
tensioned within a frame. The blade has corrugations
on its sides and along the cutting edge. As the blade
reciprocates across the stone to be cut, water and a
cutting agent is introduced into the cut. This cutting
agent can be sharp sand or various types of metalic
shot (3). In essence, the blade does not perform the
actual cutting but is a carrier for the cutting media.
The corrugations in the cutting blade prevent much
of the relative movement between it and the cutting
media. As this cutting media is gradually worn away,
it and the cut stone particles are washed away by the
water which also provides cooling and lubrication.
The modern application of diamond tools is roughly
a century old although the early use of diamond us
an engraving tool goes back to 350 BC. In Christ's
time, splinters from broken diamonds were set in iron
handles1 (2).
As this article centres on the hardness properties
of diamonds, it would be worthwhile to gain an
understanding of the hardness of diamonds. In
our early schooling we were taught Mohs scale of
hardness. This was based on the very old principal
that a material was harder than another if it could
scratch the other material. Mohs scale however gave
no indication of the quantum of hardness. There are
numerous scales of hardness used in engineering;
however, the Knoop scale is often applied to minerals
which quantify in numeric terms the hardness of
materials. Figure 1 shows the comparative hardness of
minerals comparing Mohs and Knoop scales. Note the
hardness of quartz in comparison to diamond — quartz
being one of the hardest minerals found in concrete.
0 XXX 0000
Document20
In the 1800’s, Gay devised a helicoidal or wire stone
saw that sped up the cutting process (4). Instead of
a flat blade, Gay used a continuous loop of tensioned
steel wire. This wire was comprised of three separate
circular wires twisted together to form a helix. The
wire was drawn over the stone in a continuous loop.
Water and sand were fed into the cut similar to the
frame saw described above. The cutting media was
carried in the space between adjacent wires. It is
believed the ancients used both of these methods to cut
stone. However, the helicoidal steel wire was replaced
by sinew and mounted in a reciprocating frame.
With the decline of the old imperial powers, such as
the Roman Empire, ancient knowledge and practices
were lost in history. Only with the beginning of
the modern age were the methods of cutting with
diamonds recognized once again. In 1751, Diderot
published in his Encyclopédie the first depiction of a
diamond drilling tool.
Figure 1. Hardness comparison - Mohs vs. Knoop
Scales
1 Much of the historical information came from Reference (2)
QUEENSLAND ROADS Edition No 10 March 2011
30
The next milestone in the history of diamond tools
was to take place in 1819, when the first patent for a
diamond wire-drawing die was granted to Brockendon
in England. At that time, however, it proved
impossible to implement this invention into practical
use and it took around 40 years until the first diamond
wire-drawing die was successfully made and utilised
by Milan and Balloffet in France. Meanwhile in 1824,
Pritchard started to use shaped diamond wheels to
grind and polish microscope lenses. These wheels
were made by hammering diamond grits, of adequate
fineness, into the surface of a cast iron body.
The first metal powder used was an electrolytic iron.
The idea of bonding diamond by means of meta1
powders dates back to 1883, when Gay described the
manufacture of abrasive materials by incorporating
traditional abrasives such as quartz or emery in a
metal matrix. He mentioned the use of brass, iron
or steel powders and proposed to make good use of
powder metallurgy techniques such as hot pressing or
infiltration to form the matrix. Refinements were made
to Gay's ideas in the 1920s and 1930s. This apparently
sped up the development of diamond grit impregnated
tools which found industrial application around 1940.
In 1854 a French engineer Hermann applied for a
patent for a single-crystal diamond tool for cutting,
turning and shaping hard stones which, upon
improvements made a year later, were converted into
a tool with multiple diamonds. In 1862 Leschot of
Geneva was granted a patent covering a complete
drilling rig. This was to find practical application
on a broader scale more than a century after the first
description of a primitive diamond rock drill had
appeared in Diderot's Encyclopédie. The first power
water-driven diamond drilling machine was displayed
in 1867 at the World Exhibition in Paris.
Bonds other than metal were also being developed
during this period. In 1925 the Bakelite Corporation
took out a patent on the first phenolic resin bond. In
the early 1930s resin-bonded wheels, containing
'fragmented' natural diamond grit, were patented by
Wickman Ltd. in England (1933), Voegeli & Wirz in
Switzerland (1934) and Norton Co. in the USA (1934).
Until the early 1950s the developments in diamond
tools were relatively slow. In that period only mined
diamond crystals were available. These were formed
millions of years ago under conditions of intense heat
and pressure acting on the carbon and later ejected to
the surface by volcanic eruptions (Figure 2).
The first diamond circular sawblades for cutting
stone were developed by Fromholt in France in 1885.
Thirteen years later, a large diameter blade was first
used in practice in the Euville stone quarries. The
early blades used Brazilian carbonado diamonds set
around their periphery. Carbonado was a valued
material at that time because, being a cryptocrystalline
mass of small crystals locked in random directions, it
was strong and resistant to cleavage. Such carbonado
blades were utilised to cut limestone and marble
during the construction of large buildings in Paris in
the 1900s.
Further progress in tool production took place in
the period between 1927 and 1931 when patents
describing the manufacture of metal matrix abrasive
tools. According to Gauthier (1927), the powder mix
was to be consolidated by cold pressing only, whereas
Neven (1931) was probably the first to suggest hot
pressing.
0 XXX 0000
Document21
Figure 2. Natural diamonds cut for jewellery
QUEENSLAND ROADS Edition No 10 March 2011
31
Much faster developments in the tool manufacturing
technology, which have been seen over the last 50
years or so, may chiefly be attributed to the invention
of synthetic diamonds. Efforts to manufacture
synthetic diamond crystals date back at least several
hundred years.
In 1946, Percy Williams Bridgman, who is regarded
as the father of the high-pressure and high temperature
technology, was awarded the Nobel Prize for Physics.
Research efforts had remained fruitless until 1953,
when positive and fully reproducible results were
obtained by a team of researchers at ASEA. Quite
independently, and entirely without knowledge of what
ASEA had been doing, General Electric announced
its capability to manufacture synthetic diamonds on
an industrial scale in 1955. While ASEA kept the
diamond experiments secretive, General Electric was
first to describe the process in the scientific literature
and patent it. Three years later this was followed by
De Beers in South Africa and also the USSR, where
the synthesis of diamonds was also achieved.
Permanent progress in the manufacturing technologies
fostered the commercial importance of synthetics,
which now accounts for over 95% of all industrial
diamonds consumed. It is worthwhile to mention
that the last five decades witnessed a spectacular 50
fold increase in the total consumption of industrial
diamond. Over this time modern production
techniques based on diamond tooling have been
implemented into evolving areas of industrial activity
enabling, to do the job faster, more accurately and
at less cost. This revolutionised machinery and
processing techniques in the stone and construction
industries, road repair, petroleum exploration,
woodworking, cutting frozen foods, production of
various parts and components made of glass, ceramics,
metals, plastic and rubber, etc.
The milestone progressions and development which
followed commercialisation of synthetic diamond on a
broader scale can be listed chronologically us follows:
•
1960s: Metal-clad diamond was developed for
application in resin bonds, which coincided with
the introduction of polyamides by Du Point. Wire
saws for sawing stone were produced in Italy in
1969. They contained diamond grit embedded in
an electrodeposited metallic matrix. Cubic boron
nitride (CBN) was introduced to the industry
in 1969 to complement diamond in machining
ferrous alloys.
•
1970s: Synthesis of high-quality ‘saw’
diamond was developed for demanding stone
working applications such as sawing granite.
Polycrystalline diamond (PCD) became available
on a broader scale and made extensive inroads
into applications which had been the domain of
cemented carbides.
•
1980s: Coated ‘saw’ grits were introduced into
broader application. A new class of phenol-aralkyl
thermosetting resins, offering improved tool
performance, was developed for application in
resin-bonded diamond and CBN grinding wheels.
•
1990s: Major breakthroughs in low-pressure
synthesis of PCD by chemical vapour deposition
(CVD) were achieved. This resulted in
commercialisation of CVD diamond coated cutting
tool inserts, twist drills, and ‘free-standing’ thick
CVD diamond films brazeable to the tool support.
QUEENSLAND ROADS Edition No 10 March 2011
32
Modern usage of diamond tools
Natural diamonds
In the new millennium the market for diamond tools
continues to grow rapidly. The most recent figures
indicate that the demand for diamond abrasives
reached an impressive volume of 1 billion carats in
2000 as compared with approximately 380 million
carats in 1990 and 100 million carats in 1980. The
current trend is to diversify into applications still
dominated by traditional abrasives with particular
interest in developing linear blades for sawing granite
as well as applying diamond grits on a broader scale in
the surface finishing operations.
Nowadays the rapid diamond price decline makes
industrial diamond a commoditised product capable
of competing, in terms of its price/performance ratio,
with conventional abrasives such as silicon carbide and
aluminium oxide.
Natural diamonds are mined, above all, in old, extinct
volcano conduits, where once there existed the
temperature and pressure conditions that are required
for the crystal growth. For the most part natural
diamond is used in the precious stone and jewellery
industry. Only the diamond that is deemed not suitable
for jewellery, because of its impurities, then becomes
used for industrial purposes. With this, the larger
stones are used for dressing tools, for grinding wheels
for drill bits in the oil industry and for geological
exploration bore holes. Low-quality grains are
reduced in size, cleaned and sorted according to size
and grain shape. These find use in sawing and drilling
tools and are also used in grinding tools for the glass,
metal, electronic and plastics industries (composite
materials).
For the construction of concrete structures, proof
of in situ concrete strength has placed a demand for
drill bits. Not only the cutting processes, but also
the diamond itself was the subject of investigation by
various research groups.
Synthetic diamonds
As a result of consistent development work it is
possible today, freed from all the whims of nature,
to manufacture ‘custom made’ diamonds for specific
materials and fields of application. At the end of the
1960s – prerequisite was the synthesis of diamond
- a meteoric development began in the construction
industry. Concrete became the most important
building material of our age. Through the addition of
aggregate and steel reinforcement, the compression
strength and tensile strength of concrete can be
improved but in the hardened state it is then difficult
to cut. Diamond tools have a wide field of application
in road and airport runway construction and also in
structural engineering for cutting openings in ceilings
and walls and additionally for demolition work.
Pneumatic hammers and formwork have been replaced
in part by diamond tool technology allowing greater
design, construction and maintenance efficiency in
buildings.
In the tool industry today, the overwhelming majority
of diamond that is used is of the synthetic variety.
Since this is available with great uniformity of quality,
and also with different, precisely defined quality levels
(hardness), which means that the tool can be optimally
matched to the application process.
For the manufacture of synthetic diamond, the
natural growth conditions must be simulated, but in
a substantially shorter time period. What requires
thousands of years in nature is completed in just a
few minutes during the synthesising process. The
process takes place in high-pressure, high temperature
presses. The cell in which the synthesis takes place is
filled with graphite and metal powder, which serves as
the catalyst. This cell is then heated up in a press to
approx. 1,400ºC, where it is subjected to a pressure of
more than 50,000 bar and to electric current intensities
of 1,000 amps. The metal melts and the graphite
dissolves. As soon as the metal has saturated the
graphite, the carbon crystallizes into diamond. The
time taken for the process determines the grain size
of the diamond crystals. Electric current and pressure
are switched off abruptly; the cell is removed from
the press, opened and the diamond is removed. After
the cleaning has been carried out, they are sorted
according to grain size through the use of sieves,
vibrating tables, X-ray diffractometers and various
other methods, according to the grain shape and
impurities that influence the crystal hardness.
QUEENSLAND ROADS Edition No 10 March 2011
33
Diamond wire saws
With the advent of a low cost source of high quality
synthetic diamonds, old stone cutting techniques could
be revisited. The obvious drawback with portable
diamond saws is the cut depth which is only about
a third of the saw diameter, hence deep cuts are
impractical.
Diamond wire cutting was invented in England in
the 1950s, initially by diamond electroplated beads
threaded onto a multi-strand steel cable. Over the past
30 years significant development work (by Diamant
Boart, among others) refined the concept until it was
commercially accepted in Carrara marble quarries in
Italy. Further machine and wire developments were
needed for hard-rock sawing. Early diamond wire
machines consisted of a single strand of cutting wire.
Tests began in 1994 with a prototype multi diamond
wire (MDW) machine developed by Yamana Co. in
Japan for cutting granite. The machine was equipped
with 10 wires, with a bead diameter of 10mm. It’s
believed that no production machines were ever
developed.
Fitted over this tension wire are steel carrier rings
separated from each other by helical compression
springs. Onto the outside of the carrier rings,
diamonds are either sintered or retained by an
electroplated layer (Figure 5). The final assembled
diamond wire is coated with an elastomeric compound
such as rubber (Figure 6). This helps retain the
components as well as protect against corrosion. The
working diameter of diamond wire over the carrier
rings is in the order of 10mm to 11mm.
Since then MDW machine have proliferated.
Machines with 30 wires or more are primarily used
for granite-block slabbing where they compete with,
or complement, traditional steel-shot gang saws.
Machines with a lesser number of wires are used for
sawing thick slabs for monuments or architectural
parts.
0 XXX 0000
Document22
What is a diamond wire saw?
A diamond wire saw consists of a tension element
made from a loop of high tensile wire joined
with a mechanical joiner. The wire cross section
configuration is similar to a stressing strand
(Figure 3). The end joiner is connected to the wire
using a swaging/crimping tool. Joiners can either be
permanent or can be manually disconnected (Figure 4).
Figure 3. Section through a tension element/
carrier wire
QUEENSLAND ROADS Edition No 10 March 2011
34
0 XXX 0000
Document23
Figure 4. Screwed wire joiner
0 XXX 0000
Document24
Figure 5. Mounting of diamonds
0 XXX 0000
Doc
Figure 6. Examples of diamond wire
QUEENSLAND ROADS Edition No 10 March 2011
35
The depth of cut using a circular diamond saw is
limited to approximately one third of the diameter of
the saw blade, hence deep cuts are impractical.
A diamond wire saw overcomes this problem. To
explain the principal refer to Figure 7 where a
reinforced concrete slab is being cut.
A diamond cutting wire loop is disconnected at a joiner
and then wrapped around the slab to be cut. Where
access is not possible, a small access hole is drilled
to enable the wire to be threaded through. The wire
is then passed around the slab in a continuous loop
and then reeved through the various pulleys. Water
is applied to the cutting process to cool, lubricate
and remove the cut concrete and abraded steel. As
the cutting proceeds, excess slack wire is stored in a
cassette on the cutting machine by a system of pulleys.
The tension and cutting speed of the diamond wire is
dependent on the hardness of material being cut and
the percentage of steel present. The tractive effort to
pull the wire is achieved by wrapping the wire around
a drive pulley the required number of times to create
a simple capstan drive. Safety around the wire must
be maintained because the wire is moving and could
possibly break causing a dangerous whiplash.
As well as concrete and rock (Figure 8), the diamond
wire will cut through reinforcing steel, stressing strand,
steel sections and steel plate. It has the benefit that
the process is relatively quiet unlike diamond circular
saws.
Figure 7. Diamond wire cutting a reinforced
concrete slab
0 XXX 0000
Document27
Figure 8. Deep cutting of marble using diamond wire (courtesy Diamant Boart)
QUEENSLAND ROADS Edition No 10 March 2011
36
0 XXX 0000
Document28
Figure 9. Vertical cut – standard method
Figure 10. Vertical cut – with release roller
0 XXX 0000
Document30
There are many different configurations in
which the diamond wire can be set up. The
wire can cut vertically, horizontally or as
would be expected, at any angle. Figures
9,10 &11 are just a few examples of cutting
configurations.
Figure 11. Plunge roller cutting
QUEENSLAND ROADS Edition No 10 March 2011
37
Case study
The project entailed raising the full supply level of
the Urra Dam in Bogota, Columbia. This required
the removal of a 5.2 metre high section of the existing
concrete spillway with structural modifications to
the remaining crest to accommodate new gates. This
case study entails removing 5.2m from the concrete
spillway (Figure12). An Australian company
DecoTEC completed the structural modifications in
September 2009.
Hydraulic press tool
Curved sawing marks
Figure 14. Installed hydraulic press tool
The dam design engineers were concerned that
conventional demolition using hydraulic breakers
would cause micro-cracking to the remaining
structure and damage sensitive monitoring equipment;
accordingly DecoTEC used diamond wire sawing in
conjunction with hydraulic concrete bursting tools2 .
Figure 12. 5.2m of spillway being removed
Figure 13. Coring holes to facilitate concrete
bursting
Application of the wire-sawing involved a series of
innovative solutions to complete unusually deep and
accurate cuts. The cross-section of the dam wall
was 12m wide at the cut level and the design called
for a fall in the demolished profile of 2 per cent, so
accurate cutting was vital. Access to the work area
was difficult and working platforms had to be designed
and constructed on both the upstream and downstream
faces of the dam. The dam crest was removed in two
layers so that the size/weight of the removed blocks
was manageable by crane.
Firstly full depth vertical cuts were made across the
entire width of the spillway. Next a horizontal cut
was made to form the first layer. Once the vertical
and horizontal cuts were made, 200mm diameter
holes were strategically cored to allow access of a
press tool to break the sawn concrete blocks into more
manageable sizes (Figures 13,14). The access hole
for the press tool is slightly deeper than the depth of
the tool (Figure 15). Each press tool could exert a
force of 260 tons at a rated pressure of 2000 bar. The
working pressure is considerably higher than the 700
bar normally used by engineering jacks. This press
tool utilises two pistons which press against a pressure
plate to distribute the load. The press tool allowed
time and cost savings as the cost of drilling one or two
holes per block was less expensive in terms of both
tooling and setup costs.
2 The specialist concrete cutting equipment was supplied by Tyrolit
QUEENSLAND ROADS Edition No 10 March 2011
38
0 XXX 0000
Document36
Figure 15. Operating principal of the hydraulic press tool
Conclusion
While diamond wire cutting technology is not new
to rock quarrying and demolition of large structures,
its use in other sectors is slowly growing. Within the
road and transport sector, diamond wire cutting can
be utilised in the demolition, and modification of and
extensions to, bridge structures. The process has many
advantages including low noise, flexibility, minimal
vibration or damage to any retrained structural
elements, large depth of cuts and high accuracy of cuts.
References
1. Technical Manual for Construction Cutting
Specialists. Swiss Association of Concrete
Drilling and Cutting Enterprises, Bellach,
Switzerland. 2007
2. Konstanty J. Powder Metallurgy Diamond Tools.
Powder Metallurgy Dept., University of Mining
and Metallurgy, Krakow, Poland. Published by
Elsevier Ltd. 2005
3. Smith M R. Stone: Building stone, rock fill and
armourstone in construction ( Geological Society
Engineering Geology Special Edition No. 16).
Published by Geological Society of London 1999
4. Scientific American Reference Book: a Manual
for the Office, Household and Shop. Scientific
American Publishing Co. 1921
QUEENSLAND ROADS Edition No 10 March 2011
39