Modern Mechanical Engineering, 2013, 3, 181-190
Published Online November 2013 (htt p://
Open Access MME
The Development of Decision-Making Maps for the
High-Speed Machining (HSM) of Rhyodacite (Carijó
Basalt) in Milling-Based Processing Applications
Hélio Dorneles Etchepare, Wilson Kindlein Júnior
PPG3M, Federal University of Rio Grande do Sul, Porto Alegre, Brazil
Received September 17, 2013; revised October 28, 2013; accepted November 11, 2013
Copyright © 2013 Hélio Dorneles Etchepare, Wilson Kindlein Júnior. This is an open access article distributed under the Creative
Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original
work is properly cited.
The demand for innovative produ cts that overcome competitive pricing and conquer market sh ares can be met by inter-
disciplinary approaches that bridge product design, engineering and technology. Ornamental and covering stones stand
out among the materials in need of innovation and are commonly used in architecture and construction as coverings in
urban elements, funerary art, and art and decor. In spite of the many applications of ornamental stones, products with
low added value are typically observed. Although Brazil displays significant geological potential for ornamental stones,
its actual market participation is as a supplier of un- or semi-processed stones. Even with the market’s visible expansion
and Brazil’s increased representation in the market, the technological advances used in the final processing of stones are
restricted to improve the tools used for cutting, especially the durability of diamond-coated tools, and for polishing,
which, in the short-term, meets the demands for marketing, producing and distributing semi-finished products. Accord-
ingly, a little exploited aspect of ornamental stones appears, especially for “carijó basalt” (rhyodacite), that is, the inclu-
sion of new processing and value-adding technologies or the inclusion of non-conventional processes in the sector. The
goals of this work ar e to study and develop HSM (high speed machinin g) CNC (computer nu merically contro lled) mill-
ing processes that are applicable to rhyodacite, specifically to determine the milling parameters that give th e best results
for machining time with respect to tool wear and material abrasion and to replicate the results obtained in the samples.
The results show that the raw material used in the present study, because it is natural, presents significant variations in
composition and hardness, which prevent specific milling parameters from being determined. However, using a
post-processor specifically developed for this study, it was possible to draft a decision-making map that aids in the exe-
cution of this pro cess. Additionally, equipment failure occu rred during every attempt and with every adjustment of the
milling process. This indicates that the application of multipoint tools to rhyodacite milling is difficult in this ind ustry.
Thus, the use of single-point tools should be the natural path to follow for a potential practical ind ustrial application in
Keywords: Technology; Rocks; Processing; Multidisciplinarity
1. Introduction
According to Brazil’s Ministry for Mines and Energy
(MME) [1], in a report from 2001, the country’s covering
rock sector can be divided into 18 productive groups
composed of entrepreneurial activities in 7 states and 80
municipalities. The main product in the state of Rio
Grande do Sul is basalt. The report states that Brazil has
11.500 companies in this secto r, pr ov iding 120.00 0 d irect
jobs and possessing facilities capable of processing from
40 to 50 m3/year, which represents a production of 6.0
million tons/year. Basalt stands out, with approximately
7% of this total. According to Bizzi (2003), the commer-
cial transactions in the sector, including machinery,
equipment and raw materials, corresponded to approxi-
mately US$ 2.5 billion in 2003 [2].
Carijó basalt has been used as a covering material in
construction and is extracted mainly from a region in th e
northeast of the Rio Grande do Sul state, known as the
“Basalt Region,” due to the significant number of extrac-
tion and processing companies present there. This “Ba-
salt Region” enco mpasses, according to the Basalt Maga-
zine (Syndicate of the Quarry Exploitation Industry of
Nova Prata and Region, 2000) [3], the municipalities of
André da Rocha, Guabijú, Nova Araçá, Nova Bassano,
Nova Prata, Paraí, Protásio Alves, São Jorge, Veranópo-
lis, Vila Flores and Vista Alegre do Prata (Fi g u re 1).
According to data made available by the Chamber of
Industry and Commerce (Câmara de Indústria e Comér-
cio—CIC) on the Basalt Region, the gross revenue gen-
erated from extracting and processing this material is
501.3 million Brazilian Reais, of which approximately
52.7 million Brazilian Reais are paid as taxes and 37 mil-
lion Brazilian Reais are paid as salaries. Additionally, the
an export volume is approximately 48 million Brazilian
Reais, all of which make this industry one of the most
important industries in the region due to its significant
participation in the state- and country-level economies
There are 300 mining areas in the region, according to
data published in the journal Socio-Economical Hierar-
chy of the Basalt Region. In the municipality of Nova
Prata alone, also known as the National Basalt Capital,
there are 104 registered mining and 89 basalt processing
companies, which represent 10% of the municipality’s
economy and provide approximately 3000 jobs, both
direct and indirect. Table 1 shows the main products of
basalt processing in Nova Prata, as well as their volumes
and corresponding fr actions [4].
Given the latent potential of using computer numeri-
cally controlled techniques in rock processing applica-
tions, in the present article, we seek to systematically
study the viability of using HSM milling in this context
and to determine the best machining parameters for this
2. HSM Milling
According to Dieter (1981) [5], in general, two distinct
Figure 1. The Basalt Region in Rio Grande do Sul.
manufacturing classes are utilized in the solid state, in-
cluding deformation processes, in which the desired
shape is produced through plastic deformation of the
materials while preserving their initial volume, and ma-
chining processes, in which part of the material is re-
moved through specific processes to produce the target
shape. Machining processes are used to produce parts
with high dimensional tolerance, good surface finishes
and relatively complex shapes. Currently, significant
technological developments have been achieved in ma-
chining processes, particularly with the addition of com-
puter numerically controlled (CNC) and high speed ma-
chining (HSM) techniques, which guarantee precision
and repeatability of movement. One of the machining
areas that has benefited most significantly from these
developments is, according to Faller et al. (2006), the
field of milling processes [6].
In HSM milling, the machine (Figure 2) interprets
Table 1. The products obtained from basalt.
Main products Volume produced (m³/year)(%)
Paving stone 30,000 50
Slabs 6000 10
Irregular pieces of stone paving12,000 20
Foundation stones 6000 10
Other 6000 10
Total 60,000 100
Adapted in 08/01/2011 from the Chamber of Industry and Commerce, Ba-
salt Region, 2010.
Figure 2. The CNC Digimill 3D milling centre. Adapted in
11/28/2012 from
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digital instructions and activates a set of servos and step-
per motors that control each axis of the machine (X, Y
and Z in the case of 3-axis milling machines), moving the
table or the tool in an automatic and interpolated manner
(movement can be made simultaneously along all axes).
Some or all of the numerical data are converted during
the process, e.g., distances, angles, speeds, etc., which
allows almost any shape to be conceived/manufactured in
real applications. The arrival of this technology was only
possible after the necessary tools, automation and infor-
matics were invented.
Any machining process depends critically on the ma-
terial from which the tool is made and the interaction of
the machining forces with the workpiece, where the me-
chanical properties of the tool, especially its hardness,
should be superior to those of the raw material (the
workpiece to be machined).
The development of machining tools has generally
been accompanied by technological developments, both
with respect to the specific characteristics of the raw ma-
terials and the specialisation of manufacturing processes.
Machining tools generate surfaces in two ways: by using
a profile tool, the shape of which resembles the shape of
the surface to be produced, or by advancing the tool
along the part’s length. Profile tools are relatively more
expensive but are important in line production applica-
tions. Machining parameters, such as the cutting depth,
the X-, Y- and Z-speeds, and the spindle1 rotation speed,
all of which vary according to the material and tool, as
noted by Freitas (2006) [7], should be considered to pre-
vent excessive tool and/or equipment wear. Most cutting
tools are made of cast steel or hard metal, according to
Dieter (1981), but there are also tools made of fused al-
loys and others possessing diamond coatings, with the
latter being more suited in the processing of ornamental
Figueira (2006) [8] points out that diamond-coated
tools are the most commonly employed tools in the
blasting, cutting and polishing processes for ornamental
rocks, ceramics and non-ferrous materials. According to
Stemmer (2008) [9], the extraordinary hardness of dia-
mond, which exceeds that of any other material, can vary
between 5000 and 700 0 on the Knoop scale, or 56 to 102
GPa (giga-Pascal), depending on the crystal’s orientation.
The high thermal conductivity of diamond can hinder the
performance of polycrystalline tools because of the pre-
mature tearing of the abrasive grains due to the absorp-
tion by the metallic matrix of the h eat generated fro m the
friction between the workpiece and the tool. The poten-
tial usefulness of numerical control in stone processing
has prompted the discussion of applying HSM milling to
cutting applicatio ns for this type of material to verify the
best condition s fo r its application.
3. Materials and Methods
According to the Brazilian Geological Service, CPRM
[10], the stones used in this study, extracted from mining
areas in the Basalt Region, are part of the Geological
Province of Paraná flood basalts, the Caxias Facies,
which formed in the Cretaceous period between 65 and
135 million years ago. This facies consists mainly of
massive basalt flood of intermediate to acidic composi-
tion, mafic and with fine granular texture and lamellar
structures, which explains why extraction is performed in
the horizontal orientation.
According to Motoki (2004) [11], the plateau that is
stratigraphically called the Serra Geral mountain range,
spanning across the states of Santa Catarina and Rio
Grande do Sul, is composed mainly of basalt lava with
high iron and low silica contents. However, at the top of
these mountains, the basaltic lava is covered by rhyo-
dacite, a volcanic rock with low iron and h igh silica con-
tents, which is often mistaken for and commercialised as
basalt [12].
Three plates of this material were acquired to better
assess its characteristics and to obtain an overall better
understanding of its nature: one measuring 95 × 60 × 2
cm3, labelled “control,” and two smaller plates, labelled
“random,” one measuring 74 × 11 × 2 cm3 and the other
measuring 45 × 15 × 2 cm3. The plates were obtained
from different quarries in the Basalt Region. The control
plate, which was visually darker than the other plates,
was mapped and subdivided into 425 specimens measur-
ing 3 × 3 × 2 cm3. The random plates, both exhibiting a
red tone, were subdivided into 93 samples of 3 × 3 × 2
cm3 without control of specimen position. The test bod-
ies were washed to remove surface dust and were then
dehumidified for 24 hours (Figure 3).
A set of 22 samples was selected to characterise the
rock with respect to hardness using Knoop’s test and
chemical composition using X-ray diffraction analysis.
Of these samples, 11 were taken from the control plate
and 11 from the random plates, specifically, samples B2,
B9, B17, B24, I5, I13, I21, P2, P9, P17 and P24 from the
control plate and samples 1, 9, 17, 25, 33, 49, 57, 65, 73,
81 and 89 from the random plates. For the X-ray fluo-
rescence assay, a subset of 11 samples was taken from
the aforementioned set, namely, samples I7, B2, B17, I5,
I13, I21, P9, P17, and P24 (control) and 1 and 9 (ran-
The results from the hardness tests, X-ray diffraction
and fluorescence analyses and petrography indicated that
it was not necessary to classify the samples prior to the
machining tests given their homogeneity. For the rhyo-
dacite tests, the machining parameters used for steel were
taken as the initial reference values because of the sig-
nificant hardness and well-known parameters of this ma-
terial. However, because diamond-coated (polycrystal-
1device that provides the tool with rotation.
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Figure 3. The control plate (A) was mapped (B) and subdivided into 425 specimens of 3 × 3 × 2 cm3 (C). The samples indi-
cated on the map (B) were analysed for hardness using Knoop’s test, X-ray diffraction and fluoresce nce and petrography. All
samples were washed (D) and dehumidified by evaporation for 24 h (E), and their masses w ere assessed using a digital ana-
lytical scale (F).
line with nickel matrix) tools were intended for use, the
spindle rotation was altered to 23,000 rpm. the ratio of 1/19, as recommended by the manufacturer.
For all patterns except number 4, the tests were per-
formed with one tool each, and no loss of mass was de-
tected; for pattern 4, however, it was necessary to use 4
tools in separate tests, for which the speed was gradually
reduced to 6.38 mm/sec, 25% below the standard speed
used in the steel tests and other rhyodacite tests. None of
these procedures was successfully concluded. Because of
the lack of success for pattern 4, due to the excessive
wear of the lower end of the tools being used, which was
caused by the significant number of plunges into the
sample, an alternative strategy was tested, namely, raster
machining, originally from the X-ax is to the Y-axis. This
change in the machining direction reduced the number of
vertical, i.e., Z-axis, displacements of the tool from 486
to 126, thus significantly decreasing the impact on the
sample. Maintaining the same parameters as that used for
steel, the machining time based on this new strategy, as
estimated by the ArtCAM® software, would be 57 min
and 53 sec, which corresponds to a reduction of 9 min
and 58 sec in the total machining time.
Additionally, to minimise possible variations, 100
tools of the KG Sorensen® brand model 3018 batches
2266 and 5 359 were p urchased . The too ls were classif ied
according to their diameter, measured with a Mitutoyo®
digital calliper accurate to the 0.001 mm. The diameters
of the tools varied between 2.766 and 3.005 mm, with an
average diameter of 2.911 mm and a standard deviation
of 0.04 mm. By statistically considering 95% of these
measurements to be accurate, tools with diameters smal-
ler than 2.81 mm were discarded. The mass of each tool
was measured using a precision scale and was found to
vary between 0.3193 g and 0.3372 g, with an average
weight of 0.3219 g. Measurements of the mass and
length of each tool were used to determine their wear
relative to the established machining parameters.
4. Rhyodacite Milling Tests
To initiate testing, all rhyod acite samples were calibrated
according to their planeness, and a fixing support, lev-
elled with the help of a dial gauge, was adapted to the
milling centre to allow the samples to be quickly ex-
changed. Additionally, two ISO 15488-A collet chucks
were purchased; these chucks were capable of holding
tools with shanks between 1 and 2 mm in diameter. The
goal of such procedures was to optimise the setup times.
All proposed patterns were milled according to the pa-
rameters given in Figure 4.
New assays were performed, at first excluding the dis-
placement variables in X and Y, to determine the speed
along the Z-axis, which wears the tool the least. It was
possible to conclude through these tests that the Z-axis
speed should be decreased and possibly that the speeds
along the X- and Y-axes should be increased to optimise
the processing time and minimise tool wear. This con-
clusion led to a new proposal for speed control, namely,
independent control along the X-, Y- and Z-axes, which
was not possible in the ArtCAM® and EdgeCAM® CAM
All tests were performed using water-soluble mist
coolant (Unix Solúvel 100 for light machining) diluted at
Figure 4. A finishing comparison between geometric patterns based on the dissertation of Gustavo Freitas (2006) [7] ma-
chined in plaster and “carijó basalt.”
software packages bei ng used.
Because of the difficulties encountered in finding a
software package that permits the independent control of
each speed, it was necessary to develop a post-processor
to allow control over the basic speed in the experiment.
To do th is , th e p os t-p roc esso r analyses the CNC program
generated by the CAM software, in this case a file with.
tap extension, and individually sets specific values for
the X- (or Y-, depending on the strategy adopted) and
Z-axis speeds, thus allowing precise control and machin-
ing time optimisation. Aside from independent X-, Y-
and Z-axis speed controls, the post-processor allows the
user to change the feed speeds without having to redo the
programs in the CAM software based on the analysis of
the trigonometric coordinates in X (or Y) and Z in the
program. It also allows free control of these speeds at the
user’s discretion, as well as of the negative Z-axis dis-
placement, by considering the angle of the surface to be
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machined, which can be constrained to an operator de-
fined range.
A total of 65 tests were performed using the different
machining patterns introduced in Figure 4. The parame-
ters used to execute these machining processes for pat-
tern 1 (smooth and flat geometry), 2 (tilted profile), 3
(concave profile), 5 (wave profile) and 6 (free profile)
achieved efficiencies between 85% (pattern 1) and 66%
(pattern 5). The machining process of pattern 4 had a
success rate below 10%, making it the hardest pattern to
All tests considered satisfactory had their repeatability
verified in a new specimen by using a new tool and the
same criteria and standards. Even with rigorous control
over the advancing speed in all three movement axes of
the tool, when using the post-processor, it was not possi-
ble to determine the set of optimal parameters that would
allow the procedure to be repeated without constant in-
tervention in the various established parameters.
Among the many variables inherent in any machining
process, such as variations in the equipment and tools,
greater control exists for those variables that are related
to the tools, which are easier to measure and classify ac-
cording to a pattern. However, the raw material used in
this study, rhyodacite, which is a natural material, pre-
sents variations that directly interfere with the tool’s
wear pattern, preventing uniformity and the determina-
tion of a specific set of parameters that can be used in
general HSM milling processes with this type of equip-
ment, cooling system and tool.
However, because success was obtained under certain
conditions, we can trace a decision-making map to assist
with this type of job. The map considers, as its initial
reference, the pre-established surface patterns used in
this study and the actions taken to perform the tests until
a positive result was achieved.
The development of the decision-making map is di-
vided into two steps: in the first step (decision making
map 1), only the procedures that are possible without
using a post-processor are considered; in the second step
(decision-making map 2), parameter control is performed
in a way that can only be accomplished when using the
post-processor. All patterns from Figure 4 were ma-
chined without using the post-processor. Its use, however,
optimises and makes the procedures easier, faster and
less likely to damage the tools.
Initially, in decision-making map 1, the fundamental
parameters are established based on the parameters that
yielded successful rhyodacite milling events. For patterns
1, 2, 3, 5 and 6, the feed and plunge speeds (FS and PS,
respectively), as well as the horizontal and vertical steps
(HS and VS, respectively) are equivalent because the
forces to which these tools are subjected are similar. For
pattern 4, however, the feed and plunge speeds were re-
duced to minimise these forces. A significant fraction of
the surface textures used in commercial products can be
fitted, as previously discussed, to one of the six patterns
or a combination thereof (Figure 5(A)).
Decision-making map 1 starts with the milling of a
rhyodacite surface using pre-established parameters. Af-
ter the initial procedure is completed, the success of the
procedure is ascertained. If it has not been successful, the
suggestion is to use a different cuttin g tool and restart the
process with the same parameters (Figure 5(B)). Again,
the success of the process is ascertained. If it was once
more not successful, the tool’s wear is determined, which
may occur in one of two moments, either during the
process, i.e., as the tool is actually machining, or during
entry, i.e., as the tool plunges into the surface at the start
of the process. The operator is ultimately responsible for
observing under which conditions the wear occurred
(Figure 5(C)).
In the case of wear during the process, it is suggested
that the advance speed be reduced by 10% (or 50% for
pattern 4). In both cases, this speed reduction is relative
to the initial value of the parameter. Afterwards, it is
suggested that the tool be exchanged and that the proce-
dure be restarted. If the procedure was not concluded and
no visible wear has occurred, then the tool is likely dam-
aged (broken or buckled), and a new speed reduction of
10% (or 50% for pattern 4) should be applied, along with
a 0.1 mm reduction in the vertical step to minimise axial
stresses. The process should then be started with a new
tool (Figure 5(D)).
Should the tool continue to wear or break despite all of
these recommended actions, the surface to be machined
should be zoned, i.e., divided into areas that vary ac-
cording to the dimensions of the tested samples. For each
sector, a new tool must be used, and the process must be
restarted. At the end of the procedure in the first area, the
success is ascertained (Figure 5(E)).
If success is not attained, the tool must b e checked for
damage at its tip or buckling. This wear can occu r in two
situations, either when the tool enters the rhyodacite at
the start of the machining process or during the machin-
ing process when the tool moves along the X- or Y- and
Z-axes. Here again, the operator’s attention is necessary
to determine in which situation the damage has occurred.
If damage occurs during the machining process, it is
suggested that the feed speed be reduced by 10% (or
50% for pattern 4), which minimises the axial stresses
and favours processing. Conversely, if wear is observed
during entry, the plunge speed must be reduced by 10%,
which minimises premature wearing of the tools. In ei-
ther case, the speed reduction is relative to the initial pa-
rameter. After these changes have been implemented, the
tool must be exchanged, and the procedure is restarted. If
the procedure is not concluded and no visible wear has
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Figure 5. Decision-making map, without the use of the CNC Cut Adjuster software for adjusting the machining parameters
for rhyodacite.
occurred, the tool is damaged (bent or broken), and a
new reduction in feed speed of 10% (or 50% for pattern 4)
with a 0.1 mm reduction in the vertical step, relative to
the previously used parameters, must be applied to
minimise the axial stresses during machining. The proc-
ess must be restarted at the area being worked with a new
tool (Figure 5(F)). The success of the procedure is once
more ascertained. If even with all of these interventions
there is no conclusion and no improvement in the ma-
chining conditions and/or reduction with respect to tool
damage, then it is not be possible to finalise the proce-
dure (Figure 5(G)).
In decision-making map 2 (Figure 6), the process oc-
curs after all initial parameters have been reset. This
Figure 6. Decision-making map, taking into account the use of the CNC Cut Adjuster software to adjust the machining pa-
rameters for rhyodacite.
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procedure is suggested so that the starting point is well
known. Using the CNC Cut Adjuster post-processor de-
veloped in this work, it is suggested that the vertical dis-
placement speed in Z (ZS) be made equal to the plunge
speed (PS) defined in the CAM software. This way, all
descending displacements in Z are reduced in speed,
which favours tool preservation (Figure 6(A)). Changing
the advance, Z displacement and plunge speeds is not
possible without this software. After the process is fin-
ished, its success is ascertained. In the case of failure, it
is suggested that the tool be changed and that the proce-
dure be restarted using the same parameters (Figure
6(B)). The success of the procedure is once more ascer-
tained. In case of success, it may be possible to optimise
the procedure by increasing the feed speed by 10% and
repeating the procedure. If success is obtained again, the
feed speed may once more be increased by 10%; in the
case of failure, the previous increase is retracted (Figure
6(C)). If the process failed to achieve completion, the
tool’s wear must be determined, which may occur in one
of two moments, as shown in decision-making map 1,
either during the process, i.e., as the tool is moved by the
milling machine, or dur ing entry, i.e., as the tool plunges
into the surface at the start of the process. The operator
must observe under which conditions the wear has oc-
curred (Figure 6(D)).
For wear during the process, the suggestion is to re-
duce the feed speed and Z-axis displacement speed by
10% (or 50% for pattern 4); however, for wear during
entry, the suggestion is to reduce the plunge speed by
10%. In both cases, the speed reduction is relative to the
initial parameter. Next, it is suggested that the tool be
exchanged, and the procedure is restarted. If the proce-
dure fails to conclude and no visible wear occurs, the tool
is likely damaged (buckling or breakage), which requires
a new reduction of 10% (or 50% for pattern 4) for the
feed and Z-axis displacement speeds with a 0.1 mm re-
duction of the vertical step to mini mise the axial stresses,
after which the process should be restarted with a new
tool (Figure 6(E)). Because it is easier to control the
machining parameters, it is possible, when the process
concludes successfully, to optimise the procedure by gra-
dually improving the X-speed of the tool in 10% incre-
ments. As the feed speed is increased, the chance of
damage is also increased. If the tool becomes damaged,
then it is necessary to restart the procedure with the most
recent feed speed for which success was obtained (Fig-
ure 6(F)). After implementing all of these suggestions, if
tool wear or damage continues to occur, it becomes nec-
essary to zone, i.e., to divide, the surface to be machined
according to the dimensions of the samples tested. For
each sector, a new tool must be used, and the process is
restarted. At the end of the procedure in the first area, the
success of the procedure is ascertained (Figure 6(G)).
In the case of failure, whether the tool incurred any
damage, such as wear at the tip or buckling, must be de-
termined. This wear, as previously mentioned, can occur
in one of two situations, either during the tool’s entry
into the rhyodacite, i.e., at the beginning of the machin-
ing process, or during the machining process as the tool
moves along the X- or Y- and Z-axes. The determination
of the situation in which damage occurred requires accu-
rate observation by the operator. Should the observed
wear occur during the machining process, it is suggested
that both the feed and Z-axis displacement speeds be
reduced by 10% (or 50% for pattern 4). This minimises
the axial stresses and favours processing. However, if the
wear is observed during entry, it is necessary to reduce
the plunge speed by 10%, thus minimising premature
wear of the tool. In either case, the reduction in speed is
relative to the initial parameter. After these changes, it is
necessary that the tool be changed, and the procedure is
restarted. If the procedure was not completed and no
visible wear has occurred, the tool is damaged (bent or
broken), and a new reduction of 10% (or 50% for p attern
4) in the feed and Z-axis displacement speeds must be
made to minimise the axial forces during machining. It is
necessary to restart the process in the zone being worked
with a new tool (Figure 6(H)). Once again, the success
of the process is ascertained. If the machining process
concludes, then it is possible to optimise the proc edure as
previously described (Figure 6(I)). With all of these in-
terventions, if there is no conclusion and no improvement
in the machining conditions and/or reduction in tool
damage, then it is not be possible to finalise the proce-
dure (Figure 6(J)).
5. Conclusions
In this article, we present a characterisation study of the
material behaviour of rhyodacite (“carijó” basalt), a stone
material, including its processing by high speed machin-
ing (HSM). Our approach enhanced o ur understand ing of
the necessary processing conditions for rhyodacite and
achieved a deeper understanding of this material’s char-
acteristics. The technological contributions of this study
can be found in the systematisation of the HSM milling
procedure and the development of decision-making maps
to increase the possibilities of successfully processing
this stone material.
The original contributions of this study are related to
the use of low-cost diamond-coated polycrystalline tools
for rhyodacite processing while correlating the rock pro-
perties with tool wear, with the goal of determining the
applicable parameters.
The results of this study have shown that the low-cost
diamond-coated polycrystalline tools with nickel matrix,
obtained from the market, were not able to withstand the
forces to which they were subjected. This made it neces-
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sary, here in Brazil, to elaborate a specific post-processor
to obtain more control over the parameters provided by
CAM software packages. However, it was extremely dif-
ficult to maintain the machining parameters, and count-
less failure problems were encountered with the multi-
point tool.
This study suggests th at adopting the use of HSM tools
for the industrial-scale processing of rhyod acite in Brazil
would require technological developments towards low-
cost diamond-coated tools, the cost of which should be
compatible with the commercial value of this rock; the
recommendation is to start with monocrystal diamond
tools or single-point tools fabricated with high hardness
ceramics, such as tungsten carbide, cubic boron nitride
and PCD.
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Open Access MME