Management Systems

in 2018, Volume 26, Issue 4, pp. 193-199

Production Engineering

Date of submission of the article to the Editor: 03/2018

Date of acceptance of the article by the Editor: 07/2018
DOI 10.1515/mspe-2018-0031

COMPUTER-AIDED SUPPORT FOR THE RAPID CREATION OF PARAMETRIC

MODELS OF MILLING UNITS FOR LONGWALL SHEARERS

Łukasz BOŁOZ
AGH University of Science and Technology

Leonel F. CASTAÑEDA
GEMI research group Universidad EAFIT

Abstract:
The cutting drums are the basic working components of many mining machines. The article focuses on differ-
ences in the design of cutting drums depending on the expected working conditions. Then, the unique calcu-
lation procedure is presented which allows to determine the load on the unit by reducing the forces acting on
a single pick, taking into account the picks bent on the cut-off disc. Until now, this has been omitted in the
literature. The results of the calculations for the selected cutting drum performed in MATLAB are also pre-
sented. The further section proposes to use Autodesk Inventor Professional's iLogic Tool for quick modelling
of cutting drums. The principles of creating parameterized models and compositions using programming ele-
ments in the form of iLogic scripts are presented. The articles presented a ready-made units generator, taking
into account the possibility to determine values of selected numerical parameters of the unit: diameter, web,
number of patches and cutting pitch. The generator also allows you to select the type of pick holders, conical
pick types, as well as the choice of pick system for repositioning or matching picks.

Key words: cutting drums, computer-aided support, units generator, unit load, parametric modelling, iLogic,
Audodesk Inventor Professional

INTRODUCTION however, until now iLogic has not been used and cutting
Engineering design in its widest sense makes use of com- drums have not been parameterized [13, 14].
puter-aided work support. In mechanical engineering, An important issue at the stage of selecting and designing
software is used as a basic tool for creating virtual models, the units is the load generated by the milling process and
compositions, systems and documentations (CAD – Com- the demand for power. Until now, the literature has
puter Aided Design). It is increasingly used to simulate known various methods for determining the load of a
phenomena, verify assumptions and concepts, and to op- knife (pick) during milling, as well as formulas for reducing
timize solutions (CAE – Computer Aided Engineering), as the load to determine the load of a longwall shearer arm.
well as to produce machine parts (CAM – Computer Aided However, these formulas did not take into account the
Manufacturing). However, despite the use of powerful knives swinging out on the cut-off disc, which were
programmes, their potential and capabilities are often treated as knives on the cutting and loading part of the
only exploited to a limited extent. unit [6, 10]. In this case, the MATLAB program was used
Cutting drums are examples of typical, parametric engi- to execute scripts calculating the unit load.
neering objects, which can be conveniently and quickly In the paper [1] a wide analysis of the influence of the ar-
generated using the functions available in many CAD pro- rangement of radiant knives on the variability of the unit
grams. This article describes the use of Autodesk Inventor load for different parameters was carried out. Attention
Professional's iLogic tool. The creation of a parametrised was paid to the need to optimize the knife system in order
automatic generator of cutting drums enables a quick ob- to obtain an even load of all tools and the lowest possible
taining of a conceptual model necessary at the stage of dynamics of work of the whole head.
collision analysis or presentation of the solution to the
contractor, as well as a detailed composition, which to- CUTTING DRUMS
gether with the related technical documentation consti- The milling units are the main elements in the milling of
tutes a complete design to be implemented. The subject many machines, such as cutting shearers, rock milling
of parametric design with the use of various test programs machines and road and floor milling machines. Milling
is known and widely used in mechanical engineering, units are designed to mine various types of natural and
 194 Management Systems in Production Engineering 2018, Volume 26, Issue 4

artificial mineral materials. They differ in construction,

kinematical and energy parameters, and these differ-
ences result from the place of their application, i.e. the
type of mined material. The wide range of applications is
mainly due to the possibility of implementing two pro-
cesses at the same time, i.e. the process of cutting and
loading.
The cutting drums of longwall shearers are designed for
specific mining and geological conditions. Seemingly, the
units of longwall shearers differ only in size, i.e. in diam-
eter and web, but despite their similar appearance their
parameters related to the process of loading and milling
are very different. In particular, they differ in the num-
ber of patches, the angle of winding of the patches and
the parameters of the knife system, such as the cutting
pitch [6, 7].
The cutting process, carried out by the mining machine Fig. 1 Milling augers mounted on mining longwall shearer
1. longwall shearer, 2. hub, 3. cut-off disc, 4. patches, 5. grip
with the aid of cutting tools of the unit, consists in me-
with conical pick
chanical separation of rock particles from the undis- Source: [7].
turbed soil. The cutting tools are mounted in the appro-
priate knife holders. The most commonly used cutting LOAD OF MILLING AUGERS
tools mounted on milling units are tangential-rotary During the cutting process, every knife in contact with the
knives [6, 7]. undisturbed soil is exposed to the forces of resistance in
The tangential-rotary knives, placed on the patches and mining process. These resistances were assumed to be
on the cut-off disc, form a knife system which allows the represented by three forces perpendicular to each other:
machining process to be carried out by milling. The Ps – cutting force (tangential), Pd – pressure force (nor-
knives are exposed to abrasive wear due to their direct mal),Pb – side force (Fig. 2a). Mechanical cutting of fragile
contact with the undisturbed soil. This is an unavoidable materials (e.g. coal) has been and still is the subject of nu-
process, but the correct design of the mining unit, the merous studies. To determine the components of the cut-
appropriate selection of parameters of the milling pro- ting resistance forces, an empirical model can be success-
cess as well as the optimal selection of tools allow to fully used, which is the result of many years of research
minimize and control and predict the wear of the knives on the issues of the coal cutting process [1, 6]. During mill-
[4, 5, 8, 9, 15]. It is worth noting that a similar problem ing, the knife moves in a compound motion due to the
also occurs with the mining of other natural materials, feed speed of the machine and the rotational speed of the
such as wood [11, 12]. In both cases, steel mining tools, unit. As a result, the knife makes one cut of the shape
carbide blades and possibly wear-resistant coatings are shown in the Figure 2b. The depth of cut changes from
used. zero to maximum and then decreases to zero again.
The mining units mounted on the arms of longwall shear-
ers (Fig. 1), are designed for mining coal and rocks sur-
rounding the coal undisturbed soil. Due to their design
and working method, they are called milling augers. Re-
gardless of the method of manufacture (welded or cast),
the units are made of hub 2, inside which there is a
sleeve transferring torque from the shaft on which it is
mounted. On the surface of hub 2 there are patches 4,
forming a cylindrical contour of the unit, to which the
holders of cutting knives are welded 5. The hub is usually
Fig. 2 Forces implied on pick (a) and pick blade trajectory
equipped with a cut-off disc 3, which is formed by a plate
on the unit during mining (b)
in the shape of a wheel with a specified width and diam-
eter. Mining units used in underground mining are The formulae describing the mining resistance allow to es-
equipped with external and internal sprinkler systems, timate the value of forces acting on a single tool in a spe-
where in the patches of the unit and the cut-off disc
cific position on the unit [6]. To obtain a reduced load im-
there are ducts of water supply to the sprinkler nozzles, posed on the unit, the following values must be deter-
located behind the handle and knife. Sprinkling is used mined for each knife in contact with the undisturbed soil:
to reduce dust and sparks in the workplace and to in-
ܲ௫ = ܲ௦ ‫݊݅ݏ‬ሺ߮ሻ − ܲௗ ܿ‫ݏ݋‬ሺ߮ሻ
crease the durability of cutting knives [5, 6, 7]. Apart
ܲ௬ = ܲ௕ (1)
from the typical auger construction, the milling units can
ܲ௭ = −ܲ௦ ܿ‫ݏ݋‬ሺ߮ሻ − ܲௗ ‫݊݅ݏ‬ሺ߮ሻ
be either drum or spatial [2, 3].
Ł. BOŁOZ, L. F. CASTAÑEDA – Computer-aided support for the rapid creation… 195

‫ܯ‬௫ = −ܲ௕ ‫ݖ‬௜ − ሾܲ௦ ܿ‫ݏ݋‬ሺ߮ሻ + ܲௗ ‫݊݅ݏ‬ሺ߮ሻሿ‫ݕ‬௜ ௡ ௡ ௡

‫ܯ‬௬ = 0,5‫ܦ‬௦ ܲ௦ (2) ‫ܯ‬௫௢ = ෍ ‫ܯ‬௫௜ , ‫ܯ‬௬௢ = ෍ ‫ܯ‬௬௜ , ‫ܯ‬௭௢ = ෍ ‫ܯ‬௭௜ (8)
‫ܯ‬௭ = ܲ௕ ‫ݔ‬௜ + ሾܲௗ ܿ‫ݏ݋‬ሺ߮ሻ − ܲ௦ ‫݊݅ݏ‬ሺ߮ሻሿ‫ݕ‬௜ ௜ୀଵ ௜ୀଵ ௜ୀଵ

Knife blade position:

‫ݔ‬௜ = 0.5‫ܦ‬௦ ܿ‫ݏ݋‬ሺ߮ሻ
(3)
‫ݖ‬௜ = 0.5‫ܦ‬௦ ‫݊݅ݏ‬ሺ߮ሻ
A diagram of the distribution of the cutting force compo-
nents on a single tool, with the length of the working part
Hn, shows Fig. 3. The xyz coordinates system is located in
the unit axis at its end (from the side of the sidewall). The
xn’yzn’' coordinate system is rotated as a result of changing
the position of the tool on the unit. This position is de-
scribed by an angle φo The described diagram and formu-
lae refer to the knives located on the mining and loading
part of the unit, i.e. on the cylindrical surface of the unit.
In addition to the knives placed on the side of the hull, the
milling units are also reinforced with knives on the cut-off
disc. The knife on the cut-off disc is tilted so that it pro-
tects the handle and the unit against contact with the un-
disturbed soil by cutting. The knife angle on the cut-off
disc can exceed 45, which significantly affects the distri-
bution of the load on the unit. Fig. 4 shows the force dis-
tribution diagram for the knife tilted by the angle φo, for
the backward rotation of the unit. For overshop rotations,
both diagrams are analogous. When creating the load di-
agram for the tilting knife on the cut-off disc, it was as-
sumed that the cutting force is a tangential force acting in
the direction of the blade's movement. The vectors of the
pressure and side forces, on the other hand, have been
deflected from the axis by an angle of φo. Taking into ac-
count the position of the knife on the unit, a system of Fig. 3 Diagram of the distribution of the component forces of
xn’yzn’ coordinates was obtained, similarly to an inclined the cutting resistance on a single tool
knife. The pressure and lateral force shall be tilted by an
angle of φo in the xn’y plane.
After the power distribution diagram had been devel-
oped, the load reduction formulas were derived from the
swivel blade:
ܲ௫ = ܲ௕ ‫݊݅ݏ‬ሺ߮௢ ሻ ܿ‫ݏ݋‬ሺ߮ሻ + ܲ௦ ‫݊݅ݏ‬ሺ߮ሻ
− ܲௗ ܿ‫ݏ݋‬ሺ߮௢ ሻ ܿ‫ݏ݋‬ሺ߮ሻ
ܲ௬ = ܲ௕ ܿ‫ݏ݋‬ሺ߮௢ ሻ + ܲௗ ‫݊݅ݏ‬ሺ߮௢ ሻ (4)
ܲ௭ = ܲ௕ ‫݊݅ݏ‬ሺ߮௢ ሻ ‫݊݅ݏ‬ሺ߮ሻ − ܲௗ ܿ‫ݏ݋‬ሺ߮௢ ሻ ‫݊݅ݏ‬ሺ߮ሻ
− ܲ௦ ܿ‫ݏ݋‬ሺ߮ሻ
‫ܯ‬௫ = ሾܲ௕ ‫݊݅ݏ‬ሺ߮௢ ሻ ‫݊݅ݏ‬ሺ߮ሻ − ܲௗ ܿ‫ݏ݋‬ሺ߮௢ ሻ ‫݊݅ݏ‬ሺ߮ሻ
− ܲ௦ ܿ‫ݏ݋‬ሺ߮ሻሿ‫ݕ‬௜ . . .
− ሾܲௗ ‫݊݅ݏ‬ሺ߮௢ ሻ + ܲ௕ ܿ‫ݏ݋‬ሺ߮௢ ሻሿ‫ݖ‬௜
‫ܯ‬௬ = ܲ௦ ሾ0.5‫ܦ‬௕ + ‫ܪ‬௡ ܿ‫ݏ݋‬ሺ߮௢ ሻሿ (5)
‫ܯ‬௭ = ሾܲௗ ܿ‫ݏ݋‬ሺ߮௢ ሻ ܿ‫ݏ݋‬ሺ߮ሻ − ܲ௕ ‫݊݅ݏ‬ሺ߮௢ ሻ ܿ‫ݏ݋‬ሺ߮ሻ
− ܲ௦ ‫݊݅ݏ‬ሺ߮ሻሿ‫ݕ‬௜ . . .
+ ሾܲௗ ‫݊݅ݏ‬ሺ߮௢ ሻ + ܲ௕ ܿ‫ݏ݋‬ሺ߮௢ ሻሿ‫ݔ‬௜
Knife blade position:
‫ݔ‬௜ = ሺ0.5‫ܦ‬௕ + ‫ܪ‬௡ ܿ‫ݏ݋‬ሺ߮௢ ሻሻ ܿ‫ݏ݋‬ሺ߮ሻ
(6)
‫ݖ‬௜ = ሺ0.5‫ܦ‬௕ + ‫ܪ‬௡ ܿ‫ݏ݋‬ሺ߮௢ ሻሻ ‫݊݅ݏ‬ሺ߮ሻ
The reduced unit load can be calculated by summing up
the determined forces and moments acting on each tool
that is in contact with the undisturbed soil.
௡ ௡ ௡
Fig. 4 Diagram of the distribution of cutting forces on the blade
ܲ௫௢ = ෍ ܲ௫௜ , ܲ௬௢ = ෍ ܲ௬௜ , ܲ௭௢ = ෍ ܲ௭௜ (7) of a tilted knife - backward revolutions
௜ୀଵ ௜ୀଵ ௜ୀଵ
 196 Management Systems in Production Engineering 2018, Volume 26, Issue 4

The formulae given allow to calculate the reduced load of GENERATOR OF MILLING AUGERS
the mining unit on the basis of the diagram of the knife The applications of the configurator (or in other words –
system and the assumed [6] or determined mining re- the generator) of the milling units of the longwall shearer
sistances on a single tool. On this basis, MathWorks enable a quick range of solutions without additional ef-
MATLAB developed a script to calculate the desired unit fort. The generator first of all enables quick creation of the
load and the expected power requirement. Fig. 5 shows initial design of the unit as a hull assembly and a specific
the reduced force and torque curves at the end of the unit type of knife holders with the appropriate type of tangen-
shaft. The presented curves were prepared for the unit of tial-rotary knives. Therefore, the hull was treated as one
φ1130x800 and the adopted kinematic parameters. The element, as in case of cast units. Breaking the hull into in-
power requirement determined at the moment of cutting dividual elements is not a problem and allows to generate
resistance My and the rotational speed of the unit n was a detailed model for welded units.
below 120 kW. Based on an analysis of the currently used units, the val-
ues that the user can assign to achieve the desired solu-
tion with the specified parameters have been selected.
The following parameters are taken into account in this
configurator together with their range of values:
• unit diameter: smooth change from 1400 mm to 2600
mm,
• spacing of the knife system: discrete values 30 mm, 40
mm, 50 mm, 60 mm,
• system arrangement: inversed or compatible (check
box: yes or no),
• web (automatic change): 800 mm – for diameters up
to 2000 mm, 1000 mm – for diameters from 2000 mm
including 2000 mm,
• number of patches (automatic change): three for di-
ameters up to and including 2000 mm, four for diam-
eters from and including 2000 mm,
• type of knives and knife holders: tangential-rotary
knives and appropriate knife holders according to cat-
alogue (Fig. 7),
• number of handles and knives (automatic change)
used: 48 – from 1400 mm (including) to 1700 mm (in-
cluding), 52 – from 1700 mm to 2100 mm (including),
68 – from 2100 mm to 2600 mm (including),
• other automatically generated values, such as the
thickness of the patches, the winding angle of the
patches, the thickness of the other plates and the di-
mensions of fastening are in accordance with good en-
gineering practices, but can be included as user-de-
fined values in the generator.
Fig. 5 Reduced load on the milling unit

The unit load and its variability depend to a large extent

on the diagram of the knife system, therefore it is im-
portant to control the correct insertion of knives position
into the script. The position of the knives entered into the
program is used to plot the unit diagram. The control of
data input consists in comparing the obtained graph with Fig. 7 Conical picks designated for the generator together
the designed knife system. Fig. 6 shows a knife system for with compatible grips of Gonar-Bis Ltd.
which force and moment curves, which are relevant for
the load on the mining machine, have been plotted in the The first edition of Inventor was in 1999. The basic and
drawing. most frequently used functions of the program are: 3D
modelling of parts, creation of compositions consisting in
adding bonds and relations between parts and creating
technical documentation based on created models of
parts and compositions. In addition to an advanced panel
for creating complex models and a rich library with ready-
made parts, Inventor is enriched year by year with new
Fig. 6 Picks system of the unit generated by means of a script possibilities. Working on models and parametric units is
Ł. BOŁOZ, L. F. CASTAÑEDA – Computer-aided support for the rapid creation… 197

possible thanks to such features as iFeature, iPart, iAs- The generator is based on basic programmable elements,
sembly and iMate. However, one of the functions that is such as commands of "if... then..", else, and, or, as well as
undoubtedly most developed in the context of parametric turning model elements on and off. The commands are
design is "iLogic". The principle of iLogic operation is to marked in violet in the code. In the developed units gen-
create rules that define logical conditions, equations, and erator only a small percentage was used, which proves the
automated routine actions within a part, composition, or high potential of iLogic. In addition to the mentioned com-
drawing of a technical documentation. By creating a sim- mands, also the following commands of "parameters",
ple script and using appropriate operators, you can influ- "Message.Box", "iLogicVb.RunRule", "Component.Visible"
ence the parameters and features of a given object using are used to create the configurator. Selected parts of the
an intuitive form. This feature allows you to standardize code are shown on Fig. 10. It has to be noted that this con-
and automate design by creating models, compositions, figurator required to prepare 16 rules.
and documentation in a parametric manner, as well as re-
using work that you've previously done without creating
them for iLogic purposes.
iLogic consists of several functions, where the basic one is
"Add Rule". This function allows you to name a new rule
and then create its content for selected parameters of the
automated design using templates of codes sorted in ap-
propriate categories (Fig. 8). The second essential feature
of the iLogic tab is the "iLogic Browser", which is used to
edit all the created rules, to enable or disable them and to
change the order.

Fig. 10 Sample code fragments of the configurator of cutting

drums

In case of the unit generator, its model consists of three

Fig. 8 "Add rule" function window in iLogic
basic parts: the hull, different types of knife holders and
tangential-rotary knives. However, due to its construc-
The "forms" tab is crucial for the future user of the config- tion, and in particular the presence of a variable number
urator, because it is used to create the menu of parame- of patches, modelling and creation of the composition is
ters and options selection. The menu is created using complicated (Fig. 11). The Figure 12 shows the chosen
standard elements such as buttons, sliders, selection form windows and the complete auger unit.
fields and text fields. In addition, it is possible to change
the appearance by adding a picture, changing the fonts
and colours of some elements (Fig. 9).

Fig. 11 Sample shots from the creation of a milling unit compo-

sition

Fig. 9 Menu for creating the parameter selection form

 198 Management Systems in Production Engineering 2018, Volume 26, Issue 4

It should be noted that the presented methodology allows

for the development of analogical generators for linear
pavement units, floor milling machines or road milling ma-
chines.

ACKNOWLEDGMENTS
The works were carried out within the framework of the
Dean Grant under the Agreement no. 15.11.130.838.

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dr inż. Łukasz Bołoz

AGH University of Science and Technology
Department of Mining, Dressing and Transport Machines
A. Mickiewicza Av. 30, 30-059 Kraków, Poland
e-mail: boloz@agh.edu.pl

dr inż. Leonel F. Castañeda

GEMI research group Universidad EAFIT
Carrera 49 No. 7 Sur-50, office 13-104, Medellín, Colombia
e-mail: lcasta@eafit.edu.co