Inline knockout machine is a kind of machine widely used in foundries for clean-up and separating castings and mold box. Machine is suitable for the above purpose because of simplicity of structure, reliability and provision for adjustment in vibrating direction and amplitude of exciting force. Main components of Inline Knockout Machine mainly consist of torsion bar, vibrating frame, vibrating box, vibrating motors installed on both sides of the vibrating box, spring and support device. When it works, the two vibrating motors rotate synchronously in the reverse direction. The vibration force in the vibration direction is generated by two vibration motors and the excitation force in the vertical vibration direction is equal to zero resulting in a straight line or an approximately straight line motion.
The vibrating box may break in the
long-term work, especially the sides of the vibrating box may suffer Fracture, and also
vibrating frame may suffer fracture in its structure. The main cause of mechanical failure in vibrating screen is the
vibration. Components like frame, vibrating box, spring dampers and bearings
are affected by this. The vibration will crystallize the molecular structure of
the metal causing what is known as metal fatigue to develop. The first sign
that an operator has indicating that the fatigue in the body of the screen deck
is almost at a critical stage in its development are the hairline cracks that
will appear around the vibration’s point of origin. This work adopted
components of inline knockout machine such as vibrating box, vibrating frame as
the object to study and analyze the stress distribution and deformation under
static loads, check the strength of vibrating box and analyze whether it will
resonate by calculating the natural frequencies and mode shapes of the
1.2 Vibrating Screen Working
simplest Vibrating Screen Working Principle can be
explained using the single deck screen and put it onto an inclined frame. The
frame is mounted on springs. The vibration is generated from an unbalanced
Fig1.2.1. inline knockout machine
The vibration pattern of the horizontal frit
is back and forth and the inclined vibrating screen is round. There are
different ways to produce the vibration itself. The horizontal screen uses a
double balance system. A very erratic motion is
developed when this wheel is rotated. A
double counterbalance system is used in the horizontal screen. The
counterbalance weight will alternately promote and retard the direction of
vibration depending upon where within each revolution the weights come opposite
Fig 1.2.2. Counterbalance weight
Eccentric shaft is used in the inclined
vibrating screen. The vibration of an unbalanced
flywheel is very violent. This causes mechanical failure and structural damage
to occur. The four bearing system greatly reduces this problem.
Motivation Of The Present Work
knockout machine consist of component like torsion bar,
vibrating frame, vibrating box, vibrating motors installed on both sides of the
vibrating box, spring and support device. Vibrating box may be damaged during long-term operation.
In particular, the sides of the vibrating box may break, and the structure of
the vibrating frame may also break.
The main cause of mechanical failure in
vibrating screen is the vibration. Components like frame, vibrating box, spring
dampers and bearings are affected by this. The first sign that an operator has
indicating that the fatigue in the body of the screen deck is almost at a
critical stage in its development are the hairline cracks that will appear
around the vibration’s point of origin. Failure analysis of above components will
give a closer theoretical look at the behavior of the above mentioned
2.2 Classification of Literature
Report on major literature
referred and studied. Literature review should include current thinking,
findings, and approaches to the problem. Following citation format should be
adopted. Generally there are two types of citation formats are adopted.
Turner (1963) presented
analysis of structures using stiffness matrix method. Patil and Kulkarni (1990)
developed Sample Large-Angle-of-Attack Viscous Hypersonic Flows over Complex
Lifting Configurations. Various research carried out in debris and referred
from (Jadhav, 1990). Deshpande et al. (1998) revealed new development of
this work is proposed by Patil (2011)
this work is proposed by Patil and Kadam
this work is proposed by Patil et al.
Boitumelo Ramatsetse 1 described in mineral processing
industries vibrating screens operate under high structural loading and
continuous vibrations. In this regard, this may result high strain rates, which
may often lead to structural failure or damage to the screen. In order to
lessen the possibility of failure occurring, theories and techniques for
analyzing machine structures are investigated and applied to perform a sensitivity
study of a newly developed vibrating screen. Structural strength and stability
of a vibrating screen is essential to insure that failure doesn’t occur during
production. In this paper a finite element analysis (FEA) on a reconfigurable
vibrating screen (RVS) is carried out to determine whether the structure will
perform as desired under extreme working conditions at the different
configurations of 305mm×610mm, 305mm×1220mm and 610mm×1220mm.This process is
aimed at eliminating unplanned shutdowns and minimizes maintenance cost of the
equipment. Each component of a screen structure is analyzed separately, stress
and displacement parameters are determined based on dynamic analysis. In
addition, a modal analysis was carried out for the first three (3) modes at
frequency f of 18.756 Hz, 32.676 Hz and 39.619 Hz respectively. The results
from the analysis showed weak points on the side plates of screen structure.
Baragetti 2 An innovative design solution is
presented in this paper; it allows the enhancement of structural Resistance and
the dynamic performances of a vibrating screen for inert materials. The new
design does not significantly affect the geometry of the traditional screens,
keeping the same global dimensions and almost the same mass value. In fact the
aim of this study was to design a new vibrating screen having almost the same
dimensions but that could give a much higher dynamic structural resistance at
frequencies and load amplitudes much higher than the nominal ones. Numerical
finite element models were generated to investigate the structural and dynamic
behavior of a standard vibrating screen. These analyses allowed the
modification of the geometrical parameters of the traditional screen and to
design the new one. Accurate three-dimensional FE models were so generated in
order to evaluate the best design solution, in terms of dynamic structural
resistance, able to reduce the stress values at the most stressed area. The
fatigue resistance of all the components of the new screen was checked, with
particular attention to the welding joints. Experimental full scale tests on a
prototype of the new screen were carried
out in order to validate the
numerical models and mostly to verify the structural integrity of the vibrating
screen during the working conditions. Strains at the surface of the most
stressed areas of the screen were measured in dynamic working conditions, at
different frequencies and load amplitudes; these stress values were compared
with the numerical ones in order to validate the numerical results. The new
screen was patented.
Zhao Yue-mina, Liu Chu-shenga3 The reliability is a key factor
for the design and manufacture of large vibrating screen. In the paper, He
presented a new large vibrating screen with hyperstatic net-beam structure.
Dynamic characteristic of the vibrating screen was researched and dynamic
simulation method of large screening machines was explored. He used finite
element method (FEM) to analyze dynamic characteristic of large vibrating
screen with hyperstatic net-beam structure. Multi natural frequency, natural
modes of vibration and dynamic response of the vibrating screen were
calculated. The structural size of stiffeners on the side plate was optimized
under multiple frequencies constraints and an adaptive optimization criterion
was given. The results show that the vibrating screen’s structural strength is
increased and the natural frequency of bending deformation is enhanced. The
modal frequencies are far from working frequency, and thus the structure is
able to avoid resonance effectively and reduce the destructiveness. The maximum
transverse displacement of the vibrating screen is 0.13 mm, the maximum
difference in vibration amplitude of corresponding points is 0.44mm and the
maximum dynamic stress is 16.63MPa. The structural optimization shows that the
mass of the side plate is decreased by 194.50kg, the second and third modal
frequency is increased by 1.73% and 2.91% respectively and a better optimal
effect is received.
Yongjun Hou, Pan Fang and Lian Zeng 4 In order to study the stress
distribution of dual-frequency vibrating screen and ensure the screen box has
sufficient strength and longevity, a finite element model of dual-frequency
vibrating screen was built, and the stress, modes and fatigue life of the
screen box were analyzed. The results indicate that, the stress concentration
appears at the contacting parts between the crossbeam and the stiffener of
motor seat, the crossbeam, L-type stiffening plate, baffle of material added
and screen box. The middle of crossbeam and the L-type stiffening plate are
weaker parts of fatigue; they are easily fatigue failure under high frequency
Xinyong ,Cui Hongbin ,Cao Pengxian15 A simplified model of self-balance screen was constructed
by using SolidWorks, and then imported into the Simulation to analysis its
structure and modal. The stress distribution, deformation and structural
natural frequency, mode shapes under static loads of the self-balance vibrating
screen were calculated to provide theoretical basis for the following analysis
of the dynamic characteristics and structure optimization design of vibrating
I.B. Eryu¨ rek, M. Ereke, A. Go¨ ksenli 6 In this paper the failure of the rear
suspension spring is analyzed in detail. The rear axle suspension system of the
truck and fractured flat spring is investigated. Fracture surface, mechanical
and chemical properties and microstructure of the spring material is analyzed.
A force acting on the spring is determined and strength calculations are
carried out. Later, failure behavior and cause of fracture is revealed after carefully analysis of
microstructure and results of calculations. At the end precautions to be taken
to prevent a similar failure is recommended.
2.3 Objectives of
TO generate Numerical
finite element models to investigate the structural and dynamic behavior of a
To study the stress
distribution on the vibrating box and vibrating frame under current operating
To study the stress
concentration on the vibrating box and vibrating frame under current operating
Resonable selection of
vibrating screen working frequency.
Conditions Of Inline Knockout Machine
The unit consists of the freely suspended screen and a
shaft assembly carried by the box. Near each end of the shaft, an eccentric
portion is turned. The shaft is counterbalanced, by weighted fly-wheels,
against the weight of the screen and loads that may be superimposed on it. When
the shaft rotates, eccentric motion is transmitted from the eccentric portions,
through the two bearings, to the screen frame.
Frame is mounted on vibrating box with the help of two
steel angels. Two L shaped angular plates restricts the motion on screen. The
vibrations are transferred from torsion bars to screen.
Spring dampers are mounted as per the load to
be applied on the vibrating screen, two on each side for damping purpose and
Stiffness values of spring is calculated by using above property
and used in the modal analysis as one of the input value. Damping factor is
also one of the property to be used in harmonic analysis.
Stiffness of spring calculation –
Of The Component
the failure analysis of the knockout machine the main components to be
considered are vibrating box and vibrating screen. During the cycle of process
effect of vibration is mainly observed on the side plate of the box, secondly
the vibrating screen also suffers failure as result of frequent loading of
box is divided into two parts: Vibrating frame and screen frame. Screen is
installed in the interior of screen frame. The box is located on the vibration
damper using springs. Material enters into the upper ports of vibrating box and
is discharged through the bottom ports during the working.
of the complex of structure and too many parts of screen and screen frame, the
finite element models of them are very difficult to be building by using the
ANSYS. Because CAD is mature and operational software, it can quickly create
virtual models of screen and screen frame. Therefore, the combination of CAD
and ANSYS is very necessary for analyzing vibrating screen. The combination can
improve the speed of changing model and the efficiency of analyzing vibrating
screen .The CAD model was changed into a standard format which can is imported
into ANSYS in order to get finite element model.
allows the creation of 3D areas, from 3D images, sheet metal, compounds,
shaped, made or pedaling areas up to the meaning of technical devices. The
application provides advanced technological innovation for technical
appearance. It provides tools to complete product meaning, such as functional specifications
as well as kinematics meaning. CATIA provides an extensive variety of
applications. CATIA v5 is able to read and produce STEP format files for
reverse technological innovation and surface recycling.
the analysis purpose following 2 components is considered:-
2. Vibrating screen
1. Vibrating Box-
Vibrating box is main
component of inline knockout machine which supports all other components such
as frame, dampers ,torsion bar, angle plates etc. generally the box is
combination of welding and bending process.Torsion bar is mounted by bolting a
circular plate inside the box plate. The screen is mounted with the help of
angle plate.one net like structure is present at the top of screen but is not
considered in analysis.
Fig 4.1.1-Isometric View Of Inline knockout Machine
Fig4.1.2- Detailed Drawing
Of Vibrating Box
Vibrating screen is the second part under consideration for analysis.
Function of the screen is to support vibrating net.mold boxes and castings
passes over this net. Vibrating screen act as a support for the vibrating box
and doesnot allow them to scatter over the surface.
Fig 4.1.3- Detailed
Drawing Of Vibrating Screen
ANALYSIS OF THE COMPONENTS
the Failure analysis of the machine, modal analysis and harmonic analysis
required to be carried out:
Modal analysis is used to determine a structure’s vibration characteristics natural
frequencies and mode shapes. Different mode shapes for different frequencies of
structure can be determined in modal analysis. In modal analysis no any Pre-Stress and preloading’s are
applied to the structure. Only different types of supports are considered in
the analysis. The results of modal analysis is natural
frequencies and the corresponding formation that only related to the inherent
characteristics of the system and free from external forces and the method of
fixing. Natural characteristic includes natural frequency, natural vibration
modes and other modal. Parameters. The purpose of natural characteristic
analysis is to avoid resonance and harmful vibration modes and improve the
reliability and service life of screen and screen frame.
The dynamic response of the vibrating screen at any moment can be obtained by finite element analysis and the stress distribution and weak point of the vibrating screen can be displayed on the operating frequency by harmonic analysis. In this type of analysis all types of force, pressure, moment, displacement, nodal support, fixed support, elastic support, friction less support can be applied for the analysis.
model of the screen box must be make some corresponding simplifies as possible
to reflect the true characteristics of its main structure under the premise of
units less to use or the simple unit form for finite element model.
simplified steps are taken:
(a) Some small
connectors, fixing bracket, other non-bearing components and functional parts are
chamfers, fillets, rivets and welding spots are ignored which are not the major
factors to reduce the workload of the modeling.
(c) Ignore the
technological holes and bound holes on the screen box as such small diameter
holes has little effect on general strength and stiffness of the structure, but
the mesh units will greatly increase.
(d) The parts of screen box are thin-walled
plate except the motor base.
Fig 5.1 -CAD Model
Of Inline Konckout Machine
and preloading –
Import the modal in the ANSYS for the analysis
purpose. Auto connection feature is used to define all the connection of the geometry.
Spring is used as one more connection for dampers; there are two types of spring’s
1.body-body type 2.Body- ground type.
We have used
body-ground type spring here in this type of spring reference is grounded
(fixed) to the ground i.e there is no any directional moment along any side of body,
it will act as base of spring damper. Scoping- the working part of spring is considered
as mobile direction of body, the direction in which spring is going to experience
compression or expansion. By considering all above explanation constraints of
spring will be GROUND to part 325121 00 003 (upper part of spring damper
spring 120.94 N/mm^2 is used as one of the input characteristic of spring.
Preloading i.e the approximate load which is acting on the spring is also considered
in the analysis because spring may suffer pre deformation due the load applied
by the whole structure. Approximately 3 ton preload is applied on the spring.in
this analysis only one spring is considered as working condition.
Imported model from CATIA is required to mesh for
further analysis. Efforts are made to achieve finer mesh for accuracy of results.
Finer mesh on the parts likes vibrating box, torsion bar support is achieved because
these component suffer frequent failure during working, components like frame,
supports of damper, angle plates for supporting frame etc. are relatively less finely
meshed because the failure is not frequent for these parts, also considering
time consumed for analysis it is not convenient to achieve the finer mesh for
For meshing first auto mesh is generated, face
sizing and edge sizing is applied on the edges of circular part and face sizing
is applied on side walls of the box. Mesh is hex dominant In meshing number of
nodes formed are 403425 and number of elements are 57722.
For the model analysis material
used is mild steel. Material properties of mild are as following
Modulus Of Rigidity
Modulus Of Elasticity
In modal analysis we have considered
here first ten modes of vibration for analysis.i.e the behavior of the system
for first ten mode and its corresponding frequencies.
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