FORCES AT THE MAIN MECHANISM OF A RAILBOUND FORGING
MANIPULATOR
Florian Ion Tiberiu Petrescu
Bucharest Polytechnic University, Romania
E-mail: petrescuflorian@yahoo.com
Relly Victoria Virgil Petrescu
Bucharest Polytechnic University, Romania
E-mail: petrescuvictoria@yahoo.com
Submission: 26/03/2015
Revision: 11/04/2015
Accept: 22/06/2015
ABSTRACT
Forging
manipulators have become more prevalent in the industry today. They are used to
manipulate objects to be forged. The most common forging manipulators are
moving on a railway to have a greater precision and stability. They have been
called the railbound forging manipulators. In this paper we determine the
driving forces of the main mechanism from such manipulator. Forces diagram
shows a typical forging manipulator, with the basic motions in operation
process: walking, motion of the tong and buffering. The lifting mechanism
consists of several parts including linkages, hydraulic drives and motion
pairs. Hydraulic drives are with the lifting hydraulic cylinder, the buffer
hydraulic cylinder and the leaning hydraulic cylinder, which are individually
denoted by c1, c2 and c3. In this work considering that the kinematics is being
solved it determines the forces of the mechanism. In the first place shall be
calculated all external forces from the mechanism (The inertia forces,
gravitational forces and the force of the weight of the cast part). Is then
calculated all the forces from couplers.
Keywords: Mechatronics, Railbound forging manipulator, Lifting
mechanism, Forces of mechanism, Driving forces.
1. INTRODUCTION
Heavy payload manipulators (GE, 2012) which are
special industrial robots are widely used in large forgings manufacturing,
tunnel boring, mine excavation and large work pieces loading/unloading etc.
They can greatly improve the efficiency and product quality, and lower
manufacturing costs. Heavy payload manipulators have the characteristics of
large payload capacity, multi degree of freedom, large size and high stiffness.
They have been under increasing applications in heavy payload manipulators.
Forging manipulators have become more prevalent
in the industry today (GAO, 2010). They are used to manipulate objects to be
forged (SHEIKHI, 2009).
The most common forging manipulators are moving
on a railway to have a greater precision and stability (see Figure. 1). They
have been called the railbound forging manipulators.
Figure 1: A railbound forging manipulator
Source: Dango and Dienenthal
Alternatively, these mastodons can also be
independents by the railway (see the Figure 2).
Figure 2 A mobile forging manipulator
Source: Dango and Dienenthal
Regardless of the type of construction, these
manipulators have mainly one type of mechanism (see the figure 3) (CHEN, 2009; YAN, 2009).
Figure 3: The kinematic
schema of the main mechanism
The lifting mechanism consists of
several parts including linkages, hydraulic drives and motion pairs. Hydraulic
drives are with the lifting hydraulic cylinder, the buffer hydraulic cylinder
and the leaning hydraulic cylinder, which are individually denoted by c1, c2
and c3. In lifting process, the cylinder c1 controls the vertical movement of
work piece through inputting lifting signal.
At the same time, the cylinders
c2 and c3 are perfectly closed (HEGINBOTHAM,
1979). While c1 and c3 are closed
cylinders, cylinder c2 performs horizontal movement. While, the cylinders c1and
c2 are closed the cylinder c3 realizes leaning movement by inputting leaning
signal in leaning condition (BALDASSI, 2003).
In this work considering that the
kinematics is being solved it determines the forces of the mechanism.
Forces diagram (see the Figure 4)
shows a typical forging manipulator, with the basic motions in operation
process: walking, motion of the tong and buffering.
In the first place shall be
calculated all external forces from the mechanism (The inertia forces,
gravitational forces and the force of the weight of the cast part). Is then
calculated all the forces from couplers (LI,
2010; LIU, 2010).
Figure 4: The forces schema of
the main mechanism
2. THE FORCES OF THE MAIN MECHANISM
In the forces study of a mechanism one
determines all forces instant (at a certain moment acting on the mechanism
respectively). It is based
on kinematic scheme of the mechanism loaded with all the forces acting on
the mechanism (see Figure
4). Some forces (outside or
external forces) are known, and others (forces from couplers) are not known,
but must be determined (ZHAO, 2010).
In step 1 are calculated forces known, outside
forces, composed of forces of inertia and gravitation (system 1).
(1)
Now it writes three
separate systems (2-4) which calculates the reactions of motor couplings dyad
(7, 1, 2)
Figure 5.
Figure 5:
The forces schema of the dyad 7,1-2
(2)
(3)
(4)
The calculation continues with
the next motor dyad composed of elements (6,
10, 11), systems (5-7) Figure 6.
Figure 6:
The forces schema of the dyad 6,10-11
(5)
(6)
(7)
The next calculations to the dyad (single, not
driven, comprising the elements 3, 4), can be seen in the systems (8-10) Figure
7.
Figure 7: The
forces schema of the dyad 3,4
(8)
(9)
(10)
The calculation continues with
the next motor dyad composed of elements (5,
8, 9), systems (11-13) Figure 8.
Figure 8:
The forces schema of the dyad 5,8-9
(11)
(12)
(13)
2.1 Determining driving forces of the main mechanism
In the
end we can determine and (three) driving forces. In Figure 9 can be monitored engine element c1 composed
of kinematic elements 8-9. Determine motive power Fm1 with relations
of the system 14; being two relations of calculation may be carried out a
check.
(14)
Figure 9:
Forces schema of the motor mechanism c1
In Figure 10 can be monitored engine element c2 composed
of kinematic elements 10-11, and determine motive power Fm2 with the
relations of the system 15.
Figure
10: Forces schema of the motor mechanism c2
(15)
In Figure 11 can be
monitored engine element c3 composed of kinematic elements 1-2, and determine
motive power Fm3 with the relations of the system 16.
Figure
11: Forces schema of the motor mechanism c3
(16)
3. DISCUSSION AND CONCLUSIONS
Forces diagram shows a
typical forging manipulator, with the basic motions in operation process:
walking, motion of the tong and buffering.
In the first place shall be
calculated all external forces from the mechanism (The inertia forces,
gravitational forces and the force of the weight of the cast part). Is then
calculated all the forces from couplers.
In the forces study of a mechanism
one determines all forces instant (at a certain moment acting on the mechanism
respectively). It is based on kinematic scheme of the mechanism loaded with all
the forces acting on the mechanism. Some forces (outside or external forces)
are known, and others (forces from couplers) are not known, but must be
determined (ZHAO, 2010; PETRESCU,
2009, 2011-2014).
Determination
of kinematic couplings reaction
forces from the main mechanism of a forging
manipulator is vital because with the data
obtained can properly
size the mechanism.
On the other hand, dynamic
study of the mechanism (LI, 2010) will be conducted with the help of knowledge forces acting
on the mechanism (LIU, 2010).
In forging manipulators
today one requires the use of very large weights and full automation of the
process of forging, which involves
knowing the forces of gravity that must be sustained, manipulated and
forged.
Relationships presented can
determine with a very
high accuracy the forces which acting
on the entire mechanism.
In the
end we can determine and (three) driving forces. In Figure 9 can be monitored engine element c1 composed
of kinematic elements 8-9. Determine motive power Fm1 with relations
of the system 14; being two relations of calculation may be carried out a
check.
In Figure 10 can be monitored engine
element c2 composed of kinematic elements 10-11, and determine motive power Fm2
with the relations of the system 15.
In Figure 11 can be monitored engine element c3 composed of kinematic
elements 1-2, and determine motive power Fm3 with the relations of
the system 16.
4.
ETHICS
Author
declares that are not ethical issues that may arise after the publication of
this manuscript.
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