Concept development for a suction -cup manipulator [600724]

Concept development for a suction -cup manipulator
for thin sheet metal flats

Florin Popișter, Monica Steopan, Agrijan Bogdan, Grigore Marian Pop
Department of Design Engineering and Robotics , Technical University of Cluj -Napoca, Muncii 103 -105. 400641
Cluj-Napoca, Romania
[anonimizat], [anonimizat], [anonimizat], [anonimizat]

Abstract —The general objective of the authors of present
paper was to design based on specialty calculus a articulated arm
for handling thin metal sheets, and a gripper with suction cups
model with which it can manipulate metal sheets of different
sizes.
To achieve the proposed topic ,the design of a mechanism as
simple, easily achievable with the lowest possible costs and th e
highest possible safety to be easily implemented within the
European Fabrications company which it is the end user of entire
project.
In order to employ and solve the calculus regarding the
engines, or the needed valves it was used the Mathcad software.
The concept was designed based on a SCARA type robot, which
in author’s opinion is suitable to the requirements assessed by the
company.
Keywords —competitive development, automated manipulator,
sheet metal, deburring
I. INTRODUCTION
The industrial automatio n represent a research filed that
keeps on developing and also benefits constantly from the
technological progresses that were recorded in the past years.
The exponential development of the calculation systems
and the electronic equipment’s, the almost con stant growth of
the processors calculation strength, but also the capabilities of
the storage devices, has lead to the manufacture of more and
more performing automation equipment’s, which offers real –
time control of the governing processes.[1]
The necessi ty to have a constant and safe production, to
fulfill all the orders, to have a quality of a low and guaranteed
level, are just a few arguments to include the automation
equipment in the modern production lines.
The industrial automation , Fig.1, include a series of
processes and equipment’s whose purpose is an efficient
production line. Controllers, inverters, flow meters, pressure
transducers, level transducers, electric motors, displays,
software, sensors, flowmeters, counters etc., are just a few of
the elements which are a part of the wide field of the industrial automation. Each one has its own part in improving, all in all
of a production process. [1] .

Fig. 1. Industrial automation [2]
Methods which are a part of the automation process:
 automation installati on during operations to reduce the
length of time;
 automation installation where there is a need for a
higher grade of accuracy;
 replacing the human operators for tasks which require
heavy and monotonous work;
 replacing the human operators for tasks which require a
high level of danger;
 executing tasks which are above the human possibilities
regarding the calculating speed, volume, weight,
endurance;
 releasing the human operators in order to relocate them
for more lucrative purposes. [3]
Automation advantag es:
 flow increase
 increase of productivity
 increase of quality
 increase of sturdiness
 increased workers safety

Automation disadvantages:
 vulnerabilities regarding the security and good
functioning of the programs which operate the
machineries
 security supp ly (an automated system can have a
limited intelligence level, thus is more susceptible to
make an error
 developing costs are high and difficult to prevent.
 automation of a product, the workflow or the entire
production unity implied high production costs .
The robotized manipulation of the materials is one of the
frequent industrial applications of the robots. This is usually
performed by articulated industrial robots which implement the
"pick -and-place'' type of activities, or by relatively simple
manipul ators. [ 4]
Using industrial robots to manipulate the materials leads to:
 reducing the costs for the workforce;
 replacing the human operators for the working tasks
which involve a high risk or monotonous work
 reducing the pieces deterioration during the
manipulation process comparing to the classic version
which implies human operators.
In the present paper the authors wish to resolve the problem
of manipulating some thin metallic tables, within a company
specialized in the processing of metal sheet elements . Presently
the metal sheet is lifted from the load board by a worker with
his bare hands, which most of the times due to the sheet’s big
size and weight, during the positioning on the cutting table
(Fig.2 ) the sheet will be deteriorated or scratched. Due to this
reasons there are many throw -outs, and the company’s costs
increase significantly and the profit is below expectations.

Fig. 2. CNC Nibblers – TruPunch 3000 and Trumatic 500 II. CONCEPT DEVELOPMENT
In order to resolve this problem the authors consider that i t
can be done with the help of a manipulator and a gripper to
ensure a more precise and secure grip of the metallic sheet.
During the elaboration of the articulated arm for
manipulating thin metallic sheets, one must consider the
following demands:
 positio ning of the machine tools
 the work space of the machine tools
 the place where the metallic sheet is taken from
 the manner in which the sheet is placed for
manufacturing.
The dimensions of the articulated arm must not be very
large, so it wouldn’t interced e in the barrier of the machinery’s
protection sensors. During the construction of the manipulator
there must be considered the following demands:
 must contain standard parts and have a simplest design;
 low weight;
 as low costs as possible;
 the ability to manipulate metallic sheets of different
sizes;
 the ability to manipulate weights up to 40 kg;
 easy to use by the worker;
 easy to implement in the factory.
In order to manipulate the thin metallic sheets the gripper
must be built in such manner to be able t o manipulate sheets of
different sizes and have a correct grip in order for the sheet to
not suffer any deformations.
Using a dedicated method “Voice of the customer table”,
there were determined characteristics the needed platforms and
functions which mus t be satisfy . The “Voice of the customer
table” represents a process in which are identified and recorded
the requirements, needs, preferences and expectations of the
product, and based on these elements the product’s critical
characteristics. Having ident ified the requirements, the
Analytic Hierarchy Process was used to identify the relative
importance of each requirement. The formula used is [5, 6]:

 
Where:
 Ri represents the importance index of requirement “i”
 aij represents the rel ation between element “i” and
element “j”
Stage one of the project – The first stage represents
the classification of the customer’s needs and transforming

them into technical requirements. In Fig. 3 are presented the
list of demands that was prepared afte r consulting with the
director of the company EFR – European Fabrications as well
as according to the research regarding the needs of the
manufacturing process.
Fig. 4 presents the analytical classification of the process
(AHP), which compares the client’s demands individually in
order to establish which the most important one is and which
demands more attention. The method of analytical
classification is a reliable solution used in many fields [7.8]

Fig. 3. Customer needs

Fig. 4. Analytical classification of the proc ess Stage two of the project – The concept’s fragments ( Fig.
5) present several solutions and ideas regarding the
embodiment of the constructive version. For each idea there
will be noted the associated the requirements and functions.
The TruPunch3000 mach inery which will be used to
manufacture these sheets.

Fig. 5. Concept development phases
Stage three – final concept Within the company there had
to be established and efficient way to manipulate the metallic
sheets with different sizes which range between
1000x 1000[mm] and up to 2500×1500[mm] and can reach
weights up to 15 -20 kg. Presently the metallic sheets are
positioned on the TruPunch 3000 (Fig. 6) cutting table by the
worker, which during an 8 hour shift ends up lifting over 100
metallic sheets.

Fig. 6. The cur rent principle in placing the metallic sheets on to the
TruPunch 3000 cutting table

In order to manipulate the thin metallic sheets there will be
used a gripper with suction cups ( Fig. 7) which has the
capability to manipulate metallic sheets with sizes ra nging
between 1000×1000[mm] and up to 2500×1500[mm], and
which, by its design can manipulate the metallic sheet without
buckling or deteriorating it during the entire process.
The vacuum generating process is performed by a vacuum
pomp in the shape of X -Pump SXPi / SXMPi with IO -Linksi
compact injectors, which has an absorption capability of
75l/min, and the distribution in each suction cap is performed
by a pneumatic solenoid valves distributor.
The suction cup calculation:
Entry data:
 lifting mass: 20 [Kg ]
 maximum speed on the articulation = 3 [m/s]
 acceleration time 0 -> max= 1.26 [s]
 positioning accuracy =1.5 [cm]
 acceleration = 3 [m/s2]
Negative pressure and suction cups calculation:
Consider a gripper with vacuum which must manipulate a
thin metallic sheet of sizes which can reach 2500x1500x2[mm]
and the material has a density of 7.85[g/cm3]. The gripper has 8
suction cups, each cup having a diameter of d s=200[mm]. The
distance between each suction cup is 450[mm], respectively
800[mm]. This dimension c an vary according to the metallic
sheet which is about to be manipulated.
For reasons of work protection as well as safety it is
considered a safety factor of 2 (which also considers the
moments in which the mechanism is accelerating). A
calculation is req uired of the necessary negative pressure in
order to manipulate the metallic sheet within safety conditions.
 M:=20 [Kg]
 k:=2
 g:=9.81 [m/s2]
 a:=3 [m/s2]
 μ:=0.5

FkM ga
N   
 F:=632.4 [N]
 μ – the friction coefficient for metal;
 a – the system’s ac celeration;
 k – safety factor;
 g –gravitational acceleration;
 M – weight of the thin metallic sheet;

Fig. 7. The final concept of the suction cup gripper
Foreword it is calculated the actual vacuum surface of the 8
cups. A safety coefficient it is to be consider ed a=0.9 in the
direction that it is not taken within the calculus the entire
surface of the cups.

n:=8 nr. cups;
a:=0,6 safety factor
π:=3,142
d:=0,2 [m]
200mm…………0,2 m – cup diameter

A and
22



  
A:=0,151 m2

in order to calculate the negative pressure needed for
manipulating a sheet metal it was used the formula:


PF
A  
P=4,194×103 [N/m2]
1 bar…………105 [N/m2]
x………………4,628×104 [N/m2]

xP
105  
x=0,042 [bar]

the negative pressure is: Pneg=0,042 [bar]

The chosen cup it will work within a negative pressure of
0,463 bar, the lift force needed is 39 N:
Total time in which the entire system has the needed
vacuum level is:
 t – time [min];
 v – air volume needed to be dislocated [m3];
 Q- air feed of the pump [m3/min];
 1,25 – safety coefficient ;
 n – smoothing factor acting of the negative pressure
coefficient which must be generated
 h – cup drive
 h:=3,5×10-3 [m]
 n:=1 because the negative pressure is below 0,5 bar
 V:=Axh [m3]
 V=5,278×10-4 [m3]
 V=7,971 [cm3]
 V=0,007971 [l]
 Q:=0,071 [m3/min]
 t:=1,25 [s]
 t=9,292×10-3=0,0001394 [s]
Fig. 8 presents a 3 D model of the articulated arm which
will be placed next to the machine tool in order to simplify the
worker’s job.

Fig. 8. 3D model of the suction gripper’s articulated arm
This arm has a range of 2000 [mm] and can manipulate
metallic sheets from heights of ab out 600×1500[mm] without
the worker having to exert the effort of lifting heavy weights.
Within Fig. 9, 10 and 11 are presented the internal and/or
external elements design in order to the equipment to realize
translation/rotation movements.

Fig. 9. Actuator an d harmonic gear required to achieve the translation
movement

Fig. 10. Actuator and harmonic gear required to achieve the rotation
movement between the two arms

Fig. 11. Actuator, the harmonic gear and the two ball bearings for the main
rotation movement in the device’s pillar
Fig.12 presents the final model desired by the company
EFR – European Fabrications which is set to be functional as
soon as it can be provide the necessary certification in order to
manufacture the articulated arm for manipulating the thin
metallic sheets. A utomatic model of the mechanism in which
the manipulation of the sheets is assisted with the help of the

worker, which also facilitates the worker’s job and the
company’s profit will be noticeable shortly after implementing
the mechanism Fig.13 .

Fig. 12. Final model of the automatic manipulator

Fig. 13. Final version desired to be achieved within the European Fabrications
company
III. CONCLUSIONS
After finalizing the project it was concluded that the
mechanism developed and designed can be reliably
implemented within the European Fabrications company,
because, due to the construction of the mechanism based on the
customer’s demands the number of throw -outs due to scratches
or bending will drop significantly, or there won’t be any more
throw -outs.
For an automatic pro cess the worker won’t have to exert
any effort in positioning the metallic sheets on the cutting table,
which leads to an increase of safety and quality within the
company. The costs for creating this mechanism for manipulating the
metallic sheets is relat ively small, because it generally uses
standard pieces and steel sheets with a thickness of 5 -7[mm].
Thanks to the low manufacturing cost of this mechanism,
the European Fabrications have begun an ISCIR certification
process, which deals with the essentia l security demands stated
within the European Union Directive, in order for everything to
be according to the law.
The manipulation mechanism of thin metallic sheets
can be automated by mounting two more engines, and due to
this fact it will no longer re quire a worker to assist during the
entire process, thus the worker will only have to program the
mechanism so after one sheet was cut to position the next one
for manufacturing.
After the calculus and the finite element analysis,
authors concluded that t he metallic arms of the mechanism
have the ability to manipulate weights twice as heavy as
required, fact that facilitates greatly in obtaining the certificates
for quality and work protection standards.
ACKNOWLEDGMENT
Special thanks to S.C. European Fabri cations S.R.L. and
Mechom LTD for the cooperation during the entire project
development and for the disponibility for providing the needed
information.
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