Desenvolvimento de um sistema de troca automática do nozzle de ...

Abstract
Abstract
Development of an automatic nozzle changer for laser cutting machines
This report focuses on the development of an automatic cutting nozzle changer, which is
intended to equip the Laser Cutting Centers of ADIRA S.A. The development of
this product resulted from the increasing need to reduce the setup times of the cutting
centers and, therefore, improve the efficiency of work. Currently the nozzle exchange is
a manual operation that requires de entry of an operator inside the machine and, thus,
it´s deactivation, so the goal is to develop an automated system to tighten/loosen
quickly and efficiently the nozzle to the cutting head and, thus, decrease the effect of
this operation on setup times.
In order to solve this problem were shaped two distinct solutions. The first one consists
on a rotating plate, whose operating principle is identical to that of an automatic tool
changer of the CNC machines. This dish as 24 holes, divided into two concentric tracks,
which are intended to store the nozzles and their respective supports. The rotation of the
dish allows de transport of the desired nozzle into a “Stand By” position, where are
placed to stepper motors (one for each track) which transmit the rotation to the nozzle
holder and therefore allow the tightening/loosening of the nozzle in the cutting head.
This solution was eventually abandoned at an early stage of its development, because it
required the creation of a complicated coupling system between the motor shaft and the
nozzle holder and the use of a very accurate motor to rotate the dish (splitter plate).
To solve both of these problems it was modeled a new solution, which was called
drawer. This prototype has the tightening/loosening systems always in the same position
and in constant contact with the motor, through a chain of straight toothed gears. As the
exchange operation calls for a high torque control, sought to determine the income
losses in the chain and, therefore, calculate the torque difference between the first and
the last tightening/loosening system. The results of this study led to the subdivision of
the starting chain in three smaller ones, individually powered, which minimized the
losses to only 10%.
With the two prototypes completely modeled, it was decided that the second one was
more simple and effective having then began its implementation into the cutting center.
This phase led to the development of a shield, a support and to the definition of a drive
system capable of carrying the cassette into the cutting area, which will be
accomplished by a double acting pneumatic cylinder.
At the end, it was made an economic analysis to both solutions, having concluded that
the cassette is approximately 3 times more expensive than the rotating plate. However,
this result is not accurate because the utilization of the diving plate in the first solution
would equalize the costs.
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