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ABSTRACT: The objective of this work is to automate the conventional power hacksaw machine in order to achieve
high productivity of work-pieces than the power hacksaw machine using Microcontroller. The automated machine
acquires two inputs from the user namely the number of pieces to be cut and the length of each piece that is required to
be cut. The inputs are given by the user with the help of a keypad and an LCD display, which will help the user to
verify the data given by him. The operator need not measure the length of the work-piece that is to be cut and to load
and unload the work-piece from the chuck each time after a piece has been cut. After acquiring the two inputs from the
user, the machine automatically feeds the given length of work-piece in to a chuck and starts to cut till the given
number of work-pieces has been cut. The machine feeds the work-piece with the help of a conveyor, which is driven by
a DC motor and an IR sensor ensures that the feeding stops when the specified length has been reached. A pneumatic
cylinder is used for holding the work-piece when cutting operation is done. An AC motor is used to bring about the
reciprocating motion required for cutting the work-pieces. There is a self-weight attached with the reciprocating
mechanism to provide the necessary downward force required for penetration of hacksaw blade in to the work-piece.
When a single piece has been cut, a limit switch will get triggered by the self-weight mechanism, which is sensed by
the microcontroller to start the cyclic operation again provided if the specified number of work-pieces has not been cut.
INTRODUCTION
Power hacksaws are used to cut large sections of metal or plastic shafts and rods. Cutting of solid shafts or rods of
diameters more than fifteen millimeters is a very hard work with a normal hand held hacksaw. Therefore power
hacksaw machine was invented during 1920s in the United States to carry out the difficult and time consuming work.
This power hacksaw machine shown in figure 1 is considered as an automatic machine because the operator need not
be there to provide the reciprocating motion and downward force on the work-piece in order to cut it. Once the operator
has fed the work-piece till the required length in to the machine and starts the machine, then the machine will cut until
the work-piece has been completely cut in to two pieces.
The fact that the operator has to feed the work-piece to the required length in to the vice is one aspect that motivated us
to automate the feeding of work-piece automatically. Another one aspect is that after a shaft has been cut for one time,
the operator has to unload the work-piece and advance the rest of the work-piece to the required length again and again
till the end of the work-piece is reached. The Power hacksaw machine though being able to cut the shaft or rod without
requiring any human effort to cut, it does require a human intervention to feed the work-piece many times with
measurements being taken each time before feeding. Therein, arose a need to completely automate the process of
cutting, and here we are with a proposal which will aid in eliminate the effort of the people associated with it.
A. Problem Identification
The power hacksaw machines, which are operated by human operators as aforementioned, have the demerit of
unloading and loading the work-piece many times. In industries manufacturing pumps, these machines are used to cut
the motor shafts to the required lengths. It will be difficult for the operator if he has been assigned to cut a huge
quantity of motor shafts and he has to measure the lengths each time for cutting. Since humans are not as versatile as
machines, there is a possibility that there may be inaccuracies. Besides, if there is a slight time delay in between every
cycle of cutting a piece, the cumulative delay in time will be found to have a considerable magnitude, which might
have been utilized properly if the proposed machine were in use there.
B. Proposed Methodology
The demerit of power hacksaw machine is the automatic feeding of work-piece is eliminated by feeding of work-piece
with the help of a conveyor, which directs the work-piece in to the chuck. The conveyor motor is stopped when it has
fed the specified length in to the chuck with the help of a microcontroller and IR sensor. After this, a pneumatic
cylinder is extended to hold the work-piece firmly to arrest the movement of work-pieces when being cut. This is
achieved by a solenoid operated DCV, controlled by a microcontroller. Then the self-weight attached to the blade,
which would be previously in a lifted position by means of another pneumatic cylinder will be lowered so that the
hacksaw blade will contact the work-piece at the point where the cutting is to be done. This is achieved by retracting
the weight-lifting cylinder operated by the same solenoid DCV. The cutting motor then gets turned on by the
microcontroller, so that the blade is set to reciprocate on the work-piece to cut. After a piece has been cut, the cycle
begins again from automatic feeding without any human intervention and proceeds till the specified number of pieces is
cut.
II. COMPONENTS USED AND CALCULATIONS
The components used in this project are discussed below.
A. Electric Motor
There are two electric motors in this proposed machine, a DC motor for driving the conveyor through a chain drive and
an AC motor for providing the reciprocating motion of Hacksaw blade by means of a simple crank mechanism.
B. DC Motor
The conveyor roller is coupled to the dc motor shown in figure 2 through a chain drive and is driven when the
microcontroller sends a signal to it. The conveyor runs till the specified length of work-piece is fed in to the chuck.
This is achieved with the help of an IR sensor and a toothed disc attached to the conveyor shaft, which together
function as an Encoder.