MTech

Hevea brasiliensis, the common rubber tree, is the most important
species which is the commercial source of natural rubber. The natural
rubber is harvested in the form of latex, a sticky, milky colloid through the
tapping process. The Hevea latex obtained from the bark of rubber tree
contains natural rubber particles that can be harvested and utilised for
various industrial applications. Tapping is the process of making a
controlled wound in the bark of rubber tree to cut open the latex vessels,
which cause the flow of latex for capturing the latex. The process of rubber
tapping poses potential risk of various health problems among rubber
workers. Scarcity of skilled labours for rubber tapping is one of the main
challenges in the rubber industry. Mechanization of the tapping process can
reduce the effort of the labour and reduces the human drudgery. Hence, the
present study was undertaken to develop a rubber tapping machine and to
evaluate the performance of the machine.
The developed rubber tapping machine consists of a cutting blade,
shaft, connecting rod, crank, gear assembly, bearing, coupling, frame,
casing, motor and a battery. The rubber tapping machine is connected to a
12 V, 5 Ah battery. The battery powers the motor. 0.25 hp wiper motor was
used and it delivers a rotational speed of 72 rpm. The rotary motion of the
motor is transmitted to the gear assembly using a gear shaft. The gear of 48
teeth which is connected with the motor rotates at 72 rpm. The speed is
increased to 288 rpm by meshing gear of 48 teeth with 12 teeth gear to
obtain a speed ratio of 4. A crank is attached to the gear of 12 teeth and
rotates at 288 rpm. A connecting rod linking the shaft and the crank
converts this rotary motion into reciprocating motion of the shaft. The
required stroke is achieved by an eccentricity of 15 mm in the connecting
rod. The blade is reciprocated along with the shaft with a stroke length of 30
mm and 144 strokes per minute. The reciprocating motion of the cutting
blade helps to cut the bark of the rubber tree while tapping.
The field evaluation of the developed machine was conducted in two
farmer’s field by three tappers and the performance of the was evaluated in
terms of its capacity, depth of cut of bark, bark consumption or thickness of
cut of bark, time for tapping operations and weight of the machine and
compared with manual tapping. The developed machine has an average
capacity of about 157 trees per hour. The machine cuts the bark with an
average depth of cut of 7.2 mm and a thickness of cut of 1.8 mm. The
developed machine weighs 1.6 kg without the power source and 3.6 kg with
power source. The cost of operation of rubber tapping machine is estimated
as Rs.1.16/tree whereas the manual tapping charges are Rs. 2/tree.
The developed rubber tapping machine is more advantageous for
tapping the rubber trees with less effort and human drudgery compared with
the traditionally using tapping knives.