MOTION SIMULATION OF INTERNAL GENEVA MECHANISM
AIM:
To simulate the internal geneva mechanism for the given condition and plot the graph for
- Contact force (between driving and the driven wheel) as a function of time.
- Angular Displacement of the driven wheel.
for respective condition.
INTRODUCTION:
The Geneva drive is a gear mechanism that translates a continuous rotation movement into intermittent rotary motion.
The rotating drive wheel is usually equipped with a pin that reaches into a slot located in the other wheel (driven wheel) that advances it by one step at a time. The main wheel also has an elevated circular blocking disc that "locks" the rotating driven wheel in position between steps.
An internal Geneva drive is a variant on the design. The axis of the drive wheel of the internal drive can have a bearing only on one side. The angle by which the drive wheel has to rotate to effect one step rotation of the driven wheel is always smaller than 180° in an external Geneva drive and always greater than 180° in an internal one, where the switch time is therefore greater than the time the driven wheel stands still.
APPLICATION AND ANIMATION:
- One application of the Geneva drive is in film movie projectors and movie cameras, where the film is pulled through an exposure gate with periodic starts and stops. The film advances frame by frame, each frame standing still in front of the lens for a portion of the frame cycle (typically at a rate of 24 cycles per second), and rapidly accelerating, advancing, and decelerating during the rest of the cycle.
- Other applications of the Geneva drive include the pen change mechanism in plotters, automated sampling devices, banknote counting machines, and many forms of inaxable equipment used in manufacturing (such as the tool changers in CNC machines; the turrets of turret lathe, screw machine, and turret drills; some kinds of indexing hrad and rotary table and so on). The iron ring clock uses a Geneva mechanism to provide intermittent motion to one of its rings.
- The animation of internal geneva is as follow
PROCDUCE:
- Create driving part first
- create an circle for the given dimesion and extrude it for 20mm
- Now select a face on the extruded the object and draw a circle and extrude it for 40mm
- The geneva wheel is created according to the given dimension with help of extrude, fillet , mirror and offset option.
The dimension is as follows for both driving wheel and driven geneva wheel
- Both of the part is assembled using various mating condition as in image
- The assembled image is follow and center distance between the driving and driven wheel was given as 210mm aproxx which gave neccesary distance for driving wheel shaft and driven wheel slot to mate properly and execute the mechanism
- Now we simulate the mechanism for various condition and plot the graph
CONDITION1:
SPEED 10rpm CONSTANT SPEED MOTOR
Frames per Second 60
Precise contact not considered
plot 1 :Contact force (between driving and the driven wheel) as a function of time
plot2: Angular Displacement of the driven wheel.
From the above graph we can conlude that the displacement and the force are high at time of contact i.e when shaft comes in contact with slot of geneva
CONDITION2:
SPEED 10rpm CONSTANT SPEED MOTOR
Frames per Second 60
Precise contact considered
plot 1 :Contact force (between driving and the driven wheel) as a function of time
plot2: Angular Displacement of the driven wheel.
There will be only minute changes from the above graphs as the variation is small and answer will be accurate if precise comtact is considered
CONDITION 3:
SPEED 20rpm CONSTANT SPEED MOTOR
Frames per Second 120
Precise contact not considered
plot 1 :Contact force (between driving and the driven wheel) as a function of time
plot2: Angular Displacement of the driven wheel.
CONDITION 4:
SPEED 20rpm CONSTANT SPEED MOTOR
Frames per Second 120
Precise contact considered
plot 1 :Contact force (between driving and the driven wheel) as a function of time
plot2: Angular Displacement of the driven wheel.
from the above graph we can conclude that the reaction force increases with increase in speed but the displacement changes takes place at a faster phase
selecting the option precise contact
RESULT:
From the above simulation we study and analysis the motion of the internal geneva wheel and graph are plotted from different condition . we can also note that reaction force increases at time of contact of shaft and slot and thus decreases gradually and displacement takes place faster with increase in speed . The precises contact can be used for approximate results . This mechanism has a wider range of application as stated above