SolidWorks simulation of Internal Geneva Mechanism with Motion Analysis

AIM : - Simulate Multibody Dynamics of Internal Geneva Mechanism using SOLIDWORKS.

OBJECTIVE : -

• Create cad models of Internal Geneva Mechanism in SOLIDWORKS
• Create an assembly of Internal Geneva Mechanism in SOLIDWORKS
• Simulate Multibody Dynamics of Internal Geneva Mechanism using SOLIDWORKS at 10 rpm and 20 rpm.

THEORY : -

GENEVA DRIVE MECHANISMS

The difference between Geneva Drive mechanisms (also called the Maltese Cross mechanisms) and other gears is that Geneva Drive mechanisms have unusual teeth. Unlike in typical gears, the interaction between the part being driven and the part doing the driving is not continuous and the resultant motion is intermittent. Geneva Drives work by having the driving part, or wheel, interlocking with the driven part intermittently. The number of spokes that the driven part has and the speed with which the driving part rotates determines the frequency and distance of travel. There is an elevated segment on the driving wheel which keeps the driven part in position till the next revolution is complete. The external Geneva Drive is by far the most common type, although there are other variations possible in the design. The external drive can be built to withstand higher levels of stress and are generally more robust and sturdy than other variants.

Variations of Geneva Drives include the Internal and the Spherical Geneva drives. The Internal Geneva Drive has the driving part below the driven wheel, with the driving part often being much smaller than the driven wheel.

The Spherical Geneva Drive has the driven wheel located at an angle (typically 90o) to the driving wheel. The continuous rotational movement of the driver is converted into an intermittent rotational movement that is at a different axis.

Spherical Geneva Drive Mechanism

The Geneva Drive derived its name from the town of Geneva, Switzerland. The Swiss are world-renowned watchmakers, so it’s no surprise that the oldest and most popular applications for Geneva Drives are in watches and clocks, and it is quite easy to see how they can be used to regulate the second hand on a timepiece. More robust uses are in film projectors where the mechanism is used to regulate the amount of time a frame on a film is exposed to the light from a projection lens and the image projected on the screen.

Geneva mechanism, also called Geneva Stop, one of the most commonly used devices for producing intermittent rotary motion, characterized by alternate periods of motion and rest with no reversal in direction. It is also used for indexing (i.e., rotating a shaft through a prescribed angle).

EQUATIONS

$\text{Distance between axis of driving and driven component, L in [mm]}$

$L=\frac{r}{\sin \left(\frac{180}{n}\right)}$

here

$r=\text{radius of the driver member in [mm]}$

$n=\text{Number of slots in driven component}$

INITIAL CONDITION

Case 1 :

• Drive speed: 10 rpm
• Contact Precision : No
• Simulation Frames per Second : 60 fps.

Case 2 :

• Drive speed: 10 rpm
• Contact Precision : Yes
• Simulation Frames per Second : 60 fps

Case 3 :

• Drive speed: 20 rpm
• Contact Precision : No
• Simulation Frames per Second : 120 fps

Case 4 :

• Drive speed: 20 rpm
• Contact Precision : Yes
• Simulation Frames per Second : 120 fps

RESULTS

The negative velocity is because of direction and on intermittent rotary motion velocity is maximum at middle of intermittent rotary motion. The spikes in above graph are because of impact from intermittent rotary motion to another and there are sudden velocity changes because of impact.

The Contact Force between driving and driven component are shown above. The spikes in above graph are because of impact from intermittent rotary motion to another. 

CONCLUSION :-

SIMULATION OF INTERNAL GENEVA MECHANISM WITH MULTI-BODY DYNAMICS AND PLOTS AS SHOWN,

REFERENCES :-

Kinematics Characteristics of The Internal & External Geneva

Geneva Device

common mechanism to be understand