6. Link: Machine element which moves relative
to other elements (machine)
a) Rigid link
b) Flexible link
c) Fluid link
7. Kinematic pair : When two links are joint they
constitute a pair
Joints : Junction of links
Type of motions possible between links
• Revolute
• Sliding
8. Number of Links : 4
Number of Pairs : 4
Number of Fixed Links : 4
9. Modification of a basic four bar chain
It consists of one sliding pair, three turning
pair
10. Method of obtaining different mechanisms by
fixing different links in a kinematic chain
No. of Inversions possible = No. of links
No. of Inversions for four bar mechanism = 4
14. Lower Quick Return Ratio
Vibrations due to non linear velocity
Defining Problem
Rigid structure
Selection of material
Usage of Brass Bearings
Overcoming the problem
15. 1.Forces acting on each link
2.Selecting materials
3.Suitable cross section
4.Link lengths
5.Machine power
Factors To Be Considered In Design
Design
16. Specifications and Calculations
Stroke =120mm
Q.R =3
No.of strokes/min =50
Length AC = 40mm
Length BC = = = 56.57mm
Length AP = = =84.85mm
Length PR = 20mm
18. Design of Crank
Maximum force acting on Crank = 4500 * Impact Load Factor
= 4500*2 = 9000N
Cross-sectional Area Of Crank = Max Load / Permissible Stress
= 9000/200 = 45mm2 ………..1
Considering Rectangular Cross-Section, b=2d.
C.S Area = b*d = 2d*d ………..2
Equating 1 and 2
2d*d = 45
d = 5mm
b = 10mm
19. Design Of Slotted Bar
Maximum Force acting on Slotted Bar = 6364 * Impact Load Factor
= 6364*2 = 12728N
Cross-sectional Area Of Crank = Max Load / Permissible Stress
= 12728/200 = 64mm2 ………..1
Considering Rectangular Cross-Section, b=2d.
C.S Area = b*d = 2d*d ………..2
Equating 1 and 2
2d*d = 64
d = 6mm
b = 12mm
20. Power Calculations
From Specifications
Mean Velocity = Stroke length * No. of strokes/mm
= 120*100
= 12 m/min
Power = Cutting Force * Mean Velocity
= 4500*(12/60)
= 900 watts (1.2 HP)
Including Friction and Inertia Forces 2HP Motor is
required.
21. Design For Power Transmission
RPM of the Crank = No. of Strokes per minute
To Convert 1400rpm motor motion into 100rpm motion V-Belt drive
For given loads Phosphor Bronze Bushings of required thickness should
be used at Pin Joints between the links
Due to large fluctuations in loads Vibrations are induced.
To minimize these Vibrations, Cast Iron or Wooden Frame should be used
22. Positional Analysis
Velocity Analysis
Acceleration Analysis
Force Analysis
Analysis of Quick Return
Mechanism
23. Data Acquisition System
System takes the analog output from the various sensors and
converts them into digital values.
Digital analogous value is fed into the processing unit.
The computer uses software called KDM (Kinematics and
Dynamics Of Machines).
The needed values and their characteristic curves are plotted
by the software and the output is recorded.
25. Software Analysis Procedure
Modeling the linkage using the motion simulation
application (SolidWorks).
Import the model into Ansys
Analyse the meshed model in Ansys (Structural)
Study planar mechanism kinematics (position,
velocity and acceleration) of the model using
SolidWorks
26. Position analysis includes
the position of links at
different crank angle
From this we can
determine the extreme
positions of the mechanism
Position Analysis
27. Velocity Analysis
deals with variation
in velocity of
slider at different
instances
Velocity Analysis
28. Ground length = 25mm
When crank radius
tends to ground length
, QRR tends to infinite
Crank radius = 10mm
When ground length
tends to crank radius
length , QRR tends to
infinite
QRR Vs Crank Radius , QRR Vs Ground length
29. Fabrication
Fabrication is an industrial term refers to building metal
structures by cutting, machining and drilling.
The fabrication of quick return mechanism unit involves:
Cutting
Drilling
Machining
Welding
Grinding
Carpentry work
30. Fabrication of Crank and Connecting Rod
The cutting operation can be carried out
in workshop
For better accuracy , ease and surface
finish shaping machine is preferred
Drilling of holes at ends of both sides
The holes are drilled with respect to
suitable dimensions by using drilling
machine
31. Fabrication of Slider
Wood is cut in suitable dimension
The carpentry operations are performed here
Fabrication of Frame
A frame has to withstand the load of the crank as well
as the connecting rod to avoid disturbance
A wood plank may be chosen to avoid breakage and
also prevent noise
The frame is to be cut into required dimensions using
handsaw and chisel
The frame is to be tightened with the help of adhesives
and screws for rigid support
Grinding may be done for a smooth surface finish
33. Conclusion
The purpose of the project is to design and construct a
kinematic quick return device. Beginning with general
research into quick return devices, the project has to follow
a methodology of determining the design space, building a
mathematical model and then implementing that model. The
design process as a whole has to be experienced from start
to finish and is to be incorporated as a multitude of
different aspects of engineering. Designing this mechanism
will be an excellent experience in tackling a design project
where the majority of constraints are self-imposed. The
final design produced will be an effective one. Hopefully,
with a little work, the mechanism will be operational and
seen by future kinematics students for years to come.
34. ACTIVITY TIMELINE
Project Approval July
Consulting Guide & Background
Research
August
Proposing A New Design August
Design Specifications September
Software Learning October & November
Software Implementation And
Analysis
February
Presenting The Project March
PROJECT PLAN
35. Methodology
Design of links
Analysis of links at various positions
Remodification of links (If required )
Implementation
Fabrication
Performance test
36. BIBLIOGRAPHY
Theory of Machines by R.S. Khurmi and J.K.Gupta
Design of Machine Elements by R.S. Khurmi and J.K.Gupta
Theory of Machines by Ratan
Manufacturing Technology by P N Rao
http://www.morldtechgossips.com/2012/05/fabrication-of-
slider-crank-unit.html
