In industry it is always desirable to increase the productivity or reduce the time loss. A beautiful mechanism in which, for the constant input rotation, the forward stroke takes larger time(cutting stroke) than the return stroke(idle stroke).
7. Lower Quick Return Ratio
Vibrations due to non linear velocity
Defining Problem
Rigid structure
Selection of material
Changing the slider height
Overcoming the problem
8. 1.Link lengths
2.Forces acting on each link
3.Selecting materials
4.Suitable cross section
5.Power Calculations
Factors To Be Considered In Design
Design
9. Specifications
Stroke length = 270mm
Quick return ratio = 5/3
No. of strokes/min = 100 strokes/min
Crank Length = 75mm
Length of Coupler =100 mm
10. Link Lengths
Length of AC =r/cos(90-α/2)
= 75/cos(68)
= 200 mm
Length of slotted lever (AP)=P1Q/sin(90-α/2)
= 135/sin(22)
= 360 mm
Length of AR= AQ + QR
= AP cos (90-α/2) + PR sin(90-α/2)
= 360 cos(22) + 100 sin(22)
= 375 mm
12. Mean Cutting Velocity = L*S* (360/α)
= 270*100*(360/136)
= 71.47 m/min
Cutting Power = F6 * Vmean = 596 W
Power required at Crank Pin = Power / η
= 596/0.8
= 745 W
L = length of stroke
S = number of strokes / minute
η= mechanical efficiency
13. Design of Crank Pin
Torque at Crank Pin (Tcr) = (P*60)/(2*π*N)
= (745*60) /(2*π*100)
= 71.14 N-m
Force at Crank Pin (Fcr) = Torque / crank radius
= (71.14*1000) / 75
= 948 N
Max Force at Crank Pin (Fcrm) = Fcr * I.F
= 948*2
= 1896 N
Diameter of Crank Pin = sqrt(4F/πτ)
=sqrt(4*1896 / π*50)
=7 mm
=8 mm (standard size pin)
14. Design of Shaft
Torque acting on shaft =(P*60)/(2*π*N)
=(745*60)/(2*π*100)
= 142 N-m
Diameter of the shaft (d)=cube root(16T/ πτ)
=cube root(16*142*1000 /π*75)
= 20 mm
15. Design Of Slotted Bar
Maximum Force acting on Slotted Bar = 539 * Impact Load Factor
= 539*3 = 1617N
Cross-sectional Area Of Crank = Max Load / Permissible Stress
= 1617/30 = 54 mm2 ………..1
16. ANSYS
•ANSYS is a general purpose software, used to
simulate interactions of all disciplines of physics,
structural, vibration, fluid dynamics, heat transfer
and electromagnetic for engineers.
•To validate the design QRM structural analysis
where used.
•Static Analysis-Used to determine displacements,
stresses, etc. under static loading conditions. Both
linear and nonlinear static analyses.
17. View of the model after
Applying loads
Meshed model
SLOTTED LEVER
25. Graphical Method
Graphical method starts with position analysis by
simply drawing the linkage mechanism to scale. Then
the velocity analysis is performed which requires the
angular position of the links to be determined
beforehand. Similarly it is necessary to know angular
velocities of links for acceleration analysis. Thus, the
sequence for kinematic analysis of mechanisms is -
position analysis, then velocity analysis and then
acceleration analysis.
26. 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
31. SAMPLE CALCULATION OF VELOCITY
At 100 rpm time required for 20 degrees= 20/(100*360)
= 1/30 s
Velocity of the slider at beginning = d/t
of the stroke
= 5 / (1/30)
= 0,15 m/s
Velocity of the slider at middle of the = 50 / (1/30)
stroke
= 1.5 m/s
Velocity of the slider at the end of = 35 / (1/30)
the stroke
= 1.05 m/s
32. Manufacturing and Fabrication
Fabrication is an industrial term refers to building metal
structures by cutting, machining and drilling.
For construction of mechanism in these project billets standard
of sizes were taken.
Some of the machine tools used where centre lathe machine,
radial drilling machine, tapping, vertical milling machine,
grinding machine, files, hydraulic press machine.
40. Future Scope
• Accurate instantaneous velocity measurement can be done by
using precise instruments.
• Comparison can be made with Whitworth Quick Return Mechanism.
• Vibration analysis can be performed.
• Model can be made to achieve higher quick return ratio.
• Kinematic and dynamic analysis can be performed.
42. Conclusion
• Quick return ratio is limited to strength of the material. By
incorporating stronger materials QRR can be increased.
• Backlash can be minimized by choosing close tolerances
and proper assembly techniques.
• With increase in slider height, QRR increases.
• Friction at the interface of guide ways and ram can be
minimized by using turcite tape.
• Ram velocity varies from zero at beginning, maximum at
middle of the stroke and zero at the end.
43. BIBLIOGRAPHY
• R.S Khurmi & J.K Gupta
• Joseph E. Shigley
• S S Rattan
• Thomas Bevan
•http://engineering.myindialist.com/2013/kinematic-inversions-
of-four-bar-chain-slider-crank-and-double-slider-crank-
mechanism/
•https://www.wisc-online.com/learn/career-
clusters/stem/eng20704/quick-return-mechanism-velocity-
calculations
•http://theengineeringdiary.blogspot.in/2011/06/crank-and-
slotted-lever-quick-return.htmlhttp://www.quora.com/What-are-
differences-between-crank-and-slotted-lever-mechanisms-and-
a-Whitworth-quick-return-mechanism