ken youssefimechanical engineering dept. 1 degrees of freedom any component that is unconstrained in...
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Ken Youssefi Mechanical Engineering Dept. 1
Degrees of Freedom
Any component that is unconstrained in space has six degrees of freedom.
• Translation – movement along X, Y, and Z axis (three degrees of freedom)
• Rotation – rotate about X, Y, and Z axis (three degrees of freedom)
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JointsA mechanism is a mechanical portion of a machine that is responsible for transferring motion, force, and torque from an input source to an output source. A mechanism consists of linkages and joints. Links are considered rigid parts. Joints are movable connections between links and allow relative motion between links.
The Revolute joint (pin or hinge joint) - one degree of freedom
It allows pure rotation between the two links that it connects (R joints)
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JointsThe Sliding joint (prism or piston joint) - one degree of freedom
It allows linear sliding between the two links that it connects (P joint)
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JointsThe Helical joint (helix or screw joint) - one degree of freedom
The sliding and rotational motions are related by the helix angle of the thread (H joint)
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JointsThe Cylindrical (cylindric) joint - two degrees of freedom
It permits both angular rotation and an independent sliding motion (C joint)
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Joints
The Spherical (spheric) - Three degree of freedom
It permits rotational motion about all three axes, a ball-and-socket joint (S joint)
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Joints
The Planar (flat) - Three degree of freedom
It permits rotational motion about the Z axes axis and sliding motion in x and y axes (F joint), used seldom in design
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JointsA cam joint allows both rotation and sliding between two links.
A gear connection also allows both rotation and sliding as the gear teeth mesh
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Motion Analysis
In general, there are two types of motion analysis that should be performed to check the design.
Kinematics: deals with the study of motion without regard for the forces that cause the motion. The analysis provides information about the position, velocity and acceleration of all links.
Kinetics: deals with the action of forces on the mechanism. It provides information about the forces at the joints and the required input torque.
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Motion Analysis
The process of analyzing the motion of a mechanism.
• Geometric modeling of all parts and creating an assembly model of the mechanism with proper mates.
• Generate the motion model:
Define ground (fixed) components
Define moving components
Define joints and connections
Specify driver(s) component
Specify loads; external loads, body force (gravitational)
• Perform motion analysis
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Motion Analysis
• Results visualization (post-processing)
Graphs – study the position, velocity, and acceleration of any link or any point on a given link
Animation – check the overall motion and interference
Prepare reports – graphs and charts
Query – results at specific locations for a given time
AVI and VRML – convert the motion to an AVI or export animations to VRML format for distribution on the Internet
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Motion AnalysisTools → Add-Ins and check SolidWorks Motion or COSMOSMotion
2009/102008
Motion Analysis
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Motion Analysis combines motion study elements with mates in motion. It also calculates loads that can be used in finite element analysis.
Basic Motion option approximates the effects of Motors, Springs, Collision and Gravity on assembly. This is a physics based simulation
Animation option creates simple animations based on point to point motion of parts in assemblies. Motor could also be used.
Select Motion Study 1
Motion Analysis - Toolbar
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Motion Analysis - Toolbar
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Motion Analysis - Toolbar
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No Filter, shows all items
Filter Animated, shows only the moving items
Filter Driving, shows only the items that cause motion
Filter Selected, shows only the selected items
Filter Results, shows only simulated result items
Motion Analysis - Toolbar
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2 in
ground
9 in
7 in
Motor Selection
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Select Motor type
Choose the driver, Motion type and specify speed
4-Bar in motion
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Results of Motion Analysis – 4 Steps
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1. Select a category 2. Select a sub-category
Results of Motion Analysis
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3. Select a result component
4. Select a component, 9 in. bar. You can also select a face, an edge, a vertex, or a mate
Results of Motion Analysis
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Results of Motion Analysis
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Plotting the angular velocity of the 9 in. link against the angular displacement of the 2 in. link (input)
Force Analysis
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Force
Path Analysis
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Disable Orientation and Camera Views
Motion Analysis – Slider Crank MechanismSlider-Crank components, each made in separate files.
Bearing
Slider (piston)
Crank
Pin
Connecting rod
Assembled Slider-Crank Mechanism
The last mate eliminates rotation and allows only translation between ground (Top plane) and the piston
The first three mates assemble the crank to the fixed bearing and the Right plane
The next two mates assemble the rod to the crank
The next two mates assemble the piston to the pin, allowing the piston to rotate about the pin
Animation WizardCreate simple animations automatically: rotate model about any axis, Explode and collapse model
Animation Wizard
Rotation
Explode
Collapse
Animation Wizard
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Fixing or Floating Components in Assembly
“f” stands for fixed component
“-” stands for moving component
Right click the component to change it from fixed to float
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2 in link is fixed and 7 in link is the driver
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Hinge Mate
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COSMOSMotion – Joints, 2007/8 SW
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COSMOSMotion
Straight line mechanism
Each rod drawn in a separate file and assembled using various mates. All connections are pin joints (Revolute).
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Straight line mechanism
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COSMOSMotion - IntelliMotionAt the top of the FeatureManager, select the Motion tab
.
Select IntelliMotion option
Set units
Select force and time units, mass and length will be set automatically according to your selections
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COSMOSMotion – IntelliMotion (gravity)
Specify the magnitude and direction in which gravity acts
This means that a vector of 0,-1, 0 defines the direction
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IntelliMotion – Moving and Ground Components
Designate the moving and fixed components
Select and drag over
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IntelliMotion – JointsMates specified during assembly will be displayed. You can add or modify joint type.
Linear or torsion spring can be included
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IntelliMotion – Motion
Select the driver joint
Select input motion type
Select the velocity function
Specify velocity value
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IntelliMotion – Simulation
Select duration and the number of frames.
Start the simulation
Warning – motion not completed due to mechanism discontinuity
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IntelliMotion – Animation
Create and save the animation in the AVI format
Check for interference
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Motion analysis
Path of any point on the mechanism could be traced
Linear velocity of any point could be graphed
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Motion analysis - Velocity
Display the graph
Select component and a point on the component to measure velocity
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Motion analysis – Position of ComponentsAn angular displacement between any two components could be plotted.
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Motion analysis – Select MotorRotary Motor
Linear Motor
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Motion analysis – Apply Forces
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Motion analysis – XY plots
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Motion analysis – NX5Type of jointsSelect Motion Simulation module
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Motion analysis – NX5
First select the Solution and then the Solve option
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Motion analysis – NX5
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Motion analysis – NX5
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Potato cutter (french fries)
Main body
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Chrome handle
Red slider
Plastic handle
Side bar
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Cutting blade
Chrome back plate
Pusher
Clamp
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After creating assembly model, select Motion Simulation module from the Start menu
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Assign a driver, right click on joint j006 and select Edit
Select Constant and specify velocity (deg/sec)
Select Driver Type
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After assigning the driver, select Solution and then select Solve
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Select Animation
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Interference Check
Select Type of detection
Select 2nd body
Select 1st body
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Just before interference
Check Interference and Pause on Event
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Motion analysis – NX5 (example)