Worksheet – Introduction to SolidWorks/Cosmos Motion. This is a

Worksheet – Introduction to SolidWorks/Cosmos Motion.
This is a quick introduction to using SolidWorks and CosmosMotion (which is a SolidWorks
‘add in’ package) to perform a motion analysis on a reciprocating single cylinder engine.
It is intended to present the basics of how to operate the software and how to set up a very
simple analysis of reaction forces on rotating joints within the assembly.
1.0
SolidWorks modelling:
For a quick introduction to SolidWorks work through these online tutorials:
Help > Online tutorial
Online tutorial title:
1) 30 minute lesson.
2) Lesson 1 – Parts
3) Lesson 2 – Assemblies
4) Assembly mates
5) Fillets
6) Lofts
7) Pattern Features
8) Revolves & Sweeps
1.1
Completed:
Setting up the 3d part models.
Model this block:
Download remaining parts and subassembly from: www.plymouth.ac.uk/cad
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1.2
Creating the assembly.
Create a new assembly file, insert the block component, and align it with the assembly file
origin:
Insert >Component > Existing Part/Assembly…
Browse to block.SLDPRT file and open. Press return key to align origins of assembly
space and block component.
Insert the crank.SLDPRT component to one side of the block.
1.3
Positioning the crank in the block.
Select the Front reference planes in the assembly and in the crank component
simultaneously using the CTRL key.
Create a mate between these planes to align them:
Insert > Mate…
As the planes are selected the coincident mate should automatically be created. Click the
green ticks to accept.
Repeat for the crank main shaft outer surface and the block main bearing bore.
Drag crank in the display to test freedom of movement, it should rotate.
2.0
Cosmos Motion.
Enable the CosmosWorks add in:
Tools > Addins… and tick and OK the CosmoMotion option.
Mates and components in SolidWorks may be automatically recognised. Click Yes to add
new parts, etc. Note how CosmosMotion has defined Ground parts and Moving parts.
2.1
Joints.
We need to define how parts move relative to other parts in the assembly. Ground parts do
not move by the way.
Expand the Joints feature in the CosmosMotion explorer tree. You should see the
assembly coincident and concentric mates. (Right click the Joints feature to add more if
required.)
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2.2
Motion.
Right click the Motion feature and Add Motion On a Part…
Under the Motion tab select:
Motion on:
Motion Type:
Function:
Angular velocity:
Rotate Z
Velocity
Constant
360 deg/sec (this is obviously only 60 rpm)
Under the Definition tab select the crank as the 1st component and the block as the 2nd.
For the Select Z Axis select from the model a flat end surface of the crank. You should see
a flat fat arrow indicating the plane and direction of rotation, which should be parallel with
the Z axis surface. You may need to change other selections to orient this correctly.
The assembly should now be ready to run a simulation of the motion.
2.3
Simulation.
Run a simulation. This will create a set of results which you can analyse later.
Motion > Simulation
You should see the crank rotate exactly 360º in a period of one second. To alter how long
the simulation runs for:
Motion > Options…
and look at the Simulation tab.
If you wish to change any settings and re-run the simulation you first need to delete the
active results file.
To change the rotational speed edit the Properties of the relevant Motion feature.
Motion > Delete Results
3.0
Results.
Result data from the simulation has been created. You now have to set up what you want
to analyse and how you want to present it. Usually results will be presented as a graph of
two variables.
We will have a look at the reaction forces on the Concentric1 Joint.
Expand the Joints feature and right click the Concentric1 joint, then:
Plot > Reaction Force > X Component
Observe the resulting graph. To edit the properties or delete this plot, expand the XY plots
feature under the Results feature.
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Create plots for the magnitude, Y and Z components. Do the results look reasonable?
3.1
Further work.
Experiment with the model:
•
Increase rotational speed to 3600 and then 36000 deg/sec.
•
Verify the results with hand calculations. You can extract the mass properties from
the crank part and calculate angular acceleration, forces, etc.
•
Edit the crank part and observe the effect on the reaction forces.
•
Back in assembly mode add the remaining parts: the conrod/pin assembly and the
piston to the assembly, using appropriate mates.
Go back into CosmosMotion and re-run the simulation.
•
Can you set up plots to analyse the compressive/tensile loads in the conrod?
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