Better visualisation of an assembly
Dynamic Designer 2001 from MSC.Software
The long established ADAMS dynamic analysis engine is available as a fully integrated third party module for SolidWorks, Solid Edge and Mechanical Desktop.
The product line-up has been revamped to include three variants.
The base product Simply Motion extends the core CAD assembly modeller functionality to include animations and dynamic interference checking and is provided as part of the Solid Edge package.
The middle version, Motion, adds functionality such as contacts in order to simulate models containing cams, gears, latches, chains, and belts plus the ability to plot performance information.
The flagship Motion Professional enables results such as reaction forces and moments to be generated that can be automatically transferred to other structural analysis applications.
Motion specific features are accessed from within the host modeller through the IntelliMotion Browser.
Avoiding the need to learn a different interface or the need to export geometry to another package encourages experimentation with multiple design iterations.
Once the parts have been modelled the workflow is essentially adding constraints, applying forces, running the simulation and analysing the results.
In the 2001 release a Motion model can be created with a single click using native assembly modeller constraints.
As additional components are constrained in the assembly, Dynamic Designer defines them as moving or grounded parts although this can also be achieved manually.
Length and mass units are defined for the motion model by the host modeller assembly settings and force and time are by default automatically set to be of a consistent unitary system.
Other settings include the direction and magnitude of gravity, and the size of motion symbols displayed over the model.
Assembly constraints are converted to joints in motion terminology, each constraining different numbers of translational and rotational degrees of freedom.
Motion generators are applied to the relevant joints.
All parameters are readily accessible through the IntelliMotion Browser tree although any computed results must be deleted for viewing or editing.
Defining the overall duration and number of frames that are calculated sets the resolution of the simulation.
Clearly the number of steps needs to increase with the speed of the mechanism in order to avoid both jerky animation and more importantly missing events in the behaviour of the mechanism.
The speed of the mechanism in ‘model time’ as defined by the motion parameters is independent of the animation which is largely determined by the host computer performance.
Parameters for the ADAMS/Solver can also be set in order to trade performance against accuracy.
A slider in the Browser allows any existing results to be stepped through manually and VCR style play controls are provided on the Dynamic Designer toolbar.
Animation sequences can be saved out to standalone AVI or VRML.
In addition to visualisation, the rigorous definition of the motion model parameters of each moving part to be plotted with a dynamic cursor traversing the graph as the simulation is played back.
Clicking in the plot area positions the cursor and moves the components to their positions for that point in time for assessing anomalies or extreme values.
There are around fifty parameters that can be plotted including accelerations, kinetic energy, angular momentum, friction, power consumption, reaction force and moments.
In some cases it is useful to superimpose multiple plots onto the same axes and this can be achieved by drag and drop of the component element to be analysed onto an existing plot in the browser then selection of the additional parameter to be plotted.
By arranging the plot windows over the model graphics area the graphs can be included in exported AVI files.
Chart properties such as colour, linestyle and annotations can be edited via a right click dialog and can be saved as a WMF file or via the clipboard for presentation in other applications.
If further analysis of the results is required, data can be exported directly to Excel with a plot automatically generated although the particular parameters and formatting must be selected independently of any plots generated within Dynamic Designer.
The generation of this level of information from the CAD model has the potential to minimise the number of physical models required by allowing the rapid iteration of the design.
It is always wise to validate simulation results empirically but the levels of complexity that can be modelled are impressive.
A range of forces can be applied which unlike joints do not remove degrees of freedom but rather induce or resist motion as springs or dampers.
Options include applied forces that can be constant forces or function expression, flexible connectors that resist motion and gravity.
Additional joint types include couplers that allow a ratio to be defined between the motion of two joints such as a translational distance per degree of rotation.
Cam constraints include point to curve situations that restrict a point on one component to lie on a curve on a second part and curve to curve that constrains one curve to remain in contact with a second.
Although many assembly modellers are able to calculate the minimum clearance between components, this can only be for described component positions.
Since Dynamic Designer steps through each point of an assemblies path, the true minimum clearance can be defined and the model can be driven to the point in time at which it occurs.
In the same way that 3D CAD can offer considerably better visualisation of a model than 2D, so motion modelling can provide a more accurate picture of a dynamic assembly than a static or limited configuration model.
Dynamic Designer offers a means to leverage the value of 3D CAD data and can be used as a springboard for additional analysis by the export of force data as otherwise potential difficult to define load cases for finite element analysis.
For any assemblies that involve moving components, Dynamic Designer can provide valuable insight before committing resource to creating physical parts.