Analyzing individual component tolerances
TASys Tolerance Analysis System from TASys Tolerance Solutions
The CAD division of Spanish IT company Ibermatica, C4 Advanced Engineering Services (C4 AES), distributes TASys Tolerance Analysis System developed in collaboration with the not for profit foundation Labein Technological Research Centre.
Available as an add-in for Solid Edge, SolidWorks and shortly Inventor, TASys analyses the effect of individual component tolerances in assemblies.
Of the three versions, entry level Pre_TASys enables controlling dimensions to be identified.
The full TASys product enables the tolerancing scheme to be analysed and the influence of each tolerance to be assessed.
The top of the range product INTOL optimises tolerances by automatically re-running the analyses.
Modelling and dimensioning is carried out in the host modeller as normal, although particular attention to best practice in the dimensioning scheme will aid the downstream analysis.
Once the assembly is complete, the property to be controlled such as a clearance between cylindrical faces, an angle or a distance between two parts is defined as a Response Function.
Since modellers do not define negative dimensions, situations where an interference may result in a negative clearance can be defined as the difference between two dimensions.
Although multiple response functions can be set-up, they cannot be individually selected for subsequently running a specific analysis.
The TASys search function is then able to identify all dimensions in the components and assembly that influence the response function, a useful checking function in itself.
These dimensions can then be toleranced or redefined as more appropriate geometric tolerances.
The current version only supports bilateral and symmetric tolerances so any other variants need to be redefined to suit.
At this point the tolerance scheme can be checked for any inconsistencies before initiating an analysis.
Both worst case and statistical analyses can be run.
The worst case analysis assumes that all variations occur in the worst possible way and finds the combination of defined tolerances that result in the response function being at the upper and lower limits.
Since the worst case is almost always too conservative giving results that are very pessimistic, statistical analysis can be used to take into account the low probability of a worst-case combination occurring.
MonteCarlo simulation, the Quadrature Technique and Linear root sum square stack-up methods can be selected to balance accuracy against computing time.
The MonteCarlo method can be particularly time consuming as a large number of iterations are required to give high confidence of an accurate result.
The results are saved out to disk and can be reviewed using the post-processor window.
By selecting the available response function and analysis from scroll down lists, options such as nominal, upper and lower conditions can be selected by radio button.
The update command then rebuilds the model parametrically to the calculated value for each controlling dimension.
At this point the modellers interference detection tool can be launched to identify any interference volumes.
Although the dimension values update to reflect the selected tolerance build-up, the full tolerance range is still annotated without the nominal dimension value.
It would be excellent if dimensions were at least colour coded to indicate being at max or min condition.
The post processor window also indicates the name of each toleranced dimension and their percentage contribution to the total variance.
Selecting a dimension highlights it on the model enabling excellent analysis of where tighter tolerances could make the most significant improvement or indeed an alternative dimensioning scheme may be better or alternatively others, that have a low influence in the response function, may be increased in order to reduce the manufacturing costs.
The recompute button enables the effect on the percentage contribution of changing any tolerances to be assessed.
A graph also plots the results from the analysis.
Sliders above and below the graph enable the max and min percentages to be set to reflect target or actual capability.
Results can be output together with the data table to an HTML report for all or selected response functions and analyses.
Unfortunately this does not include a descriptor of the response function or the relevant dimension and percentage contribution information.
TASys is not an instant cure-all for tolerance analysis; careful consideration is still needed in creating the tolerance scheme and the use of the analysis results.
It does however offer an excellent way of visualising and assessing complex tolerance chains.
It behaved unexpectedly on a few occasions running in SolidWorks, particularly with inconsistent geometric tolerances.
Also if TASys detects anything having changed in the model it deletes results for new ones to be calculated.
Since a changed may only have been a part colour change for instance it is somewhat inelegant to instantly lose access to previous results.
Since the process can be processor and time intensive it would be frustrating to need to recalculate essentially identical results.
A sensible future enhancement will be the better management of multiple schema, perhaps with greater integration with model configurations.
Despite these minor criticisms, it is certainly valuable to be able to conduct statistical analysis of tolerances directly on the model data and particularly to associatively rebuild the model to be able to visualise the probable consequences.