The Mirror Model Comparator (MMC) is a proprietary patented geometry verification system that ensures a high-level of accuracy in the feature-based translation of a CAD file from one commercial CAD/CAM system to another. Although the MMC is a module of the Acc-u-Trans translation engine, it has been designed with the ability to compare models translated in any way. This technology is confidential to Translation Technologies.
The Process of MMC
The MMC 1) detects
The MMC shows you if there are any differences in geometry between the original source model and the newly created target model.
The analysis for detection can be run in two modes:
- Forward mode: extract analysis data from the source model and compare it to the target model
- Reverse mode: extract analysis data from the target model and compare it to the source model
Although the MMC can be run in just one of these modes, some categories of discrepancies could go undetected in forward analysis only, but would be detected by a subsequent reverse analysis process and vice versa. Running the analysis consecutively in the two modes provides additional confidence that the translation was accomplished correctly.
Once the differences are detected, this data is then presented in an analysis report. In addition the information is visually displayed in the target model for both forward and reverse analysis. This enables the discrepancies to be observed in a very quick and effective manner. In addition, changes can be made in the target model very easily with this displayed information as a guide.
The MMC accepts user input and the user has the ability to set a number of options, such as:
- Resolution of the analysis data – a qualitative setting of High, Medium and Low. One can think of this as setting the mesh grid resolution for the model.
- Analysis tolerance – The analysis tolerance can be set as a function of the source model tolerance or to an absolute value. Setting the analysis tolerance too tightly relative to the source model tolerance can result in a number of false errors being reported by the MMC. However, theoretically the operator can set the analysis tolerance as tightly as desired.
- Full analysis, or only reanalyze items that were detected as out of tolerance previously. The user can analyze using forward mode only, reverse mode only, or both. Reanalysis options for reverse are also available.
Advantages of the Mirror Model Comparator
For many years designers have relied on comparing the mass properties of the source and target models to determine if the translation is accurate. TTI’s Acc-u-Trans technology uses mass properties comparison during the translation process to assist in detecting certain types of errors. While this methodology has it’s merits and is certainly better than not checking at all, it does suffer from certain limitations. These limitations fall into three main areas:
- Lack of Information about the position of the discrepancy – Just as important as knowing that an error exists is to know the location and magnitude of the individual discrepancies. A mass properties comparison does not indicate to a user where the error is, nor how much. The user cannot determine precisely where the error is, or its magnitude is.
- Lack of precision in mass property calculations – A mass properties analysis of a 3D CAD model is an approximation. The accuracy of the approximation depends entirely on the calculation techniques used in the CAD system to output the values and the modeling precision available in the CAD models. The most precise CAD systems only approximate these measurements to an accuracy of 0.03 to 0.1 percent of the value being measured. When a model has a volume of 200055.39 cubic millimeters (approximately the volume of the example model used in the illustrations) the accuracy of the measurement ranges from +/- 60 to 200 cubic millimeters. The error displayed in Figure 1 above causes a difference of 2.16 cubic millimeters. This error is significantly less than the analysis precision of the volume measurement (by as much as 2 orders of magnitude) and therefore would likely go unnoticed in a mass properties comparison analysis.
- Cancellation effects from multiple discrepancies – In the inevitable event that there is more than one error, it is just as likely that the errors will occur in locations that cancel or reduce the resultant effects on the differences of center of mass and moments of inertia values reported. For example, if two errors exist in the translated geometry and they are located on opposite sides of the center of mass, they will tend to cancel each other. Mass properties comparison is a useful tool for providing rough indications of the degree to which two different CAD models are geometrically the same. But in order to be sure that the two models are geometrically the same, one would have to overlay the models on top of each other and scan for differences. This is precisely the underlying philosophy of the TTI Mirror Model Comparator. The MMC surmounts all of these limitations in an effective manner and provides a very accurate comparison of the source and target models.