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10 Sep 2012

The Power of T-FLEX CAD Parametric Modeling. Part I

Sergey Kozlov, Sergey Kuraskin

Sergey Kozlov, Sergey Kuraksin

David Levin, Editor-in-Chief of Top Systems is a leading Russian private CAD/PLM company which celebrated its 20th anniversary this summer. The company is known first of all by its well-developed parametric MCAD system T-FLEX, which is quite popular in Russia and the CIS and, probably, when supported by a powerful marketing, could become sought-after globally. You can find some characteristics of T-FLEX in “T-FLEX Parametric CAD” by Deelip Menezes , “The Russian MCAD Market” by Ralph Grabowski, and in multiple publications of – such as for example “T-FLEX CAD 12 Released”.

Experts and developers of Top Systems have accumulated a huge competence and experience in engineering software, and nobody was surprised to learn at the beginning of 2012 that Top Systems became the key contractor for the project on the Russian Geometric Kernel.

Top Systems has step by step built a full scale PLM environment – also integrated with a number of ERP-modules. Some intermediate results of this direction were presented at COFES-Russia/isicad-2010 seminar. I hope that attendees of the planned COFES-Russia/isicad-2013 will be able to learn much about the latest PLM-results of Top Systems – called PLM+.

Interesting to mention that couple of days ago, I wrote in @levin_david: “Today the article (from May 21) which compares#SolidWorks vs Russian #T-FLEX received a comment No.1000“. I believe that Top Systems has not yet realized its full potential and hopefully this richly illustrated paper will increase global awareness of the company, its solutions, and competence.

In this paper we describe parametric capabilities of T-FLEX CAD - a system designed around twenty years ago by Top Systems, and since then has undergone continuous improvements. Our special “thank you” to that motivated the authors to write this paper; we also would like to emphasize the efforts of some forum members who, along with other commentators of "Poland compared T-FLEX CAD 12, SolidWorks 2012 and Inventor 2012" (in Russian - editorial), took pains to prompt the publication. We try to talk about parametric capabilities of T-FLEX CAD in plain language, without pseudoscientific or ponderous terms. To facilitate further possible discussion, we numbered all capabilities in a successive order. From the outset we have to state that it is not possible to demonstrate all aspects of T-FLEX CAD parametric capabilities since all of them can be used in arbitrary combinations. Also, various control methods for different parameters of the same model can be combined.
    We wish to apologize in advance to the supporters of both midrange and high-end “conventional” systems, if they cannot understand some capabilities, because 20-year parameterization development with due account of the needs of our users can discourage the adherents of “Configurations”. It is the term that is typically implied under “Parameterization” in other systems (although not in all of them).
Basic Parameterization Parameters in T-FLEX CAD
Initially T-FLEX CAD was designed as a parametric system. It uses a single parametric object model that enables to uniformly control any parameters of any objects. The parameterization principle is simple. Wherever users can enter a numerical or text parameter value, they can just as well employ a variable or an expression dependent on variables. It allows grouping values together, calculating them according to the formulas depending on the entry model parameters, and changing them externally (reading from a parameter file, defining in software, etc.). Using special functions, variables also enable to get values of the required parameters of any model elements (measure them), pass the necessary values to assembly components, group parameters of some model elements with others, etc.

T-FLEX CAD parametric model is based on the “direct” method of model calculating; without solving equations and iteration schemes. Thus, model recalculation is very potent in terms of timing and result accuracy. Essentially, dimensionality of a parametric model is not limited by the number of participating elements. A model can have hundreds of thousands and even millions of elements linked with each other by various dependencies.

At the same time, parametric models in T-FLEX CAD scarcely hinders those users who do not need parameterization in principle (or they just do not guess they need it, which happens more often). A drawing or a 3D model can be created using a technique customary for users of other systems.

To illustrate the above, let’s give some examples of parameters that can be defined with variables or expressions:

  • Line length
  • Distance between two lines
  • Circle radius / diameter
  • Angle between lines
  • Line color
  • Line width
  • Number of array elements
  • Extrusion length
  • Blend radius
  • Layer visibility
  • Operation suppression
  • Page size
  • Part description
  • Technical requirement string
  • Text identifying a part position
  • Dimension value
  • And the like.
A model, contained in a single file, has a single set of variables and relations between them. Model variables can be used in any model part – on any drawing page of a multi-page document, in any sketch of a 3D operation, etc.

Any object (2D or 3D) created in T-FLEX CAD immediately becomes associative and / or parametric. We’d like to emphasize that in T-FLEX CAD there is no difference between a 2D drawing and a 3D model. Any 2D image can be used as a 3D sketch.

Parametric Model Control in T-FLEX CAD
1. Parametric model control in T-FLEX CAD is exercised:

By mouse – moving lines enables to observe dynamics of a changing. At any moment one can define a precise parameter value in the active window for defining a line parameter. This example illustrates how model geometry can be easily and conveniently changed in T-FLEX CAD simply using a mouse. All dependencies in a model, set by a designer rather than “invented” by the system itself, are preserved. It is important that parametric changes do not require any dimensions. At the end of this example, one can see how easily parametric dependencies between elements of a parametric model can be predetermined in T-FLEX CAD.

By a special “Relations” command, which shows relations between elements of T-FLEX CAD parametric model, earlier set by a user. Defining parameter values, it is possible to change a parametric model. Graphic objects – markers displaying relations between elements can be left on a screen so their changes can be monitored in a “transparent mode”.

With dimensional drawing. T-FLEX CAD uses a parameterization model different from other systems (a non-dimensional one): dimensions in T-FLEX CAD are simply design elements. Nevertheless, T-FLEX CAD parametric model allows controlling model parameters by defining dimension values as in other systems. Unlike other systems, however, T-FLEX CAD does not have a concept of “under-determined” or “over-determined” state of a model. The example shows that T-FLEX CAD parametric model works perfectly when a drawing (sketch) lacks dimensions. The example also shows that a model changes perfectly when 3D dimensions change, even if more dimensions are specified that it is necessary to “define” the model, in spite of a dimension conflict (dimensions of the thickness of the part base and the lug, and their general dimensions are specified). Everything that can be created in T-FLEX CAD will be associative and parametric, and it does not depend on the model complexity or the number of specified or not specified dimensions. A parametric model in T-FLEX CAD will unequivocally work according to the principles defined by its designer.

Variables in T-FLEX CAD
2. Any parameters in T-FLEX CAD can be defined by (numerical or text) variables or expressions (formulas) with variables. To create and edit variables, a variable editor or any field for entering a parameter value is used. Variables values (parameters) can be defined:

By arbitrary formula dependencies with use of arithmetic operations, parentheses, a rich set of mathematical and other functions, as well as conditional expressions. The example below illustrates that any model parameter can be defined using variables. In T-FLEX CAD it is very easy to link any geometric parameters (and not only) in addition to already defined geometric dependencies.

By dependencies using Excel and DBMS (Access, Dbase, etc.) files. T-FLEX CAD has a capability for dynamic selection of parameter values from a database depending on the conditions and values of other parameters in the process of parametric model recalculation. T-FLEX CAD, in particular, uses this capability to create parametric library elements. In the example below, changing the bore diameter of the endcap results in automatic selection of all remaining endcap parameters according to the standard from the database using special functions.
By table dependencies. T-FLEX CAD has an embedded table editor (databases), where tables can be created (internal databases). Internal databases are stored together with T-FLEX CAD parametric model. It achieves integrity of a parametric model and its independence from external programs or data when using internal databases to select parameters in course of parametric recalculation. Using internal databases also accelerates parametric model recalculation. The next example shows that libraries of standard T-FLEX CAD elements are created on the basis of a set of tables that meet the standards, and when the basic parameters are changed all other element parameters are selected from the internal databases and a new standard element is formed.
By graphic dependencies or by calculable parameters from a drawing or a model (using measure () and distance () functions). That is, geometric parameters of a model can take part in parametric model recalculation and define values of other model parameters. The following example of a screw with geometrically changeable pitch shows that the pitch is defined with 2D spline. Changing spline geometry results in automatic changing of the pitch of 3D screw model.
By external dependencies of unknown nature, when parameter values can be transferred through an external file, that can be formed as a result of external calculations. The next example demonstrates that parameter values, calculated not in T-FLEX CAD system, can be downloaded to the earlier shown model using a simple-format file, and T-FLEX CAD system will rebuild the parametric model.
Parametric Model Control in T-FLEX CAD (Continuation…)
3. After a small deviation about variables, let’s discuss some more capabilities – parametric model control in T-FLEX CAD can be exercised:

By a specialized variable editor. Any number of model parameters can be instantly changed by a variable editor. The variable editor can use formula dependencies, a set of various functions (mathematical, trigonometric, a selection from database, geometric, if-else selection…). The variable editor operates on both numerical and text parameters.

By direct value editing on a drawing. Please see an example of a gear, which parameters can be changed directly from text information in a table, accompanying a 2D drawing.
Via dialogs created by a user without programming. To create a dialog, T-FLEX CAD forms a special page, where a required dialog is drawn, and control elements of various types (editing field, checkboxes, radio buttons, selection lists, etc.) are arranged to control the model parameters. Later the dialog is brought to the screen and it controls the model. The same dialog can appear when the drawing (model) is inserted in an assembly. More details to be given later.

Creating dialogs, there is a possibility of user-specific dialog parameterization: hiding / displaying control elements under various conditions, changing values, etc. In dialogs it is also possible to connect macros and applications for editing model variables, if the system-embedded functionality is not sufficient.

By external programs through exchange files, macro language, API. T-FLEX CAD can transfer model parameters from external applications both manually and automatically when opening the model file. The example below describes how parameters can be transferred from T-FLEX CAD to any external calculated application, and after parameters are calculated their values can be returned back to T-FLEX CAD using API T-FLEX CAD.

Examples of T-FLEX CAD Parametric Capabilities
4. T-FLEX CAD creates drawings and 3D models of any complexity with associatively bound elements. The next example of parametric assembly drawing with sufficiently complex geometry shows that geometric parameters can be tied to any other parameters, for instance, nominal press capacity. Changing press power results in automatic recalculation of dependencies of geometric parameters, selection of missing parameters from a database, and a new version of an assembly drawing of the press.
5. T-FLEX CAD enables assigning parameters for various interrelations. Such parameters can include both numerical (dimensional and other types of parameters) and text parameters. In the “Milling Cutter” example, a design engineer sets possibility to parametrically change the milling cutter width, the number of milling cutter teeth and the number of lightening holes. This example also shows that not only parameters of the milling cutter are changing, but also the text information on a dimension, with the number of holes. Changing parameters of milling cutter results in completing a finished drawing, execution of which does not require corrections.
Another example demonstrates parametric changing of 3D milling cutter.
Supporting the Standards is Still Important…
6. T-FLEX CAD supports automatic compliance to a standard when a parametric model is changed. It can be a fairly simple example; nevertheless, we would like to draw attention to it. A parametric drawing has tolerance dimensions, irregularities and form tolerances. We dynamically change model parameters and observe changes of design elements. First, this example shows automated recalculation of tolerance limits according to the standard when drawing dimensions are changed. Then the value of form tolerance also changes when the relevant dimension changes. T-FLEX CAD automatically keeps track of changes of tolerances and other design elements with parametric model changes. As a result, it is not necessary for design engineers to monitor whether a drawing is executed correctly – the system does it for them.
Examples of T-FLEX CAD Parametric Capabilities (Continuation…)
7. In T-FLEX CAD variables can have not only numerical but also text values. Apart from this, numerical variables can be entered in text strings. A simple example demonstrates that when geometry changes, text information, containing square and profile perimeter parameters, also changes. It is also easy to notice that text information changes depending on the profile perimeter value exceeding the given maximum value.
8. T-FLEX CAD allows parametric control of drawing (model) layers and visibility levels of any elements. Here we give the simplest example not from machine-building, which beautifully demonstrates parametric control over element visibility levels and drawing layers.
9. In T-FLEX CAD there is a possibility of element “extinction”. It concerns not only model parameters but also design elements. In the example below T-FLEX CAD parametric model ensures that all elements clear up themselves and, if necessary, restore themselves. Parameter “extinction” works in 2D as well 3D.
Parameterization of 2D and 3D Arrays
10. T-FLEX CAD can parameterize both 2D and 3D arrays. Arrays in T-FLEX CAD can be circular or linear and can be built in two directions. Any array parameters can be defined and calculated using variables. The first example demonstrates a 2D array that is automatically built within the given length constraints. The desired array elements can be removed and the system will itself monitor the removed elements if the array is rebuilt parametrically.
The second example shows a circular 3D array, which evenly arranges holes on a cylinder geometric pattern. Models with variable number of elements are very easy to build-up in T-FLEX CAD by changing geometry of the elements to which an array is tied. One of the examples demonstrates array parameterization, when the number of holes for perforation changes depending on the cylinder height and diameter.
The third example demonstrates a linear 3D array in two directions, which evenly arranges holes on a plate geometric pattern. The twist here is that a particular geometry can constrain array filling in the area. In this case we observe changing of the plate contour line, while the array fills in the whole changed area.
Using Graphs in T-FLEX CAD Parameterization
11. T-FLEX CAD has an embedded graph editor. Graphs can be used to define the law of variation of one parameter from another. Using a graph, it is possible to define changing one variable from another, operation parameter values, for instance, variable blend radius, the law of variation of a twist angle, etc. The examples below demonstrate how graphs can be used to define values of a variable radius for graduation.
Graphs are also used in finite-element and dynamic analysis for storing the findings as well as defining the laws of variation of calculating parameters (for instance, non-liner characteristics of spring force, non-linear laws of variation of the strength characteristics of materials when many loading cycles are included in calculations, taking into account material fatigue).

Another example shows that using graphs it is also possible to control a twist angle of a body along its trajectory and scaling a profile that is moving along the trajectory.

Examples of T-FLEX CAD Parametric Capabilities (Continuation…)
12. T-FLEX CAD parametric model ensures geometry consistency on modifications such as “notch-lug” and for symmetric re-orientation. The sketch geometry is preserved in these modifications and does not need to be redefined.
13. T-FLEX CAD has special “parametric” operations when the initial geometry is parametrically changed with changing initial parameters.

Here is an example of building up a body using parameters. A dome is built using a single operation. The dome geometry can be changed by defining operation parameters and by changing the initial profile.

An example of building a “wafer” mantle using a special command: “parametric array”. First, a structural element is built; then this element is multiplied using the above command so it fully fills in the sector of the designed mantle. When the dimensions of the designed mantle are changed, the “parametric array” is automatically restructured in accordance with the given filling conditions.
14. T-FLEX CAD enables parametric control of operation “suppression” in a model. The next example demonstrates variability of a parametric model with parametric control of operation “suppression”. This example is executed without “configurations” since there are quite a lot of combination options.
Distinct Bi-Directional Associativity of 3D Model and 2D Projection in T-FLEX CAD
15. T-FLEX CAD achieved distinct bi-directional associativity of 3D model and 2D projection. In the example below a projection is created using a 3D model. “Controlling dimensions” are automatically transferred to the projection and then one can see how changing controlling dimensions changes the 3D model. It is a standard version of demonstrating bi-directional associativity in most systems. T-FLEX CAD, however, implements distinct bi-directional associativity; further on arbitrary dimensions, that are not controlling, are put on the projection, and T-FLEX CAD enables changing the 3D model using these dimensions. In T-FLEX CAD projections are associatively connected with the whole parametric model, which allows calculating the necessary parameters to modify a model.
16. In T-FLEX CAD it is possible to achieve parameterization of separate parts of a drawing or a 3D model. Parameterization in T-FLEX CAD “does not obstruct” other, conventional modeling tools – that everybody has. For instance, a non-parametric drawing can be exported in DWG format and then a part of the drawing can be made parametric.

In the first part of the paper we described only some parametric capabilities of T-FLEX CAD system that mostly helps creating certain parts… T-FLEX CAD parametric model allows to extend parameterization not only to some drawings and models but also to assembly constructions. Any drawing (model) in T-FLEX CAD can be inserted into another drawing (model), thus forming assembly drawings (models). In the next part you’ll read about assembly parameterization, automated obtaining of detailed drawings and BOMs, creating own mini-CAD without programming, using parameterization to develop unique products, as well as the difference between distinct parameterization and “configurations”, unique capabilities for creating “smart” parametric elements and “smart” assemblies and many other interesting things about parameterization. To be continued …

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