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14 Nov 2012

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

Sergey Kozlov, Sergey Kuraskin

The authors are especially grateful to Ilya Anaskin and Pavel Ksenofontov – the members of the “Top-Systems” team who made the videos for the Parts I and II of the paper.

Sergey Kozlov, Sergey Kuraksin

The second part of the paper focuses primarily on parameterization of assembly models, various techniques of constructing parametric assemblies, adaptive technologies, as well as “advanced” procedures of parametric modeling available for T-FLEX CAD users.

17. To begin with, we’d like to demonstrate another capability of T-FLEX CAD parametric model, which frankly should be described in Part I. We are referring to embedded animation tools in the standard T-FLEX CAD version. The first example demonstrates animation of a parametric model, when one base variable changes cyclically; other changes take place through T-FLEX CAD parametric model. Executing animation, a user controls model parameters (variables). It not only allows camera movement, assembling / disassembling, but also enables such model changes that can only be obtained as a result of engaging parameterization mechanisms.

The second example shows that animation in T-FLEX CAD can be created according to an animation scenario that defines dependencies for changing a set of variables.
As a result of animation, a standard AVI-file can be created.
The Basic Principles of Assembly Parameterization in T-FLEX CAD
T-FLEX CAD parametric model extends parameterization not only to separate drawings and models, but also to assembly design. Any 2D drawing (3D model) in T-FLEX CAD can be inserted into another 2D drawing (3D model), forming assembly 2D drawings (3D models). A 2D drawing (3D model), which is inserted into an assembly in T-FLEX CAD, is called a fragment. A fragment is an ordinary T-FLEX CAD 2D drawing (3D model), created by users themselves. Formally, in T-FLEX CAD model there is no difference between a part drawing and an assembly drawing, a 3D part and 3D assembly. Any document can be used as a final document as well as a part of another document. It generates significant flexibility working with parametric elements. An assembly can be inserted at any depth. An assembly can comprise subassemblies; subassemblies – include subassemblies of the next level, etc. All T-FLEX CAD parameterization mechanisms work at any depth of assembly insertion.

In the first Part of the paper we described that any parameter in T-FLEX CAD can be defined by a variable. Now we would like to state that any variable of a model can be defined as an “external” one. An external variable can control a parametric model of an inserted drawing (fragment) from an assembly and receive its value at the moment of inserting the drawing (fragment) into the assembly. The fragment file itself will not be changed. The same fragment can be inserted into a single or several assemblies with different values of external variables, and accordingly, different parameters.

In Part II we use simple examples to describe:

  • Creating parametric elements of libraries and creating own user-specific library elements;
  • Assembly parameterization and automated production of detailed drawings and specifications;
  • Creating own mini-CAD without programming;
  • Using parameterization to design unique products;
  • Differences between distinct parameterization and use of “configurations”;
  • Unique capabilities for creating “smart” parametric elements and “smart” assemblies; and many other interesting things about parameterization.
Parameterization of 2D and 3D Fragments
Numerous libraries of standard parametric elements are supplied free-of-charge with T-FLEX CAD system: bolts, screws, nuts, washers, rivets, pins, bearings, flanges, etc. All library elements are supplied in 2D as well as 3D versions. All library elements are essentially usual parametric drawings in T-FLEX CAD that were simply created by members of Top Systems team. Any user will be able to change the supplied library elements or create one’s own library of parametric elements without employing any programming tools or other special tools. To simplify capability demonstration, videos use ready library elements; nevertheless, please bear in mind that the demonstrated capabilities are true for any parametric models that users can create themselves.

18. T-FLEX CAD enables creating parametric fragments with several views to be inserted into an assembly. Inserting into an assembly, it suffice to specify the view you wish to insert, and the system will display only the specified view in the assembly. Apart from selecting the view for insertion, you can also define values of external variables that define the standard size and variation of a library element in the assembly. Obviously, in this case, values of the controlling parameters (variables) for different views are the same. Bill of materials (BOM) data (description, part number) also are the same. Only the image (view) of an element inserted into the assembly is different. The next example also is a good demonstration of T-FLEX CAD capability to automatically remove invisible lines in assemblies in 2D design. Inserting the first bolt, its image overlaps an image of the parts with holes. Inserting the second bolt, on the contrary, the assembly image overlaps the bolt image, removing the invisible lines.

19. T-FLEX CAD enables using the same parametric fragments in different assemblies with different parameter values, without changing the initial fragment. There is no need to create “configurations” or “variations” in advance – parametric fragment recalculation happens when a fragment is inserted into an assembly with particular parameters. Variables of a fragment can be linked to assembly parameters, changing which leads to automatic recalculation of all linked fragments. The example below specially shows that the same fragment (bolt) can be inserted into an assembly, with constant values of its parameters as well as with defining dependencies of the inserted fragment parameters on assembly model parameters (hole parameters). Changing assembly parameters (hole parameters) results in changing parameter-dependent fragments (bolts) in accordance with the inserted links of parameters, while fragments inserted without links do not change. Using T-FLEX CAD it is possible to link fragment variables with assembly variables at any moment, which is further demonstrated by the example.
20. Creating parametric models in T-FLEX CAD, it is possible to control non-standard parameter values. In an attempt to enter a rogue value, the system displays a message on the screen and automatically picks the nearest standard parameter value of a parametric element. In the example the message that a parameter is non-standard appears in the system diagnostics window.
21. T-FLEX CAD parametric model can automatically pick a parameter value from a standardized series in a database. Using this mechanism, it is possible to exclude application errors when assembling elements with non-standard parameters. As a result of dynamic changing of the plate width in an assembly, the bolt length is automatically picked from the standard series and changes discretely. The same happens when the diameter of a hole in an assembly changes dynamically.
22. Similarly to other systems, T-FLEX CAD creates pre-defined model configurations to be used for assembly insertions. The first example illustrates that configurations can include not only a set of parameters defining dimensions of an inserted part, but also principally change geometry: in this example, a type of a gear. Model configurations are set in the fragment file, and the desired configuration is simply selected when inserting into the assembly.
The second example shows that configurations in T-FLEX CAD can include model parameters as well as a set of geometric operations that are necessary in a particular configuration.
Hopefully, these examples clearly illustrate that along with all other distinctive parametric capabilities T-FLEX CAD has a method of “parameterization” that uses configurations, which is “standard” for other systems.
The Layout Method
23. T-FLEX CAD has a special mechanism of “Layout” that automatically creates 3D objects binding 2D fragments on workplanes and drawing views (projections). Using this tool, a parametric 3D fragment is inserted into a 3D assembly with position and orientation according to the view of the used 2D image as well as orientation of the drawing view or the workplane, on which it was inserted. Thus, in some applied tasks it is possible to draw together complex 3D assemblies using inserts and editing exclusively 2D images, which considerably simplifies the component linking procedure. The example shows how a 3D shaft model is formed automatically using the frontal view of the shaft, on which 2D fragments are inserted by employing the layout method.
Extended Fragment Parameterization (Adaptive Fragments)
T-FLEX CAD has a powerful mechanism for creating adaptive fragments. Adaptive fragments are the fragments for which it is possible, when inserting into another model, to define not only external (determining) variables by also the “external” geometry; that is, replace geometry of the objects of a fragment model with a similar type of geometry from assembly.

24. T-FLEX CAD creates user-specific adaptive fragments, an analog of user defined feature (UDF), expanding capabilities of 3D modeling and increasing productivity of designer efforts. The next example demonstrates how one can easily create an adaptive fragment such as “lug” indicating the fragment geometry for selection when inserting into another model. Then the example shows how the just created adaptive fragment can be used to draw a “lug” with different geometry designing another part. When such an adaptive fragment is created, design of any “lug” variants in new parts comes to creating a “lug” profile and inserting the adaptive fragment.

25. Adaptive fragments are widely used in T-FLEX CAD in the system functionality. For instance, libraries of adaptive fragments are used as forming elements to design sheet metal products. Such libraries in T-FLEX CAD can be expanded by users themselves; thus, a user can enhance functionality of a sheet metal design module. Obviously, Top Systems endeavors to supply the most complete libraries; however, it’s not a big deal if a special or an extremely important for you forge element is not available. You simply need to create the required adaptive fragment, put it in T-FLEX CAD system folder, and this is it – you can use the new forge element in the standard T-FLEX CAD command for sheet metal design.
Adaptive fragments allow users to automate their efforts in any field of engineering design. The next example demonstrates use of an adaptive fragment such as a “stranded wire”. For this adaptive fragment, we can define the wire diameter and number of coils per unit length. Inserting the wire, the 3D path, where the wire must be placed, is also indicated. The adaptive element automatically calculates its length for inserting into the assembly, which is used to build BOM.
26. Parametric capabilities of adaptive fragments allow applying them in advance modeling of 3D parts, using standard 3D elements. Such elements can include, in particular, design-engineering elements, and form features. The example demonstrates insertion of a “groove” adaptive fragment to create a groove in a 3D model for grinding wheel outlet. Another adaptive fragment enables to create splines on the shaft neck in one step. The mechanism of adaptive fragments is employed simultaneously with automated application of Boolean operations to the 3D model and the adaptive fragment: as a result, a single 3D part is formed. Once again let’s emphasize that when the adaptive fragments, both the groove and the splines, are inserted they request the values of their parameters (external variables), which can be of any value rather than contain some predetermined configurations for insertion.
Materials Parameterization
27. In T-FLEX CAD it is possible to prepare assembly components (fragments) where not only geometry but materials are also parametric. Material used in a fragment model also can be defined using an external variable. As a result, when inserting a fragment into an assembly you can define not only geometric parameters of a fragment but also define the part material. The example below demonstrates this capability. This 3D fragment allows replacing all rectangular parts in a LEGO set. At the end of the video, the followers of the “configuration” method can watch an assembly – a house assembled from a fragment - a part of LEGO with different parameters and different materials. Still the single fragment is used!
Creating Parametric Assembly Design
Finally, we’ve got to the examples on parametric capabilities of T-FLEX CAD for designing assembly constructions. In this section we are going to describe in a consistent manner capabilities for designing parametric assembly constructions. All capabilities are displayed using different examples in order to describe each capability separately. Everything that you‘ll see obviously can be used in any combination to design any assembly.

28. T-FLEX CAD enables creating parametric assembly constructions, where assembly parameters control parameters of the assembly parts and units. This is true for both 2D and 3D assemblies. The example: a parametric clutch. When assembly parameters are changed, it changes all parts of the assembly. The parametric model allows preparing any variants of the clutch and its parts in a matter of seconds, recalculating the model after the parameters have been changed.

29. Assembly parameterization enables T-FLEX CAD users to automatically form a set of detailed drawings and 3D models according to assembly parameters. An embedded BOM module, coupled with the aforesaid, allows obtaining ready assembly BOM tables after parameters of assembly and all parts were changed. Assembly parameterization in T-FLEX CAD has an important capability to control an assembly structure depending on any parameters. The example of a parametric conductor demonstrates all the above-mentioned capabilities: 2D and 3D assembly model according to the “bottom – up” approach - from parts to the assembly. All parts are linked parametrically with each other. First, the video shows an assembly, an example of a detailed drawing of a single part – body and a BOM, where we see the assembly structure under the current parameters, including 2 screws and 2 bushes. Then we measure the length of the part fixed in the conductor. Upon recalculating the assembly, the 2D and 3D assemblies are changed, the assembly structure is changed, and the BOM is changed automatically in accordance with the new structure (1 screw and 1 bush instead of two). After this, it is possible to get a new set of fully executed detailed drawings through the example of the same body. The drawing is then changed in accordance with the new assembly parameters. One hole is also automatically removed on the drawing and the whole execution of the drawing is automatically rebuilt.
30. T-FLEX CAD supports automated assignment of part numbers and descriptions of parametric elements for BOM on an assembly product. A simple example enables to see that parametric changing of an assembly construction automatically changes part numbers of a bolted assembly, which is reflected in a BOM.
31. When inserting a fragment or an assembly unit in T-FLEX CAD, it is possible to determine, with which assembly variables the external variable of this fragment or assembly unit should be linked. Inserting this parametric element into an assembly, it will only be necessary to indicate binding location, while its parameters will be automatically synchronized with the assembly parameters. This mechanism allows automating assembly processes and excluding errors related to non-standard parameters of inserted elements.
32. When an assembly model is created using parametric components, T-FLEX CAD can automatically provide a full set of detailed drawings and 3D models. The earlier example with the conductor assembly demonstrated how applying the first method it is possible to get a set of detailed drawings and 3D models in manual mode, when each drawing must be opened through detailing function. In the second method files of parts (fragments) can be saved automatically when assembly is saved after its geometric parameters were changed. With the second method a detailed drawing is prepared, an original fragment does not change and assembly (project) files are copied, assembly parameters are applied to them and saved in a separate folder. You get a completed project of the changed assembly construction and parts. In the second method a user can easily update parts exactly for this construction. For instance, if this technique is used for work with metal structures, parts can be updated in the assembly context or separately modeling holes for fasteners or grooves for welding seams.

The example demonstrates creating a parametric assembly metal structure – a tower from a single adaptive fragment – angle. The “auto-save” option is set for the fragment – angle. After the assembly is created and saved, all fragments comprising the tower are copied in a separate folder with new names and are saved with parameters conforming to the assembly. The one angle is selected and updated (a hole is created) in the assembly context. We see that only this angle has changed (a hole appears), all other angles remain without holes. Further editing of the assembly parameters enables changing the assembly and all its parts. The updated angle, which also changes parametrically, has a hole. All other angles are also recalculated parametrically but they do not have holes. This method allows to automatically getting a completed project of a new assembly unit with changed parameters including all assembly parts.

33. T-FLEX CAD controls composition of assembly model depending on qualitative or quantitative parameters. In the example below dynamic changing of the width of the fastened parts not only automatically changes the standard dimension of a bolted assembly but also, if a width value is exceeded, replaces the type of the bolted assembly.
34. As you’ve probably already understood, inserting an assembly unit into an assembly in T-FLEX CAD it is possible to define the values of external parameters and the unit model will be recalculated with insertion. In addition, T-FLEX CAD has another mechanism for working with parametric assemblies, when parameters of an inserted assembly unit can be controlled by directly defining the values of the part parameters. In this case, parameters of assembly components are controlled “through a level”. In the example below, three identical assembly units are inserted into the assembly (the lifting cylinder), that do not have external parameters to control their own parameters. At the same time, the cylinder contains parametric sub-assemblies. In one of the assembly units sub-assembly parameters are changed and a changed assembly unit is obtained. The same is done with another assembly node. Now we have three different assembly units in the same assembly. The file of the assembly unit has not been changed at all – effectively, we have changed parameters of the assembly unit instance within the assembly, without affecting the file of the assembly unit and its parameters at all. Naturally, the detailing mechanism will take such changes into account and adequately insert parameters defined “through a level”.
35. Another method of editing parts in a parametric assembly in T-FLEX CAD is control parameters of parts of the assembly units through external dimensions that can be defined within a part or an assembly unit. Inserting such a fragment in an assembly, external dimensions must be shown that will be reflected in the assembly. Then the parameters of the inserted part or the assembly unit will be edited by editing values of 3D dimensions. The example below demonstrates this capability.
Automating Assembly Processes
36. T-FLEX CAD has a powerful mechanism for automating creation of parametric assembly constructions. T-FLEX CAD enables creating parametric elements – the so-called “connectors” in fragments and assemblies. Connectors are “smart” tie-in elements that are able to tie to other connectors and that contain a set of parameters, which also can be automatically synchronized with parameters of other connectors. Connectors can be used in both 2D design and 3D modeling.

Let’s illustrate this with an example. We insert the first parametric fragment into a plate – a hole, defining specific parameter values for the hole. The inserted fragment has a connector. All other fragments – a bolt, a washer and a nut are inserted into an assembly using the connector: we simply move the bolt to the hole, position the bolt and confirm the insertion. The hole parameters automatically synchronize with the bolt parameters – there is no need to define and link anything. We do the same with the washer and the nut. The result is a parametric assembly. Changing hole parameters will automatically change parameters of all other inserted fragments. Using connectors in T-FLEX CAD fully eliminates parameter synchronization errors in designing assembly constructions. All library elements of T-FLEX CAD include connectors, which significantly simplifies their use in assemblies.

37. Connector technology allows our users to create their own libraries, by using which the procedures of creating assembly construction come simply to dragging the necessary elements from a library to an assembly. The next example demonstrates automatic creation of a “fir-tree” assembly construction. The assembly elements are automatically synchronized according to the parameters. The library elements were designed in such a manner that fasteners of correct type and size will appear in assembly automatically when elements are mated. Developing such user-specific library in T-FLEX CAD fully eliminates assembly design errors and errors in kitting fasteners for assemblies, which are automatically calculated and entered in specification (BOM). Changing the parameters of the base element, results in automatic recalculation of the whole “fir-tree” assembly construction.
38. The following example demonstrates use of connectors in 3D modeling of assemblies. 3D elements of pipelines are connected through the connector mechanism, which automatically synchronizes not only geometric parameters of flanges but also the number of holes for fastening. A specially created adaptive fragment with fasteners, that also contains connectors, fastens flanges with each other in one step.
Creating Mini-CAD Using T-FLEX CAD Parametric Capabilities
Designing unique products with parametric elements

39. Typically, it is considered that parameterization is only used in standardized design. T-FLEX CAD disproves this statement. Let’s give an example: our users created a mini-CAD to design a clamping strap. Always a unique fixture – a clamping strap – is created from a set of parametric elements that T-FLEX CAD combines in a single product. First, a blank is selected from standard representatives and its parameters are defined. Then the type of the front part of the clamping strap is selected (again from standard variants) and its parameters are defined. Finally, the type of the clamping strap is defined. As a result of parametric recalculation, a unique product is created - the clamping strap. Subsequent changes of the blank, the front part of the clamping strap and the type of the clamping strap almost instantaneously create a new, unique clamping strap. The mini-CAD for the clamping straps allows creating an unlimited number of variants of clamping straps, which would never be possible with the “configurations” mechanism. Everything that you see in this example is created using standard T-FLEX CAD functionality without programming and other special tools.

40. T-FLEX CAD significantly increases productivity of designers due to knowledge accumulation. Even parametric 2D design in T-FLEX CAD can speed up releasing design documentation by an order of magnitude. An example from our users: CAD-design of heat exchangers. A form was developed in T-FLEX CAD to enter the main parameters, on which the type and calculations of heat exchangers, manufactured by the company, depend. Then designers drafted parametric documentation for nearly all heat-exchanging products that the company can manufacture. The documents contain all necessary calculations, assembly and part drawings, specifications. When the form is filled in, all parameters are entered to the database using T-FLEX CAD. Then a designer calls the required parametric drawings and initiates parametric recalculation. Heat-exchanger’s parameters entered in the database are read to parametric drawings and they are rebuilt. As a result, through parametric recalculation of the parameters of all drawings designers obtain almost fully completed documentation for the ordered heat-exchanger – impressive productivity! All displayed capabilities are supported by the standard T-FLEX CAD functionality.
41. A mini-CAD for design of ladder constructions shows that using T-FLEX CAD it is possible to design not only unique products from separate parametric components but also unique assembly construction from standard parametric fragments. This mini-CAD was developed by a Top Systems employee on order of a particular company. As a result, the company obtained a tool for creating ladder-type constructions for any cylindrical reservoirs. The example shows that to design a ladder for this reservoir it is simply required to fill in the form with the target parameters. When the form is filled in, correctness of the entered parameters is controlled. When parameters are filled in correctly, a parametric 3D model is recalculated automatically and a ladder draft is ready. A special report is also prepared, which calculates the required quantity of rolled steel, the quantity of steps and fasteners, and calculates the total mass of the construction. Complete drawing documentation is issued for the ladder variant. By using this CAD, the company has considerably shortened the period for releasing new products and has fully eliminated errors in design. At the end, the video demonstrates the manufactured product. The whole system is executed using standard T-FLEX CAD functionality.
42. Out Polish friends not only can compare productivity graphs in T-FLEX CAD with other systems, but also offer important assistance for Polish companies so they can use all parametric power of T-FLEX CAD to design their products. Next is an example of a “parametric” bath or a water treatment plant, developed by a Polish company. All nomenclature of such “bath tubs” was included in a single T-FLEX CAD parametric mode (model)! As a result, the company gets the necessary documentation about any tailor-made product for their production operations within minutes. A designer simply defines the target construction elements and their parameters, while T-FLEX CAD recalculates the parametric model and generates a completed product. Splendid employment of T-FLEX CAD parametric capabilities! Well done, our Polish friends!
Optimization in T-FLEX CAD
43. Standard T-FLEX CAD delivery includes a comprehensive optimization module that enables solving various optimization tasks. Apart from solving standard tasks for optimizing mode parameters, T-FLEX CAD allows including optimization in parametrical model recalculation. The example demonstrates solving an optimization task for identifying an angle of location of a rolling element so the belt length is 1000. T-FLEX CAD finds a perfect solution. Then an indicator appears in T-FLEX CAD that this optimization task must take part in parametric recalculating of the model. We see that changing position of different rolling elements automatically changes the angle of a tension roller in such a way that the belt length remains unchanged = 1000.

Next example shows how the task of optimal selection of the five parameters – angles of rolling elements to minimize the belt length – is solved using an optimization module.

Phew! Perhaps, that will do for now. In the second part of the paper we have endeavored to present parametric capabilities of T-FLEX CAD as best as possible – for both parts and assemblies, we have also described adaptive technologies and technologies for automating assembly constructions, and presented demonstrative examples from our users on creating their own mini-CAD, etc. However … this is not everything! In the third Part we are going to discuss capabilities of parametric design in T-FLEX CAD: the “top-down” approach - from an assembly to parts, both in 3D and 2D; and the end-to-end intersystem parametric technology of T-FLEX PLM+.

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