Manage Large Assemblies - Ways to improve performance

There are several items that the CATIA end user can change to improve performance when
working with large assemblies. Some of these changes deal with improving the performance of
local transformation (rotation, moving, and zooming), some deal with reducing the time to open
an assembly, and others deal with ways of reducing the addressable memory usage to obtain
better overall performance when working with the large assemblies.

Each of these methods is a trade off: in order to obtain better performance, the user will need to
reduce what is seen on the display, change the way saving is done, and change the way of
working with the overall large assembly.
Some of these changes can be achieved by making some changes under CATIA’s
Tools>Options, while others are done interactively with some contextual menu changes and
other selections.
The following examples show some of the changes that the end user could do to improve
performance when working on large assemblies. For detailed information on each of these
items, the user should consult the CATIA online documentation.
Examples of Interactive Changes
Use Visualization mode to improve loading time and decrease addressable memory usage.
When parts are displayed in Visualization Mode, just a subset of the data is loaded in memory.
The remaining data is loaded when needed. Switch to design mode only the parts to be edited
or needed for constraint creation.
Select the option “Do not activate default shape on open” prior to opening an assembly. This
reduces unneeded information in no-show space, and improves performance. This option
should be used in combination with the Visualization mode to further improve performance.

Manage Large Assemblies - Ways to improve performance

Removing the edges when shading improves display performance.Create Selection Sets to
manage working configurations such as multi-selecting components to be activated.
Examples of Tools – Options Changes
Lowering the level of detail displayed on the screen will improve local transformation.This is
done by increasing the setting values of the “Level of Detail” and “Pixel Culling” for “While
Moving”, so that less data is displayed while moving.
Decrease the Undo Stack. By default, the last 10 interactions can be undone at any time. But,
this option uses a lot of addressable memory. By decreasing the Undo Stack Size to 2,
addressable memory is freed up to allow the loading of larger assemblies.
Activating the use of Cache optimizes the use of Visualization Mode by reducing addressable
memory usage and the time to open the assembly.
Disable the Automatic Save. Automatic Save enables the recovery of a user’s work in case of a
CATIA crash, but in most cases, assemblies cannot be recovered after a crash. Since automatic
saves can take almost a minute for very large assemblies, disabling this option will eliminate
CATIA hangs every 30 minutes or so.

Open assemblies with every component deactivated, and activate only the Representation of
the part needed for design. This will improve local transformation performance and reduce
addressable memory usage

Importing Toolbars from any workbench to the required workbench

During the design process sometimes necessity arises where you to use toolbars in other
workbenches in the current workbench.

For example, while working with the Part design workbench, sometimes it is necessary to
perform certain tasks using the tools available in the Surfaces toolbar in the Shape design
workbench.

Following steps can be followed to import Surfaces toolbar in the Part design workbench from
the Shape design workbenches:

1.Select Start > Mechanical design > Part design to invoke the Part design workbench. The
default user interface for Part design is displayed.
2. Select the Customize option from the Tools pull-down menu; the Customize dialog box is
displayed, as shown in Figure
3. Select the Toolbars tab from the Customize dialog box. The options available in the Toolbars
tab are displayed, as shown in the Figure
4. Choose the New button from the Toolbars tab of the Customize dialog box; the New Toolbar
dialog box is displayed.
5. Select the Shape design workbench from the Workbenches area; all the toolbars available in
the Shape design workbench are displayed in the Toolbars area. Select the Surfaces toolbars
from the Toolbars area of the New Toolbar dialog box. Name of the toolbar is displayed in the
Toolbar Name edit box. See Figure
6. The Surfaces toolbar is now displayed in the Part design workbench.Similarly you can import
and use any toolbar from any workbench to the required workbench.

Methodology for Drafting Large Assemblies

There are many different techniques that can be employed to improve the performance when working with the drafting of large assemblies. Simply put, use smart drafting techniques to generate in drafting only what is needed for the views. This will keep the data size down, which yields the best performance. If the smart drafting techniques aren’t sufficient, the assemblies should be simplified using the Convert Product to CATPart function. The following two sections show some of the smart drafting techniques and discusses simplified assemblies.

Examples of Smart Drafting Techniques for Large Assemblies

· Limit the number of scenes to the minimum number necessary to convey the Visualization of the assembly. Each scene created substantially increases the size of the CATProduct.

· Create Raster-generated views as images. This allows the user to quickly generate overall views for large assemblies that can be opened in visualization mode. Although there are restrictions on generating raster views, when used, they reduces data size andimprove addressable memory usage.

· Manually manage which elements are shown in the assembly, before generating them views. Anything that shouldn’t be seen in the view should not be visible in the assembly.

· Create views by multi-selecting only the nodes in the tree of the elements intended to be seen in the drawing, not the entire assembly.

Simplified Assemblies

A simplified assembly is created when the contents of an assembly are merged into one or more CATParts and then reassembled into a new CATProduct. The selected components of the original CATProduct(s) are converted into individual bodies within the CATParts. Assemblies over 200MB should be considered for the creation of simplified assemblies. Assemblies should be simplified using the Convert Product to CATPart function if the smart drafting techniques are not sufficient. Simplifying assemblies is best done after the design is nearly completed and ready for detailing. This technique is not intended to be used during the stages of the design when changes often occur because manual synchronization of the original data is required if there is a change.

 

CATIA V5: BIW WELDING FIXTURE DESIGN

CATIA V5: BIW WELDING FIXTURE DESIGN

BIW WELDING FIXTURE DESIGN

BIW WELDING FIXTURE DESIGN

No matter what your knowledge about fixture design, you use the following stages in design of your BIW weld fixture:

Study and understanding of process Concept design Create 3D-Modeling

You study your process

You start design by study production process of body-in-white (BIW) this process provides valuable information for the design phase.

The purpose of study BIW process includes the following:

The special focus on the structure of a body (BIW) enables you to find the logic and flow of body panels, and the relationships between them. The select of master control point, which are holes or surfaces related to your body part & assembly to arrive at the dimensional integrity of the BIW by giving the steel parts in the correct position during joining. The analyzing of body is made up of several hundreds of stamped components which are joined together by spot welding with welding gun for understanding of welding points and allocate them to welding operations. Study of cycle time diagrams, for check reach ability and optimizing it. Cycle time is estimating the required working time for each station.

You create your concept design based on process study

Now you can use of process study for defining the design criteria and finding or verifying the concepts.

The welding fixture design is created with the following steps:

The clamping plans for accurate positioning of components, while the components are aligned to a suitable plane for welding they are designed in the carline plane (as in BIW). Design of the weld fixture is unit based on clamping plan, therefore there are a number of fixture unit types used in the welding fixtures for the purpose of each unit and due to the complexity and shape of the component geometry, the choice of elements as well as configuration of each unit tends to change from case to case. The check of weld accessibility and spot weld for unrestricted access to each weld point, before and after the fixture design, the accessibility of the weld guns to all the spot points can be simulated and studied thoroughly to avoid guns colliding with other fixture elements.

You create 3D Modeling fixture

You need knowledge and experience in 3D Modeling software for creating 3D-Model and 2D drafting, detailing & 3D concept design.

The 3D Modeling becomes the basic for following item:

Create 3D Modeling of the weld fixture for visualizing the entire fixture in a three-dimensional environment. 3D Modeling of weld fixture generated by cad software, which lets you detect collisions, check reach ability spot weld and carry out weld accessibility study for ensuring your fixture efficiency. The 3D CAD Model of weld fixture unit enables you to make CAD Model of clamp location plan for ensuring that plan problems and waste are discovered before your fixture drawing to send for manufacturing. By 3D Modeling of weld fixture, you can quickly prepare manufacturing drawings. PRODUCTION PROCESS OF BODY-IN-WITHE (BIW) In the study phase of planning process you find or verify the concepts of the body-in-white manufacturing process. For design welding fixture, trying to understand processes is essential. It is starting with process logic and flow, and defines the relationships between operations. The process study is a solution that to help you quickly define and evaluate process to arrive at the best plan for designing your fixture. The result is process study containing a full description of how a product is assembled, manufactured and increases your profitability by improving critical success factors in your fixture design. The process study allows designer to leverage and optimize existing resources and to better integrate the designing process from beginning to end can not only help designer create fixture faster, but you can also begin design earlier in the overall cycle or even start later, in order to accommodate unanticipated changes. The Assembly Process studying allows evaluating alternatives, coordinating resources, optimizing throughput, plan for multiple variants, implement changes and estimate costs and cycle times, from the very early stages of concept planning through process. Studying, Analyzing and Managing Manufacturing Processes enables you to collaboratively plan and analyzing manufacturing processes for your fixture. You can create optimal design and accommodate multiple plan variations, quicker and faster than ever before. Process study provides a collaborative environment for planning designing processes. A broad range of applications enable you to define and verify body assembly sequences, create clamping plan layout, define the required time for each operation, verify plan performance, perform plan balancing and analyze of spot welding and guns. The body-in-white Manufacturing Process includes: Automotive body assembly Electric resistance welding Cycle time diagrams Automotive body assembly The major process of an automotive body is electric resistance welding. Resistance welding is a group of fusion welding processes that use a combination of heat and pressure to accomplish coalescence and where electric resistance welding is not applicable ,CO2,ARC WELDING and MIG-BRAZING are performed. The body of automotive is made up of several hundreds of stamped components which are joined together by spot welding process. Overall quality of the car body (BIW) and quality of the sub assemblies, apart from quality of each stamped part, depends remarkably on quality of the welded joint. You should study of part joining, welding operations such as spot-welding and define welding points and allocate them to welding operations. The study of welding process can be classified as follow: The number of welding spot The position and volume number of welding spot The type of welding gun The material and sheet metal thickness for setting of welding condition Cycle time diagrams The cycle time is estimating the required working time of each station. Cycle time study is based on the information such as: Part loading Clamping Gun forward Welding Gun retreat Unclamping Part unloading PORTABLE WELDING GUN Almost all of the automotive body parts are assembled by resistance spot welding. A spot welder consists of a transformer to obtain a large welding current, timer to control the time in which to feed the current, electrodes to hold welded articles, pressurizing cylinder to apply the necessary for the material being welded. Secondary cable lets necessary current through transformer flow to gun, spring balancer to lighten the welding gun and the cable. Resistance spot welding is passed between two copper electrodes, the process can be performed by the operator holding a portable welding machine and moving it around the parts being welded. These portable machines called portable welding guns. The manual weld guns can have easy access to weld the components together. The resistance spot welding machines are classified according to combinations of individual sections as follows: Fixed type Stud type Portable type: Conventional weld gun Integral weld gun Conventional weld gun Conventional weld guns have a large transformer located remotely from the weld gun. The welding current is delivered to the weld gun arms through a large, water-cooled secondary cable. J type or C type S type or X type The conventional weld guns were used in various applications because the weld controllers did not have the ability to detect and react to any hazard associated with using primary power connected directly to the weld gun. Integral weld gun Integral weld gun or tarn's guns have a smaller transformer located right on the weld gun, from which the current is delivered through short jumpers or shunts that are air cooled. Tran's guns are also called weld guns, because the transformer is part of the unit. The two configurations of portable tarn's guns are: C gun Scissors gun For example C gun for welding around a door opening on a small flange and Scissors gun for welding large, deep boxes requiring a long reach. There are following characterizes for tarn's guns: Design Flexibility Ergonomics Cost efficiency

CLASS A SURFACING

A Class surfacing and its importance: A class surfaces are those aesthetic/ free form surfaces, which are visible to us (interior/exterior), having an optimal aesthetic shape and high surface quality.

Mathematically class A surface are those surfaces which are curvature continuous while providing the simplest mathematical representation needed for the desired shape/form and does not have any undesirable waviness.

Curvature continuity: It is the continuity between the surfaces sharing the same boundary. Curvature continuity means that at each point of each surface along the common boundary has the same radius of curvature.

Why Class A is needed:

We all understand that today products are not only designed considering the functionality but special consideration are given to its form/aesthetics which can bring a desire in ones mind to own that product. Which is only possible with high-class finish and good forms. This is the reason why in design industries Class A surface are given more importance.

Understanding Class A surfaces:

1. The fillets - Generally for Class A, the requirement is curvature continuous and Uniform flow of flow lines from fillet to parent surface value of 0.005 or better (Position 0.001mm and tangency to about 0.016 degrees).

2. The flow of the highlight lines - The lines should form a uniform family of lines. Gradually widening or narrowing but in general never pinching in and out.

3. The control points should form a very ordered structure - again varying in Angle from one Row to the next in a gradual manner (this will yield the good Highlights required).

4. For a Class A model the fillet boundary should be edited and moved to form a Gentle line - and then re-matched into the base surface.

5. Matched iso-params in U & V direction are also a good representation of class A.

6. The degree (order) of the Bezier fillets should generally be about 6 (also for arc Radius direction) sometimes you may have to go higher.

7. Also you have to take care of Draft angle, symmetry, gaps and matching of surfaces Created with parent or reference surfaces.

8. Curvature cross-section needles across the part - we make sure the rate of Change of curvature (or the flow of the capping line across the top of the part) is Very gentle and well behaved.

The physical meaning: 

Class A refers to those surfaces, which are CURVATURE continuous to each other at their respective boundaries. Curvature continuity means that at each "point" of each surface along the common boundary has the same radius of curvature.

This is different to surfaces having;

Tangent continuity - which is directional continuity without radius continuity - like fillets.

Point continuity - only touching without directional (tangent) or curvature equivalence.

In fact, tangent and point continuity is the entire basis most industries (aerospace, shipbuilding, BIW etc ). For these applications, there is generally no need for curvature.

By definition:

Class A surface refers to those surfaces which are VISIBLE and abide to the physical meaning, in a product. This classification is primarily used in the automotive and increasingly in consumer goods (toothbrushes, PalmPC's, mobile phones, washing machines, toilet lids etc). It is a requirement where aesthetics has a significantcontribution. For this reason the exterior of automobiles are deemed Class-A. BIW is NOT Class-A. The exterior of you sexy toothbrush is Class-A, the interior with ribs and inserts etc is NOT Class-A.