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.

GSD: Difference between join and healing

The maximum Join merging tolerance you can specify is 0.1mm. As in previous responses, Join will not modify the underlying surface. i.e if you have a step od 0.1mm and run a NC tool path over the join, you would still see a step in the result, yet visually you woul not see any step in the CAD geometry. Whereas Heal will physically modify all or part of the surfaces.

LAW CREATION

I fought the Law and…

I won!  Surfacing Laws can be evasive, so this is my humble attempt to make them clear.

If you have been given the task of creating a surface that smoothly transitions from one

closed curve to the next, while controlling the intermediate cross-sections, Laws are for YOU!

Simply put, the concept is to match the Law to the planar area of the Generating curves

in a Surf2+Curve+Crv-Crv.

In order to do this, you must first analyze the enclosed area of the sections by creating a planar face with Limit2.

With the Analysis+Inertia routine, using the default density of 1.00, determine and record the areas of the G-Curve

generated Faces.  Be sure to keep these in order in your notes, since their order is important to the definition process.

The next step is to create a plane through each of the planar G-Curves, and place them adjacent to the curves for clarity

and reference.  Place a Limit point on one of the planes at the furthest extremity in the stack of G-Curves.

Now, use Curve2+Spine to define the flow from one section to the next by selecting the point and first through last

planes in order (The point lies on the first plane in the series).

After generating the Spine, Analysis+Numeric the curvilinear length of the Spine curve.

Limit1+Break the Spine at each section plane, and analyze the length of each segment,

keeping good records of each span and which pair of G-Curves each span lies between.

Limit1+Concatenate+Curve the Spine back together, since you need it intact for the Law

to be distributed along.

Now for the FUN part!  Solve the following equation for R on each section:

Sqrt of Area/Pi = R.  The conversion of the Area to a Radius value is necessary for the

successful completion of the Law.

In 2D, somewhere slightly away from the part, draw a line the same length as the Spine you

analyzed earlier.  Use Point+Limits to create end points on the line.  With Point+Spaces,

select the line and the start point, followed by the value equal to the first segment of the Spine

length, and so on.  At one end of the line, use Point+Coord to select the end point and key in

0,(Radius value) to establish the first point offset for the Law.  Continue this process, basing the

coordinate point on the next consecutive value of R that you solved earlier.  In other words,

you are charting a gap defining the Radius resultant for each consecutive G-Curve Area, at the

specific point that it will occur along the Spine.

Once these points are charted, an Arc can be calculated through these points, and it is a good

idea to impose tangency at each end, so that the area is held momentarily as the surface exits

the final G-Curve.

Law+Create+Area:  In 3D mode, select the Varying Arc that you just calculated through the

Radius points, then the Line that was initially created in 2D, then the Spine that was concatenated,

Yes:Compute and type in a name for the Law.

This law can now be used in Surf2+Curve+Crv-Crv as one of the variables controlling your

new surface.  You will notice that Area is an input parameter in your FK Menu after Spine

selection and before G-Curve selection.  For a complete list of possible inputs, look at the

Analysis panel with Alt+ on the 10-key pad (Alt- removes the analysis panel).