CLASS A SURFACING

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.
 
 
CLASS A SURFACING
 
 
 
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.
 
QUESTION:
What is Body_in_white?
What is class A surface?
Are the interior trim (A,B,C pillar, dash board, center console, handles) of a car using class A surface?
Anybody using the basic design bundle of UG for class A surfacing? UGShape Studio?
How does it compare with Catia?
 
 CLASS A SURFACING
Ans:1
A class A surface is anything that you the customer sees. i.e. exterior panels and interior surfaces.
A Class B surface is something that is not always visible i.e. the underside of a fascia that you would have to bend down to see.
A Class C surface is the back side of a part of a surface that is permanently covered by another part.
BIW is stuff like the body side etc..
 
 
Ans:2
Actually ‘body in white’ is the term used to describe the whole vehicle body after it has been welded/bolted together before it is painted or any parts are attached on the fit up line.
 
 
Ans:3
We also use it to mean after it has been painted – I always assumed that the white bit refers to primer. Next step is to fit the windscreen and backlight, when it becomes the glazed body in white, or BIW+G.
 
ANS: 4
BIW – Some surfaces are Class A, i.e. body side, roof, sill appliqué.
I heard some time ago from a old designer that the term BIW comes from when cars were built from wood, they were painted white as it gives the frame a uniform color so imperfections were easily visible.
 
 
Ans:5
BIW meaning Body In White is so called due to its appearance after the application of the primer to the entirely Body panel assembled vehicle just before going into the painting process.
Usually the primer is white or silver grey which gives the so called name.
 
 
ANS: 6
Catia is mostly used for BIW design (Ford switching to catia, and Toyota).  Is this because it
could easily create quintic surfaces? With UG with Design bundle only, most of the surfaces created are cubic.
 
 
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ANS: 7
A class surface means – it is not just seen surface and unseen surface In normal no technical words,
 
A class surface means
It is smooth looking reflective surface with no distortion  of light highlights, which moves in a smooth uniform designer intended formations.
when you create – car body panel, due to their complex shapes it not possible to create the surface with one single face /patch so you make multiple face/patch ( surface is a group of face/patch added together.)
 
when these things are added, at the boundary of joining you need to have connectivity and continuation of minimum order two.
for example
In case one,  at the connecting boundary of two patches you have common boundary but it is sharp corner. this does not qualify as A class surface.
In case two –   at the connecting boundary of two patches have common boundary and no sharp corner – but you have tangent continuity, this also does not qualify as A class surface.
In case two –   at the connecting boundary of two patches have common boundary and no sharp corner –  you have tangent continuity and curvature continuity this  does  qualify as A class surface.
( sine curve is good example for curvature continuity. but you can not call it a A class surface )
reason is very simple  the real requirement of aesthetic and good looking and designer intended shape is not there.
 
 CLASS A SURFACING
ANS: 8
For obtaining Class-A surfaces, CATIA is more commonly used due to its inherent ability to model very high quality surfaces in general. But, any engineering software (CATIA, UG, IDEAS, Pro-E, etc) cannot develop a Class-A surface. This being due to engineering calculations involved in any surface generated by such softwares. For pure Class-A surfaces you would need styling softwares like Alias, Studio, etc.
The use of any software would depend on the level of expectations placed on you. If your projects need only the modeling of the trim, generic engg softwares will do, but if you intend to go down right from styling, you would need Studio, etc.
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ANS: 9
 
IMHO, Catia V4 has included an instrument called Blend surf that can acquire virtual ebb and flow congruity. Beforehand, in any event, styling was OK with models-and subsequently apparatuses characterizing filets with conics, and numerous OEMs despite everything acknowledge this for Class-A surfaces. Catia V5 has GUI interfaces to force ebb and flow progression a similar way that Alias-Wave front Studio Tools (Auto Studio) does. They are both dependent on piece-wise polynomial conditions, for what its value. While a conic filet isn’t actually arch constant, there are numerous vehicles, including extravagance models, that have used them for Class-A surfaces and downstream-parts. Thinking about the resiliences in making molds and passes on and afterward creating parts from them… . a sheet metal board isn’t a math model.
 
 
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ANS: 10
 

The facts confirm that it is hard to make great ebb and flow nonstop surfaces in UG, yet not feasible.

Recall one thing A-class doesn’t mean just ebb and flow congruity. what’s more, smooth reflections on CAD surface. it is significantly more than that. Envision. what befalls your A-class surface on the off chance that squeezed sheet metal body board. also, shaped plastic segments.

They need to hold there planned perfection and different qualities to stay A class.  to accomplish this part of different things must be dealt with while structuring A-class surfaces.

For instance :

1-Line highlights on body side outside board and highlight on the hood board which is normal, are to be intended to abstain from slipping while they are squeezed. moreover

2 – Flange width and different things are to be dealt with while planning the bumpers wheel curve zone for abstaining from swelling impact and sliding impact.

3 – Fuel top opening region, plunged spine for swell impact.

4 – Panel extending should be dealt with. A great deal numerous different things go in structuring A class sheet metal boards for entryway, rooftop, and so on.

5 – For the situation of plastic, sink marks  and different things.

ANS: 11

In Europe an ‘A’ class surface is commonly taken to be the noticeable side of any part/gathering – a ‘B’ class surface by and large identifies with the inverse (or inside) face of an ‘A’ surface – for example the surface which characterizes the thickness of the part, and is the place the mounting and strengthening subtlety will in general be located.  ‘B’ class surfaces can likewise be alluded to as ‘building surfaces.  I have not actually known about any surface being alluded to as a ‘C’ type.

Catia, while it is alright for surfacing will in general be more utilized for creating building surface detail and strong models  –programming bundles like ICEMSURF will in general be more utilized for producing visual quality surfaces.

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ANS: 12

Genuine A-class surfacing – particularly on vehicle outsides goes farther than G2 or “arch” coherence.

G3 is regularly looked for on the more significant square surfaces. G3 manages ebb and flow “increasing speed”, for example the pace of progress of ebb and flow over a limit.

G2 implies as has been depicted before that the bend esteem is the equivalent over a limit.

G3 implies that the surface ebb and flow prompting the limit is changing shape at a similar rate. It resembles driving a vehicle around a twist, you start off straight at that point tenderly add guiding lock to where you need not any more, at that point you delicately wind off the controlling until you’re straight once more. In the event that you take a gander at the bend your vehicle made, this would be G3.

A-Class and B-class would allude to the surface quality required for the segment which is distinctive to A-side and B-side which alludes to which is the noticeable/nonvisible piece of a segment.

ICEM surf is viewed as the best instrument for quick A-class surfacing because of the modernity of its continuous diagnostics.

The outcome:

The outcome of these surfaces separated from outwardly and truly tasteful shapes is the manner in which they reflect the real world. What might one hope to see over the limit of sets of point congruity, digression coherence, and curvature progression surfaces while mirroring a straight and dry tree stump in the desert????

point Continuity (otherwise called G0 congruity) – will deliver a reflection on one surface, at that point at the boundary disappear and re-show up at an area marginally extraordinary on the other surface. The equivalent intelligent marvel will show when there is a hole between the surfaces (the line markers on a street reflecting over the hole between the entryways of a vehicle).

digression Continuity (otherwise called G1 progression) – will create a reflection on one surface, at that point at the boundary have a crimp, and proceed. Not at all like Point progression, the reflection (rehash REFLECTION) is constant but has a digression brokenness in it. In similarity, it is “like” a more prominent than an image.

ebb and flow Continuity (otherwise called G2 congruity, Alias can do G3!) – this will create the solid and smooth reflection over the limit.

to accomplish a similar Class ‘A’ surfaces that car makers request, shopper product manufacturers have benefited themselves of the equivalent propelled surface demonstrating instruments. What is a Class ‘A’ surface? The basic answer is that it is an entirely smooth surface without any inconsistencies, wherein all bordering surfaces have bend congruity. This implies where two surfaces meet, the graduation of one into the other is accomplished without detectable unexpected advances. The procedures used to make Class ‘A’ surfaces typically reside in high level surface displaying programming created for the engine business, instead of mid-extend mechanical CAD bundles that have developed from 3D strong demonstrating for mechanical congregations.

Source: https://catiatutor.com/class-a-surfacing/

 

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