Week 1:- Introduction to BiW and Fixtures Challenge

Question 1: What is BIW & define its parts?

BIW (Body in White) refers to the welded sheet metal components which form the vehicle structure to which the other components will be married, i.e., chassis, exterior trim, interior trim, & engine. Here the structure is unpainted.

The BIW is still called white even though most of them are grey because in the early year, car shells were kept in white before assembling and it is kept white to give a color choice to customers.

Today’s automobile sector aims to decrease the weight of vehicles and increase the efficiency of vehicles so therefore most of the BIW nowadays are made up of aluminum and composite materials and steel is still used but it has lost its dominant market share due to weight restrictions.

Types of BIW construction:

1. Monocoque construction:

Monocoque body construction integrates the body and chassis of a vehicle into a one-piece structure. Automobile using monocoque construction: - 1962 Lotus 25 Formula race car, McLaren MP4-12C, Ferrari 458, Jaguar XJR-15, McLaren 720s, Bugatti Chiron, etc.

Advantages: Weight reduction, Increased internal space. Aerodynamic, Improved safety, Increased rigidity

Disadvantages: Increased cost, Complex repairs

 

2. Semi Monocoque Chassis: 

A semi-monocoque chassis is like a monocoque chassis, but it gains some structural strength from conventional means, such as an internal skeleton. This chassis is also lightweight and strong but is not as durable and light as an actual monocoque chassis. Automobiles using semi-monocoque chassis: - Audi A-series, BMW X-series, and Porsche Cayenne

 

3. Body-on-frame construction:

Body-on-frame construction consists of two major components, a rigid ladder-like frame network that carries the engine and drivetrain and a separate body construction that is mounted on it.

 

4. Unibody design:

Unibody construction refers to a structural design where the body and chassis are integrated into a single unit, but the structure relies on additional internal reinforcements, such as subframes, braces, and pillars, to share and distribute the loads.

In a unibody construction, the body panels and other structural components work together with these internal reinforcements to provide the overall strength and rigidity of the vehicle. In simpler terms, the key difference lies in the level of load-bearing responsibility placed on the external body panels. Monocoque construction primarily relies on the external skin for structural integrity, whereas unibody construction utilizes a combination of the external skin and internal reinforcements.

Automobiles using unibody design: 1922 Lancia Lambda, 1934 Chrysler Airflow, Land Rover Defender, Hyundai Santa Cruz

 

5. Space-frame design:

Space frame vehicle construction, also known as space frame chassis or space frame design, is a structural approach that utilizes a lightweight and rigid framework to support the vehicle's body and mechanical components. It involves constructing a skeletal framework using interconnected beams, tubes, or other structural elements to create a strong and efficient structure.

Automobiles using space frame design: - 1946 Cisitalia D6, 1959 Maserati Tipo 61, Audi R8, Ferrari 360, Lamborghini Gallardo, Mercedes-Benz SLS AMG

                   Audi R8 Spaceframe

 

 

 

BIW components can be categorized into five categories:

1. Body Sides

• A-pillar: frontmost support to the roof.
• B-pillar: second support to the roof
• C/D pillar: C- is the rearmost support to the roof in case of a two-row seating system, it will third one. D- is the fourth support, usually the rear side of the quarter panel.
• Ring Panel: a structure panel connecting the rear and front portion.
• Quarter Panel: rearmost panel of a body side structure
• Drip rails/Gutter: an exposed channel applied to the roof over the side windows to direct water away from the windows

 

2. Underbody

• Dash panel: provides partition b/w engine and the driver cabin.
• FRT floor provides a base for seats
• Raiser: connects front floor to rear floor by providing the level difference
• Rear floor: floor on the rear of the car and provides partition from ground and base for rear seats.
• Rear wheelhouse

3. Closures

• Front door
• Rear door
• Hood
• Decklid

 

4. Roof

• Roof
• Header: structural member above the windshield at the juncture with the forward edge of the roof panel
• Bows

5. Front End Structure

• Plenum Panel: a chamber located b/w the throttle body and runner of the intake manifold.
• FRT wheelhouse (Fender): is an encasement around the wheel.
• Wing Panel: outermost side panel in the front
• Cowl: portion of the body bounded by the front fenders, the base of the windshield, and the rear edge of the hood.
• Upper tie bar: upper panel in the front connecting the two sides of the front structure.
• Lower tie bar: lower panel in front connecting the two sides of the front structure.

 

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Question 2: What do you understand by BIW nomenclature?

BIW Nomenclature refers to the identification and labelling system used for various components and assemblies in the body shop during the production of a vehicle's body structure. It is a standardized system that helps track and manage the multitude of parts involved in the assembly of the BIW.

 

Items	UK Description	US Description
A	Inner Wing Panel	Motor Compartment Side Panel
B	Upper Wing Member	Motor Compartment Upper Rail
C	Suspension tower	Shock tower
D	Upper ‘A’ Pillar	‘A’ – Pillar or Windshield Pillar
E	Windscreen header rail	Windshield header or front header
F	Roof Stiffener	Roof bow
G	Rear Parcel tray	Package shelf
H	Contrail	Side roof rail
I	Backlight frame	Backlite header or Rear header
J	‘C’ - Pillar	‘C’ – Pillar
K	‘D’ - Pillar	‘D’ - Pillar
L	Rear Quarter Panel	Rear Quarter Panel
M	Boot Floor Panel	Rear Compartment Pan
N	Rear Seatback Ring	Rear Seatback Opening Frame
O	Rear Seat Panel	Rear Seatback panel
P	‘B’- Pillar	‘B’- Pillar or Centre Pillar
Q	Floor Panel	Floor Pan
R	Sill	Rocker or Rocker Panel
S	Lower ‘A’-Pillar	Front body hinge pillar (FBHP)
T	Dash Panel	Dash Panel
U	Engine (longitudinal) rail	Motor Compartment Lower Rail
V	Front Bumper	Front Bumper
W	Spare Wheel Well	Spare Tire Well
X	Centre (Longitudinal) Tunnel	Tunnel
Y	Rear Seat Crossbeam	# 4 Crossbar
Z	Rear Suspension Support Beam	# 5 Crossbar

 

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Question 3: What is fixture & its types?

The fixture is a device that holds a workpiece to be processed (welded by using the 3-2-1 Principle).

Welding fixtures are normally designed to hold & support the various components (workpieces) to be welded. It is necessary to support them in a proper location which can prevent distortions in the workpiece during welding. For this the locating elements need to be placed carefully, the clamping fore must be light but firm, the placement of clamping elements has to be clear of the welding area & fixtures have to quite stable & rigid to withstand the welding stresses.

General Types of BIW Fixture:

1. Production Fixtures — mass production purpose

The function of Production Fixtures:

• Workpiece Stability: Fixtures hold the workpiece securely in place, preventing movement or vibration during machining, welding, or assembly operations.
• Precise Positioning: Fixtures provide precise alignment and positioning of the workpiece to ensure accurate and repeatable manufacturing processes.
• Accessibility: Fixtures may incorporate features like clamps, supports, or guides to provide access to specific areas of the workpiece for assembly, welding, or other operations.

 

2. Pre-production operation fixtures (PPO) — For initial batch production to study the feasibility.

These fixtures are designed to facilitate and streamline various pre-production operations, ensuring efficiency, accuracy, and readiness for full-scale production.

They are specifically employed before the start of regular production to aid in tasks such as prototyping, tooling, testing, and process validation.

 

3. Checking fixtures — For car panel geometric inspection purposes.

Checking fixtures is a specialized tool or fixture used to verify the dimensional accuracy, alignment, and functionality of manufactured parts or assemblies.

It is an essential tool in quality control and inspection processes to ensure that parts meet the required specifications and standards.

 

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Question 4: What is the basic principle of fixture design?

The principle of Fixture Design is the 3-2-1 Principle.

For a fixture designer, the major portion of design time is spent deciding how to locate the work piece in the fixture.

For any free body there are total of twelve degrees of freedom as below:

6 translational degrees of freedom: +X, -X, + Y, -Y, +Z, -Z

And six rotational degrees of freedom:

• Clockwise around X axis (CROT-X)
• Anticlockwise around X axis (ACROT-X)
• Clockwise around Y axis (CROT-Y)
• Anticlockwise around Y axis (ACROT-Y)
• Clockwise around Z axis (CROT-Z)
• Anticlockwise around Z axis (ACROT-Z)

You must fix all the 12 degrees of freedom in order to locate the work piece in the fixture. So, 12 degrees of freedom of the work piece need to be fixed & thus we can achieve zero degree of freedom for the work piece.

A workpiece will be completely confined when blanked against:

• 3 points in one plane: The “3” in 3-2-1 refers to 3 locators (passive fixture elements) on the primary locating/datum surface.
• 2 points in another plane: The “2” in 3-2-1 refers to 2 locators on the secondary locating/datum surface.
• 1 point in a third plane: The “1” in 3-2-1 refers to 1 locator on the tertiary locating/datum surface

The location arrangement depends on the type of operation, degrees of required accuracy.

• Flat locators: These are used for the location of the flat machined surfaces of a component.
• Cylindrical locators: These are used for the location of components with drilled holes.
• Conical locators: These locators are used to support the workpieces with cylindrical holes.
• Jack pin locators: These locators support rough workpieces.
• Drill bush locators: These locators hold and locate the cylindrical workpieces.
• Vee locators: These locators hold circular and semi-circular workpieces.

 

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Question 5: Elaborate types of BIW Stations.

BIW stations are specific workstations or areas within the automotive manufacturing process where the body structure of a vehicle is assembled.

The assembly line is where the different types of panels are joined together in each specified zone. Each panel categories will have individual zones, as underbody zone, Door’s zone, Hood zone etc.,

Each zone is comprised of several stations:

1. Tool

A tool is a fixture which consists of a number of units together to hold a car part in general.

• Geo Tools: A geo tool is a fixture in which the geometry of the panels which are welded together is defined accurately. The pin tolerance for a geo pin will be of closer tolerance i.e. - 0.15 in general.

 

• Re-Spot Tools: A re-spot tool is a fixture in which the remaining weld spots which are not achieved in geo tool are welded for the pre welded panel from the geo tool. The pin tolerance for a re-spot pin will be of tolerance with -0.28 in general.

• Hemming or Marriage Tool: A marriage or a hemming tool is a fixture in which the inner panel assembly and outer panel assembly are joined together. These are done by welding or by hemming in case of closure panels.

2. Checking Station

A Checking Station tool is a fixture which is used to check the automotive parts or assemblies, ensuring all the coordinates, relative dimensions & positions as per the

tolerances. A checking station can be a gauge type, fixed type and automated checking fixtures.

A Checking gauge is a tool where work piece is held & various measuring gauges are introduced to ensure the dimensions & repeatability.

A fixed type checking fixture is used where the work piece is fixed with clamps & pins & a CMM machine is used which measures the coordinates of different points of the panel or assembly, compares it with the nominal values & gives a report.

3. Gripper

A Gripper is a device or a fixture which holds the car panel and is fixed to the manipulating end of a robot or an end effector. Also known as EOAT — End of Arm Tooling.

• Material Handling Gripper: Material Handling gripper are designed for handling the car panel from one tool (Station) to other tool (Station)

• Process Gripper: Process gripper are designed for handling the car panel from one tool (Station) to other tool (Station), And in addition to that it undergoes process like pedestal welding, pedestal riveting, gluing, sealing, etc.,

• Combo Gripper: Combo gripper are designed for handling the car panel from one tool (Station) to another tool (Station), Also with combination of weld gun at another side of the gripper for welding. For Example: Gripper + Weld Gun

• Dual Gripper: Dual gripper are designed for handling the car panel from one tool (Station) to another tool (Station), With two-sided gripper. For Example: Gripper + Gripper

 

4. Stands

• Pedestal Gun Stand: Weld gun is mounted to a fixed stand which is grouted to the floor permanently, Where the process gripper carries the car panel to weld the spot with this fixed weld gun.

• Gluing and Sealer Stand: Gluing gun or sealer gun is fixed to a welded or a standard stand which is grouted to the floor permanently.

• Docking Stand: When robots are selected for multi-tasking like material handling & welding, which cannot carry both due to some limitations (payload capacity of the robot or space constraint) the robot will drop and pick the gripper or gun after completing the respective operation with the help of Docking stands.

• Date Stamp Stand: The panel will get the date embossed on to it, with the date stamping device mounted on this date stamp stand.

 

5. Miscellaneous

• Buffer Storage: A buffer storage stand is a storage solution used in manufacturing or assembly processes to temporarily store components, parts, or products during production. It serves as an intermediate storage area between various stages of the production line, allowing for smoother workflow and reducing the risk of bottlenecks or interruptions.

• Rack: Racks refer to specialized structures or frameworks used for organizing, storing, and transporting fixtures.

 

• Takeout Trolley: Take out trolley is used to take the car panel out of the robotic working cell between the cycle for purpose.

• Conveyor: A conveyor is a material handling system that consists of a continuous belt, chain, or other flexible surface that moves materials from one location to another.

• Curing: In this Station product received after sealing application, is kept idle at ambient temperature, which allows sealant to get dry with better bonding between the panel.

 

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Question 6: What are the basic terminologies used in the BIW fixture?

Basic Terminologies used in fixture design are:

 

• NC/MYLARS/FINGERS: MYLAR is one kind of block that touches the panel and holds or clamps the panel. Mylars are always designed in CAR LINE. Mylar is also called NC (Numerically Controlled) Block. Mylars are mounted on any block or plate with Shimming, so that height of mylar can be adjusted accordingly at the assembly level. For ‘A’ class surfaces Nylon mylars are used. So that surface can be saved from scratches.

 

• PRINCIPAL LOCATING POINTS (PLP): Principal locating points are the points that are used for the accurate location of the part to maintain the geometry of the There is lots of holes on the panel which are not accurate due to stamping operation. The PLP are defined in the drawing. The positional dimensions or relative dimensions are very precise in stamping & in fixtures also.

 

• BLADE: The plate which connects Riser to the Clamp cylinder is named Blade. This plate plays an important role in building the unit. The plate can be of any shape.

 

• RISERS: The part which is mounted on the base plate and holds a clamp or pin cylinder on it, is called Riser. Riser can be Standard Part or manufactured part; it varies from project to project. A riser can be a Single part or welded part. Standard risers also have various shapes and sizes.

 

• SHIMS: A shim is a thin plate to adjust receiving panels. Shims are typically used to support, adjust for better fit, or provide a level surface. Shims may also be used as spacers to fill gaps between parts subject to wear.

 

• ROUGH LOCATORS: Rough locator is a type of locating feature or component used in fixtures to provide initial or coarse positioning of the workpiece. They are designed to align the workpiece quickly and roughly within the fixture before precise or fine positioning takes place.

 

• HARDWARES: Hardware refers to various components and fasteners that are used to assemble, secure and adjust the different elements of the fixture system.

 

• CMM: A coordinate measuring machine, also known as a CMM, is a piece of equipment that measures the geometries of physical objects. CMMs use a probing system to detect discreet points on the surfaces of objects.

• UNITS: A unit represents an individual element or module that serves a particular purpose in supporting, positioning, or securing the workpiece during the manufacturing process. Example: - Clamping Unit, Locating Unit, Support Unit, Adjustment Unit, Sensing Unit, etc.

 

• NUMBER PLATE: A number plate in a fixture refers to a plate or tag that is affixed to the fixture, displaying a unique identification number or code assigned to that fixture. The number plate is typically used for tracking, inventory management, and identification purposes within a manufacturing facility.

 

• CO-ORDINATE PLATE: A coordinate plate, also known as a coordinate reference plate or a coordinate system plate, is a component used in fixtures to establish a fixed reference point or coordinate system for positioning and aligning the workpiece. It provides a consistent and standardized reference frame that allows for accurate and repeatable positioning of the workpiece within the fixture.

 

• NAME PLATE: A name plate in a fixture refers to a small plate or tag that is attached to the fixture, typically near its identification or reference points. It contains relevant information about the fixture, such as its name, identification number, manufacturer's logo, and other details that help identify and track the fixture.

 

• CLAMP ARM: A clamp arm is a component used in fixture systems to secure and hold workpieces in a fixed position during machining, assembly, or inspection operations. It is designed to exert a clamping force on the workpiece, ensuring stability and precision during the manufacturing process.

 

• PIVOT: Pivot refers to a component or mechanism that allows rotational movement or adjustment within the fixture. It enables the workpiece or specific fixture elements to rotate or pivot around a fixed point or axis.

 

• CLASS 'A' SURFACE/SKIN SURFACE: Class ‘A’ surfaces are primarily used in the automotive environment and refer to those surfaces which are visible in a product. In other words: A - class surfaces are those aesthetic/free-form surfaces, which are visible to us (interior/exterior) and have an optimal aesthetic shape and high surface quality.

 

• REED SWITCHES: A reed switch is a type of electrical switch that operates based on the presence or absence of a magnetic field. It consists of two thin, ferromagnetic metal reeds sealed within a glass or metal tube filled with an inert gas. The reeds are typically made of materials such as nickel-iron or nickel-cobalt alloys.

 

• SENSORS: A sensor is a device that measures physical input from its environment and converts it into data that can be interpreted by either a human or a machine. Most sensors are electronic (the data is converted into electronic data), but some are simpler, such as a glass thermometer, which presents visual data.

 

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