Week 1:- Introduction to BiW and Fixtures Challenge

1

The term “Body in White” (BIW) refers to the stage in automotive manufacturing where the car body’s sheet metal components are assembled before the addition of moving parts and other components. During this stage, techniques such as welding, riveting, or bolting are used to join the body panels together. The BIW represents the structural and outer shell of the vehicle before it receives its final paint job and other finishing touches. Subsequent stages involve adding moving parts like doors, hood, trunk lid, front fenders, as well as various components such as the chassis, engine, and trim elements like windshields, seats, upholstery, and electronics.

UNDER BODY :

The underbody is a crucial component of the BIW, providing structural support and housing various important elements. As we mentioned, it typically includes sub-assemblies such as the engine room, rear floor, and chassis. Let’s briefly break down these components.

• Engine Room: This is the area of the underbody where the engine is located. It includes the structure and mounting points for the engine, as well as components like the engine cradle and mounts.
  
• Rear Floor: The rear floor is the section of the underbody located at the back of the vehicle. It provides support for the rear suspension components and contributes to the overall structural integrity of the vehicle.
  
• Chassis: The chassis is the framework of the vehicle, consisting of the structural elements that support and connect various vehicle components. It plays a crucial role in determining the vehicle’s overall strength, durability, and handling characteristics.

UPPER BODY :

There are various components that make up the upper body of a vehicle. Each of these components plays a specific role in the overall structure and design of the car. Here’s a brief description of each .

• Body Side L/R (Left/Right): These are the main panels on the sides of the vehicle, covering the space between the front and rear fenders. They contribute to the overall shape and aesthetics of the car.
  
• Roof Panel: The roof panel is the topmost horizontal surface of the vehicle, covering the passenger compartment. It provides protection from the elements and contributes to the car’s structural integrity.
  
• Cowl & Dash: The cowl is the area at the base of the windshield, while the dash refers to the dashboard inside the car. Together, they form the front interior area of the vehicle, housing various components like the steering column, instrument panel, and controls.
  
• Front Fender: The front fender is the panel on each side of the vehicle that covers the area above the front wheels. It protects the wheel well and enhances the vehicle’s appearance.
  
• Rear Fender: Similar to the front fender, the rear fender covers the area above the rear wheels. It contributes to the overall design and aerodynamics of the vehicle.
  
• All Pillars: Pillars are vertical or nearly vertical supports that help define the structure of the car. Common pillars include the A-pillar (between the windshield and front side window), B-pillar (between front and rear side windows), and C-pillar (between the rear side window and rear windshield)
  

MAIN BODY :The main body consists of two parts: the Under Body and the Upper Body. The Under Body likely refers to the lower portion or chassis, while the Upper Body could include the framework, cabin, or other upper components.

CLOSURES: In the automotive industry, doors, bonnets (hoods), and deck lids are commonly referred to as closures. The term “closure” is used to describe the movable parts of a vehicle that can be opened and closed to access various compartments, such as the passenger compartment, engine bay, and trunk. These closures play a crucial role in providing access to different areas of the vehicle and are essential for maintenance, repair, and everyday use.

2

Nomenclature is used to define the name for the parts, there are 2 different nomenclatures US & UK.

A part will have different terms between US & UK.

eg: If in US suspension tower, in UK it is called as Shock tower , like this there are different terms.

3

A device which is used to hold, locate and support the component in the manufacturing industry is called fixture. Fixtures ensure to provide the stability to the part when any process is being done on that part. That process can be welding, riveting, grinding, drilling etc. In BIW fixture design Fixture works on 3-2-1 principle.

Production fixture

Pre production fixture

Checking fixture

4

The design process must take into account a number of factors, including:

• The location and orientation of the components
• The type of welding process being used
• The accessibility of the weld joints
• The need to maintain accurate dimensions and tolerances
• The safety of the operators
• 321 Principle is followed while clamping the part.

5

Geo station:

• In this station geometry of two parts are fixed. it can be either using welding or riveting . In this station precision and geometry of the finished product is defined Locating pins have closer tolerance of 0/-0.15.
• Suppose the hole dia of panel is 16mm then the pin dia minimum can be 15.85.
• Diameter of locating pins should be lesser than the panel hole dia. So Tolerance in locating pin is given in negative value.

Respot Station :

• Once product comes out of the Geo Station and there are left out spots where spot welding or riveting is to be done. then it is moved to another station , that station is called Re-spot station.
• These left out spots may be the due to clamp plan, cycle time, robot reach ability or any other various reasons.
• In this station pins have tolerance up to 0/-0.28.

Pedestal Station :

• In this station , Pedestal gun is mounted on a tool and panel is manipulated manually or by robot to weld the panels.
• Pedestal station is generally a Re spot station.
• Re spot station and Pedestal station, both perform same kind of operation . but to decide whether to go for pedestal or a re-spot station some parameters needs to consider like cycle time, floor space, no. of welds, clamp plan, or size of the panel.

Loading Station :

• This station is used for loading of panel and same station is used to change the orientation of the if it is required in the upcoming station.
• Sometime this station is used when Robots are unable to transfer panel from one station to another.

Buffer Station :

This station is used to make the balance between the process.

Some stations carry out process in lesser time as compared to their respective stations. In that case panels can be stored in one station so that assembly line process remains smooth.

Sealer Station :

In this station Sealant application is carried out. This process can be carried out manually or by using robots. Sealer is used in between two panels so that panels do not flatter due to friction.

Marriage Station :

In this Station inner and outer panels are joined. In this station to avoid the impression on the outer panel(A class surface), copper strips are used in between the weld tip and A-class surface.

Curing Station :

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.

6

NC/Mylars/Fingers:

Mylars are the component that holds the panel while These are placed from topside & from the bottom side also. The top side Mylars called Clamping Mylars & the bottom side Mylars called Resting Mylars. Every clamping Mylars have resting Mylars. It doesn't allow deformation of the part due to welding stresses.

Principle locating point (PLP):

These are the points that are used for the accurate location of the part to maintain the geometry of the part. 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.

Risers:

Risers are of different types like L-typer rises, Square tube riser Riser is the manufacturing part which gives height to the assemblies.

Blade:

Blades are plates mounted on the Other parts like cylinder, arms, etc are mounted on the blade.

Shims:

• Shims are the small part that comes with the thickness of 0.1mm, 0.2mm, 0.5mm, etc. These will compensate for the stackup tolerance which reflects at the panel holding part called We give tolerance to all the parts of the fixture. Due to this tolerance, the Mylars will either lift up or goes down from their defined position.
• If the Mylars go down from the defined height it will make an impression or dent on the panel.
• If the Mylars lift up then there will be a distortion due to welding stress. To adjust the Mylars At its defined position we use shims so the panel won't be deformed & also don't get any impression on it.

Rough locators:

The operator can place the part in the wrong orientation The rough locator will work as a guide while placing the part in the fixture & the part will be loaded in the desired orientation. It is a part of fool proofing.

Hardware:

Hardware is like the Hex head bolts, Allen Bolts, Hex nuts, Spring washers, Self-locking nuts

CMM:

CMM stands for coordinate measuring machine. It is a device that measures the geometry of physical objects by sensing discrete points on the surface of the object with a probe. It generates a report by comparing the data with the CAD file data.

Unit:

The fixture is the assembly of different types of units to form a part. There are different units like pin unit, base unit, clamping unit, etc.

Number plates:

The number plate is the aluminum embossed plate placed on each unit for easily recognizing the part unit.

Nameplate:

The data like manufacturing company name, fixture type, Fixture weight is embossed on the plate & joined to the fixture.

Clamp Arm:

The clamp arm is the part of the clamp unit which moves an Over clamp arm the Mylars are mounted.

Pivot:

It is an axis about which the clamp arm will rotate

Class A Surface/Skin surface:

• The outer panels of the car like a hood, door, backdoor, fender, roof are visible to the customer.
• The outer panels should be aesthetically very good. No scratches or dent is acceptable over it.
• While designing the fixture to the skin surface the clamping material should be soft, so that it could not able to left any impression or dent over the skin. generally, nylon or PU material is used for clamping purposes.

Reed switches & sensors:

These are the electric components used in automated The reed switch is an electrical switch operated by an applied magnetic field. The detects the panel is loaded or not is done by sensors.