Week 1:- Introduction to BiW and Fixtures Challenge

1. What is BIW & define its parts?

BIW-Body in White

In the Automotive Industry BIW (Body in White) is the common terminology used to mention the car sheet metal welded structure (body shell).

In today's situation, automotive BIW is made of steel (various steel grade material -DP, DD, HDP etc.) as well as made of aluminium alloy (e.g. AUDI A8).

Sub-assemblies like Under body, Body side Left Hand Side/ Right Hand Side, Front End, Roof etc. gets welded together by various metal joining process e.g. resistance spot welding, Laser welding, MIG welding to make welded metal shell (Without Door, Trunk-lid / Tailgate) , Fender, Bonnet Center) called Body in White.Automotive car shell made before painting is called Body in White.

BIW joinery decides the exterior and interior look of any car.

All the Interior Parts(Commonly used in Automotive) e.g. Dashboard, Trim (Door Trim, Pillar Trims, Roof liner, Seats are mounted on the BIW shell with the help of various brackets or nuts mounted on the BIW.Exterior (Commonly used term in car industry) components e.g. Front Bumper, Rear Bumper, Fender LH/RH, Side Mirrors are mounted on the BIW shell with the help of various brackets or mounting systems.

In car industry outer look defines the style. BIW sheet metal part shell defines overall car style.

• Who designs car profiles via sketch, prepares clay model.

• Who makes concept vehicles for auto show display?

• Who makes concepts and present to Top Executives who design product strategy?

BIW product designer- R&D Engineers

• Who design the sheet metal individual components as per the styling data?

• Who brings the styling to reality via designing individual components in details?

• Who decide the product specification?

• Who decides no of spots as per the geometry and strength requirement?

BIW process engineer

• Who plans the BIW weld shop layout?

• Who decide the assembly sequence of sheet metal in discussion with die designer?

• Who decides no of stations required to join BIW panel /sub-assemblies.

• Who decides no of equipment as per the JPH (jobs per hour) requirement?

Die Designer/ Tool designer

• Who decides the no of tools and process to make the sheet metal?

• Who design the die for sheet metal component?

BIW Fixture designer Engineer

• Who works with product designer, process planner and die designer

• Who decides or help product designer to decide the PLP.

• Who designs spot welding fixture.

• Who works with process planner to finalize the cycle time?

Body Shop Engineer

• Who weld the panels/sub assembles to form sub-assemblies/assemblies

• Who is responsible to get the BIW painted as per the requirement?

TCF Engineer

• Who is responsible for assembly of other aggregates on BIW in TCF lines?

• Which are these aggregates -Seat, Interior trim, Engine, Exhaust System, and Axle? Fender, Head lamp, tail lap and all wiring harness.

BIW is mainly categorized as:

1. Body side

2. Under body

3. Closures

4. Roof

5. Fender

6. Reinforcements

BODY SIDE consists of:

1. Body side outer

2. Body side inner

It generally refers to both the sides of the car that is left and right side. It mounts various BIW components like A-pillar, B-pillar, C-pillar, Panel side sill etc.

UNDER BODY consists of:

1. Front end under frame: This is the compartment are where the engine and other components of automobile like battery, radiator etc mounts.

2. Main floor: This is the compartment where the interior parts like seats; infotainment panel etc will be mounted.

3. Rear end under frame: This compartment shapes the rear end of the car. This is what provides space of mounting of rear closure parts and boot space.

CLOSURE components consist of:

1. Front door: Two front doors on each side.

2. Rear door: Two rear doors on each side.

3. Hood: To cover the engine compartment.

4. Trunk lid: To cover the interior and boot space.

ROOF consists of:

1. Roof inner

2. Roof outer

FENDER: The component seats between side body and front end under frame. The below image shows precisely what a BIW of monocoque consists of

2. What do you understand by BIW nomenclature?

A fixture is a device which holds and locates a workpiece during an inspection or for a manufacturing operation. The fixture does not guide the tool.

In construction, the fixture comprises a different standard or specially designed work holding the device, which is clamped on the machine able to hold the work in the position. The tools are set at the required positions on the work by using gauges or by manual adjustment.

A fixture is a work-holding or support device used in the manufacturing industry. Fixtures are used to securely locate (position in a specific location or orientation) and support the work, ensuring that all parts produced using the fixture will maintain conformity and interchangeability. Using a fixture improves the economy of production by allowing smooth operation and quick transition from part to part, reducing the requirement for skilled labor by simplifying how workpieces are mounted, and increasing conformity across a production run.

A fixture differs from a jig in that when a fixture is used, the tool must move relative to the workpiece; a jig moves the piece while the tool remains stationary.

BIW Fixture Types:

• Production fixtures

• Pre-production operation fixtures(PPO)

• Checking fixtures

1. Production fixtures:

This fixture is used for mass production It requires high consistency through its operation to maintain the geometry of the parts so the material used is well tested for hardness & aesthetics. The quality for maintaining the dimensions & tolerances are also checked. The production fixtures need to easy for maintenance purposes. The fixture needs some maintenance after completing no. of operations. The time requires for assembly & disassembly should be as low as possible which saves lots of time.

2. Pre-production operation fixtures(PPO):

These fixtures are designed as a prototype fixture to check the feasibility of initial batch production & to check which things need to be improved before starting the These fixtures can be taken as the base fixtures which sets the benchmark & criteria which help us to rectify the errors that we could get from preproduction operation fixtures. In this many manual operations are involved, many engineers & quality-related persons are required. It has a large cycle time as compared to production fixtures. It requires lots of time & cost also. We have to maintain the cost of the car as low as possible so we directly go to the production fixture by considering standards, a checklist to maintain the error-free production.

3. Checking fixtures:

As the name suggests these fixtures are used for checking No operations like welding gluing or hemming are carried out in these fixtures. The gauges are used in these fixtures to get the dimensions & the tolerances part having & the data is compared with the designed dimensions to check whether the part is ok or not. The geometry of the welded parts is also checked in these fixtures to ensure the parts maintain the required dimensions & geometry.

4. What is the basic principle of fixture design?

3-2-1 principle is used for the design of the fixtures

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

• You know that any free body has a total of twelve degrees of freedom as below:

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

6 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)

To make sure the proper fixing of the part we need to restrict all 12 degrees of freedom of the workpiece. The major portion of the time of BIW fixture designer is spent deciding how to fix these all DOF.

PRIMARY LOCATOR:

First, the three locators or supports are placed under the workpiece. It will be positioned on the primary locating surface also known as a datum. It will restrict 5 degrees of freedom.

• Axial Movement downward along Z-axis

• Rotation about the X & Y axis

SECONDARY LOCATOR:

The next two locators are normally placed on the secondary surface, restricting an additional 3 degrees of freedom.

• Axial movement along the Y+ axis

• Rotation about the Z-axis

TERTIARY LOCATOR:

This locator is positioned at the end of the part. It restricts one degree of freedom

• Axial moment along the X-axis

• All these 6 locators will restrict a total of 9 degrees of freedom. The remaining 3 degrees of freedom (1,4&5) will be restricted by the clamps.
• To minimize the time consumption in assembly and disassembly, Have to use minimum numbers of pins to arrest a maximum number of degrees of freedom.
• The jig and fixture are tools used for holding the workpiece in a correct location for mass production. Various types of fixtures (like drilling fixtures, milling fixtures, and welding fixtures) are used in industry. The 3-2-1 method is the fundamental principle for all types of fixture design.

5. Elaborate types of BIW Stations?

The BIW assembly line is where different types of panels are joined together in each specified zone like Underbody
zone, Hood zone Etc.

These zones are further subdivided into stations, where various processes like welding gluing and inspection are
done to the part of that particular zone before they are being assembled together. For instance, in the roof zone,
various reinforcement is to be added before they are married to the side zone.

The BIW assembly line can be classified as follows:

1. Tools

2. Grippers

3. Stands

4. Miscellaneous

A tool is a fixture which consists of number of different units together to hold a car panel or assembly.

Geo Tool:

• A geo tool is a fixture in which the geometry of the panel which is welded together is defined accurately.
• In geo fixture two panels will be loaded and welded together.
• Pin tolerance for geo fixture is about -0.15mm.

Re-spot Tool:

• Are-spot tool is a fixture where already welded panels are brought to be welded further.
  
• For example, on a certain panel we needed to have 50 weld but due to assembly line constrains we managed
  to achieve 30 on geo tool, then the remaining 20 will be achieved on the re-spot tool.
  
• Pin tolerance for the re-spot tool is -0.28mm.

Marriage or hemming tool:

• Marriage or hemming tool is a fixture in which the inner panel and outer panel is joined together.
• Hemming is not done for every part but only for those parts where we want to join two panels without other
  joining process as it may affect the aesthetics of the car.
• Hemming can be found on Hood, Back door etc.

Checking stations:

It is used to check the automotive part or assembly to ensure all the coordinated, relative dimensions and positions
are as per tolerance. It can be classified as follows:

• Gauge type checking fixture is where the work piece is held and various gauges are introduced to ensure the
  dimensions and repeatability.
• Fixed type checking fixture is where the work piece is fixed using clamps and pins and the Coordinate
  Measuring Machine is used to measure the coordinates of different points of the panel and compare it with the
  nominal value and give its report to rectify any errors.
• Automated checking fixture is where the automated setting are being done through sensors, PLCs, switches etc,
  to give a signal in case of any irregularities which can be rectified. As it is expensive, it is not widely used.

Grippers Stations:

A gripper is a device that enables the holding of an object to be manipulated. The easier way to describe a gripper is
to think of the human hand. Just like a hand, a gripper enables the holding, tightening, handling, and releasing of an
object. A gripper is just one component of an automated system. A gripper can be attached to a robot or it can be
part of a fixed automation system.

Different grippers are used in BIW as follows,
1.A) Material handling gripper

• As the name suggests These grippers are used for material
• These grippers can pick assembly from one station & will drop the assembly at another

B)Process grippers

• These grippers are used to carry out some specific processes like gluing, welding, riveting in addition to
  material handling.
• The gripper will go under gluing stand in case of gluing process & will goes under the pedestal weld stand in
  case of the welding process.

C)Combo Gripper

• Combo grippers are the ones which can carry out multiple tasks like it can do material handling & also it can
  carry out some specific process like gluing, welding as well.
• Weld gun + Gripper
  

1.D) Dual Gripper

• These are two-sided In case when we want one LH & one RH part, these grippers are used. It can handle the
  material from one station to another station
• Gripper + Gripper

3)Stands Stations

Stands are used to hold the part when not in use or also it is used to mount some parts or bodies on it.

Different stands are used in BIW

1. A) Pedestal stands

• Weld gun is mounted on the fixed stand which is mounted to the floor The gripper can carry the panel under
  the stand to do the operation.

B) Gluing & sealer stand

• Gluing gun or sealer gun is fixed to a welded or a standard stand which is grouted to the floor

C) Docking stand

• The robots have some limitations such as the payload capacity of the robot & also due to lack of
• When we select the robot for multitasking it can’t do both the task simultaneously due to
• In this kind of case, we add a docking stand to put some equipment that is not in use for the current operation
  but will be required for next
• Hence the robot can drop a gripper or gun & pick the next operation equipment to complete the task from the
  docking

D) Date stamp stand

• Every manufactured product has some data to stamped or to be embossed on it like serial no, batch no, Date
  for some future reference, or for data collection.
• The required data is stamped or embossed by using the stamping device mounted on the

4) Miscellaneous stand

A) Curing

• After gluing it needs some time to cool down, so we put the assembly on some belts & it will take the panel to
  another station & meanwhile gluing will cool down.

B) Buffer Stand

• After some operation, we can put the no. of assemblies in this stand which is buffer stock & it can be
  transported to another station in easy They are also used to store the inventory while the machine is
  undergoing some maintenance.
  

C) Take out trolleys

• Itused to take out some panels for inspection to rectify the process is going in the right or not between the
  cycle.

D) Conveyor

• The conveyor is the rotating path that transport the part to the next station which are kept over it.

6. What are the basic terminologies used in the BIW fixture?

Basic terminologies used in the BIW fixture

• The following terminologies are used in BIW

A) 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.

B) Principle locating point (PLP)

• These 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.

C) Risers

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

D) Blade

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

E) Shims

• Shims are the small part that comes with the thickness of 0.Imm, 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 distorsion 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.

F) 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 foolproofing.
  G) Hardware
• Hardware is like the Hex head bolts, Allen Bolts, Hex nuts, Spring washers, Self-locking nuts

H) CMM

• CMM stands for coordinate measuring 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.

I) Unit

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

J) Number plates

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

K) Nameplate

• The data like manufacturing company name, fixture type, Fixture weight is embossed on the plate & joined to
  the fixture.
  L) Clamp Arm
• The clamp arm is the part of the clamp unit which moves an Over clamp arm the Mylars are mounted.

L) Pivot

• Itis an axis about which the clamp arm will

M) 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.

N) 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.