Week 1:- Introduction to BiW and Fixtures Challenge

Q1) What is BIW & define its parts

BIW (Body In White)

BIW refers to the stage in the automobile manufacturing in which a car body's components have been joined together, using one or a combination of different techniques: welding (spot, MIG/MAG), riveting, Hemming, clinching, bonding, laser brazing etc.

BIW is a stage in the production of automobiles in which all sheet metal components such as the roof, body side, under body, back door, cross members, and other components are welded together and the resulting body is dipped in a primer solution, which has a greyish colour and thus gives the body its name. The car shape is determined by the BIW, which is obtained after welding and before painting.

BIW IS MAINLY CATEGORIZED AS:

1) Body side

2) Under body

3) Closures

4) Roof

5) Fender

6) Reinforcement

Body side consists of:

1) Body side outer

• Visible from the outside, include door opening, window frames and wheel arch outlines.
• Made from stamped sheet metal
• Designed for aesthetics and aerodynamics, but also plays a structural role.

2) Body side inner

• Provide the structural strength
• Include reinforcement for pillars (A, B, C, D), rocker panels, door sills, support the roof, doors and crash protection elements.

Under body consists of:

1. Front end under frame: This is the compartment where the engine and other components like battery, radiator are accommodated.
2. Main floor: This is the compartment where the interior parts like seats, instrument panel etc. will be mounted
3. Rear end under frame: This compartment gives shapes the rear end of the car. This part provide the space for mounting of rear closures parts and boot space.

Closure parts consists of:

1. Front door: Two front doors on each side
2. Rear door: Two rear doors on each side
3. Hood: Two cover the engine compartment
4. Trunk lid: Two cover the interior and boot space

Roof consists of:

1. Roof inner
2. Roof outer

Fender

The component seat between side body and front end under frame.

Q2) What do you understand by BIW nomenclature.

Basically nomenclature is devising or choosing names for things. As we know that BIW has many number of parts in it and all of them have different names.

Automotive industry is a spread all over the world, so the sub part in BIW has different names in different countries.There are some BIW nomenclature from US and UK mentioned below.

Q3) What is fixture and its types

• A fixture is a device which holds the workpiece to be processed (Welded), by using 3-2-1 principle.
• A fixture is work- holding or support device used in the manufacturing industries. Fixture are used to securely locate (position in a specific location location or orientation) and support the work, Ensuring that all part produced using the fixture will maintain the conformity and interchangeability.
• In general a welding fixture consist of number of units together to hold the car panel, and is mounted on a base unit.
• Welding fixture are normally designed to hold and support the various components to be welded. it is necessary to support them in a proper location which is capable of preventing distortions in workpiece during welding. For tis the locating elements needs to be placed carefully, clamping has to be light but firm, but placement of clamping elements has to be clear of the welding area and the fixture has to be quite stable and rigid to withstand the stresses generated during welding process.

Types of fixture- The general type of BIW fixture are :-

1) Production fixture

As the name suggests, this fixture is used for mass production. It is a type of fixture on which car body get assembled. These type of fixture high consistency through its operation to maintain geometry of the part. so, material used for these type of fixture should be well tested as well as hardness level. The quality in terms of dimension, tolerance should be met. These fixture needs to maintain after certain period of time. The assembly and disassembly of products should be easy as as possible. So the maintenance people can be easily access with reducing time.

BIW WELDING FIXTURE

2) PRE PRODUCTION FIXTURES

It is generally defined as prototype fixture. It is designed to study feasibility of initial batch production to check which things are needed to be improving before starting the mass production. This fixture is base of production fixture in bench mark and criteria & helps us to rectify the error. In pre-production fixture there will be more involvement of manual operations, engineer & quality person. It has larger cycle time than production fixture, but designers will not practice by designing pre production fixture because it takes lot of time & cost. We have to maintain the cost of car as low as the possible, so we directly go to production fixture by considering the standards, checklist to maintain error free production.

3) CHECKING FIXTURE

As the name suggest this fixture is used for checking assembly. Checking fixture are same as geo fixture except there are no operation done like welding, gluing & hemming. Instead of that we use different in built gauge or external gauge to check the various dimension, gap, relative dimensions, tolerance. These data is compared with data provided by the designer or design team. The geometry of the welded part is also checked in this fixture to ensure the part maintains the required dimensions & geometry.

Q4) WHAT IS THE BASIC PRINCIPLES OF FIXTURE DESIGNING

The major portion of design time is spent deciding how to locate the work piece in the fixture. We know that any free body has a total of 12 degree of freedom.

Those are six translational degree of freedom +X, -X, +Y, -Y, +Z, -Z

6 rotational degree of freedom-

• Clockwise around the X axis
• Anticlockwise around the X axis
• Clockwise around Y axis
• Anticlockwise around the Y axis
• Clockwise around the Z axis
• Anticlockwise around the Z axis

To make sure the proper fixing part we need to restrict all 12 degree of freedom of the workpiece.

Primary locator-

First, the three locators or supports are located under the workpiece. It will be positioned on the primary locating surface also known as datum. It will restricts 5 degree of freedom.

Secondary locator-

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

Tertiary locator-

This locator is positioned at the end of the part. It restricts the 1 degree of freedom.

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

Q5) Elaborate the type of BIW stations

BIW station is the part of BIW assembly line. The BIW assembly line divided into zones and these zones are divided into stations

The BIW stations are further divided into following-

1)Tool station

2) Gripper station

3)Stand station

4) miscellaneous station

TOOL STATION

1) Geo fixture

• A geo tool is a fixture in which the geometry of the panel welded together is defined accurately. The pin tolerance for a geo pin will be closer tolerance, i.e. -0.15 in general. For example- Consider a panel hole size 20 mm, the pin diameter should be 19.85 mm.
• In geo fixture spots/MIG welding done in such sequence that after taking out from the fixture it achieve the desired accuracy and doesn't get disturbed during transportation from geo fixture to re-spot fixture. Geo fixture controls the sub assembly accuracy in all 3 axis.

2) Re-spot fixture

• Re-spot fixture is fixture in which the remaining weld spots which are not achieved in geo tools are welded for the pre welded panel from the geo tool.
• The pin tolerance for respot pin will be of tolerance within -0.28 in general.
• For example - Consider the panel hole size 20mm, the pin diameter should be 19.72 mm.

3) Marriage/Hemming fixture

• A marriage or hemming tool is a fixture in which the inner panel assembly and outer panel assembly are joined together.
• These are done by welding or hamming.

4) Checking fixture

• These are used to check the assembly of parts, tolerance & dimensions.
• It can be of gauge type, fixed type of automated checking.
• A checking gauge is tool where the workpiece is held & different measuring gauges are introduced to ensure the dimensions and repeatability.
• A fixed type checking fixture is used where the workpiece is fixed with clamps, pins & CMM is which measures the coordinates of the different of the panel or then is compares with the CAD data and gives a report.

GRIPPERS STATION

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 a part of of fixed automation system. Also known as EOAT (End of Arm Tooling)

Different type of grippers used in BIW:-

A) Material handling gripper

Material handling grippers are designed for handling the car panel from one tool to another tool

B) process gripper

Process grippers are designed for handling the car panel from one tool to other tool. In addition of that these grippers are also used to carry out some specific process like gluing, pedestal welding, pedestal riveting, sealing, etc.

C) Combo grripper

• Combo grippers are the one which can carry out multiple tasks like it can do material handling and also with combination of weld gun at the another side of the gripper for welding.
• Gripper + weld gun

D) Dual gripper

• Duel grippers can also handle material and 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

Stand stations

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

Different type of stand s used in BIW-

A) Pedestal stand

Weld gun is mounted on the fixed stand which is mounted to the floor permanently, where the process gripper carries the car panel to weld the spot with the weld gun.

B) Gluing and sealer stand

Gluing gun/Sealer gun is fixed to a welded or a standard stand which is mounted to the floor.

C) Docking stand

• The robot has some limitations such as the payload capacity of the robot.
• When we select the robot for multitasking it cant do the both tasks simultaneously.
• 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 operation.
• So, 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 number, date for some future references or for data collection.

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 & mean while 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 easily. They are also used to store the inventory while the machine is undergoing the some maintenance.

C) Take out trolleys

It used to take out some panel for inspection to rectify the process is going in the right or not, between the cycle.

D) Conveyer

Conveyer is the moving path that transports the part to the next station which are kept over it.

Q6) WHAT ARE THE BASIC TERMINOLOGIES USED IN BIW

The following terminologies are used in BIW.

A) NC/MYLAR/FINGERS

Mylars are the components 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 part deformation due to welding stresses.

B) Principe locating point (PLP)

These are used accurately locate the workpiece on the fixture to process the work piece.

C) Blade

Blades are the plates which are attached to the risers.

D) Risers

Risers are of different type like L-type rises, welded, square tube riser. Riser is the manufacturing part which gives height to the assemblies.

E) Shims

• Shims are the small parts that comes with the thickness of 0.1 mm, 0.2 mm, 0.5 mm, etc. These will compensate for the stackup tolerance which reflect at the panel holding part. We give the tolerance to all part of the fixture. Due to this tolerance , the mylers will either lift up or goes down from their desired positions.
• If the mylers go down from the defined height it will make an impression or dent on the panel.
• If the mylars liftup 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 and also didn't get deformation 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 and the part will be loaded in the exact location.

G) Hardware

Hardware are the hex headed bolts, allen bolts, hex nuts, spring washers & self locking nuts.

H) 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 generate a report by comparing the data with CAD file data.

I) Units

The fixture is the assembly of different type of units. There are different units like pin units, Base units, clamping units etc. which makes a complete assembly.

J) Number plate

The number plate is the aluminium embossed plate placed on each unit for easily recognize the units.

K) Coordinate plate

Every fixture has a tooling hole through which the whole fixture is checked, coordinate plates are used to cover the hole.

L) Name plate

Name plate the is the metal pate which consists the data like manufacturing company name, fixture type, fixture weight is embossed on the plate and joined to the fixture.

M) Clamp arm

The clamp arm is the part of the clamp unit which moves with the mylars mounted on it to hold the assembly.

N) Pivot

It is an axis about which the clamp arm will rotate or move.

O) Class A surface/skin surface

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

P) Reed switches & Sensors

These are the electric components, the reed switch and sensors are only used automated fixture. They detect the defective panel is loaded or not on the fixture assembly.