Week 1:- Introduction to BiW and Fixtures Challenge

• What is BIW & define its parts?

BIW stands for Body in White. BIW is an assemblage of all welded sheet metal panels as before going for priming and painting. BIW refer to the welded sheet metal structure to which other component will be married i.e. engine, chassis, exterior and interior trim.

Body in white or BIW refers to the stage in automotive design or automobile manufacturing in which car body sheet metal ( including door, hoods and deck lids) has been assembled or designed but before the components ( chassis, motor) and trim ( windshields, seats, upholstery, electronics, etc.) have been added. All activities in the production of a vehicle body or shell before it goes to the paint shop are done in a weld shop and the end product of a Weld shop is referred to as BIW.

BIW Parts are mainly categorized –

• Body side
• Body side outer
• Body side inner
• • Under body
  • Front end under frame ( Engine compartment)
  • Main door
  • Rear end under frame (Rear compartment)
  • Closures
  • Front door
  • Rear door
  • Hood
  • Deck lid
  • Roof
  • Roof inner
  • Roof outer
  • Fender
  
  

  What do you under stand by BIW nomenclature

  BIW nomenclature means the details of the BIW at each and every point and parts. Nomenclature is basically choosing names for thing. BIW have no. of parts in it. All parts have different names.

  As automotive industry is spread worldwide. Every nation has its own language. So the same part in BIW have different name in its region.

  For example, One component of BIW is called suspension tower in UK & same component called shock tower in U.S.

What is Fixture and its types

A fixture is device which holds the work piece to be processed by using 3-2-1 principle. In general, a welding fixture (Tool) consists of no of units together to hold the car panel, and is mounted on the base unit.

Welding fixtures are normally designed to hold and support the various components to be welded. It’s necessary to support them in proper location which is capable of preventing distortion in work piece during welding.

Types of Fixtures:-

• Production Fixtures:- Its used in mass production purpose.
• Pre-production operation fixtures (PPO):-For initial batch production to study the feasibility.
• Checking Fixture:-For car panel geometric inspection purpose.

• Production fixtures:-

This fixture is used for mass production it requires high consistency through its operation to maintain the geometry of the parts so that material used is well tested foe hardness and aesthetics. The quality for maintaining the dimensions and tolerances are also checked. The production fixtures need to easy maintenance purpose. The fixture needs some maintenance after complete no. of operations.

• Pre-Production Fixtures:-

Theses fixtures are designed as a prototype fixture to check the feasibility of initial batch production and to check which things need to be improved before starting.

These fixtures can be taken as the base fixtures which set the benchmark and criteria which help us to rectify the errors that we could get from preproduction operation fixtures. In this many engineers and quality-related persons are required.

Checking Fixtures:-

As the name suggested 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 and the tolerances part having and the data is compared with the designed dimensions to check wither the part is ok or not. The geometry of the welded part is also checked in these fixtures to ensure the part maintain the required dimensions and geometry.

What is the basic principle of fixture design?

The 3-2-1 principle of location (six point location principle) is used to constrain the movement of work piece along the three axes XX, YY, and ZZ. This is achieved by providing six locating points, 3 pins in base plate, 2 pins in vertical plane and 1 pin in a plane which is perpendicular to first two planes

DEGREE OF FREEDOM CONTROLLED BY 3-2-1 PRINCIPLE

3-2-1 PRINCIPLE is the heart of the fixture design and world holding devices.

In BIW FIXTURE design the panels are always fixed with the help of 3-2-1 .because it always minimizes the usage of unwanted components to hold the panels with the help of 3-2-1 principle we can arrest the six degrees of freedom which means six degrees of rotational and six degrees of translational axes

Elaborate types of BIW station

BIW STATIONS

BIW Station is the part of BIW assembly line. The BIW assembly line is divided into zones & these zones are again divided into stations. - In BIW we consider Tack / Geo Fixture. In Geo fixture tack welding done for all the parts to be assembled in that fixture.

The BIW stations are further divided into following

• Tool Stations-

Geo Fixtures -A geo tool is a fixture in which the geometry of the panels are welded together is defined accurately, and these parts are located with 2 locating pins.

Ex - If 20mm panel hole is given the pin diameter should be of 19.85

Respot Fixture -It 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.

Ex - Panel hole 20 mm, then the pin diameter should be 19.72

Marriage fixture -In this marriage of different assemblies is carried out in this fixture.Inner panel of the assembly and outer panel of the assembly are joined together using the techniques like welding,riveting etc.,

Framer Fixture -Framer fixture is next station after the marriage fixture, In framer fixture the roof is attached to the output of the marriage fixture and it form like frame hence it is called as framer tool.

Checking Fixture -It is to check the assembly parts, dimensions and tolerances adn co-ordinates. These are two types of fixtures, Gauge type, automated checking fixture.CMM (Co-ordinate Measuring Machine ) is used to measure different points in the panel or assembly.

• Gripper Stations-

A Fixture which holds the car panel and it is fixed to the manipulating at the end of a robot.

Material Handling Gripper [MH] -These grippers are designed for handling the car panel from one tool to another tool.

Process Gripper -These grippers undergo same operation as MH and In addition to that it carry out specific process like gluing, welding , riveting , sealing etc.,

Combo Gripper -These are the grippers which undergoes multiple task like material handling and process at same time.

• Dual Gripper -These are same as MH but with dual side LH+RH

Stand Station- Stands are used to mount the parts when they are not in operation

Gluing or Sealer Stands -Gluing gun or sealer gun is fixed to a welded stand

Docking Stands -It is a stand used to put some equipment which is not required for current operation but used for later operation.

Date Stamp Stands -The required data is stamped on the stand by using stamping device.

• Miscellaneous Stations-

Curing-To cool down the gluing part, mean while the assembly will be carried out to some other station.

Buffer Stand -Some sets of same parts manufactured and kept in a stock and will carried to another station which is easy to be transported.

Conveyor -It is a rotating part which is connected to next station and the material kept on this rotating part will be carried over.

Take out trolley -It is used to take some parts for inspection in order to make to make sure wheather the process is going correct or not.

What are the basics terminologies used in the BIW fixture

The basic terminologies used in the BIW fixtures be

NC/MYLARS/FINGERS -Mylars is the component which holds the panel while operation.These are placed from top side and bottom side also.

Top side mylars are called as Clamping mylars and Bottom side mylars are called as Resting Mylars.

Every Clamping mylars have resting mylars.

It dont allow deformation of the part due to welding stresses.

PRINCIPLE LOCATIONG POINT (PLP) -These are points which are used for the accurate location of the part to maintain the geometry of the assembly.

They are lot 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 and in fixtures also.

RISERS -Risers are of different type like L type Riser,Square tube riser etc.

Riser is the manufacturing part which gives height to the assemblies.

BLADE -Blades are plates mounted in the riser.Other parts like cylinder,arms etc are mounted on the blade.

SHIMS -Shims are the small parts which comes with the thickness of 0.1mm,0.2mm,0.5mm etc.,These will compensate the stackup tolerance which reflects at the panel holding part called mylars.

We give tolerance to all the part of the fixture.Due to this tolerance the mylars will either lift up or goes down from its defined position.

If the mylars goes down from the defined height it will make 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 wont deformed and also get any impression on it.

ROUGH LOCATORS -The operator can place the part in wrong orientation mistakenly.The rough locator will work as a guide while placing the part in the fixture and the part will be loaded in desired orientation.it us a part of fool proofing.

HARDWARES -Hardwares are like the hex head bolts,allen bolts,hex nuts,spring washers.self locking nuts etc.,

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 on object with a probe.

It generates report my comparing the data with the cad file data.

UNIT -The fixtures is the assembly of different types if units to form a fixture.they are different units like pin unit,base unit,clamping unit etc.,

NUMBER PLATES -Number plates is the aluminium embossed plate placed on the each unit for easily recgnising the unit.

NAME PLATE -The data like manufacturing company name,fixture type,fixture weight etc.,That is embossed on the plate and joined to the fixture.

CLAMP ARM -Clamp arm is the part of clamp unit and it moves over a axis.over clamp arm the mylars are mounted.

PIVOT -It is a axis about which the clamp arm will rotates.

CLASS A SURFACE/SKIN SURFACE -The Outer panels of the car like hood,door,backdoor,fender,Roof etc.,are visible to the customer.The outer panels should be asthetically very good.

No any scratches or dent is acceptable over it.While the 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 skin.Generally nylon or PU material is used for clamping purpose.