Basics Of BIW Fixture Design Week 1 Challenge

1.WHAT IS BIW AND DEFINE ITS PARTS

BIW :

BODY IN WHITE refers to the stage in automotive design or automotive manufacturing in which a car body sheet metal components have been welded together.

(or)

BODY IN WHITE refers to the stage in the automobile manufacturing in which a car body components have been joined together using one or a combination of different techniques like welding,brasing etc.

• BIW is the body steel structural shell design of an automotive product such as cars.
• It is a sheet metal welded structure.
• BIW will not have doors,engines,chassis or any other moving parts.
• BIW is made up of steel or aluminium panels,mostly steel.

BIW PARTS :

BIW structures can be divided into Following sub structures

1.UNDERBODY STRUCTURE

2.FRONT END STRUCTURE

3.BODY SIDE STRUCTURE

4.CLOSURES

5.ROOF STRUCTURE

6.FENDER

1.UNDERBODY STRUCTURE

DASH PANEL - Provides partition between engine and the driver cabin.

FRT FLOOR - Provides base for seats.

RAISER - Connects front floor to rear floor by providing level difference.

REAR FLOOR - Floor on the rear of the car and provides partition from ground and base for rear seats.

REAR WHEEL HOUSE

2.FRONT END STRUCTURE

PLENUM PANEL - A chamber located between the throttle body and runners of the intake manifold.

WING PANEL - Outer most 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 front connecting the two sides of front structure.

LOWER TIE BAR - Lower panel in front connecting the two sides of front structure.

3.BODY SIDE STRUCTURE

A-PILLAR - Front most support to the roof.

B-PILLAR - Second support to the roof.

C/D PILLAR - C is rear most support to roof in case of two row ing system, It will be third one.

RING PANEL - A structure panel connecting the rear and front portion.

QUARTER PANEL - Rear most panel of a body side structure.

DRIP RAILS/GUTTERS - An exposed channel applied to the roof over the side windows to direct water away from the windows.

4.CLOSURES

ALL DOORS

HOODS/BONNETS - A hinged panel providing access to the engine compartments.

5.ROOF STRUCTURE

ROOF

HEADERS - Structural member above the windshield at juncture with the forward edge of the roof panel.

BOWS

6.FENDERS

It is an encasement around the front and rear wheel.

2.WHAT DO YOU UNDERSTAND ABOUT BY BIW NOMENCLATURE ?

The word BIW nomenclature is a term used to choosing of names for things or parts.BIW nomenclature is used in autombile industries throughout the WORLD.In different regions have the different names for the parts.

Differ in names of the parts but not in components or parts.

EX - Petrol tank - gas tank,Wing -Fender etc.,

3.WHAT IS FIXTURE AND ITS TYPES ?

FIXTURE

A fixture is a device which holds,Supports and locates the workpiece for a specific operation but does not guide the cutting tool.

(or)

A fixture is a device which holds the work piece to be processed (Welded) by using 3-2-1 principle.

• Fixtures should be securely clamped to the table of the machine upon which the work is done.
• Fixtures are specific tools used for particularly in miling machine,shapers and slotting machine.
• Gauge blocks may be provided for effective handling.
• Heavier in construction.

BIW FIXTURE REQUIREMENTS

• It should prevent distortions in work piece during welding operation.
• Make some locating points adjustable.
• The fixture should maintain its consistancy to do defect free operations.
• The clamping need to be light but firm means the clamoing force should be able to maintain the part at its required position without damaging the part.
• Avoid complicated clamping arrangements.

FEATURES OF BIW FIXTURES

Reduction of idle time – Should enable easy clamping and

unloading such that idle time is minimum.

Cleanliness of machining process – Design must be such that not

much time is wasted in cleaning of scarfs, burrs, chips etc.

Rigidity and stability – It should remain perfectly rigid and stable

during operation. Provision should be made for proper positioning

and rigidly holding the jigs and fixtures.

Position of clamps – Clamping should occur directly above

the points supporting the workpiece to avoid distortion and

springing.

Safety – The design should assure perfect safety of the operator.

MATERIALS USED

High speed Steel: Cutting tools like drills, reamers and milling

cutters.

Die steels: Used for press tools, contain 1% carbon, 0.5 to 1%

tungsten and less quantities of silicon and manganese.

Carbon steels: Used for standard cutting tools.

Collet steels: Spring steels containing 1% carbon, 0.5%

manganese and less of silicon.

Non shrinking tool steels:

High carbon or high chromium

Very little distortion during heat treatment.

Used widely for fine, intricate press tools.

Nickel chrome steels: Used for gears.

High tensile steels: Used for fasteners like high tensile

screws.

Mild steel:

Used in most part of Fixtures

Cheapest material

Contains less than 0.3% carbon

Cast Iron:

Used for odd shapes to some machining and

laborious fabrication .

CI usage requires a pattern for casting.

Contains more than 2% carbon.

Has self lubricating properties.

Can withstand vibrations and suitable for base.

BIW FIXTURE TYPES

1.PRODUCTION FIXTURES

• It is for mass production purpose,The successful running of any mass production depends upon the interchanageability to faciliate easy assembly and reduction of unit cost.
• Mass production methods demand a fast and easy method of positioning work for accurate operations on it.
• This fixtures are used for mass production purpose.It requires high consistancy through its operation to maintain the geometry of the parts so the material used are well tested for the hardness and asthetics.
• The quality fot maintaining the dimensions and tolerances are also checked.
• The production fixtures needs to easy for maintainance purpose.
• The fixture needs some maintainance after completing number of operations.
• The Time requires for assembly and disassembly should be as low as possible which saves a lot of time.

2.PREPRODUCTION OPERATION FIXTURES (PPO)

• For intial batch production to study the feasibility.
• a model or prototype is made according to the OEM\'s and is used to check the feasibility.
• In this quality is checked from this it is easy to rectify and correct the errors whicj are occured during the testing of prototype.
• It is a time and cost consuming method but it is so useful after the start of batch production in order to eliminate the delay in the stations or in operational areas.

3.CHECKING FIXTURE

• After the completion of production of the part,The quality,dimensional tolerances etc will be checked and confirmed.
• For car panel geometric inspection purpose.
• The gauges are used in these fixtures to get the dimension and the tolerances part having the data is compared with the designed dimesions to check wheather the part is ok or not.The geometry of the welded parts is also checked in this fixtures to ensure the parts maintain the required dimensions and geometry.

4.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 workpiece 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 .

FIRST PLANE

This is the \"3\" in 3-2-1. So, three specific points are used to define the first plane.
Fewer than three points cannot define a plane, and in the real world dimensional tolerances mean that four or more points will not be coplanar. A real-world, less than ideally perfect part placed on four or more reference points will, in fact, rest on only three of the points due to its less than perfect surface. Different parts may rest on different combinations of three points, resulting in variation between finished parts.
A stool can be used to illustrate this concept. A two-legged stool would certainly be unstable. A three-legged stool sits rock-solid. A four-legged stool is often found to rock.
In the illustration, a three dimensional part, represented by a cube, is placed on a datum plane defined by three support points. The part’s six degrees of freedom have now been reduced to three. It can still move along the X or Y axes, and it can still be rotated about the Z axis. (The part cannot move along the Z axis because it is held against the plane by clamping force.

TIPS

• Use the largest surface of the part for the first (\"primary\") reference plane.
• Position the three support points as far apart as possible.
• If more than three support points are required to prevent deflection, make the additional points adjustable.

SECOND PLANE

A second plane, if it is perpendicular to the first, can be defined by two points, the \"2\" in 3-2-1. The part is now constrained to one degree of freedom: movement along the Y axis. (The part cannot move along the X or Z axes because it is held against the planes by clamping force.

TIPS

• Use the largest surface of the part for the first (\"primary\") reference plane.
• Position the three support points as far apart as possible.
• If more than three support points are required to prevent deflection, make the additional points adjustable.

THIRD PLANE

A third plane, if it is perpendicular to both of the first two planes, can be defined by one point, the \"1\" in
3-2-1. The part is now entirely constrained. It cannot move along or rotate about the X, Y, or Z axes. (Remember that the part is held against each of the three planes by clamping force.)

TIPS

• If more than one support point is required to prevent deflection, make the additional points adjustable.

5.Elaborate types of BIW Stations?

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 furthur divided into following

• Tool Stations
• Gripper Stations
• Stand Station
• Miscellaneous Stations

1.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.

2.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

3.STANDS

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.

4.MISCELLANEOUS STAND

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.

6.What are the basic 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.

READ SWITCHES AND SENSORS -

These are the electric components used in automated fixtures.

the reed switch is an electrical switch operated by an applied ,magnetic field.that detects the panel is loaded or not by sensors.