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.

 BIW PARTS

BODY SIDES
Body side outer
Body side inner

UNDER BODY
Font end under frame
main floor
Rear end under frame

CLOSURES
Front door
Rear door
Hood
Deck lid

ROOF
Roof inner
Roof outer

FENDER

2.What do you understand by BIW Nomenclature?

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. Below fig show BIW nomenclature.

 3.What is fixture & its types?

 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.
1. What is fixture & its type? Answer: Fixture is device which holds the work piece to be processed (Welded) by using 3 2-1 principle

In general a welding fixtures (tool) consist of number of units together to hold car panel together. Welding fixtures are normally designed to hold and support the various component to be welded. It is necessary to support them in proper location which is capable of preventing distortions in work pieces during welding. For this the locating elements need to be placed carefully, clamping has to be light but firm, placement of clamping elements has to be clear of welding area and the fixture has to be quite stable and rigid to withstand the welding stresses.

 BIW fixture type:

1.Production Fixture - As name suggest this fixture is used for mass production. It is fixture on which car body get assemble & go to end customer. These types of fixture require high constancy through its operation to maintain geometry of parts So material used for these types of fixture should be well tested as well as hardness level aesthetic. The quality in terms of dimension, tolerance should be met. These fixture need to maintain after certain period of time. The assembly & disassembly should be easy as low as possible. So. maintenance person can easily access with saving time,

 2 Pre-production Fixture it is generally defined as prototype fixture. It is designed to study feasibility of initial batch production to check which things are need to be improving before starting production This fixture is base of production fixture in benchmark and criteria & helps us to rectify error in preproduction operation fixture there will be more involvement of manual operations, engineer, and quality person it has larger cycle time than production fiature But won't practice by designing preproduction lature because it takes lots of time & cost. We have to maintain cost of car as low as possible so we directly go to production fixture by considering standards checklist to maintain error free production

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

 4.What is the basic principle of fixture design

Basically 3-2-1 principle is used to lock all six degree of freedom.

The 3-2-1 principle is a Component holding principle where three pins are located on the 1st principle plane, i.e. either XY, YZ, ZX. And two pins are located on the 2nd plane which is perpendicular to the 1st plane, and at last one pin on the plane which is mutually perpendicular to the 1st and 2nd planes.By using this method Componet can be arrested in all six degrees of freedom.

5.Elaborate types of BIW Stations?

An assembly line is a process in which car panel/car body parts are joined as the semi finished assembly moves from one station to another station  until the final product is produced.In the process of joining in assembly line , panels are moved from one section to another sections.Those sections are called Station. In BIW fixture designing we have various stations which are used to locate the panels so that joining processes can be done.

Some of these stations are:

• Geo Station
• Respot Station
• Pedestal Weld/Rivet
• Loading Station
• Buffer Station
• Marriage station
• Sealing station
• Curing station

1.Geo station:

In this station geometry of two parts are fixed. it can be either using welding or riveting . In this station precision and geomatry of the finished product is defined Locating pins have closer tolerence 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 Tolrence in locating pin is given in negative value. 

2.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 ahve tolrence upto  0/-0.28.

3.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

4.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 upcomin station.

Sometime this station is used when Robots are unable to transfer panel from one station to another.

5.Buffer Station:

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

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

6.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.

7.Marriage Station:

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

8.Curing Station:

In this Station product recieved after sealing application, is kept idle at ambient temperature, which allows sealent to get dry with better bonding between the panel.

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

The basic terminologies used in BIW are

1.NC/MYLARS/FINGERS-These are parts are used to hold panel. They are globally called as Mylar. Top side Mylar is called as clamping Mylar & bottom side is called resting Mylar. Every clamping Mylar should have resting Mylar. It is jaw type. It prevents panel from deforming while welding

2.Principle locating point (PLP) - These are point which are used for the accurate location of part to maintain the geometry of assembly means principle locating points are those where we use pin for locating panel. These are defined in drowing. The positional dimensions or relative dimensions are very precise in stamping & in fixture also.

3.Risers- Risers can be of L-type, welded or square tube or frame type. These are basically manufactured parts are used to give height to assembly

4.Blades- Blades are plates attached to riser. Other part likes cylinder, arms etc are mounted on the blade.

5.Shims in fixture we are providing tolerance to each part mostly manufactured. Those tolerances tend to stack up & reflect together. In order to avoid that we use shims so we can easily adjust after assembly so whatever stock up there we will rectify it through shims. Shims come in thickness of 0.1, 0.2, 0.5 etc

6.Rough locators- Rough locators are those used majorly for manual fixture. There is chance that operator can place part in wrong orientation mistakenly. The rough locator will work as a guide while placing the part in the fixture & part will be loaded in desired orientation.

7.Hardwares- Hardwares are like the hex head bolts, Allen bolt, hex nuts, spring washers, self-locking nuts etc.

8.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 object with probe. It generates report by comparing the data with the CAD file data

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

10.Number plates - Number plate is the aluminium embossed plate placed on each unit to the unit

11.Co-ordinate plate When we discuss about fixture on every fixture we have tooling hole which is called master hole through all fixture checked on CMM mastering that particular hole Cover that hole so that it won't get other impurities & hole       does not get any wear, tear& distortion
12.Name plate-The plate on which basic information described like company name, fixture name, fixture weight, panel name are embossed & joined to fixture.

13.Clamp Arm-Clamp arm is part of clamp unit which moves about axis. Over clamp are mylars are mounted

14.Pivot- It is axis about which clamp arm will rotates.

15.Class 'A' surface/ skin surface- The outer panels of car like hood, door, backdoor, fender,roof etc are visible to customer. The outer panels should be aesthetically very good. No any scratches or dent mark is acceptable over it. While designing 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.

16.Reed switches & Sensor-These are the electric components used in automated fixtures. The sensor & reed switches are used only in that situation where fixture is fully automatic or semiautomatic that run through PLC, control panel etc. Sensor are used to detect part present or not, clamp is close or open whereas reed switches confirms position of piston l.e. it is at top or down. Below fig shows unit used in BIW