Week 1:- Introduction to BiW and Fixtures Challenge

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, clinching, bonding. laser brazing etc. BW is termed before painting and before the motor, chassis sub assemblies, or trim (glass, door locks/handles, seats, upholstery, electronics, etc.) have been assembled in the frame structure.

BIW parts le categorised as below

1 Underbody structure

2 Frond and structure

3 Body side structure

4. Clusure

5 Hool

BIW NOMENCLATURE AS FOLLOWS:-

Nomenclature is basically choosing of names for things.BIW have no. of parts in it.

All parts have differenent names.

- As the Automotive industry is spread worldwide. Every nation has its own language. So the same part of the BIW have different names in its region.

For example, The one component of the BIW is called suspension tower in Uk & the

same component is called shock tower in US

FIXTURE & ITS TYPES:-

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

In BW fixture, the fixtures are designed to hold no of parts during welding, it is necessary to hold the parts at proper location to avoid the distortions & to maintain the required geometry of the parts.

BIW fixture requirements

• It should prevent distortions in work piece during welding operation
• The clamping need to be light but firm means the clamping force should be able to maintain the part at its required position without damaging the part.
• Placement of clamping need to be clear of welding area.
• Fixture need to be quite stable & rigid to withstand the welding stresses.
• The fixture should maintain its consistancy to do defect free operations.

BIW fixture types

1 Production fixtures-

This fixtures are used for mass uction 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 & asthetics. The quality for maintaining the dimensions & tolerances are also checked. The production fixtures needs to easy for mainatainace purpose. The fixture needs some maintainance after completing roof operations. The time requires for assembly & disassembly should be as low as possible which saves lots of time.

2. Preproduction operation fixtures (PPO):-

These Toxtures are design as a prototype future to check the feasibility of initial batch production & to check which things need to be improved before starting the production. These beturis can be taken as the base beures which sets the benchmark & Critena which help us to restify the ers that we could get from preproduction operation fedures in the many manual operations are involved many ang neats & quality wated persons are required. It has the large cycle time as compare to production has requires lits of cost Wouve to mantent of the car as low also be so we hectly go to the production fixture by considering standards, checklist to maintain the error free production.

3. Checking fixtures-

As name suggests these fixtures are used for the checking purpose. No operations like welding gluing or hemming are carried out in this 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 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 & geometry.

THE BASIC PRINCILPAL OF FIXTURE DESIGN

For a fixture designer, the major portion of design time is spent deciding how to locate the work piece in the fixture

You know that any free body has a total of twelve degrees of freedom as belows

6 translational degrees of freedom: X XY. 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 (CROT-Y)

Clockwise around Zaxis (CROT-Z)

Anticlockwise around Z axis (ACROT Z)

TYPES OF 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.

The BIW stations are further divided into following

1) Tool stations

2) Gripper stations

3) Stand station

4) Miscellaneous stations

1)Tool stations -

A)Geo Fixtures -

- In BIW we consider Tack / Geo Fixture. In Geo fixture tack welding done for all the parts to be assembled in that fixture.The geo fixture defines the geometry of the part.

- All the parts must be located with two locating pin (Pin.can be.common for two or more parts.)

- These ligs have tight accuracy standard. In case of Geo fixture all the machine parts individually should be made with max tolerance of 0.02 mm. Where as positional accuracy of pin should be within-0.15 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 disturb during transportation from Geo fixture to re-spot fixture. Geo fixture control the sub assy accuracy in all the 3 axis.

B)Re-spot Fixtures -

- In BIW we consider Re-spot Fixtures. In Re-spot fixture remaining tacks are completed.

- Suppose in a assembly we need 50 weld tacks. On one station we cannot complete all these operation beacause it will take more time & another station relative to the assembly will be in ideal condition.

- In this type of case, we carefully choose some weld tack points which will define the geometry of the part & also the assembly will not get deformed after opening the clamping or in transportation due to the welding stresses.

The remaining weld tacks will be completed in Re-spot fixture as per needed. By performing this kind of operation no station will be ideal Hence we use Re-spot

fixtures.Re-spot fixtures also have very light positional accuracy. Re-spot jig pin tolerance

will be 0.28 mm.

C) Marriage Fixture

- As name suggests the marriage of different assemblies is carried out in this fixture.

- In different zones of assembly line different assemblies are completed like under body. Side body. Front body, Rear body etc.

After this all the parts comes the station where this all parts are gets assembled

by using various joining techniques like welding, Gluing, Riveting etc. This station is

called as marriage tool.

D)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 & it form like frame hence it is called as framer tool.

E) Checking Fixture -

- These are used to check the assembly of parts. Tolerance Dimensions & coordinates.

It can be of gauge type, Fixed type ot automated checking fixture. A checking gauge is a tool where work piece is hold & different measuring gauges are introduced to ensure dimensions & repeatability.

- A fixed type checking fixture is used where the work piece is fixed with clamps & pins & CMM is used which measures the corodinates of the different points of panel or assembly. Then is compares with the CAD data & gives report.

2)Grippers -

A gripper is a device which 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 holding, tightening, handling and releasing of an object. A gripper is just one component of an automated system. Apper can be attached to a robot or it can be part of a fixed autoration system.

Different grippers are used in BIW as follows,

A)Material handling gripper -

- As the name suggest These grippers are used for material handling.

- These grippers can pick assemly from one station & will drop the assembly to another station.

B)Process grippers -

- These grippers are used to carryout some specific process like gluing, welding, riveting etc. in addition with material handling.

- The gripper will goes under gluing stand in case of gluing process & will goes under

the pedestal weld stand in case of welding process.

C)Combo Gripper

- Combo grippers are the one which can carry out multiple tasks like it can do material handling & also it can carryout some specific process like gluing, welding etc. as well.

- Weld gun + Gnpper

D)Dual Gripper

- These are two sided grippers 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.

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

1) Number plates Number plate is the aluminium embossed plate placed on the each unit for easily recognising the unit.

K) Name plate - The data like manufacturing company name, fixture type, Fixture weight etc. is embossed on the plate & joined to the fixture.

L) Clamp Arm - Clamp arm is the part of clamp unit which moves over a axis. Over clamp arm the Mylars are mounted.

M) Pivot - It is a axis about which the clamp arm will rotates.

N) 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 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.

O) Reed switches & sensors These are the electric componnents used in automated fixtures. The need switch is an electrical switch operated by an applied magnetic field. The detects the panel is loaded or not is done by sensors.