Week 1:- Introduction to BiW and Fixtures Challenge

1. What is BIW & define its parts?

Body in White, or BIW, is a stage in the production of automobiles in which all sheet metal components such as the roof, body side, under body, backdoor, 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's shape is determined by the BIW, which is obtained after welding and before painting.

BIW PARTS:-

BIW is mainly categorized as:

1. Body side
2. Under body
3. Closures
4. Roof
5. Fender
6. Reinforcements

1)BODY SIDES:-

      The side word parts of the BIW structure falls into this category.

1.Body side Outer:-This refers to the sidewards outer parts of body/frame.

2.Body side inner:-This refers to the sideward inner parts of the body/Frame.

2)UNDER BODY:-

     The bootom/downward parts of the BIW structure falls into this category.

1.Front end under frame:-This refers to the frame under the front end i.e under the engine bonnet.

2.Main floor:-This refers to the frame under the middle i.e,. under the seats.

3.Rear end under frame:-This refers to the frame under the rear end i.e.under the boot cabin.

Closueres:-

     The closing parts of the BIW structures such as doors/lids parts fall into this category.

1.Front Door:-This refers to the parts of front door panels of the automobile.

2.Rear Door:-This refers to the parts of rear door panels of the automobile.

3.Hood:-This refers to the closure door the hood of the automobile.

4.Trunk lid:-This refers to the closure lid of the deck of the automobile.

5.Roof:-The top covering parts of the biw structure falls into this category.

5.Fender:-

       A fender is the curved portion of the car's body that sits over and houses the wheels.Its primary purpose is to prevent sand,mud,rocks and other road spray from being thrown into air by the rotating tire.

6. Reinforcement

The part which is used to support and provides stiffness and strength to other components of BIW is known as the Reinforcement component. Some of the reinforcement components are shown below in the picture.

   

2. What do you understand by BIW nomenclature?

A nomenclature in BIW is basically naming every part of the body. These names can be said as subparts of the already categorized parts above. The nomenclature differs a little bit from region to region but the overall idea is to name individual automotive sheet metal components. Below images show the nomenclature of BIW: 

3. What is fixtures and its types?

        A fixture is device which holds the workpice to be processed by using 3-2-1 principle.In general,a welding fixture (Tool) consist 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.Its necessary to support them in proper location which is capable of preventing distortion in workpiece during welding.

Types of Fixtures:-

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

Production Fixture – As the name suggests, this fixture is used for mass production. It is a type of a fixture on which car body get assembled. These types of fixture require high consistency through it's operation to maintain geometry of parts. So, material used for these types 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 & disassembly should be easy as possible. So maintenance person can easily access with saving time.

BIW Welding fixtures

BIW Orientation Fixtures

2. Pre-production Fixture(PPO)- 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 pre-production fixture there will be more involvement of manual operations, engineer, and quality person. It has larger cycle time than production fixture,but designers will not practice by designing preproduction fixture 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. 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. The geometry of welded part also checked in this fixture to ensure the part maintains the required dimension & geometry.

4)What is the basic principle 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 below:

6 translational degrees of freedom: +X, -X, +Y, -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 (ACROT-Y)

– Clockwise around Z axis (CROT-Z)

– Anticlockwise around Z axis (ACROT-Z)

                               Fig- shows degrees of freedom

    To make sure the proper fixing of the part we need to restrict all the 12 degree of freedom of the workpiece.The major portion of the time of BIW fixture designer is spent deciding how to fix these all degree of freedom.

Primary Locator:-

      First,the three locator or supports are placed under the workpiece.It will be positioned on the primary locating surface also known as a datum.It will restrict 5 degree of freedom.

1.Axial Movement downward along z-axis

2.Rotational movement around X and Y axis.

Secondary Locator:-

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

1.Axial movement along the Y +axis

2.Rotation about the Z-axis

Tertiary Locator:-

    This locator is positioned at the end of the part.it restict 1 degree of freedom.

Axial movement along the x-axis.

all these 6 locators will restrict a total of 9 degree of freedom.the remaining 3 degree of freedom (1,4 and 5)will be resticted by the clamps.To minimize the time consumption in assembly and dessembly,Have to use minimum number of pins to arrest a maximum number of degree of freedom.

5. Elaborate types of BIW Stations?

 BIW station is the parts of BIW assembly line is divided into zones & these zones are again divided into the station.

1. TOOL STATIONS
2. GRIPPER STATIONS
3. STAND STATIONS
4. MISCELLANEOUS STATIONS

TOOL STATIONS

A). GEO FIXTURES:-

• In BIW fixture we consider  Tack/Geo fixture tack welding done for all to be assembled in that fixture. the geo fixture defines the geometry of the part.
• All the parts must be located with two locating pins (pin can be common for two or more parts)
• These jigs have tight accuracy standards. in the case of geo fixtures, all the machines parts individually should be made with max tolerance of (±0.02mm">±0.02mm±0.02mm). whereas positional accuracy of the pin should be within ( -0.15mm.)

Geo fixture spots/ MIG welding is done in such sequence that the taking out from the fixture achieves the desired accuracy and does not get disturbed during transportation from the geo fixture. Goe fixture controls the sub-assy accuracy in all 3 axes.

B) RE-spot fixture:-

                            

• In BIW we consider a Re-spot fixture. In Re-spot fixture, remaining takes are completed.
• suppose in an assembly we need 50 weld tacks .on the station we can't complete all these operations because it will take more & 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 the re-spot fixture as per needed. by performing this kind of operation no station will be ideal hence we re-spot fixtures.
• Re-spot fixtures also have very tight positional accuracy. re spot jig, pin tolerance will be -0.28mm.

 C) Marriage fixture or Hamming tools:-

                                                         

• As the name suggests the marriage of different assemblies is carried out in this fixture.
• In different zones of the assembly line, different assemblies are completed like underbody, side body, front body, rear body, etc.
• After this all the parts come to the station where all parts are gets assembled by using various joining techniques like welding, Gluing, Reverting, etc this station is called marriage tools.

D) FRAMER FIXTURE:-

• Framer fixture is next station after the marriage fixture
• In a framer fixture, the roof is attached to the output of the marriage fixture & it forms like a frame hence it's called a framer tool.

E) CHECKING FIXTURE:-

                           

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

GRIPPER STATIONS:-

A gripper is a device that enables the holding of objects to be manipulated. the easier way to describe a gripper is to think human hand just like a hand. rippers enable the holding, tightening, handling, and releasing of an object. A gripper is just one component of an automated system.

A) Materials handling gripper:-

• As the name suggests these grippers are used for materials handling
• These grippers can pick assembly from one station & will drop the assembly to another station

B) Process grippers:-

• These grippers are used to carry out some specific processes like gluing, welding, reverting, etc in addition to materials handling.
• The grippers will go under gluing stand in case of gluing process & will goes under the pedestal weld stand in case of the welding process.

C) Combo Gripper:-

• Combo grippers are the ones that can carry out multiple tasks like it can do material handling & also it can carry out some specific processes like gluing, welding, etc as ell.
• weld gun+ gripper

D) Dual gripper:-

These grippers are two-sided grippers. in the case when we want one LH & one RH part, these grippers are used can handle the materials from one station to another station

STAND STATIONS

The stand is used to hold parts when not in use or also it is used to mount some parts or bodies on it. the different stands are used in BIW.

                                              

A) Pedestal stands

• weld gun is mounted on the fixed stand which is mounted to the floor permanently.The gripper can carry the panel under the stands to do the operation

B) Gluing & sealer stand:-

• Gluing gun or sealer gun is fixed to a welded or a standard stand which is grouted to the floor permanently.

C) Docking stand

• The robots have some limitations such as the payload capacity the robot & also due to lack of space.
• when we select the robot for, multitasking it cannot do both the task simultaneously due to limitations.
• 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 the next operation.
• Hence the robot can drop a gripper or gun & pick the next operation equipment to complete the task from the docking stand.

D) Date stamp stand:-

• Every, manufactured product has some data to stamp or to be embossed on it like serial no, batch no, date, etc for some future reference or for data collection.
• The required data is stamped or embossed by using the stamping device mounted on the stand.

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 & meanwhile gluing will cool down.

B) Butter stand:-

After some operation, we can put the no .of assemblies in this stand which is buffer stocks & it can be transported to another station in an easy way. they are also used to store the inventory while the machine is undergoing some maintenance.

C) Take out trolleys:-

It used to takeout out some panels for inspection to rectify the process is going in right or nat between the cycle.

D) Conveyer:-

The conveyor is the rotating path that transports the parts to the station which are kept over it.

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

  - The following terminologies are used in BIW

  A) NC/Mylars/Fingers- Mylars is the component which holds the panel while operation. These are placed from top side & from bottom side also. The top side Mylars called as Clamping Mylars & the bottom side Mylars called as Resting Mylars. Every clamping Mylars have resting Mylars. It dont allow deformation of the part due to welding stresses.

  B) Principle locating point (PLP) - These are the points which are used for the accurate location of the part to maintain the geometry of the assembly. There are lots 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 & in fixtures also.

  C) Risers - Risers are of different type like L-typer rises, Square tube riser etc. Riser is the manufacturing part which gives height to the assemblies.

  D) Blade- Blades are plates mounted on the riser. Other parts like cylinder, arms etc are mounted on the blade.

  E) Shims - Shims are the small part 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 parts 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 distorsion due to welding stress. To adjust the Mylars At its defined position we use shims so the panel won't deformed & also dont get any impression on it.

  F) Rough locators - The operator can place the part in wrong orientation mistakanely. The rough locator will work as a guide while placing the part in the fixture & the part will be loaded in desired orientation. It is a part of fool proofing.

  G) Hardwares - Hardwares are like the Hex head bolts, Allen Bolts, Hex nuts, Spring washers, Self locking nuts etc.

  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 generates report my comparing the data with the CAD file data.

  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.

  J) 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 reed switch is an electrical switch operated by an applied magnetic field. The detects the panel is loaded or not is done by sensors.