Week 1:- Introduction to BiW and Fixtures Challenge

INTRODUCTION TO BIW AND FIXTURE

1. What is BIW & define its parts ?

BODY IN WHITE (BIW)

It refers to the welded sheet metal components which form the vehicle’s structure to which the other components will be attached, i.e., engine, chassis, exterior, and interior trim.

Automobiles have always been the greatest invention as it connects each and every part of the world. To manufacture them is a very long and complex process. “Body in White (BIW) “, sounds new? Well that’s great if it doesn’t. But if you heard this word right now, I will take you through the interesting facts in this journey. BIW refers to the stage in automobile manufacturing in which the vehicle body sheet has been assembled. This means that the vehicle’s body frame has been joined together including doors, hoods, trunk, bumper and deck lights. At this stage all the chassis assemblies are welded together before painting.

REQUIREMENTS OF BIW STRUCTURE

• Comfortable space
• Strength & stiffness
• Low weight material
• Corrosion resistant
• Aerodynamic & good appealing structure: BIW joinery defines the exterior and interior look.
• Sufficient space for packaging and provisions made for inner trim and aggregates
• Pedestrian and occupant protection during roll-over accident
• Structure should support
• All interior parts like dashboard, trims, seats, etc.
• All exterior components like front bumper, rear bumper, fenders, mirrors, etc.

BIW TYPES

There are mainly two types,

• Frame Mounted Body Structure
• Monocoque Body Structure

FRAME MOUNTED BODY STRUCTURE

• Its also called as Body on Frame construction.
• In this type Body is mounted on the Chassis/Frame.
• Powertrains and suspension are mounted on chassis.
• Used in utility vehicles, trucks, buses.

MONOCOQUE BODY STRUCTURE

• It also called as Chassis in built in Body.
• Chassis/Frame is inbuilt with BIW itself and there is no separate chassis.
• Powertrains and suspension are directly mounted to BIW.

BIW PARTS

• Under Body Structure
• Front End Structure
• Body Side Structure
• Closures
• Roof

UNDER BODY STRUCTURE

• Dash panel - provides partition b/w engine and the driver cabin.
• Front 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

FRONT END STRUCTURE

• Plenum Panel - a chamber located b/w the throttle body and runners of the intake manifold.
• Front wheel house(Fender) - is an encasement around the front wheel.
• 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.

BODY SIDE STRUCTURE

• A - pillar - front most support to the roof
• B - pillar - second support to the roof
• C/D pillar -
  1. C is rear most support to roof in case of two row seating system, it will be third one.
  2. D is the fourth support usually rear side of quarter panel.
• 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.

CLOSURES

• All doors
• Hoods/Bonnet - a hinged panel providing access to the engine compartment.

ROOF

• Roof
• Headers - structural member above the windshield at juncture with the forward edge of the roof panel.
• Bows

2. What do you understand by BIW nomenclature ?

Nomenclature is term, The accurate naming of objects in the natural world has resulted in a variety of international nomenclatural codes.

BIW nomenclature is the names of BIW parts is called BIW nomenclature.

As, I understand UK & US description parts names should be changed e.g. UK called as Inner wing panel same thing US called as Motor compartment side panel.

refer image below.

3. What is fixture & its types ?

FIXTURE

Fixture is a workpiece locating and holding device used with machine tools. It is also used in inspection welding and assembly. Fixture does not guide the cutting tool, but is always fixed to machine or bench. By using fixture, responsibility for accuracy shifts from the operator to the construction of machine tool.

When a few parts are to be machined, workpiece clamp to the machine table without using fixture in many machining operations. However, when the numbers of parts are large enough to justify its cost, a fixture is generally used for holding and locating the work.

BIW FIXTURE TYPES

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.

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 fixture. But won’t practice by designing pre-production 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.

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.

3. What is the basic principal of fixture design ?

3-2-1 PRINCIPAL    

In the automotive tooling industry you will hardly get any designer who does not know 3-2-1 principle.

If the any part e.g. steel block to be machined using milling machine, 1st question the milling machine operator will think how I will hold the part.

Operator will use the various clamp to hold the job to withstand the cutting forces.

Ideally 3-2-1 principle is used to locate the job.

What 3 means?

What 2 means?

What 1 means?

Simple they represent the directions.

Any part which has to be fixed during welding or during machining process has to be fixed. With this principle, every object is having 6 degrees of freedom.

1. Translational movement along X -axis
2. Translational movement along Y-axis
3. Translational movement along Z-Axis
4. Rotational  movement along X -axis
5. Rotational movement along Y-axis
6. Rotational  movement along Z-Axis

Without 3-2-1 principle it’s very difficult for the BIW product engineer, BIW process engineer or BIW fixture design engineers to have same clamping and location scheme. 

Any geometry is fixed or hold in position with the 3-2-1 principle. To restrict it transverse motion in X, Y and Z direction and rotational movement in X, Y & Z direction object will be held in position with 3-2-1 principle.

e.g. Consider a solid cube lying on a XY Plane and Z is height.

3 Points in Z direction defines the plane and restrict it movement along Z and rotation along X and Y.

2 Points in X direction restrict its movement in X and rotation along Z.

1 Point in Y restricts its movement in Y.

This fundamental is used during the automotive body component design and welding tool design for its manufacturing.

• Why 3 points are required to rest any component. - Basic mathematics.
• How many points are required to define a Plane? - 3 Points required to define any plane. 

ax+by+cz=d (Equation of a Plane). Minimum 3 points are required to define a plane.

5. Elaborate types of BIW stations ?

In BIW assembly line is in where different types of panel are joined together in each specified zones. Each panel categories will have individual zone. As under body zone, door zone, hood zone etc. These zones are further divided into stations. There are following types of station in BIW. A Station is the place where an operation is done by couple of tools. For example, a station can contain one Geo set weld fixture (weld tool), robots, end effectors, etc. to perform a single operation in the assembly line. So there will be proper flow of inventory.

TOOLS STATION

1. GEO TOOL

In Geo fixture tack welding done for all the parts to be assembled in that fixture. Standard guideline for Geo fixture, all the parts must be located with two locating pin (Pin can be common for two or more parts. These Jigs have tight accuracy standard. In case of Geo fixture all the machine parts individually should be made with max tolerance of ± 0.02 mm. whereas positional accuracy of pin should be within ± 0.1 mm and of Mylar within ± 0.2 mm.

In case of re-spot jig it may varies up to +_ 1.0 mm or more,

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 fixtures control the sub assembly accuracy in the entire 3 axis.

2. RE-SPOT TOOL

• It is a fixture in which the remaining weld spots which are not achieved geo tool are welded for the pre welded panel from the geo tool.
• The weld spot which has been done in this tool is only for rigid or stiffness purpose. where the geometry of the panels are already controlled in Geo Tool.
• For example: consider panel hole size 20mm, then the pin should be 19.72mm.
• The pin tolerance for a re-spot pin will be of tolerance with -0.28 in general.

3. MARRIAGE TOOL

A Marriage Tool is a fixture in which the inner panel assembly & outer panel assembly are joined, hemming in case of closure panels.

4. FRAMER TOOL

• The station after marriage tool is the framer tool.
• In this tool roof will be attached from the output of the marriage tool.
• After roof is attached with the help of framer tool, a car will now form a frame so the names arise is framer tool.

5. CHECKING TOOL

• As from name we understand this type of fixtures, used for the checking purpose of the part or assemblies.
• A checking fixture is used to check the automobile parts or assemblies, ensuring all the coordinates, relative dimensions & positions as per the tolerances
• A checking fixture can be a gauge type, fixed typed & automated checking fixture.
• A checking fixture is a tool where workpiece is hold & various measuring gauges are introduced to ensure the dimensions & repeatability.

GRIPPERS STATION

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. A gripper can be attached to a robot or it can be part of a fixed automation system.

1. MATERIAL HANDLING GRIPPER

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

2. PROCESS GRIPPERS

• These grippers are used to carry out 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.

3. COMBO GRIPPER

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

4. 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.
• Gripper + Gripper

STANDS STATION

Stands are used to hold part when not in use or also it is used to mount some parts or bodies on it.

1. 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 stand to do the operation.

2. GLUING & SEALER STAND

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

3. DOCKING STAND

• The robots have some limitations such as the payload capacity of the robot & also due to lack of space.
• When we select the robot for multitasking it can't do both the task simultaneously due to limitations.
• In this kind of case, we add docking stand to put some equipment which is not in use for the current operation but will be required for next operation.
• Hence the robot can drop a gripper or gun & pick next operation equipment to complete the task from the docking stand.

4. DATE STAMP STAND

• Every manufactured product have some data to stamped 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 STATION

1. CURING

After gluing it needs some time to cool down, so we put assembly on some belts & it will take the panel to another station & meanwhile gluing will cool down.

2. BUFFER STAND

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

3. TAKE OUT TROLLEYS

It used to take out some panels for inspection to rectify the process is going in right or not between the cycles.

4. CONVEYOR

Conveyor is the rotating path which transport the parts to the next station which are kept over it.

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

BASIC TERMINOLOGIES USED IN BIW FIXTURES

The basic terminologies used in BIW fixtures are,

• NC/Mylars/Fingers
• PLP (Principle locating points)
• Blade
• Raiser
• Shims
• Rough Locators
• Hardware’s
• CMM
• UNITS
• Number plates
• Co - ordinate plates
• Clamp arm
• Pivot
• Class 'A' surface (or) Skin surface
• Reed switches
• Sensors
• Name plate

NC/MYLARS/FINGERS

• Mylars are the parts which are holding the panel from top & bottom.
• It is a Jaw type, during welding it won’t deforms from its position.
• It is also known as fingers.
• It don’t allow the deformation of the part due to welding stresses.
• Mylars are of two types, they are
  1. Clamping mylars
  2. Resting mylars

1. CLAMPING MYLARS

The part which are holding the panel from top is known as Clamping mylars.

2. RESTING MYLARS

The panel which rests on the part is known as Resting Mylars.

Every clamping mylar will have a resting mylar.

PLP (PRINCIPLE LOCATING POINTS)

• These are the points which are used for the accurate location of the panels sub-assemblies to maintain the geometry of the assembly.
• There are lots of holes on the panel which are not accurate due to stamping operations. so the PLP are defined in the drawings.
• The PLP holes must be very much precise.

BLADE

• Blades are the plates which are attached to raiser.
• Blade is also attached or mounted with cylinders, arms etc.

RAISER

• Raiser is a manufacturing part used to raise/height the assemblies of fixtures.
• One end of the raiser will be attached to the base unit while the other end will be attached to the Blade.
• Raiser can be of two types. They are,
  1. 'L' type raisers
  2. Square tube raisers

1. 'L' TYPE RAISERS

'L' type raisers are of welded type. where the stiffener will be added at the center for support. As shown in the below figure the wedge shaped structure is known as stiffener which is used as a support / to withstand load.

2. SQUARE TUBE RAISERS

Square tube raisers are of frame type.

SHIMS

• In general, a shim is a thin and often tapered or wedged piece of material, used to fill small gaps or spaces between objects.
• Shims are typically used in order to support, adjust for better fit, or provide a level surface.
• Shims may also be used as spacers to fill gaps between parts subject to wear.
• Shims are the small parts which comes with the thickness of 0.1mm, 0.2mm, 0.5mm, & 1.0mm etc.
• These will compensate the stack up tolerance which reflects at the mylars.
• We give tolerance to all parts of the fixture. Due to this tolerance the mylars will either lift up moves down from its defined position.
• To adjust the mylars for getting the defined position we use shims.
• Shims will be added above the mylar for adjusting according to tolerance.

APPLICATION OF SHIMS

• In automobiles, shims are commonly used to adjust the clearance or space between two parts. For example, shims are inserted into or under bucket tappets to control valve clearances. Clearance is adjusted by changing the thickness of the shim.
• In assembly and weld fixtures precision metal shims are used between two parts so that the final production parts are created within the product drawing's specified tolerance.

TYPES OF SHIMS

Wood shim, Stone shim, Plastic shim, Metal shim, Paper shim.

ROUGH LOCATORS

• Rough locators are used in manual fixtures usually provided at the end of panels.
• It acts as a guide for the operator and helps to place the panel in the fixture in right position.
• Also used to identification purpose, to understand for operator easily.

HARDWARE’S

Hardwares are nothing but the fasteners which are used to connect/lock the parts of the fixture together in fixed position. The hardware are Hexagonal bolt, Hexagonal Nut, Allen bolt, Washers, self-locking nuts, etc.

CMM

• CMM - Coordinate Measuring Machine.
• A coordinate measuring machine (CMM) is a device that measures the geometry of physical objects by sensing discrete points on the surface of the object with a probe.
• Various types of probes are used in CMMs, including mechanical, optical, laser, and white light.
• Depending on the machine, the probe position may be manually controlled by an operator or it may be computer controlled.
• CMMs typically specify a probe's position in terms of its displacement from a reference position in a three-dimensional Cartesian coordinate system (i.e., with XYZ axes).
• CMM Plays a vital role in large number of industries like automobile, aerospace, Healthcare, Food processing, Paper, Plastics, semiconductors, etc.

TYPES OF CMM

• Bridge type CMM
  1. Moving Bridge
  2. Fixed bridge
• Cantilever type CMM
• Gantry type CMM
• Horizontal arm CMM
• Column type CMM

BRIDGE TYPE CMM

1. MOVING BRIDGE TYPE CMM

• Most widely used.
• Has stationary table to support work piece to be measured and a moving bridge.

Advantages - Reduce bending effect.

Disadvantages - With this design the phenomenon of Yawing can occur which affects the accuracy.

2. FIXED BRIDGE TYPE

• In Fixed bridge type, the bridge is rigidly attached to the machine bed.
• This design eliminates the phenomenon of yawing and provides high rigidity.

CANTILEVER TYPE CMM

• A vertical probe moves in a Z-Axis.
• Carried by a cantilever arm that moves in the Y-Axis.
• This arm moves laterally through the X-axis.
• The cantilever design offers a long table with relatively small measuring ranges in the other two axis.
• Suitable for measuring long, thin part.

Advantages

• A fixed table allows good accessibility to the work piece.

Disadvantages

• The bending is caused by a cantilever design.

GANTRY TYPE CMM

• The support of work piece is independent of the X & Y axis, both are overhead, supported by four vertical columns rising from the floor.
• This setup allows you to walk along the work piece with the probe, which is helpful for extremely large piece.

HORIZONTAL ARM TYPE CMM

• As a moving arm, and the probe is carried along the Y-axis.

Advantages - Provides a large area, unobstructed work area.

COLUMN TYPE CMM

• Often referred to as Universal Measuring Machine instead of CMM.
• The column type CMM construction provides exceptional accuracy and rigidity.
• These machines usually reserved for gage rooms rather than inspections.

UNITS

The fixture is the assemblies of different types of units.

There are different units like,

• Base unit.
• Pin unit.
• Clamping unit.
• Rest unit. etc.

BASE UNIT

Base unit is the unit designed to mount all other units such as Clamp unit, pin unit, rest unit etc., of tool, also other parts necessary for a tool like pneumatic valve box, trucking cable path will also be mounted on to be a base unit.

PIN UNIT

Typically, the locating pins are used to locate a body part in a position sufficiently accurate to execute a welding process. The body part is constrained by a set of appropriately locating pin so total constraint by locating pin should be fully constrained at all times to prevent any movement.

CLAMPING UNIT

Clamping unit is used to clamp the part which is to be welded after location using pin unit. Clamping is achieved with the help of pneumatic cylinders and clamp arms.

NUMBER PLATES

• Number plate is an aluminium embossed plate on each unit.
• Each unit has a number which is embossed on that aluminium plate for identification purpose.
• To recognize the unit easily number plates are used.

CO - ORDINATE PLATES

• In every fixture we have tooling holes, where every unit will be fixed through it.
• These holes will reflect the position of the units and also the panels.
• So these holes in coordinate plates will be useful for checking in CMM.

CLAMP ARM

• Clamp arm is a part of clamping unit which moves over the axis.
• Clamp arm is which the clamp & mylars mounted.
• Clamp arm is a rotatable one which helps to hold the panel firmly.

PIVOT

• Pivot is a axis about which the clamp arm rotates.
  Thus the rotation tends the clamp to rotate & hold the panel.

CLASS 'A' SURFACE (OR) SKIN SURFACE

• In automotive design, a class A surface is any of a set of freeform surface of high efficiency and quality. Although, strictly, it is nothing more than saying the surfaces have curvature and tangency alignment – to ideal aesthetical reflection quality, many people interpret class A surfaces to have G2 (or even G3) curvature continuity to one another
• Class A surfacing is done using Computer aided industrial design applications. Class A surface modelers are also called "digital sculptors" in the industry. Industrial designers develop their design styling through the A-Surface, the physical surface the end user can feel, touch, see etc.
• In automotive design application Class A surfaces are created on all visible exterior surfaces (ex; body panels, bumper, grill, lights etc.) and all visible surfaces of see-touch & feel parts in interior (ex: Dashboard, seats, door pads etc.). This can also include beauty covers in the engine compartment, mud flaps, trunk panels and carpeting.
• In the product design realm, Class A surfacing can be applied to such things like housing for industrial appliances that are injection moulded, home appliances, highly aesthetic plastic packaging defined by highly organic surfaces, toys or furniture.
• Aerospace has styling and product design considerations in interiors like bezels for air vents and lights, interior roof storage racks, seats and cockpit area etc. In recent years Airbus used ICEM Surf for generating the exterior surface geometry for Aesthetic and aerodynamic optimization before delivering the surface to downstream CAD software like CATIA.
• While designing a fixture to a skin surface the clamping material should be soft, so that it could not able to left any impression or dent over the skin. In general nylon will be used for clamping purpose.

REED SWITCHES

• These are electric parts used in automated fixtures which run through PLC programming.
• These electrical switches are operated by an applied magnetic field.
• Reed switches are placed in the sides of the pneumatic cylinders to confirm the clamping of panels.

SENSORS

• Sensors are also an electrical part like reed switch, it is also used in automated fixtures.
• Sensors will be attached where the main part of panel & sub-assemblies of panels are placed.
• If in case operator forgot/missed to keep one sub-assembly in fixture, then after welding process it can’t be assembled to the car due to the missing part and it may leads to a big problem also affect the production capacity, time and cost. So to avoid such problems sensors are introduced under each and every assembling parts.
• Sensors are also introduced for the awareness of operators. So that they can place every sub-assemblies without fail which will help to run the assembly line smoothly without affecting such factors like production capacity, cost, time, etc.,

NAME PLATE

In name plate where the basic information like panel name, model name, panel number, fixture type, fixture weight, Company name, Asset ID etc. will be engraved or embossed and attached with the fixture.