Week 1:- Introduction to BiW and Fixtures Challenge
ANSWER:
- BIW ( BODY IN WHITE) is the welded sheet metal which forms the vehicle structure to which the other components will be married .
BIW is the stage in automotive design in which the car body sheet metal components are been assembeled by welding or other joining process.
BIW is submerged in a liquid called primove before painting or after welding.
There are tho kinds of BIW:
1.Monocoque body structure.
2.Frame mounted body structure.
MONOCOQUE BODY STRUCTURE:
1.In monocoque body structure, the chassis is built in with BIW itself.
2.There is no seperate chassis.
3.The wheels are directly mounted on BIW with the help of suspension system.
FRAME MOUNTED BODY STRUCTURE:
1.Body is mounted on seperate chssis or frame.
2.The wheels are mounted on chassis not to the body.
BIW
BODY SIDES UNDER BODY CLOSURES ROOF FENDER
1.Body side inner 1. Front end under body 1.Front door 1.Roof inner
2.Body side outter ( Engine compartment) 2.Rear door 2.Roof outter
2.Main floor 3.Hood
3.Rear end under body 4.Deck lid
( Rear compartment)
2.BIW NOMENCULTURE:
1.ABCD PILLERS:
- 'A'Piller is the front support to the roof.
- 'B'Piller is the second support to the roof.
- 'C/D'Piller is the last support to the roof.
2.DASHBOARD MOUNTED PANEL:
A Dashboard (Also called dash,interior panel(IP), or fascia) is a control panel which is located directly between the vehicle dirver and the hood.
3.WINDSCREEN AND REAR WINDOW RAIL:
Windscreen protects the driver from dusts,wind,rain water,etc.,and is designed aerodynamically to reduce the drag froce.
4.CANT RAIL:
It is the construction of the body sides.It is canted so that the top is allinged to match the roof profile.
5.SIDE SILL:
It is longitudeinally extended part at each of laterally opposite sides of lower portion of the vehicle's body ( below front door and rear door).Its construction is box like cross section.
6.QUARTER PANEL OR WINDOW:
Quarter panel is a body panel of a automobile which is located between the rear door and the deck lid.It is similar to the front door and the wood.It is bacially made of sheet metal or fiberglass or carbonfiber or plastic reinforced fiber.
7.ROOF STRUCTURE:
It is the structure above the dashboard.It is to protect the passengers from rays of sun ,heat , rain and other climate environments.
8.CROSS MEMBER:
A cross member is a structural section which is tranverse to the main structure.It is located under the engine comparment and other body parts .It must be more rigid and strong to hold load of the body parts and passengers.cross member is connected to the suspension system to absorb shocks,vibrations.In monocoque body structure the crossmember is built within the biw itself.
9.FRONT AND REAR VELANCE:
Front velance is located below the front bumper and attached to the fenders. The rear velance is a metal part that runs under the rear bumper between the quarter panel.
10.SCUTTLE:
It is the structure which lies below the dashboard panel .It helps to divert the water which fall on windscreen without in contact with the engine.
11.FIREWALL:
It is the part of automobile body that seperates the engine compartment and the passenger compartment.
13.FLOOR,SEAT AND BOOT PANEL:
Floor panel is the large panel of the automobile body which incorporates with the smaller parts welded in it. In monocoque body structure , th floor seat and boot panel are built in with the body itself.It server as the foundation of most of the structures and other components.
14.FRONT AND REAR SPRING TOWER:
It is also called as shock towers.A shock tower includes first and second portion for attaching a suspension dampers and thus provide a control to the vehicle body.
15.CENTRAL CONSOLE:
It refers to the control bearing surface in the center of front of vehicle interior.The name is applied to the area at the beginning of the dashboard and continuing beneth it and mergs with the transmission tunnel which runs between the front driver and passengers seats of many vehicles.
16.FRONT AND REAR WHEEL ARCH:
A break between the pannels,wheels and planes are accomodate with the guards.
17.TOE BOARD:
The front vehicle part that provides support to the pedals and to the passenger's feet usually inclined towards the front and spot welded to the floor board at its bottom.
18.HEEL BOARD:
The vertical transverse sheet metal which extends across the width of the car interior at the front edge of the rear seat well, this panel is linked to the rear seat well to the floor and provides rigidity to the pannels.It is also called heel plate.
3. FIXTURE:
Fixture is a device which holds the workpiece to be processed ( welded) by using 3-2-1 principle. The fixture must have zero degrees of freedom to locate the work piece in the fixture.
Welding fixture consits of number of units together to hold the car panel and is mounted on a base unit.
Fixture must be a stable and it does not distort while operation . If it distorts from its original position which leads to rejection of workpeice. It must withstand high vibration and gives accurate dimensions . Selection of material for a fixture is important, the material should withstand high temperature and have high hardness.
TYPES OF FIXTURES:
1.PRODUCTION FIXTURE: Production fixtures are used for mass production purposes.This fixture is used when there is large amount of car panels should be processed or welded in a minimal time. The fixture must be quite accurate and more stable.If there is a problem in a production fixture which results delay in production.
2.PRE-PRODUCTION OPERATION FIXTURE (PPO): Pre-production operation fixture is a prototype fixture for initial batch production to study the feasibility.It is the base fixture for production fixture.If there is any need to make improvement in the production fixture that improvement will be done on pre-production operation fixture first.
3.CHECKING FIXTURE: Checking fixture is used for car panels inspection purpose.checking fixture is a tool where workpiece is hold and various measuring gauges are introduced to ensure the dimensions and repeatability.A fixed type checking fixture is used where workpiece is fixed with the help of clamps and pins and CMM machine is used to measure the coordinates of the different points of the panel or assembly, and compares with nominal value and gives report.
4. PRINCIPLE OF FIXTURE DESIGN:
For any free body there are 12 degrees of freedom(DOM).Which means it can move or rotate in 12 different ways.
There are six translational degrees of freedom, they are:
+X, -X
+Y, -Y
+Z, -Z
There are six rotational degrees of freedom, they are:
1.Clockwise rotation around X - axsis (CROT-X).
2.Anticlockwise rotation around X-axsis (ACROT-X).
3.Clockwise rotation around Y - axsis (CROT-Y)
4.Anticlockwise rotation around Y-axsis (ACROT-Y).
5.Clockwise rotation around Z - axsis (CROT-Z)
6.Anticlockwise rotation around Z- axsis (ACROT-Z).
We must fix all the 12 degrees of freedom except three transitional degrees of freedom(-X,-Y,-Z) in order to locate the workpiece in the fixture.so, 9 degrees of freedom of the work piece is need to be fixed.
We can restrict 9 degrees of freedom by using 3-2-1 principle.
Without 3-2-1 principle it is diffficult to design a BIW fixture.Any geometry is fixed using 3-2-1 principle.To restrict its transverse motion in X,Y and Z direction and rotational movement in X,Yand Z direction object will be held in 3-2-1 principle.
for example,
consider a solid cube which is shown in the above figure, which is lying on xy plane and z is the hight.
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 restricts its movement in X and rotation along Z.
1 point in Y restricts its movement in Y.
This fundamental principle is used in automotive body component design and welding tool design for manufacturing.
5. BIW STATIONS:
There are four BIW stations such as;
1.Tools
2.Grippers
3.Stands
4.Miscellaneous
TOOLS:
Tool is a fixture consists number of units togethere to hold a car part.
Types of tools:
1.GEO TOOL:It is the fixture in which geometry of the panel which are welded togethere are defined accurately.The pin tolerance for geo tool is -0.15mm.
For eg;
consider a panel hole size of 20mm, the pin size should be 19.85mm.
2.RE-SPOT TOOL:It is the fixture in which the remaining weld spots are welded which are not achived in the geo tool for pre-welded panel from the geo tool.The pin tolerance for re-spot tool is -0.28mm.
For eg;
consider a panel hole size of 20mm, the pin size should be 19.72mm.
3.MARRIAGE TOOL: A marriage tool or hemming tool is a fixture in which the inner panel assemb ly and outter panel assembly are joined together.these are done by welding or hemming in case of closure panels.
4.CHECKING STATION:It is a fixture to check the automotive parts or assemblies ,ensuring all the coordinates ,relative dimensions and positions as per the tolerance. A checkin station can be gauge type ,fixed type or automated checking fixtures.
It is the tool in which the workpiece is hold and various measuring instruments are introduced to check the tolerances and repeatability.
A fixed type checking fixture is used to fix the workpiece with the help of clamps , pins and CMM machine is used to measure the coordinates at different points of panels or assembly, also compares with the nominal value and gives a report.
GRIPPERS:
It is a device or fixture which holds the car panel and is fixed to the manipilating end of a robot or an end effector.It is also called as EOAT-END OF ARM TOOLING.
Types of grippers:
1.MATERIAL HANDLING GRIPPERS(MH):MH Grippers are designed for handling a car panel from one tool( station) to another tool(station).
2.PROCESS GRIPPER:Process gripper are designed to handle a car panel from one tool( station) to another( station) and also it undergoes process like pedestal welding,pedestal riveting,gluing,sealing etc.,
3.COMBO GRIPPER: Combo gripper is designed to handle the car panel from one tool (station) to another (station).Also with the coordination of weld gun on the other side of gripper for welding.
gripper+weld gun
4.DUAL GRIPPER:Dual gripper is designed to hold the car panel from one tool(station0 to another tool (station) with two sided gripper
gripper+gripper
STANDS:
Types of stands:
1.GLUING OR SEALER STAND: Gluing stand or sealer stand is fixed to the welded or standard stand which is grouted to the floor permenently.
2.DOCKING STAND:When the robots selected for multitasking like material handling and welding,it cannot carry both due to similar limitations ( pay load of the robot or space constraint).The robot will drop and pick the gripper or gun after completing the respective operation with the help of docking stand.
3.DATA STAMP STAND:The panel will get the data embossed on it, with the data stamping device mounted on the data stamping stand.
4.PEDESTAL STAND:Weld gun is mounted on the stand which is grouted to the floor permanently,where the process gripper carrry the panel to weld the spot with this fixed weld gun.
TAKEOUT TROLLEY:
Take out trolly is use to take the car penel from the working cell between the cycle for inspection purpose.
6.BASIC TERMINOLOGIES:
1.MYLARS/NC/FINGERS:
It is the part of the geo fixture which holds the car panel firmely.Basically material used for mylars is nylon, because it should not damage the car panel or even a scratch.There are two mylars one is holding mylar and other one is resting mylar.Holding mylar holds the upper side of the car panel and the car panel is rest on the resting mylar.
2.PLP(PRINCIPLE LOCATING PONTS):
Principle locating points are the important points which needs to be welded first with the help of geo tool.The remaining points are welded by re-spot tool.
3.BLADES:
Blades are the structure above that the clamps , shims and mylars are mounted.The blade is mounted on the raisers.
4.RAISERS:
Raisers are the metal structures with box like crossection.Raisers are fixed with bolts and nuts .It gives the required hight for the geo tool.The hight can be adjusted through raisers.
5.SHIMS:
Due to geometric tolerances , not every panels are in same dimensions.if the dimensional variation is high , there will be a gap between mylars and the car panel which results in improper holding and improper welding .To solve this problem, shims are attached to the mylars.It is thickness of 5mm.If there is a gap between mylars and car panel ,shims are used to adjust the gap and helps to hold the panel firmly.
6.ROUGH LOCATORS:
Rough locators helps the operator to fit the workpiece correctly between those locators .It helps to reduce the improper positioning of the work piece.
7.HARDWARS:
Hardwars are nothing but bolts, nuts ,screws etc.,These hardwares helps to assemble the different units in the geo tool.
8.CMM:
CMM are fixed in the checking fixture to measure the coordinates,relative dimensions and tolerances of the car panel as per the design.
9.UNITS:
A fixture consists of differents like pin unit , clamp unit,etc.,Each units have different parts which needs to be assembeled to hold car panel.
10.NUMBER PLATE:
Every units have number plate fixed to it.If there is any problem in any unit ,it is difficult to identify which unit has problem.If number plate is fixed ,It is easy to identify unit which is in problem.For eg; we can say unit 12 has this issues instead of saying this unit has this issues.
11.NAME PLATE:
Name plate is fixed in every tool or fixture. It shows the name of the fixture and load capacity of the fixture and type of the fixture.
12.CLAMP ARM:
Clamp arm is the extended part which holds the shims and mylars.It is mounted on the blades.
13.PIVOT:
Pivot is the piont through which the clamp rotates. To hold the workpiece,the clamp should rotate in some degrees through this pivot point.
14.CLASS 'A' SURFACE OR SKIN SURFACE:
Class 'a' surface or skin surface is the outter surface of the car panel.It should be plaine and do not have any damage not even a scratch and it must be smooth.so that the clamping is not tight and it must be firm.
15.REED SWITCHES:
Reed switches are switches which tells that calmp arm is open or closed.It is fixed in the cylinders of power clamp or swevel clamp.The cylinders are piston type arrangement so if the piston moves upwards it shows clamp is closed if the piston moves downwards it shows clamp is in open.
16.SENSORS:
Sensors are fixed in most of the units in the geo tool.If there is any problem in any unit, the sensors detects problem and gives a red alert.which means that unit has some problem which needs to be rectified.