Week 1:- Introduction to BiW and Fixtures Challenge
Challenge 1-Week 1-Introduction to BIW and Fixture
Q1. What is BIW & Define its parts?
Body-in-white (BiW) is the phase of the automobile manufacturing process in which the various sheet metal components/parts of the vehicle, such as the hood, fender, roof, backdoor, engine compartment frame, body side, etc., are assembled/married together before being immersed in an electrolytic bath just before the body painting stage. The optimized BIW mass design is essential to achieve high performance. The BIW cover almost 27 % of car’s weight. The BIW structure is made of steel or aluminum with the thickness of 0.7-2mm. For the sheet metal stamping operation is done to get the required design.
BIW can be made into two structures:
a) Body-on-frame
It is an old automobile construction method where a separate body is mounted on a relatively rigid vehicle frame or chassis that carries the powertrain (the engine and drivetrain).It was the original method of building automobiles.
b) Monocoque
It also called as Unibody Body construction. In this, the chassis is integrated with the metal body as a one piece frame. It provides support to all mechanical components as well as safety to occupants.
BIW Parts:
The BIW parts categories in four different major section Body side (Body sides outer, body side inner), Under body (Front end under frame, engine components, main floor, rear end under frame, components), BIW Closures (Front and rear door, hood, deck lid), roof (Roof inner and outer) and Fender.
Q2. What do you understand by BIW nomenclature?
The BiW nomenclature is a collection of part names or words used when addressing a certain part/component. One single element or component has a distinct name in different parts of the world. For example Roof rails is also called roof stiffeners and more example are presented in the below Figure.
Note Different country have their own nomenclature.
Q3. What is Fixture & its types?
It is a device that uses the 3-2-1 principle to hold the components/workpiece to be worked/processed. Fixtures are designed to hold and support components, as well as to ensure that
distortion does not occur in the workpiece while it is being processed.
Types of Fixtures:
Production Fixture:
It is used for the mass production. It provide high accuracy consistency throughout the process to maintain the required geometry structure and tolerance.
Pre-Production Operation Fixture:
These fixtures are used in operations that are part of the planning process and the execution of every task that must be completed before production begins.
Checking Fixture:
The equipment used to hold a part in place for CMM (Coordinate Measuring Machine) checks or other purposes. CMM Fixture is another name for it.
Q4. What is the basic principle of fixture design?
The 3-2-1 principle states, ''the six locators (Body face) are sufficient to restrict the all degree of freedom i.e. six dof, however if considering positive and negative then 12 dof for anybody. In this, motion is constrained using clamps and locators. All the 12 dof (6 rotation and 6 translation , positive and negative) must be fixed to locate the any work piece in the fixture.
Q5. Elaborate types of BIW stations?
Many tools are kept at one place together to performed the work is called station.
Geo Station:
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. 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. 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 assembly accuracy in all the 3 axis.
Respot Station:
In Respot already welded panel will be welded in Respot fixture. For example if we need 15 spots to be welded between two panels, we load two panels and hold them individually and we will weld 8 spots. And remaining spots will be welded in second fixture. Here first is geo fixture and second is Respot fixture.
Marriage or hemming station:
Under this tool inner and outer panels are joined together using the hemming or welding operation. In this station to avoid the impression on the outer panel (A class surface), copper strips are used in between the weld tip and A-class surface.
Checking Station:
Under this station tool, automotive parts or assemblies, all the coordinates system, relative dimension and position as per the tolerance are evaluated. This station can be gauge type, fixed
type and automated checking fixture.
Sealing 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.
Curing Station
In this Station, the product received after sealing application is kept idle at room temperature, allowing the sealant to dry and improve bonding strength between the panels and parts.
Pedestal Weld/Rivet:
In this, weld gun is mounted to fixed stand which is grouted to the floor permanently, where the process gripper carries the car panel to weld the spot with fixed weld gun.
Take out Trolley station
It is used to take the car panel out of the robotic working cell between the cycles for inspection purpose.
Buffer Station:
Buffer storage supports fast and smooth production processes. Buffer storage areas or systems are used to temporarily store items that will soon be needed for production or orders. Normally buffer storage does not have fixed storage positions for specific items. Buffer storage areas are often located near the shipping and receiving docks, and in spaces between two production zones along manufacturing lines to ensure smooth-running processes.
Q6. What are the basic terminologies used in the BIW fixture?
a) NC/MYLARS/FINGERS: MYLAR is type of block that touches the panel and holds or clamps the body. Mylars are always used in car line. Mylar is also called NC (Numerically Controlled) Block.
b) PIN: Pins are used to ristrict the rotational motion of the panel. Generally there 2 types of Pins, one is round Pin and another one is a diamond pin. We use two and three directional shimming for pins as per the angle of the pin w.r.t. the carline.
c) BLADE: The plate which joine Riser to the Clamp cylinder is known Blade. This plate plays an important role in building the unit structure.
d) WELDMENT: Weldment is the assembly of two or more then two parts that are coupled together by welding. To make a weldment it is the thumb rule to have a 5 mm overlay on each other plates so that space can be provided for welding.
e) PIN BOCK: Pin Block is also called Pin Retainer. This block holds the pin and resist the rotational motion of the pin.
f) RISER: The part which is mounted on the base plate and holds a clamp or pin cylinder on it, is called Riser. Riser can be Standard Part or manufactured part, it varies from project
to project.
g) L BLOCK: A plate shaped as L is called an L block. This is used as a connection between mylar and Blade. Generally, L blocks are used to provide shimming.
h) Principal Locating Points (PLP): PLP are the space at which the car panels are located onto the fixture. The welding fixture is designed with locator units to aid the
operator to load the car panels onto the fixture at the specified location and orientation.
i) SHIMS: 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.
j) ROUGH LOCATORS: Rough locators are used to help locate workpieces in the automation process. Locating refers to the desired location where you want the workpiece to be when it is getting worked on either by a person, team, or robot.It is a device to establish and maintain position of a part in a jig or fixture.
k) PIVOT: It is central point/connecting unit, pin, or shaft on which a mechanism turns or oscillates w.r.t. each other.
l) CLAMP ARM: It is a part of clamp unit which moves over a particular axis.
m) NUMBER PLATE: It is a plate attached to each unit with a unique number for the identification.
n) REED SWITCHES & SENSORS: A reed switch is an electromagnetic switch help to control the flow of electricity in a panel board. They are made from two or more ferrous reeds within a small glass tube, which become magnetised and move together or separate when a magnetic field is moved towards the switch. And it is used to check whether the panel is loaded or not.
m) CLASS-A SURFACE: Class-A ('Strak') is a term used in specifically in automotive industries.It describes the final production surface data for the aesthetic parts of the car.
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