• Underbody structure.
• Front end structure.
• Body side structure.
• Closure.
• Roof.

2.

BiW nomenclature is the different names given to different components in sheet metal structure of body.

BiW or Body in White is basically spread into various different parts and components and to define them BiW nomenclature is used.

Through nomenclature, we give different names to different parts so that it becomes easier to define them.

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.

Though the two terms are used interchangeably, jigs and fixtures are actually very different devices that are mostly used in conjunction with one another. These devices are mostly used in machining operations to help reduce human effort during mass production.

However, in this guide, we’ll focus primarily on different types of fixtures, their purpose, advantages, and what industry relies on them the most.

The Most Common Types of Fixtures Used in Manufacturing

Fixtures are specifically designed for applications where the cutting tool can’t be easily guided via different types of jigs. Since they’re used in almost any machining operation based on the precise relationship between the workpiece and the cutting tool, these devices are often identified by the machining tools they’re used on. Below, we differentiate the following types based on fixture design:

Turning Fixtures

They are usually mounted on chucks of the machine spindle during turning operations, like on lathes. Depending on the part that’s being machined, turning fixtures may be equipped with counterweights to balance an unbalanced fixture.

Milling Fixtures

Milling fixtures are usually mounted on machining tables facing the faceplate or the spindle of the milling machine. The workpiece is placed at the base of the fixture and clamped before starting milling operations. However, during operation the cutting tool remains in place while the machining table, alongside the piece, shifts in relation to the cutter.

Boring Fixtures

Boring fixtures incorporate the principles of drill jigs since the boring bar is guided through a pilot bushing, similar to drill bushing. Its main function is to hold the workpiece in the correct position relative to the boring bar. Since they aren’t subject to strong cutting forces, boring fixtures don’t need to be as sturdy.

Grinding Fixtures

There are several different forms of grinding fixtures used in grinding machines to hold, locate, or support workpieces that are subject to grinding operations. Regardless of their form, however, these should have provisions for the supply and exit of coolant.

Tapping Fixtures

These work holding devices are specifically designed to position and secure workpieces for tapping operations — cutting internal threads in drill holes. They’re primarily used on odd-shaped and imbalanced parts, especially in mass production, for drilling, tapping, and reaming.

Indexing Fixtures

These are specifically used for machining parts that must have machined details evenly spaced.

Welding Fixtures

Welding fixtures are designed to hold and support different components intended for welding operations and to prevent any possible distortions in welded structures. The structure of these fixtures has to be rigid and stable, and the clamping elements need to be positioned clear of the welding area.

Duplex Fixtures

Duplex fixtures are designed to facilitate simultaneous machining of two parts at separate machining stations. Depending on the manufacturing needs, these parts can be machined identically or in sequence.

Assembly Fixtures

These are used to hold various parts and components together for assembly purposes. They’re similar to welding fixtures, but instead of hot joining, these are used for mechanical assembly.

Broaching Fixtures

Mostly used with plate fixtures, broaching fixtures are used to hold the workpiece during broaching operations.

The art of metalworking has a primary concern, locating the part to be machined relative to the platform. A CNC machine starts machining at a specific point corresponding to the fixture and proceeds from there. Therefore, the preciseness with which a job is machined is dependent on the accuracy that holds in the fixture. The accurate location of every part loaded into the fixture is essential. Any deviation in part location adds to the dimensional tolerance that must be assigned to the finished pieces. Furthermore, improper supporting and securing the part in the fixture affects surface finishes by temporarily or permanently deforming it. Hence, techniques for supporting, clamping, and locating must be considered together to assure repeatability from part to part.

Basic principles of Jigs and Fixtures design

LOCATING POINTS: Locating the work is a prime necessity and requires suitable facilities. The correct setup ensures smooth insertion of a workpiece in the proper position and removing a workpiece from a jig without operational hassles or time consumption. The workpiece position needs to be precise with the guiding tool in the jig or setup pieces in the fixture.

FOOLPROOF: A foolproof design of jigs and fixtures does not permit a tool or workpiece to be placed in any other way other than the intended one.

REDUCTION OF IDLE TIME: Jigs and Fixtures must be designed in such a way that ensures smooth loading, clamping, machining, and unloading of a

WEIGHT OF JIGS AND FIXTURES: A jig and fixture must be compact, easy to handle, and low cost regarding the number of materials used without giving up stiffness and rigidity.

JIGS PROVIDED WITH FEET: Some jigs require feet so that they can be placed on the table firmly.

MATERIALS FOR JIGS AND FIXTURES: Jigs and Fixtures are usually created with hardened materials to resist wear & tear and avoid frequent damage—for example, Mild steel, Cast iron, Die steel, High-speed steel, Caesium.

CLAMPING DEVICE: A suitable clamp is rated for its strength. It should be able to hold a workpiece firmly in its position while bearing the strain of the cutting tool simultaneously, without springing.

 

5.In BIW fixture designing we have various stations which are used to locate the panels so that joining processes can be done.

Some of these stations are:

1. Geo Station
2. Respot Station
3. Pedestal Weld/Rivet
4. Loading Station
5. Buffer Station
6. Marriage station
7. Sealing station
8. Curing station

 

  1. Geo station:

In this station geometry of two parts are fixed. it can be either using welding or riveting . In this station precision and geomatry of the finished product is defined Locating pins have closer tolerence of 0/-0.15.

Suppose the hole dia of panel is 16mm then the pin dia minimum can be 15.85. 

Diameter of locating pins should be lesser than the panel hole dia. So Tolrence in locating pin is given in negative value.

  2. Respot Station :

Once product comes out of the Geo Station and there are left out spots where spot welding or riveting is to be done. then it is moved to another station , that station is called Re-spot station.

These left out spots may be the due to clamp plan, cycle time,robot reach ability or any other various reasons.

  3. Pedestal Station :

In this station , Pedestal gun is mounted on a tool and panel is manipulated manually or by robot to weld the panels.

Pedestal station is generally a Re spot station.

Re spot station and Pedestal station, both perform same kind of operation . but to decide whether to go for pedestal or a re-spot station some parameters needs to consider like cycle time, floor space, no. of welds, clamp plan, or size of the panel.

  4. Loading Station :

This station is used for loading of panel and  same station is used to change the orientation of the if it is required in the upcomin station.

Sometime this station is used when Robots are unable to transfer panel from one station to another.

  5. Buffer Station :

This station is used to make the balance between the process.

Some stations carry out procees in lesser time as compared to their respective stations.In that case panels can be stored in one sation so that assembly line process remains smooth.

  6. Sealer 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.

  7. Marriage Station :

In this Station inner and outer panels are joined. In this station to avoid the imprssion on the outer panel(A class surface), copper strips are used in betweenn the weld tip and A-class surface.

  8. Curing Station :

In this Station product recieved after sealing application, is kept idle at ambient temperature, which allows sealent to get dry with better bonding between the panel.

 

 

6.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.