Week 2:- BiW Fixture Basics Challenge

1. What is the process of project execution activity?

Project activities for a BIW assembly refers to the activities carried out within an organisation, from the start, when a project is received from the customer till when a project is fully finished with customer approval for the fixture.

1. RFQ received : RFQ stands for request for quotation. The project starts from RFQ stage. In RFQ the customer specifies its specific requirements like the technical order, commercial order and the project timeline in the form of documents or data sheets.

2. 1st Spec Discussion meeting : The quotation provided by the customer is studied on this stage based upon which the documents like technical order, commercial order and the timeline of the project is prepared. The time required for design and detailing, simulation time, fixture units required to be manufactured, bought out parts and the time required for assembly, installation and commissioning is analysed and the overall offer is prepared.

3. Offer submission : The documents prepared in the 1st spec meeting discussion is submiited to the customer.

4 LOI/ PO receipt : The customer studies the offer details and by the same time it also compares with the offers provided by the other suppliers/vendors and selects the best suitable offer and then release a purchase order.

5. Schedule Preparation : After receiving the PO the official beginning of the project takes place. The schedule and plan is prepared to ensure that the project is completed within the given timeline and there is no delay.

6. BOM preparation : The bill of materials consists of the list of all the parts and each of its quantities required to complete the fixture assemblies.

7. Design concept preparation : The design concept is prepared as per the the data received from the customer like 3D data of the car panel, design standards, drawings standards, manufacturing standards.

8. Customer approval : After the design concept preparation, it is sent for customer approval where the customer checks whether all the design requirements have been understood and will be met by us. The customer checks and suggests the design changes and also the additional requirements to be provided in our fixture. After making the necessary changes the customer finally approves the design concept.

9. Detailing and drawing release : After finsihing the 3D designing of the fixture assembly and its child parts, the 2D drawing and detailing of the assemblies and its childs parts is done which includes motor specifications, piston cylinder specifications etc. to be bought out and dimension, tolerances, standards, material specifications, quantities for fixture units to be manufactured by machining.

10. Manufacturing/BOP ordering : The fixture units to be manufactured and bought out are ordered by providing with drawing and detailing.

11. Mechanical/Electrical assembly : The ordered parts received are sent for Quality Control checking to check all the parts are within the specifications.After which the mechanical and electrical assemblies are prepared as per the design.

12. Quality inspection : The assemblies are sent for quality inspection wherein the coordinates and dimensions of the clamping units, locating units and mounting units are checked whether it satisfies the drawing specifications.

13. Internal trial and testing : After the quality inspection the BIW assembly is placed upon the fixture and checked whether the fixture is clamping the assembly properly or not, whether the pin units are locating within the holes or not, the welding feasibililty of the fixture is also analysed if whether the welding operation is been able to be carried out with ease and in the right sequence.

14. Online trials : In the online trials all the electrical connections are checked to ensure whether the material movement and welding operation is carried out in the automated sequence by the fixture assembly.

15. Packaging and dispatch : While transportation of the fixture parts there are chances that the parts might get damaged. Hence proper packaging is necessary to ensure the parts are safely transported without any damage.

17. Installation as per layout : The installation of the dispatched parts is carried out as per the layout and functionality of the robotic arm to perform welding operation and material handling of the workpieces at the customer end.

18. Trial and testing at customer end : After the installation process the trials are carried out at the customer end where the production commitment of the fixture to carry out the specified no. of assemblies in the specified amount of time is achieved. After the successful trials training is provided to the employees at the customer end.

19. Buy off meeting and final handover : After production trial and training, buy off meeting takes place where the customer checks whether the fixture mets the prescribed requirements as per the quotation, and also checks the additional requirements if any. After the remaining and additional requirements are fulfilled the finl handover takes place.

2. What are the types of joining processes ?

The durabilty and performance of any structure is largely dependent on the quality and design of the component joints.

Two fundamental optionns for joining materials and components are : mechanical joining and metallurgical joining.

Metallurgical joining

Welding : Welding is a fabrication process whereby two or more parts are fused together by means of heat, pressure or both forming a join as the part cools. The base metal and a filler material melts and forms weld pool which forms the weld joint as the part cools.

Different types of welding processes include : Arc or fusion welding, resistance welding, elecron beam welding, laser beam welding.

Soldering : Soldering is a process in which two or more metals are joined together by melting and putting a filler metal (solder) into the joint, the filler metal having lower melting point than the workpiece forms the joint.

Brazing : Brazing is a process in which two or more items are joined together by melting and putting a filler metal whose melting point is above 840 degree Celsius into the joint. The brazing joint is compartatively stronger comapared to soldering.

Adhesive bonding : Adhesive bonding is used to fasten two surfaces together, usually producing a smooth bond. The joining technique involves glues, epoxies, or various plastic agents that bond by evaporation of a solvent or by curing a bonding agent with heat, pressure or time.

Mechanical joining

Mechanical fastening : The joining of a material combinations which cannot be easily welded such as prepainted steels or very dissimilar materials.

Ex : Al application in auto body make use of mechanical fastening technique to overcome the poor inherent welability of Al.

The joining of materials in applications where fatigue life is critical compared to static strength.

The joining of materials where a long tool life is of relative importance. Ex : Screws and bolts.

Self piercing riveting : Self piercing is a high speed mechanical fastening process for point joining sheet material typically steels and aluiminium alloys. It is a single step technique, generally using a semi-tubular rivet to clinch the sheets in a mechanical joints. There is also a process variant which utilises solid rivets.

As the name suggests, pre drilled holes are not required, allowing the joint to be made rapidly in one operation. The process cycle is shown in cross section below.

Hemming and seaming process : Hemming and seaming are two similar metal working processes in which a sheet metal edge is rolled over onto itself. Hemming is the process in which the edge is rolled flush to itself, while a seam joins the edges of two materials.

3. What is resistance welding and its application in automotive sector ?

Resistance welding is a welding technology widely used in manufacturing industry for joining metal sheets and components.

The weld is made by conducting a strong current through the metal combination to heat up and finally melt the metals at localised points predetermined by the design of the electrode and workpiece to be welded.

A force is always applied before, during and after the application of current to confine the contact area at the weld interfaces and in some applications to forge the workpieces.

Types of resistance welding :

1. Resistance spot welding :

The process is used for joining sheet metals and uses shaped copper-chromium or zirconium alloy electrodes to apply pressure and convey the electrical current through the workpieces.

Heat is developed mainly at the interface between two sheets, eventually causing the material being welded to melt, forming a molten pool, and the weld nugget.

The molten pool is contained by the pressure applied by the electrode tip and the surrounding solid metal.

Advantages :

• Short weld time and hence high weld speed.
• Highly adaptable to automation and robotic techniques.
• Typical BIW contains 5000 welds.
• Strength and durability of automobiles largely depends on quality of RSW.

2.Resistance projection welding :

Projection welding is a resistance welding process for joining metal components or sheets with embossments by directly applying opposing forces with electrodes specially designed to fit the shape of the workpieces.

The current and heat generation are localised by the shape of workpiece either with their natural or with specially designed projection.

Large deformation or collapse will occur in the projection part of the wokpiece implying high.

Application : Used for mechanical fixing of autobody structures. eg : weld nuts

3. Resistance seam welding :

Seam welding is a resistance welding process for joining sheet metals in continuous, often leak tight and seam joints by directly applying opposing forces with electrodes consisting of rotary wheels.

The current and heat generation are localised by the peripheral shape of the electrode wheels.

Applications : Seam welding is mostly applied in manufacturing of containers, radiators and heat exchangers.

4. What is fusion welding and types of fusion welding and its application ?

Arc welding or fusion welding process involves either consumable or a non consumable electrode (rod or wire). An arc produced between tip of the electrode and workpiece to be welded, by use of an AC or DC power supply.

Types of Arc welding ;

1. Manual metal arc welding :

Manual metal arc welding (MMAW) also known as Shielded metal arc welding (SMAW) or stick welding. Stick welding is a process where the arc is struck between the metal rod (electrode flux coated) and the workpiece, both the rod and workpiece surface melt to create a weld.

2. Gas Shielded Metal Arc Welding (Metal Inert Gas (MIG) Welding) :

Metal Inert Gas (MIG) welding is an arc welding technique in which a consumable electrode is used to weld two or more workpieces.

MIG welding makes use of following components :

• Consumable electrode
• Inert Gas supply
• Welding head
• AC or DC power supply.

3. Gas Shielded Tungsten Arc gas welding :

Tungsten Inert gas (TIG) welding also known as Gas tungsten arc welding (GTAW) is an arc welding process in which a non consumable tungsten electrode is used to weld two or more workpieces. A filler rod is used which melts along with the workpieces to form the weld.

The following components are used to perform tungsten inert gas welding:

• Power supply
• Non consumable tungsten electrode
• Inert gas supply
• Filler rod (depend on the nature of workpiece)
• Welding head

4. Submerged Arc welding:

Submerged arc welding is a joining process which involves the formation of electric arc between a consumable electrode

and the workpieces to be welded. A blanket of powdered flux surrounds and covers the arc, and when molten, provides the electrical connection between the metal to be joined and the electrode. It also generates a protective gas shield and a slag, all of which protects the weld zone.

5. Plasma arc welding :

Similar to TIG, plasma arc welding uses an electric arc between a non-consumable electrode and an anode, which are placed within the body of a torch. The electric arc is used to ionise the gas in the torch and create the plasma, which is then pushed through fine bore hole in the anode to reach the base plate. In this way, the plasma is seperated from the shileding gas.

5. What is the 3-2-1 principle?

Fixtures must correctly locate a workpiece in a given orientation with respect to a cutting tool or measuring device, or with respect to another component. Locating and clamping are the critical functions of any workholding fixures.

A workpiece free in space can move in an infinite number of directions. For analysis, this motion can be broken down into 12 directional movements or degrees of freedom. All 12 degrees of freedom must be restricted to ensure proper referencing of a workpiece.

The best and most cost effective method of part location is referred to as the 3-2-1 method.

(3) Minimum : three locator blocks to establish part plane. Three locators, or supports, are placed under the work piece. The three locators are usually positioned on the primary locating surfaces. This restricts one axial movement downward and 4 radial movements upward. The 3 clamps holds the workpiece right above the three blocks to restrict the motion in axial movement upward. Thus totally 6 degrees of freedom are restricted.

(2) Round locating pin in a round hole that defines location in four directions (4-way) perpendicular to the plane previously established. This restricts four axial movement.

(1) Locating pin in a slot that defines two of the directions of the other pin (2-way). This restricts two axial movements.

6. Define Body Coordinate system?

The body coordinate systems have been widely used in the automotive industry for the body parts, products and process design.

A coordinate system is a set of system consisting of set of points, lines and surfaces, used to define position of points in space in either two or three dimensions.

In general BCS is called as car line and body line.

Here X = Longitudinal direction (Fore & After - F/A) or (Front O Line - FOL)

Y = Transverse direction (Cross Car - CC) or (Center O Line - COL)

Z = Vertical direction (Up and Down) or (Bottom O Line - BOL)

The origin of the body coordinate system (OX) is defined as the front centre of a vehicle, it indicates a length of a car and the coordinate system(OZ) is below its underbody indictes height of the car, and the coordinate system (OY) its starting point is the centre of car body indicates width of the car.

7. Elaborate Body plane systems and its essentials.

Body planes are the refrence planes in an automotive car. These planes are used to define the GD&T of all car parts in an automotive domain.

Body planes are 3 mutually perpendicular imaginary planes. These are generally considered to be present at the driver position or sometimes at the engine position or at the front end of the car body depending on the customer.

The measurements from the body planes to the parts are called as body line measurements.

These body planes are called as

• FOL Front O Line
• COL Centre O Line
• BOL Body O Line
• The measurement along FOL or X axis is called as F/A Front Aft.
• The measurement along COL or Y axis is called as C/C Cross car.
• The measurement along Body O Line is called as U/D Up Down.

Body line dimensions are essential for the reasons stated below.

• It defines the exact position of each product in the vehicle w.r.t. fixed position.
• It ensures flawless design for assembly.
• While designing lines, all the designs are carried out relative to the bodyline, viz., fixture, turn tables etc.
• It assists easy location of different parts in a vehicle.
• It aims in creating a standarised system.
• It assists in Quality checks.