Week 2:- BiW Fixture Basics Challenge

1. What is the process of project execution activity?

Project Execution activity:

• Project execution is the methodology of developing product from the scratch(raw material) to the final stage of achieving desired final product.

• Project execution is the stage of the project where everything has been planned is put into action. The main objectives are:

  • To keep the work on track.
  • To organize team members.
  • To manage timelines.
  • To make sure the work is being done according to the original plan.

1. RFQ:

• Request For Quotation (RFQ) is the first step involved in project execution phase.
• In this activity the customer quotes his/her recquirements and specifications regarding the project in a detailed document.
• Besides the technical offer, commercial offer, expected timeline of the project and oether details are also provided.

2. First spec discussion meeting:

• After the RFQ is received, there will be a discussion meeting about the technical offer, commercial offer, project execution, timeline required to complete the project and the crew will make a final decision based on the result.
• In addition, the time required to complete the project from the begining of data study,3d concept design, simulation validation, quality check,2D drawing release,manufacturing,etc., are calculated and prepared in the technical offer.
• Based on technical offer commercial offer will be finalized.

3. Offer submission:

• After finailizing the offer is submitted to the customer .
• The customer will also receive more offers from other companies. The customer will go through the offers and analyse it.

4. LOI/PO receipt:

• After the customer has analysed the offers in all aspects, the final LOI/PO (Purchase Order) will be issued to the respective manufacturer.
• Once the PO is received the project work has to be started by respective manufacturer.

5. Schedule preparation:

• After receiving the PO, the project schedule preparation will be done to meet the project deadlines specified by the customer in order to complete the project.
• All the stages in the project are considered for the calculation of time recquired to complete the actions such as kick-off meeting, design data study, DAP, simulate quality check, 2D detailing, drawing check, release of BOM, manufacturing, boughts out of electrical and mechanical components, assembly of fixture, paints,etc.,
• The above mentioned activities are traced in the schedule preparation chart.
• If the date obtained does not match with the dead lines, then the schedule is revised accordingly and meetings are held.

6. BOM preparation:

• Bill of materials like cylinders, motors,bolts, nuts,etc., are listed and prepared.

7. Design concept preparation:

• Before this step a complete study of design data is done as per the customer recquirements.
• During the design data study activities some rough sketches are done to get the flow of design.
• It undergoes conceptualization of basic data like spot plan,cycle time,etc.,
• To avoid collision of weld guns with the clamps while traveling, spot plan is made in the initial stage.

8. Customer approval:

• In this step the customer reviews the design data and checks whether the design fulfills the recquirements of the proposed design or not based on the technical offer.
• If it is ok then the customer will finalize the approval and if it is not ok, several steps are to be taken to re-examine the schedule and design. After that the result must be submitted for approval.

9. Detailing and drawing release:

• Once the customer approved the project, the detailed drawings and designs are prepared at the manufacturer end.
• It is released for all the parts recquired with the appropriate dimensions,tolerances,quantity,specifications,etc.,

10. Manufacturing/BOP ordering:

• In this stage the recquired components for manufacturing like motors,cylinders,sensors,gripper,etc., are ordered as per the specifications recquired.

11. Mechanical/ Electrical assembly:

• After all the parts from the BOP ordering are received, they are subjected to quality check by the quality department with respect to the specifications.
• Then the mechanical and electrical parts are assembled.

12. Quality inspection:

• Quality checking is again done once after the assembly is finished.
• The dimensions, positional accuracy, coordinates are checked by using CMM machine.
• Only the approved assembly is passed to the next level, rest is sent back to the assembly for re-assembly work.

13. Internal trial& testing:

• The next to quality check is the internal trial which is done to evaluate the operation of the fixture.
• It is the inhouse testing where the seating of the assembly/panel, clamping,postion of pins into holes are checked for proper outcome.

14. Online trial:

• It is done in automated mode by using electrical connections.The process sequence is checked as per the designed way in front of the customer for further approval.

15. Packaging:

• It is done to avoid damage during transportation which may affect the proper function and aesthetic look of the fixture.
• Hence proper packaging is done to ensure the geometry of the fixture.

16. Dispatch:

• After the fixture has been properly packed, it will be dipatched to the customer end with the mentioned address.

17. Installation as per layout:

• At the initial stage itself the layout for the fixture assembly is prepared which defines the space for the robots,fixture,etc.,
• The layout is prepared by considering the functionality,application, process sequence,etc., Hence the installation is to be done as per the layout.

18. Trials and training at customer:

• Production trials will be carried out at the customers end. As the technical offer defines the 'n' number of assemblies will be completed in 8hrs/ 12hrs shift.
• So the production trial is carried out to ensure the capability of the fixture as per the technical offer terms.
• Once it is achieved, training will be provided to the workers, engineers, operators about handling the fixture like loading, unloading of the part,etc., also the sequence of process will be explained.

19. Buy off meeting:

• In this meeting the customer reviews are taken and in some cases the customer may ask for some additional features to be included in the fixture.
• Those requests are analysed and finalized by conducting meetings.
• All the doubts from the customer end are clarified and process is moved further.

20. Final handover:

• In this step, the product is finally handed over to the customer.
• The documents like clamp validation document, ergo sheets, BOMs,etc., will also be handed over to the customer along with the fixture.
• We can carry a proof for our work done as documents.
• Every automobile industries will follow some document standards like ISO & IATF.
• IATF(International Automotive Task Force) is a group which is followed by most industries now-a-days.

2. What are the types of joining processes?

The durability and performance of any structure is largely depends on quality & design of components joints. Whole structure can’t be made in one piece. Two fundamental option for joining material & components.

1. Metallurgical joining
2. Mechanical joining.

Metallurgical joining:

In welding two or more parts are heated & melted or forced together, causing the joined parts to function as one. In some welding method filler material is added to make the merging of materials easier. Examples of metallurgical joining are:

• Welding
• Brazing
• Soldering
• Adhesive Bonding
• Diffusion Bonding etc.

Metallurgical joining -

Metallurgical joining includes fusion welding, pressure welding and brazing/soldering which use different energies.There are also methods of chemical joining that use adhesives.

Different types of metallurgical joining are described below

(A) Welding -

Welding is a joining process for metals wherein the work pieces to be joined as well as the welding or filler material used experience some melting. A common method for welding, known as arc welding, consists of generating an electric arc between an electrode (which contains the welding or filler material) and the work pieces to be welded together.The arc generates enough heat to melt the electrode and the areas of the work pieces were the welding is performed.

As the electrode passes over a region while the arc is present, molten metal from the electrode and molten base metal from the work pieces all get mixed together, solidifying to form a strong joint upon cooldown.The electrode contains some flux material, the purpose of which is to stabilize the arc formed by generating gases (carbon dioxide, carbon monoxide, water vapor) that shield the arc from the surrounding atmosphere.

The high temperature of the welding process alters the microstructure of the welded areas of the work pieces, i.e., these areas (known as the 'heat-affected zone' or HAZ) undergo grain coarsening at the very least. This results in a reduction of the tensile strength and toughness of the metal. Residual stresses that develop as the metal cools down also reduce the strength of the welded joints. Thus, the welding process must be optimized (by optimizing heat generation, metal compositions, and cooling rates) in order to minimize microstructural changes and residual stresses in the welded joints. Post-welding treatments are also often performed to relieve residual stresses and make the microstructure of the welds more uniform.

(B) Brazing -

Brazing is a process for joining two work pieces together with a filler metal that is sandwiched between them, wherein only this filler metal undergoes melting, i.e., the work pieces do not experience any melting. The temperature at which brazing is done must therefore be high enough to melt the filler material, but not the work pieces. Materials used as fillers for brazing are those that melt above 450 deg C. Flux is also used during brazing for the purpose of eliminating oxide films from the surfaces of the work pieces and preventing oxidation.This would ensure a good metallurgical bond between the work pieces and the filler once the brazing process is completed.Once melted, the brazing material fills up the spaces between the surfaces being joined, and even manages to get into tight spaces by capillary action. A strong joint is obtained after the brazing material has cooled down.

(C) Soldering -

Soldering is a joining process that's similar to brazing, except that it is performed at much lower temperatures than brazing. Thus, soldering is also a process of joining two work pieces together with a filler metal, such that only this filler metal undergoes melting, i.e., the work pieces do not experience any melting. Brazing materials are those that melt above 450 deg C, so soldering materials would be those that melt at less than 450 deg C.

Common soldering materials include tin-lead, tin-zinc, lead-silver, and cadmium-silver alloys. Like welding and brazing, soldering also employs flux materials to clean the surface to be soldered and improve metallurgical bonding. Residues from fluxes, however, must be removed after soldering to reduce the risk of the occurrence of corrosion.

(D) Adhesive Bonding -

Adhesive Bonding is a process for joining parts using bonding chemicals or materials known as adhesives. It is employed to join polymers and polymer-matrix composites, as well as polymers to metals, metals to metals, and ceramics to metals. Adhesive-bonded joints can withstand shear, tensile, and compressive stresses, but they do not exhibit good resistance against peeling. To overcome the weakness of adhesive bonding against peeling, joints mated together by adhesives must have a good design, i.e., the adhesion area is maximized and mechanical interlocking is employed.

High adhesive bond strength is achieved if chemical bonds are formed between the adhesive and the base material, or adherent. However, compared to welding, brazing, and soldering, it is not easy to achieve primary bonding (ionic, covalent, and metallic) in adhesive bonds because of the relatively larger interfacial gaps between the adhesive and the adherent. Secondary bonds, which do not involve electron transfer or electron sharing but instead rely on coulombic forces of attraction, is therefore more likely to form in adhesive bonding.

To maximize adhesive bonding strength, surfaces to be joined by adhesives must be cleaned thoroughly. This, in essence, minimizes the interfacial gap between the adhesive and the adherent. Making the surfaces 'rough' also improves adhesive bond strength because of the mechanical interlocking that the 'roughness' provides.

(E) Diffusion Bonding -

Diffusion Bonding, or diffusion welding, is a solid-state joining process wherein the joined parts undergo no more than a few percent macroscopic deformation. It can be accomplished at temperatures higher than half the absolute melting point of the base material. Diffusion bonding generally occurs in two stages: 1) deformation processes that result in the surfaces to be joined coming into intimate contact; and 2) formation of bonds by diffusion-controlled mechanisms such as grain boundary diffusion and power law creep. Diffusion bonding is capable of joining a vast array of combinations and sizes of metal and ceramic parts.

Mechanical joining:

Mechanical joining is a process for joining parts through clamping or fastening using screws, bolts or rivets. Advantages of mechanical joining include versatility, ease of use, and the option to dismantle the product in cases where regular maintenance requires it. The ability to join dissimilar materials is another benefit. Examples of mechanical joinings are

• Mechanical fastening
• Self piercing riveting
• Hemming & seaming process

Different types of Mechanical joining are described below

(A)Mechanical fastening:

The joining of material combinations which cannot be easily welded such as pre-painted steel or very dissimilar metal. Ex. Al application in auto body makes use of mechanical fastening to overcome the poor inherent weld ability of AL

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

The joining of materials where high tool life is of relative importance screw, bolts etc.

(B)Self-piercing riveting

Self-piercing riveting is high speed mechanical fastening for point joining sheet material, typically steel & aluminium alloys. It is single step technique generally using a semi tubular rivet to clinch the sheet in mechanical joint. There is also process variant which utilizes solid rivets

As name suggest pre drilled hole are not required allowing joint to be made rapidly in one operation The process cycle is shown in cross section below

(C)Hemming & seaming process:

Hemming & seaming are two similar metal working processes in which a sheet metal edge is rolled over on to itself. Hemming is process in which edge is rolled flush to itself, while seam joins edges of two materials. Hems are commonly used to reinforce an edge, hide burrs and rough edges, and improve appearance Seams are commonly used in the food industry on canned goods, on amusement park cars, in metal rooting (with a roof seamer). and in the automotive industry. The process for both hemming and seaming are the same, except that the tonnage requirement is greater for seaming. The process starts by bending the edge to an acute angle. A flattening die is then used to flatten the hem. Below figure illustrate hem formation.

3. What is Resistance Welding & its application in the automotive sector?

Resistance welding, sometimes called electric resistance welding (ERW),is a process by which metals can be joined together by applying pressure and conducting a strong electric current through the metal combination to heat up the welding joint and melt the metals, forging them together.

It has various forms and applications, and no other materials are needed, which makes it a highly cost effective process.

Resistance welding is generally used to join two plain metal work pieces together. An electric current is delivered to the metal sheets (or any work pieces being joined) through weld electrodes which apply force to the sheets. This force is then converted to heat. The heat is generated so that it melts the metal at the point where they join – the point of ‘resistance’ between the faying surfaces. The electrode then extracts heat from the molten weld area which forms a weld nugget at the point where it solidifies. A force is applied before, during and after a current is applied, which confines the contact area.

There are many resistance welding processes with different uses, such as spot welding, seam welding, and butt welding. Each one has a different specific welding application that makes it optimal for a particular situation.

1. Resistance Spot Welding

Resistance Spot Welding has been used extensively in the automotive industry for the joining of steel and in the aerospace industry for airframe components made from aluminium alloys. It is one of the oldest and simplest forms of resistance welding, in which a weld nugget is produced by passing an electric current between the two metal components whilst they are held together between electrodes, typically made from copper-based alloys due to its superior conductive properties.

2. Resistance Seam Welding

Resistrance Seam Welding is a variation of the standard spot welding form, however instead of spot one nugget, a series of overlapping nuggets is produced. This is usually done by replacing the conventional spot welding electrodes with wheels, which turn as the parts are fed between them. The process thus produces a continuous welded seam rather than a single spot. Seam welding is often used in the production of thin sheet, leak-tight containers such as fuel tanks, and is generally unsuitable for welding aluminium.

3. Resistance Projection Welding

Resistance projection welding is a form of resistance welding where the electricity, force, and weld time are concentrated on raised ‘projections’ across the surface. Projection welding is generally used for welds using thicker materials than the thinner metal pieces that spot welding is usually required for, and often not metals. It is used primarily in the electrical, automotive and construction industries.

4. Resistance Butt Welding

Resistance butt welding is a process in which the two components of similar cross section can be joined together in one operation that takes place simultaneously across the entirety of the affected object, rather than just in small spots. The welding application of butt welding is often in wires and rods with small diameter measurements, generally up to about 16mm diameter.

5. Flash Butt Welding

Flash butt welding is similar, but in this case the energy transfer is primarily provided by the resistance heat arising from the parts themselves. This is a faster type of resistance welding where the welder joins the parts by applying some pressure, then by passing a heavy current through the joint which burns away surface irregularities. After the weld has generated enough heat, the parts are connected by applying heat and pressure simultaneously. This produces a forge butt weld with no melted metal remaining in the joint.

Advantages

• Similar and dissimilar metals are capable of being welded
• Highly automated
• Efficient with high production rate and high welding rate
• Cost-effective
• Environment-friendly, produces little waste or pollution
• No need for filler metal or extraneous materials such as rods, fluxes, inert gasses, oxygen, or acetylene are required

Disadvantages

• Complex and often high-cost machinery – a resistance welding machine generally requires a high level of technically trained personnel to use
• The thickness of the work piece is often limited
• It is less efficient for high conductive materials
• High electric power required

APPLICATION:

• Resistance welding is widely used in the automotive industry.
• projection welding is widely used in the production of nuts and bolts.
• seam welding is used to produce leak-proven joints required in small tanks and boilers.
• flash welding is used to welding pipes and tubes.

4)What is fusion welding & types of fusion welding with its application in the automotive sector?

- Fusion welding is a process that uses heat to join or fuse two or more materials by heating them to melting point. The process may or may not require the use a filler material. External application of pressure is not required for fusion welding processes, except for resistance welding, where substantial contact pressure is required during welding for sound joining.

- Fusion welding processes can be grouped according to the source of the heat, for example, electric arc, gas, electrical resistance and high energy.

Shielded Metal Arc Welding (SMAW)

- also known as manual metal arc welding (MMA or MMAW), flux shielded arc welding or stick welding.is a manual arc welding process that uses a consumable electrode covered with a flux to lay the weld.

- An electric current, in the form of either AC or DC from a welding power supply, is used to form an elctric arc between the electrode and the metal to be joined. The workpiece and the electrode melts forming a pool of molten metal that cools to form a joint. As the weld is laid, the flux coating of the electrode disintegrates, giving off vapors that serve as a shielding gas and providing a layer of slag, both of which protect the weld area from atmospheric contamination.

- Because of the versatility of the process and the simplicity of its equipment and operation, shielded metal arc welding is one of the world's first and most popular welding processes. It dominates other welding processes in the maintenance and repair industry, and though flux cored arc welding is growing in popularity, SMAW continues to be used extensively in the construction of heavy steel structures and in industrial fabrication. The process is used primarily to weld steels (including stainless steel).

fig-shows SMAW welding

Metal Inert Gas Welding (MIG)/ Metal Active Gas Welding (MAG)

- Also known as Gas Metal Arc Welding (GMAW). MIG and MAG welding are the most common arc welding processes, in which an electric arc forms between a consumable wire electrode and the workpiece leading them to melt and join. Both use a shielding gas to protect the weld from airborne contaminants, or oxidation in the case of MIG welding.

- The process can be semi-automatic or automatic. A constant voltage, Direct current power source is most commonly used with GMAW, but constant current systems, as well as AC, can be used. There are four primary methods of metal transfer in GMAW, called globular, short-circuiting, spray, and pulsed-spray, each of which has distinct properties and corresponding advantages and limitations.

fig-shows MIG welding

Tungsten Inert Gas Welding (TIG)

- Also known as Gas Tungsten Arc Welding (GTAW). This arc process uses a non-consumable tungsten electrode to create the arc between the electrode and the base plate. An inert shielding gas is used to protect from oxidation or other atmospheric contamination.

- This process can be used autogenously on thin parts, but will require the addition of a wire, rod, or consumable to be added for thicker parts.

- A Constant current welding power supply produces electrical energy, which is conducted across the arc through a column of highly ionized gas and metal vapors known as a Plasma.

- GTAW is most commonly used to weld thin sections of stainless steel and non-ferrous metals such as aluminium.

fig-shows TIG welding

plasma arc welding: This process uses an electric arc created between an electrode and the torch nozzle. The electric arc ionises the gas (usually argon) in the chamber creating what is called a 'plasma.' It is then forced through a fine bore copper nozzle that constricts the arc and directs it to the workpiece, allowing the plasma arc to be separated from the shielding gas (which is usually made from a mixture of argon and hydrogen).

fig-shows plasma arc welding

Automobile application of arc welding -

• Arc welding is used to weld the chasis parts in automotive industry.
• Arc welding wire for automotive steel sheets
• Solid wires suitable for robot welding that generate compara-tively small amounts of slag and fume are chosen for welding of au-tomotive parts.
• Arc welding is used to weld the body parts in Automotive industry-
• Low heat input welding of thin steel sheetsPrevention of burn-through due to excessive heat input is im-portant in the welding of car body parts of thin sheets. For this rea-son, thin welding wire with a diameter of 0.9 mm, which enables stable welding at low currents, and low-heat-input welding power sources
• TIG welding is used to join thin stainless steel parts & various piping parts inautomobile industry.
• MIG welding is used for the repairing work in automobile industry wheather they are small, big, light or heavy.

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

The 3-2-1 principle of location principle is used to contain the movement of the workpiece along with the three-axis XX, YY, ZZ. this is achieved by providing six locating points, 3 pins in the base plane, 2 pins in the vertical plane, and 1 pin a pin which is perpendicular to first two planes.

it is known as the SIX point location principle. In this, the three adjacent locating surfaces of the blank (workpiece) are resting against 3,2 and 1 pins respectively, which prevent 9 degrees of freedom. the rest three degrees of freedom are arrested by three external forces usually provided directly by clamping. the 3-2-1 principle states that the six locators are sufficient to restrict the required degree of freedom of any workpiece. This motion is restricted using clamps and locators. A three-pin base can restrict five motions and six pins restrict nine motions.

METHODOLOGY OF THE 3-2-1 PRINCIPLE:

for this refer to the below images,

• The workpiece is resting pins A, B &C which are inserted into the base of the fixed body.
• The workpiece can't rotate about the axis XX, YY, and also can't move downward.
• In this way, the five degrees of freedom 1,2,3,4 & 5 have been arrested.
• Two pins D and E are inserted in the fixed body, in a plane perpendicular to the plane containing pins A, B & C.
• Now the workpiece can't rotate about the Z-axis and also it can't move towards the left.
• Hence the addition of pins can't D and E restrict three more degrees of freedom, namely 6, 7and 8.
• Another pin F in the second vertical face of the fixed body arrested degree of freedom 9.

The above method of locating a workpiece in a fixture is called the 3-2-1 principle.

LOCATING PROCESS:

We have two objectives when mounting a part in a fixture for machining:
1. Accurately position the part at the desired coordinates.
2. Restrict all six degrees of freedom so that the part cannot move.
A widely used method of accomplishing these two objectives uses the 3-2-1 principle, so-called because it entails three steps that employ three, then two, then one fixed point of known location. Since that adds up to six fixed points, it’s also known as the six-point method.
In the three steps of the 3-2-1 method, three mutually perpendicular planes, called datum planes, are introduced, one at each step. These three planes define the workpiece position, and together with opposing clamping forces fully constrain the part. Let’s take a look at the details of the 3-2-1 method

The Locating Process: Degrees of Freedom

In order to completely specify the position in space of a three-dimensional

object (such as the cube that’s shown), we refer to six coordinates:

1. Translational position along the X-axis
2. Translational position along the Y-axis
3. Translational position along the Z-axis
4. Rotational position about the X-axis
5. Rotational position about the Y-axis
6. Rotational position about the Z-axis

These six coordinates are known as the six degrees of freedom of a three-dimensional object. As the double-headed arrows indicate, the translational and rotational positions can vary in either direction with respect to each of the three axes.

To completely prevent movement, all six degrees of freedom must be restricted.

The Locating Process: 3-2-1 Method

6. Define Body coordinate system?

Body coordinate system:


A coordinate system is a reference system consisting of set of points, lines and planes used to define points in space in either 2 or 3 directions.
Body Coordinate system refers to the coordinate system that a car follows so that it is easy to locate the postion of a particular part or panel. I general, Body Coordinate System is also called Car Line or Body Line. A car BIW is made up of numerous panels that are welded together using different welding techniques. Welding of Car Panels happens at Assembly lines. These panels are welded at different zones(Front body, Side Body, Rear Body) and each zone is further divided into stations like Dash Assembly, Rear Floor, Side Doors, Under body, Rear Floor. Now it becomes tedious to guess where the panel will be installed in the car body.

X= LONGITUDINAL DIRECTION[(FORE & AFTER-F/A) OR (Front O Line-FOA)]
Y= TRANSVERSE DIRECTION[(CROSS CAR-C/C) OR (Centre O Line-COL)]
Z= VERTICAL DIRECTION[(UP & DOWN-U/D) OR(Bottom O Line-BOL)]

Origin of Body Coordinate System(OX) lies at the front cenre of the car. In some manufacturers it also lies somewhere near the engine along the X direction. It indicates the length of the car and coordinate system OZ's starting point lies at the bottom of the car and indicates the height of the car and finally, Coordinate system OY's starting point lies in the centre of the car and indicates the width of car. While designing lines, all designs are carried out relative to the body lineviz. fixtures, turntables etc. It also assists in quality checks as CMM can easily locate the position of actual car panel with the help of tooling holes and can tell if the car panel is at its right position.

In the above Panel, we are checking the coordinates of the panel and trying to guess the location of the car part. Coordinates are:
X= 4042
Y= -38
Z= 1087

Note that all dimentions are in mm

+X dimension means that the component lies towards rear from the car origin at a distance of approximately 4 metres. Since cars are around 4 metres to 5 metres long, we can assume that it lies at the rear end.

-Y dimension indicates the direction towards the left of car but since the distance is only 38mm we can assume it to be in the centre.

+Z dimension indicates that the component is aroud 1 meter from the car origin in the Z direction which means it is not very high from the ground.

Hence, we can conclude that this can be a Rear Floor Panel.