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1Q) What is the process of project execution activity? Ans: PROCESS OF PROJECT EXECUTION ACTIVITY: …
SUNIL KUMAR BALIVADA
updated on 25 Apr 2021
1Q) What is the process of project execution activity?
Ans: PROCESS OF PROJECT EXECUTION ACTIVITY:
Fig shows the project activities
1 RFQ:
2 FIRST SPEC: DISCUSSION MEETING:
Fig:2 A basic example of a technical offer for manual welding fixture
Fig 3: Technical offer for design & manufacturing of Robotic cell
3 OFFER SUBMISSION:
4 LOI/PO RECEIPT:
5 SCHEDULE PREPARATION:
Fig shows Example of schedule preparation chart
6 BOM PREPARATION:
7 DESIGN CONCEPT PREPARATION:
Fig shows spot plan
The red spot marks are the area to be welded & R1 & R2 are the robots.
8 CUSTOMER APPROVAL:
9 DETAILING & DRAWING RELEASE:
10 MANUFACTURING/BOP ORDERING:
11 MECHANICAL / ELECTRICAL ASSEMBLY:
12 QUALITY INSPECTION:
After the assembly again the quality check is done.
13 INTERNAL TRIAL:
14 ONLINE TRIAL:
15 PACKAGING:
16 DESPATCH:
17 INSTALLATION AS PER LAYOUT:
18 TRAILS & TRAINING AT CUSTOMER:
19 BUYOFF MEETING:
20 FINAL HANDOVERS:
2Q) What are the types of joining process?
Ans: Joining processes are the processes that are used for joining metal parts. Also defined as joining of two metal parts either temporarily or permanently with or without the application of heat or pressure.
There are many joining processes used in BIW like welding, gluing.
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.
Different types of metallurgical joining are described below:
a. Welding: welding is process of permanently joining material welding joins different metal/alloys with a number of processes in which heat is supplied either electrically or by means of torch. Welding is done by application of heat or both heat & pressure. Pressure may be employed, but this is not in many processes essential. The welding process involves applying heat to the workpiece. The heat applied should be such that the workpiece should melt, i.e, the temperature at which welding is done, should be more than the melting point of the workpiece to be welded. Welding is a fabrication or sculptural process that joins materials, usually metals or thermoplastics, by using high heat to melt the parts together and allowing them to cool, causing fusion,. Welding is distinct from lower temperature metal joining techniques such as brazing and soldering, which do melt the base metal. In addition to melting the base metal a filler material is typically added to the joint to form a pool of molten material (the weld pool) that cools to form a joint that, based on weld configuration, (butt, full penetration, fillet etc.), can be stronger than the base material (parent metal). Pressure may also be used in conjunction with heat or by itself to produce a weld. Welding also requires a form of shield to protect the filler metals or melted metals from being contaminated or oxidized. Many different energy sources can be used for welding, including a gas flame (chemical), an electric arc (electrical), a laser, an electron beam, friction, and ultrasound. While option an industrial process, welding may be performed in many different environments, including in open air, under water, and in outer space. Welding is a hazardous undertaking and precautions are required to avoid burns, electric shock, vision damage, inhalation of poisonous gases and fumes, and exposure to intense ultraviolet radiation.
There are many different types of welding operations, such as the various arc welding, resistance welding and oxyfuel gas welding methods. Below fig illustrate different types of welding process.
b. Brazing: During brazing process a filler metal is melted & distributed in between multiple solid metal components after they have been heated to proper temperature. The filler metal must have been melting point that is above 840 degrees. Brazing is a metal-joining process in which two or more metal items are joined together by melting and flowing a filler metal into the joint, the filler metal having a lower melting point than the adjoining metal.
Brazing differs from welding in that it does not involve melting the workpieces and from soldering in using higher temperature for a similar process, while also requiring much more closely fitted parts than when soldering. The filler metal flows into the gap between close-fitting parts by capillary action. The filler metal Is brought slightly above its melting (liquids) temperature while protected by a suitable atmosphere, usually a flux. It then flows over the base metal (in a process known as wetting) and is then cooled to join the workpieces together. A major advantage of brazing is the ability to join the same or different metals with considerable strength.
c. Soldering: Soldering is a process in which two or more items are joined together by melting and putting a filler metal (solder) into the joint, the filler metal having a lower melting point than the adjoining metal. Unlike welding, soldering does not involve melting the workpieces. In brazing, the work piece metal also does not melt, but the filler metal is one that melts at a higher temperature than in soldering. In the past, nearly all solders contained lead, but environmental and health concerns have increasingly dictated use fo lead-free alloys for electronics and plumbing purposes. Soldering is used in plumbing, electronics, and metal work from flashing to jewellery and musical instruments.
d. Adhesive bonding: Adhesive bonding (also referred to as gluing or glue bonding) describes a wafer bonding technique with applying an intermediate layer to connect substrates of different types of materials. Those connections produced can be soluble or insoluble. The commercially available adhesive can be organic or inorganic and is deposited on one or both substrate surfaces. Adhesives, especially the well-established SU-8 and benzo cyclobutene (BCB), are specialized for MEMS or electronic component production. The procedure enables bonding temperatures from 1000 degree centigrade down to room temperature. The most important process parameters for achieving a high bonding strength are adhesive material, coating thickness, bonding temperature, processing time, chamber pressure, tool pressure.
Adhesive bonding has the advantage of relatively low bonding temperature as well as the absence of electric voltage and current. Based on the fact that the wafers are not in direct contact, this procedure enables the use of different substrates, e.g.: silicon, glass, metals and other semiconductor materials. A drawback is that small structures become wider during patterning which hampers the production of an accurate intermediate layer with tight dimension control. Further, the possibility of corrosion due to out-gassed products, thermal instability and penetration of moisture limits the reliability of the bonding process. Another disadvantage is the missing possibilities of hermetically sealed encapsulation due to higher permeability of gas and water molecules while using organic adhesives.
e. Diffusion Bonding: Diffusion bonding or diffusion welding is a solid-state welding technique used in metal working, capable of joining similar and dissimilar metals. It operates on the principle of solid-state diffusion, where in the atoms of two solid, metallic surfaces intersperse themselves over time. This is typically accomplished at an elevated temperature, approximately 50-70% of the absolute melting temperature of the materials. Diffusion bonding is usually implemented by applying high pressure, in conjunction with necessarily high temperature to the materials to be welded, the technique is most commonly used to weld “sandwiches” of alternating layers of thin metal foil, and metal wires or filaments. Currently the diffusion bonding method is widely used I the joining of high strength and refractory metals within the aerospace and nuclear industries.
2. 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. A drawback of using mechanical joining is the lack of a continuous connection between parts, because the joint is achieved through discrete points. Also, holes created for joining are vulnerable to fractures and corrosion.
Mechanical Joining also called joining by forming, has become interesting for the automotive industry due to the request to reduce fuel consumption and there by emissions. In order to reduce weight on the car body, the usage of light weight materials in the body-in-white application has increased. This includes aluminium, high-strength steel alloys, polymers, and composites. Here the different type of mechanical joining becomes important. All mechanical joining methods are cold forming techniques. One general benefit for all mechanical joining methods is the mobility of the material after joining. At the same time mechanical joining offers an impressive strength.
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 autobody makes use of mechanical fastening to overcome the poor inherent weld ability of Al.
E.g.: 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 & 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.
3Q) What is Resistance Welding & its application in the automotive sector?
Ans: Resistance welding: Resistance welding is the joining of metals by applying pressure and passing current for a length of time through the metal area which is to be joined. The key advantage of resistance welding is that no other materials are needed to create the bond, which makes this process extremely cost effective.
There are several different forms of resistance welding (e.g. spot and seam, projection, flash and upset welding) which differ primarily by the types and shapes of weld electrodes that are used to apply the pressure and conduct the current. The electrodes, typically manufactured from copper-based alloys due to superior conductive properties, are cooled by water flowing through cavities inside the electrode and the other conductive tooling of the resistance welding machine.
Resistance welding machines are designed and built for a wide range of automotive, aerospace and industrial application. Through automation, the action of these machines is highly controlled and repeatable allowing manufactures to staff production readily.
TYPES OF RESISTANCE WELDING APPLICATIONS:
A. SPOT WELDING: Resistance spot welding, like all resistance welding processes, creates welds using heat generated by resistance to the flow of welding current between the faying surfaces, as well as force to push the workpieces together, applied over a defined period of time. Resistance spot welding uses the face geometries of the welding electrodes themselves to focus the welding current at the desired weld location, as well as to apply force to the workpieces. Once sufficient resistance is generated, the materials set down and combine, and a weld nugget is formed.
Fig shows Resistance spot welding
Resistance spot welding is automated and used in the form of robotic spot welding in automotive industries to weld the sheet metals to form car body. Industrial robots spot welding the car body in production line is shown in the photograph given.
Fig shows industrial robot welding on car body
Following are advantages of resistance spot welding:
B. SEAM WELDING: Resistance seam welding is a subset of resistance spot welding using wheel-shaped electrodes to deliver force and welding current to the parts. The difference is that the workpiece rolls between the wheel-shaped electrodes while weld current is applied. Depending on the particular weld current and weld time settings, the welds created may be overlapping, forming a complete welded seam, or may simply be individual spot welds at defined intervals.
Resistance seam welding is mostly applied in manufacturing of containers, radiators & heat exchangers etc.
Fig shows resistance seam welding
C. RESISTANCE PROJECTION WELDING: Like other resistance welding processes, projection welding uses heat generated by resistance to the flow of welding current, as well as force to push the workpieces together, applied over a defined period of time. Projection welding localizes the welds at predetermined points by using projections, embossments or intersections, all of which focus heat generation at the point of contact. Once the weld current generates sufficient resistance at the point of contact, the projections collapse, forming the weld nugget.
Solid projections are often used when welding fasteners to parts. Embossments are often used when joining sheet or plate material. An example of projection welding using material intersections is cross-wire welding. In this case the intersection of the wires themselves localizes heat generation, and therefore resistance. The wires set-down into one another, forming a weld nugget in the process. It is used mechanical fixing of Autobody structures example weld nut.
Fig shows the resistance projection welding
4Q. What is fusion welding & types of fusion welding with its application in the automotive sector?
Ans: In fusion-welding processes, heat is applied to melt the base metals. In many fusion welding processes, a filler metal is added to the molten pool during welding to facilitate the process and provide strength to the welded joint. When no filler metal is used, that fusion welding operation is referred to as autogenously weld. Fusion welding is unique however, because of its ability to “fuse” the respective objects. Assuming the objects are made of the same or similar materials, the heat produced by a welding rig will melt their surfaces, thereby allowing the objects to fuse together.
Classification of Welding Process.: The types of welding process classified into:
a. Fusion welding:
Fig shows Fusion Weld Joint
Fig shows Thermit welding process
2. Arc welding:
Here I have detailed the some of Arc welding’s:
a. Manual Metal Arc Welding:
Fig shows SMAW welding
b. Metal Inert Gas Welding (MIG)/ Metal Active Gas Welding (MAG):
Fig shows MIG Welding
c. Tungsten Inert Gas Welding (TIG):
Fig shows TIG Welding
d. Plasma Arc Welding (PAW):
Fig shows plasma arc welding
3. Gas Welding:
Here I have detailed about the most commonly used gas welding
a. Oxy – acetylene welding:
b. Electric Resistance Welding: Resistance welding is a welding technique widely used in the manufacturing industry for joining metal sheets & components. This type of welding is very much used in BIW assemblies most common. The weld is made by conducting strong current through the metal combination to heat up & finally melt the metals at localized points predetermined by design of the electrodes or the workpiece to be welded. A force is always applied before, during and after the application of the current to confine the contact area at the weld interfaces and in some application to forge the workpieces. Types of Resistance welding are:
Here I will discuss some of important types of resistance welding in detailed.
1. Resistance spot welding:
2. Resistance Seam Welding:
3. Resistance Projection Welding:
c. Solid state welding: Solid-state welding is a welding process, in which two workpieces are joined under a pressure providing intimate contact between them and at a temperature essentially below the melting point of the parent material. Bonding of the materials is a result of the diffusion of their interface atoms.
The following processes are related to solid state welding:
1. Forge welding:
2. Cold Welding (CW):
3. Friction Welding (FRW):
Friction Welding
4. Explosive Welding (EXW):
5. Diffusion Welding (DFW):
6. Ultrasonic welding (USW):
Automotive application of arc welding technology:
5Q) What is 3-2-1 principle?
Ans: Degree of freedom: The degree of freedom defines as the capability of a body to move. Consider a rectangular box, in space the box is capable of moving in twelve different direction (sim rotational & six axial).
6 translational degrees of freedom: +X, -X, +Y, -Y, +Z, -Z and 6 rotational degree of freedom.
Each direction of movement is counted as one degree of freedom i.e., a body in space has twelve degree of freedom.
Above fig shows a body in space & its possible direction of movement. The body can move two directions along each axis of three mutually perpendicular axes: also can rotate about this axis either clockwise or anticlockwise. There ae twelve degree of freedom for body in space.
In machining process, in order to attain specific results, the degrees of freedom is constrained by using work holding devices, jig & fixture & locating devices. There must be a definite relationship between cutting tool & surface of workpiece in order to perform the accurate cutting operation. To achieve high precision in machining, the workpiece must be located accurately: it is called locating of workpiece. Location of components is significant to the design of jig & fixture so that it influences the accuracy of final product. The locating device designed so that each successive workpiece loaded must occupy the same position in work handling devices.
Locating: the positional & dimensional relationship between workpiece & cutting tool.
Locator: the device to establish & maintain the position of the workpiece in work holders such as jig & fixture to ensure repeatability of work holder.
The best & most effective method of part location is 3-2-1 principle. Holding fixtures used in assembly operations often follow a 3-2-1 locating scheme to position parts. Under this scheme, three locators position a part in a primary plane or direction (e.g., high/low). Two locators then position the part in a secondary direction (e.g., in/out), leaving one locator for the tertiary direction (e.g., fore/aft). This approach fixes the part in 3-dimensional space and satisfies the six degrees of freedom constraint.
(3) minimum plane: Three locator blocks to establish part plane. Three locator or supports are placed under the workpiece. Three locators are usually positioned on primary locating surface. This restricts one axial movement downward, & 4 radial movements. Together, the three locators restrict five degrees of freedom.
(2) Round locating pin in a round hole that defines location in four direction (4 ways) perpendicular to the plane previously established. This restricts four axial movements.
(1) Round locating pin in slot that defines two of the other pin (2 way). This restricts two axial movements.
The better way of understanding of 3-2-1 principle that considers 12 degrees as of 6 degrees of freedom. It includes clockwise & anticlockwise as one rotation. Movement in positive & negative direction as one translation motion. So, we have three translation motion in x, y, z axis & three rotational motion about x, y, z axis.
In this, (3) means restricting three degree of freedom as translation motion in z axis i.e., upward & downward, two rotational motion about x & y axis.
Secondly, (2) means restricting two degrees of freedom. Translation motion in x i.e. (positive or negative) & y direction i.e., (positive or negative)
& (1) means restricting one degrees of freedom i.e., rotational motion about z axis clockwise or anticlockwise. So car panel or body cannot move in any direction with or without application of external force so properly fixed in fixture. This is basic concept of designing fixture.
Conclusion:
The jig & fixture are tools used for holding the workpiece in a correct location for mass production. Various types of fixtures (like drilling fixtures, milling fixtures, and welding fixtures) are used in industry. The 3-2-1 method is the fundamental principle for all types of fixture design.
6Q) Define body Co-ordinate system?
Ans: BODY COORDINATE SYSTEM (Part Locating System):
The body coordinate system has been widely used in the automotive industry for drawing of body parts, product & process design. A coordinate system is a reference system consisting of a set of points, lines & surfaces, used to define the positions of points in space in either two or three dimensions. In general, BCS is also called as car line & body line.
Car lines are the (grid lines) shown on the fixture, which virtually represent the same location in BIW. All the car line on fixture displays the coordinate at corner for reference. With these lines one can easily relate the location in BIW.
Sometimes single coordinate hole is given in fixture that also represents the car line coordinates, from that reference point fixture is made & can be inspected. Body coordinate are mentioned near hole. Below fig shows car line on fixture.
Automotive sheet metal components are designed in CAD (Computer Aided Design) software e.g., CATIAv4, UG, Pro-E, Ideas,
In any cad tool, there is a default axis system X, Y, Z.
Let’s us consider if every designer starts the design of the BIW Door Assembly part a default axis system, then it will be difficult to assembly or position the part with respect to each other.
Due to avoid this issue, BIW car panels are designed with reference to car axis means at their, Original position of the final car built.
Reference axis system of the software is used for the design of the various features of the parts (e.g., hole, fillet, threads,). To correlate the position of all the automotive components during the final assembly the axis system of the vehicle is used. Most of the time vehicle axis system and software axis system is the same, e.g. In most of European OEM, The X-axis represents the length of the vehicle Y-axis represents the width of the vehicle Z-axis presents the height of the vehicle. Y-axis is considered to be located at the front axle. All BIW welding fixtures are designed with reference to the car line.
These datum schemes provide a reference system for all part surfaces and features using body coordinates. Fig below illustrates a typical body coordinate system. This system replaces the traditional X, Y, and Z directional designations with fore/aft (X), in/out (Y) and up/down or high/low (Z). the O, O, O point of the car is the front, lower, and center position.
VEHICLE ORIENTATION: All vehicle product drawings are identified numerically relative to three vehicle planes described and shown below.
X = longitudinal direction (fore & after -F/A) or (Front O line-FOL).
Y = transverse direction (Cross car -C/C) or (Centre O line-COL).
Z = vertical direction (Up & down – U/D) or (Bottom O line-BOL).
The origin of the body coordinate system (OX) is defined at the front centre of a vehicle. It indicates a length of car & the coordinate system (OZ) is below its underbody indicates height of car & the coordinate system (OY) its starting point is the centre of car body indicates width of car.
Maintaining X, Y & Z coordinates in fixture is very important factor.
We should try that the coordinates of locating & clamping points should not be in three decimals (e.g., X=100.124, Y= 245.127, Z= 450.458)
They should be in the whole no’s or max up to 1 decimal. Once these coordinates are maintained automatically the BIW base structure is maintained.
7Q) Elaborate Body plane system & its essentials?
Ans: Body planes are the reference plane in an automotive car. These planes are used to define the GD&T of all car parts in a automotive domain.
Body planes are three mutually perpendicular imaginary planes. These are generally considered to be present at the driver position or sometimes at the engine location or at the front end of the car depending on the customer.
The measurements from the body planes to the parts are called as body line dimension.
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 BOL or Z – axis is called as U/DUP down.
In below fig origin is somewhere below driving sheet as it depends or changes from customer to customer. But axis system is commonly same.
Bodyline dimensions are essential for the reasons stated below.
These are basic essential thing that body line dimension would help in BIW. It could help in designing lines like welding lines, assembly lines or car body through fixture & turntable etc. This help in designing every tools. Particular assembly or parts are designed w.r.t body lines or an axis system or car line also helps in quality while doing CMM of that system. CMM is basically done with the help of coordinate. It has related particular fixture with that car part, because that dimension, coordinates of hole & pin should match so it will help in quality check also. we just give co-ordinates, that belong to that hole both coordinates should match, with this matching means quality is approved. Below fig shows some examples.
Below fig show use of X plane to define the length of car
Below fig show use of Y plane to define width of car
Below fig shows use of Z plane to define height of car
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