Week 2:- BiW Fixture Basics Challenge

1. What is process of project execution activity?

Answer:

Project activities are those basically are being processed or being practiced in general project of BIW begins. Project activities are task from start to end of project. There are various step involved in project. Below fig. show flow chart of project activities.

 

RFQ:

In BIW fixture design project begins. It starts with basic requirement or RFQ that we receive from customer. RFQ means request for quotation where in customer give his requirement specification etc. in form of some document or data to study or to work on information include such as technical offer, commercial offer, timeline of project Based on that we have processing to execute project.

1^st specification discussion meeting & offer submission:

In this the documents related technical offer, commercial offer, project execution, timeline required to complete the project are prepared. The time required to 3D design, analysis of design, drawing & detailing, manufacturing, assembly & commissioning etc. is considered. Then cost of all operation is considered. By considering these kinds of things the offer is prepared & submitted to customer. Below fig. show document that how technical offer is made.

These are technical offer based on this commercial offer will be placed. 

PO/LOI: Once we submitted offer customer will study the offer at the same time he will get offer from different supplier & vendor. He compares these technical offers & based on cost whichever suit best for his requirement. Then he will release LOI or PO with its terms & conditions as stated earlier.

Schedule Preparation: In project each activity depends on previous activity. So if previous activity has not completed on time it will cause delay in next activity date is fixed so that it will move further. Each activity has assigned specific time i.e. when activity is starting & when it is ending? So we have some back plan so that final date comes to close final delivery date. There need to be proper scheduling to be done to complete project in time. “On time delivery” is one of the major requirements from customer side also customer wants commitment must be follow in respect of time.

BOM Preparation: BOM preparation is listing down of part list which includes bought out parts, vendor parts, and consumable items with qty. of each item. Through BOM preparation material budget will be fixed. B/O parts include motor, gear box, cylinder, pneumatic & hydraulic valves etc. Also vendor parts include all machined, fabricated parts etc. whereas consumable includes like oil, grease, glue, loctite etc. .

Design concept preparation: Further step is to design a concept. A concept is based on all specification, received data from customer as 3D data of car panel, drawing, drawing std., design std., manufacturing std. After studying all data design concept is build.

Customer approval: As design concept ready then it is send to customer for its approval. It is also known as design approval process (DAP) or customer approval process. In that customer will check that all his specification consider or not in specifications. Whether it is as per technical offer submitted then only he approves prepared concept. Some points will be raised by customer. These changes are updated to design team by project team. Design team again work on it some modification or changes are necessary to improve design like clamping need to be improved or this mechanism will work fine, sensor should be of this make. These changes are again updated to customer. Once he gave final approval we will move further for detailing & dwg. release.

Detailing & Dwg. release: In detailing all assemblies broken down into its child parts. Parts of assembly are segregated into std. as well as manufactured. For std. parts own data sheet or specification sheet prepared to purchase it from catalogue. e.g. motor power, motor current rating, torque produced, shaft rpm which suit for our application. For vendor parts all detail should be provided on dwg. Like all dimension of part with tolerance, surface finish, surface treatment, hardness, welding note all should be mention on dwg. These dwgs are checked & released for manufacturing.

Manufacturing & B/O ordering: Manufacturing department will receive all dwg to start manufacturing of items like mylar, blade, riser, base frame. Also purchase team will place order for B/O parts like motor, gearbox, cylinder & valves. As material get ready, QC team should inspect all part received is as per specification or not otherwise it will create issue later which will waste our time

Mechanical & electrical assembly: After qc check, parts are available for assembly. A station is integration of all mechanical as well as electrical assembly. Assembly team will do all assembly as per dwg. All station are build as per layout Then again qc team should be involved for checking assembly as per final dwg., all coordinate dimension should be  ok as per design data.

Internal trial & testing: After approval of qc team, Internal trials & testing started. The first step involves putting assembly in fixture manually to check that it being fix properly, locating pin match with hole, clamping is ok, loading & unloading of part is easy. Also operating height is also checked, it is ergonomically correct. Then start taking trials on fixture for welding feasibility, gun approachability in fixture. Then go for online trial.

Online training: After successful of trial next step is online training. In online training has two mode manual & automated. In online trial system is run through control panel. All sensor, actuator, motor current & temperature, noise, all alarm, also safety should be tested. All process must be executed as per sequence also cycle time meet. In online training system run for certain cycle & actual production taken to ensure system run successfully.

Packaging: After trial get successful, customer give approval to dispatch system. To dispatch whole system needs to disassemble station wise & pack properly. Delicate material should be packed properly otherwise there is chance of damage aesthetically or functionally during transportation. During packaging labeling, special handling instruction should be pasted on particular parts to convey message of taking care during handling & transportation.

Dispatch: All material transported at customer site through trucks, container, and ships or by air.

Installations: All system is assembled & installed at customer end as per layout approved initially in DAP. All station, robots, conveyor mounted as per distance specified in layout. Robot arm should be reachable to station, pick & drop point. It shouldn’t foul with other equipment. Also some adjustment should be provided for leveling purpose at robot conveyor base, station base frame like leveling stud to align with other equipment. Layout is always specified at the time of initial design stage & it has to be approved by customer.

Trial & training at customer end: Once installation is done trial start at customer end. So there will be production trial, online trial. Production trial is necessary because at the time of designing fixture, it also committed no. of unit that will be manufactured from that fixture also whether it is meeting quality, bench mark or not.  Also in technical offer it is committed that there will be 100 units per 8hrs shift will manufactured from that fixture with weld quality. So during production trial fixture capability will be ensured. Once this goal is achieved then there will be training to operator, staff member, engineers to let them to understand how process is working?

Buy off meeting: Once training is completed there is buy off meeting between customer & project team with discussion on if there other things need to be incorporated, anything missing that described in LOI/PO or offer submission. Then customer will raise point or sometimes customer wants modification that will lead to extra quotation, extra costing according work is done as per buy of meeting.

Final handover: Once all points raised by customer will be closed then all will go for final handover. All data, technical manual, soft hard documents will submit to customer. These are main project activity.

 2. What are types of joining processes?

Answer: 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.

1. Metallurgical joining
2. Mechanical joining.

1. 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.

 1.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 not 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 often 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. Below fig. show principle of welding.

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. Brazing is a metal-joining process in which two or more metal items are joined together by melting and flowing a filler metalinto 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 work pieces and from soldering in using higher temperatures 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 (liquidus) 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 work pieces together. A major advantage of brazing is the ability to join the same or different metals with considerable strength. Below figure show brazing process.

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 work pieces. 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 of lead-free alloys for electronics and plumbing purposes. Soldering is used in plumbing, electronics, and metalwork from flashing to jewellery and musical instruments. Below figure shown as an additional information.

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 benzocyclobutene (BCB), are specialized for MEMS or electronic component production. The procedure enables bonding temperatures from 1000 °C 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 possibility of hermetically sealed encapsulation due to higher permeability of gas and water molecules while using organic adhesives. Below figure shown for an additional information.

e. Diffusion bonding:

Diffusion bonding or diffusion welding is a solid-state welding technique used in metalworking, capable of joining similar and dissimilar metals. It operates on the principle of solid-state diffusion, wherein 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 in 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 thereby emissions. In order to reduce weight on the car body, the usage of lightweight materials in the body-in-white application has increased. This includes aluminum, 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. AI application in autobody makes use of mechanical fastening to overcome the poor inherent weld ability of AI.

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

E.g. screw, bolts etc

b) Self piercing riveting:

Self piercing riveting is high speed mechanical fastening for point joining sheet material, typically steel & aluminum 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 roofing (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 automotive sector?

Answer:

• Resistance welding is technology widely used in manufacturing industry for joining sheet metal & component.
• The weld is made by conducting a strong current through metal combination to heat up & finally melts metal at localized points predetermined by the design of electrodes and or the work piece to be welded.
• A force is always applied before, during & after application of current to confine the contact area at weld interface & in some workpiece to forge the wokpiece. Below fig. shows resistance welding technique.

Types of resistance welding:

1. Resistance spot welding
2. Resistance seam welding
3. Resistance projection welding.

1). Resistance spot welding-

Resistance spot welding widely used in BIW joining processes. The process is used for joining sheet materials & uses shaped copper chromium or zirconium alloy electrode to apply pressure & convey electrical current through the workpiece. Heat is developed mainly at interface between two sheet, eventually causing material being welded to melt, forming a molten pool & weld nugget. The molten pool is contained by the pressure applied by electrode tip & surrounding solid metal. When circuit is completed current will flow from that panel or sheet metal which will generate amount of heat that is sufficient enough to melt that will be melted & get welded together. The molten pool should not move outside of that zone to ensure that proper pressure is applied through electrode tip & surrounding sheet metal. Forcing a large current through the spot will melt the metal and form the weld. The attractive feature of spot welding is that much energy can be delivered to the spot in a very short time (approximately 10–100 milliseconds). That permits the welding to occur without excessive heating of the remainder of the sheet. Strength & durability largely depends on quality of RSW. Below figure illustrate principle of resistance welding.

 

Following are advantages of resistance spot welding.

• Short weld time & hence high weld speed
• Highly adaptable to automation & robotic technique. Below figure show robot used in automotive industry for spot welding. Typical BIW contains 500 weld. RSW is automated and used in the form of robotic spot welding in automotive industries to weld the sheet metals to form car body. Below figure illustrate typical application of spot welding using robots.

2).Resistance seam welding:

Resistance seam welding is welding process for joining metal sheets in continuous, often leak tight, and seam joints by directly applying opposing forces with electrode consisting of rotary wheel. It differs from flash welding in that flash welding typically welds the entire joint at once and seam welding forms the weld progressively, starting at one end. The current & the heat generation are localized by peripheral shapes of electrode wheel Seam welding is mostly applied in manufacturing of containers radiators & heat exchangers etc. Resistance seam welding is used where leakage proof continuous welding required. Like spot welding, seam welding relies on two electrodes, usually made from copper, to apply pressure and current. The electrodes are often disc shaped and rotate as the material passes between them. This allows the electrodes to stay in constant contact with the material to make long continuous welds. The electrodes may also move or assist the movement of the material. Seam welding produces an extremely durable weld because the joint is forged due to the heat and pressure applied. A properly welded joint formed by resistance welding can easily be stronger than the material from which it is formed. A common use of seam welding is during the manufacture of round or rectangular steel tubing. Seam welding has been used to manufacture steel beverage cans but is no longer used for this as modern beverage cans are seamless aluminum. In automobile industries, this welding process is used to produce leak proof fuel tanks.

3).Resistance projection welding:

Projection welding is process for joining metal components or sheets with embossment by directly applying opposing forces with electrode specially designed to fit the shape of workpieces. The current & heat generation are localized by shape of workpieces either with their natural shape or with specially designed projection. Large deformation or collapse will occur in projection part of workpiece. This process has the benefit of forcing the welds to occur in very specific and tiny locations, and minimizing the dissipation of heat to the rest of the metal sheets.

It used for mechanical fixing of auto body structure e.g. to weld nut. In BIW body there will be many welded nut, stud, bolt that need to be welded on sheet. It will use further stages for fastening process. So to weld these things we use process like resistance welding. Concept & mechanism is same to use two electrodes. The current will flow, pressure will be applied metal will melt & get welded together. Spot welding will have rounded tip at end of electrode. In projection welding tip will be same as per part as per profile.

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

Answer:

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. Fusions welding are categorized according to source of heat for example electric arc, electric resistance, gas, high energy.

1) Arc Welding:

The most popular type of fusion welding is arc welding. The process involves either consumable or non consumable electrode rod or wire. Arc welding lives up to its namesake by relying on an electric arc to join two or more objects.  An arc produced between tip of electrode & workpiece to be welded by an AC or a DC power supply. With electric arcs measuring up to 6,000 degrees Fahrenheit, this fusion welding process is highly capable of melting even toughest metals. Furthermore, arc welding can be performed underwater, making it an ideal solution for offshore welding projects. This process can be categorised into two different types; consumable and non-consumable electrode methods. Below figure shows.

a).Manual metal arc welding or Shielded Metal Arc Welding (SMAW):

Also known as manual metal arc welding (MMA or MMAW), flux shielded arc welding or stick welding is a process where the arc is struck between the metal rod (electrode flux coated) and the work piece, both the rod and work piece surface melt to form a weld pool. Simultaneous melting of the flux coating on the rod will form gas, and slag, which protects the weld pool from the surrounding atmosphere. This is a versatile process ideal for joining ferrous and non-ferrous materials with a range of material thicknesses in all positions. Below figure shows.

b).Gas shielded metal arc welding or metal inert gas welding or MIG:

Metal inert gas (MIG) is an arc welding technique in which consumable electrode is used to weld two or more workpieces. MIG welding are most common arc welding processes, in which arc forms between consumable wire electrode & workpiece leading them to melt & join. Both use a shielding gas to protect the weld from airborne contaminants or oxidation in case of MIG welding. The process can be automatic or semi automatic. A constant voltage, direct current power is most commonly used with GMAW, but constant current system, as well as AC can be used. There are four primary methods of metal transfer in GMAW, called globular, short circuiting spray, each of which has distant properties & corresponding advantages & limitations. MIG welding make use of following components,

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

c) Gas- shielded tungsten arc welding or TIG:

Tungsten inert gas welding, also known as gas tungsten arc welding (GTAW), is an arc welding method that uses a non consumable tungsten electrode to weld two or more workpieces. An inert shielding gas is used to protect from oxidation or other atmospheric contamination. The 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 & metal vapors known as plasma.  It is very much similar to metal inert gas welding (MIG). Following components are necessary 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.

d). Plasma arc welding:

The Plasma arc welding (PAW) is similar to GTAW or gas tungsten welding. In this kind of welding process, the arc will generate among work part as well as the tungsten electrode. The major dissimilarity among plasma arc welding and gas tungsten welding is that the electrode is located within the torch of Plasma arc welding. It can be heated the gas at the temperature of 30000°F & changes it into the plasma to attack the welding region. Below figure show working principle of plasma arc welding.

e). Submerged Arc Welding:

The Submerged arc welding (SAW) can be extensively utilized within an automatic welding method. In this kind of welding process, an electrode is completely submerged by the granular coating of flux, and this flux can be an electric conductor which will not oppose the electric supply. The solid coating of flux stops the melted metal to ultra-violate radiation and atmosphere. Below fig. show

Automotive application of arc welding technology:

• Arc welding is used to weld the chassis parts in automotive industry.
• Arc welding is used to weld body parts in automotive industry. Low heat input welding of thin steel sheets prevention of burn through due to excessive heat input is important in the welding of car body parts of thin sheets. For this reason thin welding wire with a diameter of 0.9 mm, which enable welding at low currents & low heat input welding power source.
• TIG welding is used to join thin stainless steel parts & various piping parts in automobile industry. TIG welding can work on both AC and DC power sources. One of the greatest strengths of TIG welding is that it can be used for welding non-ferrous metals like aluminum, copper, magnesium, copper, nickel, titanium, etc.
• Rebuilding: MIG welding is used for repairing work in automobile industry. To repair especially to dismantle & reassemble with new parts. Example: to rebuild an old car. When it comes to fixing broken parts in the field, there are three steps to master: cutting & removal of the failed component, preparation of the new joint/ part, welding & cleanup. Worn parts can be repaired using MIG welding in variety of coatings (stainless steel, bronze, nickel, aluminum or hard surfacing) & in a range of hardness, for a fraction of the cost of purchasing a new part.

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

Answer:

Degrees 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 directions (six rotational & six axial).

6 translational degrees of freedom: +X, -X, +Y, -Y, +Z, -Z.

And 6 rotational degrees of freedom:

- Clockwise around X axis (CROT-X).

- Anticlockwise around X axis (ACROT-X).

- Clockwise around Y axis (CROT-Y).

- Anticlockwise around Y axis (ACROT-Y).

- Clockwise around Z axis (CROT-Z).

- Anticlockwise around Z axis (ACROT-Z).

Each direction of movement is counted as one degree of freedom. i.e. a body in space has twelve degree of freedom.

Above figure shows a body in space & its possible direction of movement. The body can move two directions along the each axis of three mutually perpendicular axes; also can rotate about this axis either clockwise or anticlockwise. There are twelve degree of freedom for body in space.

In machining process, in order to attain specific results, the degrees of freedom is constrined 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 directions (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 include clockwise & anticlockwise as one rotation. Movement in +ve & -ve 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. +ve or –ve)

& y direction i.e. (+ve or –ve)

& (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 and fixture are tools used for holding the work piece 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.

6). Define body co-ordinate system?

Answer:

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 figure show car line on fixture.

Automotive sheet metal components are designed in CAD (Computer aided Design) software e.g. CATIAv4-v5, UG, ProE, Ideas,

In any cad tool, there is a default axis system X, Y, Z.

Lets 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. Figure 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 0,0,0  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 decimal (e.g. X=100.124, Y=245.127, Z=450.458)

They should be in the whole nos or max upto 1 decimal. Once these coordinate are maintained automatically the BIW base structure is mainteined.

 

7. Elaborate body plane system & its essentials.

Answer: 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 figure 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,

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

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 relate 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 coordinate should match. With this matching means quality is approved. Below figure shows some example.

 

Below fig show use of X plane to define the length of car.

Below figure show use of Y plane to define width of car.

Below figure shows use of Z plane to define height of car.