Week 2:- BiW Fixture Basics Challenge

1)What is the process of project execution activity?

                                                               

1)RFQ received - This is the first step in any project. RFQ stands for Request for Quotation. In this customer specifies his requirements,specifications etc. in form of documents or data. Also customer specifies its Technical offer, commercial offer, how the project will be executed & timeline to complete the project in it.

2) 1st spec discussion & 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 & commisioning etc. is considered. Then the cost of all the operation is also considered. By considering these kind of things the offer is prepared & submitted to the customer. 

3) LOI/PO Receipt - The customer will study the offer submitted. He will also take quotations from others. The customer will study all the offers, compare offers & then select oner offer which suits best. The customer will generate po means Purchase order to start the work.

4) Schedule preparation - After receiving the PO the project officially start. The timeline is fixed so there should be plan to beat the deadline & to complete the project. All the activities step by step are taken into account like po receipt, 1st meeting, design date analysis, 3D design preparation & simulation etc. the time required to finish the individual activity is calculated. By calculating all the steps the total time required is calculated. It should beat the timeline & if not then modifications is done in schedule to beat the timeline of the project. We should have some back up plan for this Because due to some reasons our tasks not complete on the fixed date or the next task is dependant on previous task.

5)BOM preparation - Bill of material is prepared for the project like the  parts, grippers, cylinders, motors etc. which are required.

6) Design concept preparation - The customer gives data or the specifications for the design. Based on that data design process is start which fulfills all the customer requirements.

7) Customer approval - After designing the concept the approval of the customer is required. Customer checks the design fulfills the requirements or not according to the technical offer. If yes the customer gives approval for the design or customer will also ask for some addition or the changes in the design. By doing the necessary changes final approval is taken from the customer.

8) Detailing & DWG release - After the approval from customer DWG are released whic shows the detailed specifications of all the parts required. Like dimensions, Qty, Specifications etc.

9) Manufacturing BOP ordering - The BO parts like motors, cylinders, sensors, gripper etc. required for manufacturing are ordered as per the design specifications.

10) Mechanical/ Electrical assembly- Once the parts are received they goes for the prior Quality control checking. In this all the parts are checked as per the specification. After QC checking the Mechanical or electrical assemblis are prepared as per the design.

11)Quality inspection - After the assembly again the quality is checked. In this all the dimensions, positional accuracy, Coordinates are checked by using CMM machine.

12) Internal trial & testing & online trial - After the QC check internal trials are taken to check the fixture can do the operation or not for what it is designed. The simulation is done for this purpose at early stage. In this the fixture is checked for the clamping of the part, welding ,proper loading & unloading of the part etc.

  After this online trial is taken in which all the operations done in automated mode by using electrical connections. The process sequence is checked as per the defined way in design in automated mode. Customer is also involved in online trial for taking the approval.

13) Packaging & dispatch - The assemblies are packed in proper manner. Because in trasportaion the fixture will be damaged hence it distorts the geometry of the fixture & also the functionality of the fixture. Hence the proper packaging is very important. Once the packaging is done the fixture is dispatched to the customer address.

14) Installation as per layout - layout is the space defined for the parts like fixture, robots etc, according to the functionality,application, process sequence etc. The layout is done at very initial level & according to that installation is done.

15) Trials & training at customer - Production trials are taken at customers end. In tecnical offer we have specified the quality benchmarks for the fixture, the capability of the fixture for production etc. The trials are taken to check the capability of the fixture. Once it is done then training is given to the operator, staff  & engineer for the process sequence, how the fixture works, loading & unloading of the part etc.

16)Buy off meeting & Final handover - After production trial & training Customer check all the prescribed things in the offer are done or not. Sometime customer want some addition work also, so according to the rquirement all the points are closed & after that project finally handovered to the customer.

2)What are the types of joining processes?

 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 two types of joining processes named as -

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.

(2) Mechanical joining -

         Mechanical Joining is a process for joining parts through mechanical methods, which often involve threaded holes. Joining parts using screws or nuts and bolts are common examples of mechanical joining.  The threaded holes employed for mechanical joining are vulnerable to fractures.  In ductile materials, the fracture can come from fatigue, while in brittle materials, the fracture can simply result from mechanical overloading. Thus, mechanical joints must be designed with fatigue failure and brittle fracture in mind.  Another issue to be considered when designing mechanical joints is galvanic corrosion, which is a type of corrision that affects different types of metals that are in contact with each other.

3) What is Resistance welding & its application in the automotive sector?

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 applications. Through automation, the action of these machines is highly controlled and repeatable allowing manufacturers to staff production readily.

Types of Resistance Welding Applications:

(a)Spot Welding 

(b)Seam Welding

The welding process in which two similar or dissimilar materials are joined at the seam by the application of heat generated from electrical resistance is known as seam welding. The seam welding is a types of resistance welding, in which weld is produced by roller electrodes instead of tipped electrodes.

Most seam welding processes produce a continuous or intermittent seam weld near the edge of two overlapped metals by using two machine driven roller electrodes. As in the seam welding process, the roller electrodes move over the metal workpieces, the workpieces are under pressure and the current passing through them heats the two workpieces of the metal to the melting point. Thus, this process, sometimes, also called the seam spot welding.

Resistance seam welding is one of the most common welding process used to join metal sheets with a continuous weld. In seam welding process, when two similar or dissimilar materials are pressed together, there will be a small gap between them because of irregularities in the metal surface. This gap causes an electrical resistance between the two materials and results them to heat up at the seam.

The schematic diagram of the seam welding process is shown in the figure.

                                                      

In seam welding process, the welding current is the main parameter, i.e., the amount of heat generated at the seams depends upon the magnitude of welding current flowing through it.

(c)Projection Welding

Projection welding is the resistance welding process which joins the metal pieces together by using the heat generated by an electric current. In this welding process, different projections are formed on the workpieces for effective welding, which is why the name "projection welding."

Projection welding does not use electrodes for concentration of heat, instead the projection on the workpiece is used for this purpose. Actually, projection welding is a modified version of spot welding. It consists of forming slight projections on one of metal.

Working of Projection Welding

                                            

• The set up used for projection welding consists of two copper electrodes.

• The metal pieces to be welded are kept between these two electrodes as shown in the above figure.

• After that, the projections are accurately formed in precise locations on the metal workpieces by using a special set of dies.

• Once the projections are formed, the raised portions on one workpiece are pressed into contact with another workpiece.

• At the same time, a high electric current is passed through the workpieces.

• When the raised portions touch the second workpiece of metal, the electric current flows through the contact points, which heats and fuses the two metal workpieces together.

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 comparatively small amounts of slag and fume are chosen for welding of automotive 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 reason, 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 Locating Process: 3-2-1 Method