Wednesday, March 26, 2014

Car/ Vehicle Manufacturing Process at Mahindra and Mahindra - Kandivali Plant

Models manufactured in the Kandivali Plant

Maxx Pikup
Bolero Maxi Truck
XL Flatbed
XL Single Cab
Bolero Pik Up
Bolero CNG Pik up

The major divisions called Product Units (P.U) in the plant under Automotive Sector are:-

Axle P.U
Body P.U
Engine P.U
Foundry P.U
Transmission P.U
Vehicle P.U


 In this department various parts of vehicle are assembled together which comes from other departments & vendors. The specialty of this department is that all the models are manufactured on a single line.

Different cells of Vehicle P.U.

Body Trim shop
Chassis line
Body drop
Test cell
FAI (Final Acceptance Inspection)
CAI (Customer Acceptance Inspection)
RFI (Ready For Inspection)
Yard Check
NOVA-C(New Overall Vehicle Audit-Customer)
RFD (Ready For Dispatch)

Manufacturing Process

The bulk of the world’s new cars come from the moving assembly line introduced by Ford, but the process is much more refined and elaborated today. Although technological advancements have enabled many improvements to modern day automobile assembly operations, the basic concept of stationary workers installing parts on a vehicle as it passes their work stations has not changed drastically over the years since it was first invented by Henry Ford in early 1900.

The modern automobile consists of about 14,000 parts and comprises several structural and mechanical systems. These include the body, containing the passenger and storage space, which sits on the chassis, or steel frame; the internal-combustion gasoline engine, which powers the car by means of a transmission; the steering and braking systems, which control the car’s motion; and the electrical system, which includes a battery, alternator, and other devices. Subsystems involve fuel, exhaust, lubrication, cooling, suspension, and tires.

The automobile body is the assembly of sheet-metal, fiberglass, plastic, or composite-material panels together with windows, doors, seats, trim and upholstery, glass, and other parts that form enclosures for the passenger, engine, and luggage compartments.

Supply Chain

To understand the car manufacturing process, you have to understand the underlying supply chain that drives domestic vehicle assembly. Today’s cars are primarily “sourced out” to produce various sub-assemblies in over 4,000 disparate locations as far away as China. This means a car’s “production” plant is an active assembly point, where skilled workers and robotic systems bring together all of the necessary loose components to create a final product on a “just-in-time” basis.


Although the bulk of an automobile is virgin steel, petroleum-based products (plastics and vinyls) have come to represent an increasingly large percentage of automotive components.

The automobile assembly plant represents only the final phase in the process of manufacturing an automobile, for it is here that the components supplied by more than 4,000 outside suppliers, including company-owned parts suppliers, are brought together for assembly, usually by truck or railroad. Those parts that will be used in the chassis are delivered to one area, while those that will comprise the body are unloaded at another.


Introducing a new model of automobile generally takes three to five years from inception to assembly. With the help of computer-aided design equipment, designers develop basic concept drawings that help them visualize the proposed vehicle’s appearance. Based on this simulation, they then construct clay models that can be studied by styling experts familiar with what the public is likely to accept. Aerodynamic engineers also review the models, studying air-flow parameters and doing feasibility studies on crash tests. Only after all models have been reviewed and accepted are tool designers permitted to begin building the tools that will manufacture the component parts of the new model.

Assembly Process

There are three main assembly lines, trim, chassis and body drop. On the first the body panels are welded together, the doors and windows are installed, and the body is painted and trimmed (with upholstery, interior hardware, and wiring). On the second line the frame has the springs, wheels, steering gear, and power train (engine, transmission, drive shaft, and differential) installed, plus the brakes and exhaust system. The two lines merge at the point at which the car is finished except for minor items and necessary testing and inspection. A variation on this process is “unitized” construction, whereby the body and frame are assembled as a unit. In this system the undercarriage still goes down the chassis line for the power train, front suspension, and rear axle, to be supported on pedestals until they are joined to the unitized body structure. Most passenger vehicles today are manufactured by the unitized method, and most trucks and commercial vehicles still employ a separate frame.

Press Shop

This is where the production process starts, with most of the Metal parts getting pressed out of Steel Sheets. The door panels, Roof, Bonnet, Boot Lid etc. are typically pressed in to form the basic structure of the automobile. The pressing process is a multi-step process where the sheets are pressed into shape in stages.

Weld Shop

The Weld shop is typically the place where the automobile is born. The point of birth for most design cars is where the Underbody takes shape from the Pressed parts. It can be the marriage of the Underbody front & rear or in some cases the entire underbody can be a single pressed unit. In stages, the Side panels, the roof are then welded to the underbody and the automobile begins to take its shape. The welding process is typically Tungsten Inert Gas (TIG) welding, mostly done by Robots and is a treat to watch, wherein you have all these multi axis robotic arms work in unison and utmost precision.


The chassis of the car is the baseline component. All other parts are integrated on, or within the chassis. The typical car or truck is constructed from the ground up (and out). The frame is the main structural member to which all other mechanical chassis parts and the body are assembled to make a complete vehicle. The frame forms the base on which the body rests and from which all subsequent assembly components follow. The frame is placed on the assembly line and clamped to the conveyer to prevent shifting as it moves down the line. From here the automobile frame moves to component assembly areas where parts that are sequentially applied to the chassis include the engine, complete front and rear suspensions, gas tanks, rear axles, rear-end and half-shafts, transmission, and drive shafts, gear boxes, steering box components, wheel drums, and braking systems are sequentially installed.

An off-line operation at this stage of production mates the vehicle’s engine with its transmission. Workers use robotic arms to install these heavy components inside the engine compartment of the frame. After the engine and transmission are installed, a worker attaches the radiator, and another bolts it into place. Because of the nature of these heavy component parts, articulating robots perform all of the lift and carry operations while assemblers using pneumatic wrenches bolt component pieces in place. Careful ergonomic studies of every assembly task have provided assembly workers with the safest and most efficient tools available.


Generally, the floor pan is the largest body component to which a multitude of panels and braces will subsequently be either welded or bolted. As it moves down the assembly line, held in place by clamping fixtures, the shell of the vehicle is built. First, the left and right quarter panels are manually disengaged from pre-staged shipping containers and placed onto the floor pan, where they are stabilized with positioning fixtures and welded.

The front and rear door pillars, roof, and body side panels are assembled in the same fashion. The shell of the automobile assembled in this section of the process lends itself to the use of robots because articulating arms can easily introduce various component braces and panels to the floor pan and perform a high number of weld operations in a time frame and with a degree of accuracy no human workers could ever approach. Robots can pick and load 200-pound (90.8 kilograms) roof panels and place them precisely in the proper weld position with tolerance variations held to within .001 of an inch. Moreover, robots can also tolerate the smoke, weld flashes, and gases created during this phase of production.

The body is built up on a separate assembly line from the chassis. Operators perform most of the welding on the various panels and bolt the parts together. During welding, component pieces are held securely in a jig while welding operations are performed. Once the body shell is complete, it is attached to an overhead conveyor for the painting process. The multi-step painting process entails inspection, cleaning, undercoat (electrostatically applied) dipping, drying, topcoat spraying, and baking.

As the body moves from the isolated weld area of the assembly line, subsequent body components including fully assembled doors, deck lids, hood panel, fenders, trunk lid, and bumper reinforcements are installed. Although robots help workers place these components onto the body shell, the workers provide the proper fit for most of the bolt-on functional parts using pneumatically assisted tools.

Paint Shop

The output of the Weld Shop is called as a BIW or a Body In White. These are the cabs that enter into the Paint Shop. The painting process is one of the most complex and cleanest of process. The Paint booths for example have to be completely dust free. The various sub-process in the Paint Shop include

(a) Pre-treatment where the BIW is dipped into an electrolyte solution which would help in better paint deposition on the Metal.

(b) Sealant: Prior to the application of paint, the BIWs enter the sealant area where the sealant is applied.

(c) Paint Booths: The BIWs enter the paint booths, for the final painting process. This is typically an area where it is mostly robots again which do the job, or you would need highly skilled human workforce. A highly clean environment is maintained and access is limited and if at all, it has to be with wearing the right kind of overalls.

(d) Oven: The painted bodies are then passed through the oven where the final baking process of the Paint takes place.

(e) Wax Booths: Where application of a fine layer of wax takes place. This is sometimes skipped for some local market vehicles or the lower variants.

(f) Polishing: One of the most laborious processes and the most time consuming one as well. Each of the cars are polished to give the right shine and gleam. A simple rule of thumb, the longer and more elaborate the Polishing process, the better is the shine. So the costlier the car, the longer would have been the polishing done on it.

Prior to painting, the body must pass through a rigorous inspection process, the body in white operation. The shell of the vehicle passes through a brightly lit white room where it is fully wiped down by visual inspectors using cloths soaked in hi-light oil. Under the lights, this oil allows inspectors to see any defects in the sheet metal body panels. Dings, dents, and any other defects are repaired right on the line by skilled body repairmen. After the shell has been fully inspected and repaired, the assembly conveyor carries it through a cleaning station where it is immersed and cleaned of all residual oil, dirt, and contaminants.

As the shell exits the cleaning station it goes through a drying booth and then through an undercoat dip—an electrostatically charged bath of undercoat paint (called the E-coat) that covers every nook and cranny of the body shell, both inside and out, with primer. This coat acts as a substrate surface to which the top coat of colored paint adheres.

After the E-coat bath, the shell is again dried in a booth as it proceeds on to the final paint operation. In most automobile assembly plants today, vehicle bodies are spray-painted by robots that have been programmed to apply the exact amounts of paint to just the right areas for just the right length of time.

Once the shell has been fully covered with a base coat of color paint and a clear top coat, the conveyor transfers the bodies through baking ovens where the paint is cured at temperatures exceeding 275 degrees Fahrenheit (135 degrees Celsius).

The body and chassis assemblies are mated near the end of the production process. Robotic arms lift the body shell onto the chassis frame, where human workers then bolt the two together. After final components are installed, the vehicle is driven off the assembly line to a quality checkpoint.

After the shell leaves the paint area it is ready for interior assembly.

Interior assembly

After the structure is entirely painted, painted shell proceeds through the interior assembly area where workers assemble all of the instrumentation and wiring systems, dash panels, interior lights, seats, door and trim panels, headliners, radios, speakers, all glass except the automobile windshield, steering column and wheel, body weather strips, vinyl tops, brake and gas pedals, carpeting, and front and rear bumper fascias.

Next, robots equipped with suction cups remove the windshield from a shipping container, apply a bead of urethane sealer to the perimeter of the glass, and then place it into the body windshield frame. Robots also pick seats and trim panels and transport them to the vehicle for the ease and efficiency of the assembly operator. After passing through this section the shell is given a water test to ensure the proper fit of door panels, glass, and weather stripping. It is now ready to mate with the chassis.

Chassis/Body Mating- Body Drop Stage

The chassis assembly conveyor and the body shell conveyor meet at this stage of production. As the chassis passes the body conveyor the shell is robotically lifted from its conveyor fixtures and placed onto the car frame. Again, this process is executed via computer and control machines (C&C) to ensure speed, and perfect the fit between the body assembly and the chassis. Assembly workers, some at ground level and some in work pits beneath the conveyor, bolt the car body to the frame. Once the mating takes place the automobile proceeds down the line to receive final trim components, battery, tires, anti-freeze, and gasoline.

The vehicle can now be started. From here it is driven to a checkpoint off the line, where its engine is audited, its lights and horn checked, its tires balanced, and its charging system examined. Any defects discovered at this stage require that the car be taken to a central repair area, usually located near the end of the line. A crew of skilled trouble-shooters at this stage analyzes and repairs all problems. When the vehicle passes final audit it is given a price label and driven to a staging and waiting line for transportation to its final dealer destination.

Quality Control

All of the components that go into the automobile are produced at other sites. This means the thousands of component pieces that comprise the car must be manufactured, tested, packaged, and shipped to the assembly plants, often on the same day they will be used. This requires no small amount of planning. To accomplish it, most automobile manufacturers require outside parts vendors to subject their component parts to rigorous testing and inspection audits similar to those used by the assembly plants. In this way the assembly plants can anticipate that the products arriving at their receiving docks are Statistical Process Control (SPC) approved and free from defects.

Once the component parts of the automobile begin to be assembled at the automotive factory, production control specialists can follow the progress of each embryonic automobile by means of its Vehicle Identification Number (VIN), assigned at the start of the production line. In many of the more advanced assembly plants a small radio frequency transponder is attached to the chassis and floor pan. This sending unit carries the VIN information and monitors its progress along the assembly process. Knowing what operations the vehicle has been through, where it is going, and when it should arrive at the next assembly station gives production management personnel the ability to electronically control the manufacturing sequence. Throughout the assembly process quality audit stations keep track of vital information concerning the integrity of various functional components of the vehicle.

This idea comes from a change in quality control ideology over the years. Formerly, quality control was seen as a final inspection process that sought to discover defects only after the vehicle was built. In contrast, today quality is seen as a process built right into the design of the vehicle as well as the assembly process. In this way assembly operators can stop the conveyor if workers find a defect. Corrections can then be made, or supplies checked to determine whether an entire batch of components is bad. Vehicle recalls are costly and manufacturers do everything possible to ensure the integrity of their product before it is shipped to the customer. After the vehicle is assembled a validation process is conducted at the end of the assembly line to verify quality audits from the various inspection points throughout the assembly process. This final audit tests for properly fitting panels; dynamics; squeaks and rattles; functioning electrical components; and engine, chassis, and wheel alignment. In many assembly plants vehicles are periodically pulled from the audit line and given full functional tests. All efforts today are put forth to ensure that quality and reliability are built into the assembled product.

Interesting improvement projects are described in this report.


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