Savings by design

Tata Motors at Sanand is behind the Nano and its challenge of producing and marketing the car at the given price point

The Tata Nano still holds the title of the world’s most inexpensive new car. But the question remains, how do they do it? How does Tata manage to manufacture a car – a good car – that has a retail price of approximately $2,500?

While savings could have been immediately realized by deciding to produce the Nano at an existing facility, Tata elected instead to build the model at a brand new plant. Well-documented problems at the original site in West Bengal forced a change of location, which required the completed production line to be broken down for shipping from Pantnagar to the new location in Sanand, Gujurat state, a distance of 2,100km. In all, 495 containers and 3,341 truck journeys were required to move all the production equipment – including the full paintshop.

Having taken delivery of the last shipment in April 2009, the Sanand facility started test production in December of the same year, with series production of the Nano starting in February 2010. AMS spoke with K. Venkadesh, Assistant General Manager (Production), to find out if the manufacturing process had been altered in order to help achieve the required price point.

AMS: Are all parts for Nano production made at Sanand? K. Venkadesh: The A1-class stamping dies were originally moved to our plant in Pune and another supplier, AMW Bhuj, which is located near Ahmedabad (the major city close to Sanand). Powertrain production, engines and gearboxes, was also moved to our Pune location.

AMS: Are you still getting body parts from these suppliers?

KV: No, we have a Komatsu press line. It is a tandem line, which features one 2,000 tonne press and four 1,000 tonne presses. Bodysides are produced in a single cavity press, but we can press other parts two at a time, doors, fenders, etc. All functions of the line are automated, except part removal at the end of the line. This manual palletizing allows inspection of 100% of the parts.

AMS: Do you have a blanking press?

KV:We will have a blanking press installed in about three or four months. Until then, we are still receiving blanks from our Pune plant. We receive a total of 11 outer skin panels, including doors, roof, fenders, hood and tailgate.

AMS: Who is your steel supplier and what gauge is used for the Nano?

KV: The steel is delivered by JFE, from Japan. The gauge is 0.65mm. Where another car would use different steel gauges, the Nano uses the same gauge for all parts.

AMS: Does that help with production times, hemming operations?

KV: We use table top hemming for closures, a die process. The gauge of steel does not improve production times.

AMS: How do you address die maintenance?

KV: After seven sequences we examine the tooling for cracks and other problems. We can fix these problems to stop further deterioration of the tools.

AMS: Is there anything in press that you have done to cut costs?

KV: Not really, it is a complete press solution, using brand new equipment. It operates at about 14 punches per minute, producing 500 bodysides in a run.

AMS: Moving on to welding, are there a lot of manual operations?

KV: The level of automation in the weld shop is about 70%. I think it is one of the most automated weld shops in India.

AMS: Which company supplied the equipment?

KV: The complete line solution was developed by Wooshin, from South Korea. They acted as the integrator. The robots are Fanuc and the weld heads were sourced from Obara.

AMS: What types of joining methods do you use?

KV: It’s mostly spot resistance welding. A very small portion of the metal joining, between the cab and the chassis, uses MIG welding, but that’s less than 1% of all joins.

AMS: How do you carry out weld tests?

KV: The number of spots can be counted automatically. As far as weld quality, we perform chisel tests. Over each shift we pull bodies and chisel check 25% of the welds. Test four bodies and you’ve covered 100% of the welds.

AMS: Do you perform any ultrasonic testing?

KV: Yes, but this is carried out away from the line.

AMS: Does the welding sequence follow the standard floorpan, bodysides, roof assembly?

KV: It’s a little different, as the floor is mounted on a ladderframe. Once this is completed, the hemmed parts are added and the body is ready for paint.

AMS: Did you take any steps to reduce the cost of the welding process?

KV: The savings were achieved by building a highlyproductive workshop. We have reduced the takt time to 53 seconds by having about 200 stations. Throughout the process, the bodies are moved on Geo Pallets (from FATA Automation). This saves money, as other weld shops use a variety of conveying systems across weld. Also, there is no off-line kitting. All welding is done on the line.

Colour considerations

Before the permanent paintshop could be installed, the Sanand plant used what is referred to as a mini-paintshop, a small paint installation where all operations were completed manually. With the permanent paintshop equipment now in place, the mini-paint facility has been mothballed, although it could be used at a later date at another Tata plant.

AMS: The Sanand plant now features a paintshop supplied by Dürr. That’s not going to reduce the bottom line.

KV: It’s a world-class facility. It has a pre-treatment line, EV coat, sealant, primer and top coat. It features a RoDip system, which allows us to achieve an even coating over all areas of the body. Even in the box sections, the rocker panel and B-pillar, we are achieving coating between eight and 10 microns.

AMS: Does the fuel filler flap have to be removed for paint?

KV: (The Nano) doesn’t have a filler flap. The fuel nozzle is under the hood. (See ‘Cost saving analysis’ box, page 29, for more on design features specific to the Nano).

AMS: How are the cars arranged for the paint process?

KV:We paint cars in batches according to colour, but just to reduce cost. We want to save paint material, not flush it out of the heads.

AMS: How many versions of the Nano are there?

KV: There are three trim levels, Standard, Deluxe and Luxury.

AMS: Are these batched to help balance the assembly line?

KV: Over the 58 second takt in assembly, we can build any combination of trim level in any number. The only requirement is to deliver models in terms of market demand.

AMS: How do you handle kitting of the doors?

KV: We have a pre-picked box of parts that travels with the door. It helps to reduce the movement of the worker within the station and it reduces the amount of required space. Plus there’s no racking. Only glass has to be supplied separately.

AMS: What operation is first on the assembly line?

KV: The harnesses are applied, based on the electrical equipment, air conditioning, etc. There are two IPs, for cars with and without AC.

AMS: Who supplies these?

KV: Harnesses are supplied by Tata Izkea. Seats are supplied by Tata Johnson Controls – both of these are delivered justin- time and just-in-sequence. Glass is supplied by St. Gobain and Asahi and wheels are delivered by Wheels India. Wheels and tires are assembled onsite, and the cockpit is also assembled in-house on a sub-assembly line.

AMS: Where are the companies located that deliver these parts?

KV: The two Tata companies are located here. Everyone else is located remotely and delivers to nearby warehouses.

AMS: What’s next on the assembly line?

KV: After the harnesses, the rack-and-pinion is installed. Then the fuel tank. All the plastics on the car are delivered from Tata Taco, they also supply the pre-painted bumpers. Plastic trim parts and other trim components are delivered by Supreme Trims. After this, the front suspension is added and the car carries on into Trim 2, where the IP and cockpit and installed. Then the steering column and seats are applied. Glass is fitted at the end of Trim 2.

AMS: How is the glass operation carried out?

KV: The adhesive is automatically applied and the glass is put in place manually.

AMS: Is there any other automation on the assembly line?

KV: To maintain 100% quality, we use DC tooling in critical areas. There is nowhere else in India that does this. We use this tooling in 42 different operations: seats, suspension, brakes, clutch, steering. We use battery-powered tools for all other operations; there’s no compressed air on the line.

After glass, we have the marriage station. We receive the engine and gearbox from our supplier fully-dressed. We then place the engine in a frame and add suspension parts, semi-trailing arm, driveshaft, and the brakes. The engine is installed from above, using an electric hoist.

AMS: Is there a foundry on site delivering the engine blocks and other castings?

KV: The engine blocks are produced by various vendors to our specifications. The crankshaft is delivered unfinished and we complete this in our own machine shop, which is fitted with Makino work centres.

AMS: What type of conveyors are used in the assembly area?

KV: The trim line is a friction conveyor and final assembly uses a power-and-free conveyor system. These were supplied by Hyundai Heavy Industries.

AMS: How is testing handled?

KV: We put 100% of the cars through the roller and water ingress tests and on the test track. The testing phase is still being set up, but we have some cars that have been tested to 1,000km or more.

AMS: On the T-shaped assembly line, you have a large area dedicated to rework. Why is that?

KV: In the initial stages (of production) this much space is required, but when the system matures, the size of this area will be reduced. At the present time, it’s a good investment in space that allows us to maintain quality.

AMS: What pass-through rate is achieved at the plant?

KV: It’s difficult to say, as we’re still in the initial stages of production. Our goal is to reach a 98% pass-through rate.

AMS: Do you have quality gates on the assembly line?

KV: Of course! There are 12 quality gates, where we have employees checking pre-defined areas. Any defects are recorded on a PC and once cleared, they are removed. If they are not removed, the vehicle will not be passed.

AMS: You have instituted the Nano Operating System. What does this incorporate?

KV: We are promoting a Kaizen culture, working with people on the line so they can forward improvements. We offer cash rewards for any Kaizen that is put into practise - so far we have received 10,000 ideas. We want to train people in build techniques so that they are capable of solving problems on their own.

AMS: As this is loosely based on the Toyota Production System, have you incorporated any other elements?

KV: We have an Andon system, and we also follow a Pokayoke-type of management. Standardization of the job also helps with locating and resolving problems.

AMS: Across the plant there seems to be a lot of additional room. Will Tata be extending the production mix at Sanand with the addition of other models?

KV: Yes, there will be other models in the future, but no plans have been made with this in mind.

AMS: Lastly, why was Sanand chosen as the location for the new facility over places such as Pune or Chennai?

KV: Pune already has two Tata plants. The philosophy of Ratan Tata is to share, where posisible to give to the people. He selected the location as it would benefit the greatest number of people.