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We enter the second part of the car manufacturing process. After this the car will go to the dealerships. Even though all other car design courses end the process once the car has been produced, we will not stop there and we will complete the cycle of car development. During the next two posts we will reveal some secrets and concepts of the automotive business.
At this point we have the car assembled, there are still three more phases of the process
3. Car painting process
4. Assembling components
5. Final quality control
Step 3: Automobile Painting Process
This phase seems simple, but it is the most complex and important of all the phases that we will see in this week.
Paint isn't merely aesthetic, it protects the car from rust. If cars didn't have a paint to protect them from the elements, the metals would rust and this in turn would cause a really serious structural weakening. We saw in previous posts some notions about the importance of steels in the car design, all this would not make sense if the rust easily attacked the steel of the car.
A vehicle whose structure was weakened would lose its rigidity, and therefore its stability. In addition, in the event of an accident, the car would be much more unsafe, because the metal components would break more easily and of course, they wouldn't deform in an adequate way to "absorb" the inertia of the impact. In fact, if the rust creates any holes in the metal, this would lead to an additional stress concentration and would lead to crack propagation in that area, therefore, it would be much less resistant.
Note: Impact time is actually delayed, energy is never "absorbed".
Car painting process
1- The bodywork is cleaned and degreased with a series of high-temperature water washes and degreasing products to dissolve any oil.
Each car goes through a phosphating and chromic passivation process to improve the adhesion of the particles. The vehicle is placed in an acid phosphate bath. This eliminates any remaining oxidation and creates a layer of phosphates that will give it greater resistance to corrosion and improve the adherence of the paint particles. Each car goes through at least two different phosphate baths in this process.
Afterwards, pressure washing is carried out with osmotized or deionized water to remove the remains. After this, another passivation wash is carried out to conclude this first process. At the chemical level, a series of processes are produced to achieve anticorrosive properties.
2 - This is the most important and well-known part of the car painting process: the famous cataphoresis bath in which the particles adhere to the metal by cathodic immersion.
In this process, an electrical voltage is applied to the body (negative pole - cathode) and in turn, the other electrical charge is applied to the electrolytic bath in which the body is submerged (positive pole - anode). So there will be an electrical charge both in the tank and in the car body.
We already know that opposite charges attract each other, therefore when the body is submerged in the tank it will attract all the paint particles dispersed in the tank. Thanks to this, all the gaps in the body are covered. If this process were done with a paint gun, there would be uncovered gaps and unprotected against oxidation.
This mode of applying paint to a vehicle is called electrodeposition of paint or electrodeposition coating. It's a very clever way to paint something without using a spray gun, with a homogeneous result that will cover any gap.
After this, the body goes through a series of washes and an oven at a temperature of 140 ° C - 200 ° C. For example, in the Skoda oven we see below, the bodywork moves sideways and hot air enters through the engine compartment and the windshield.
3 - Finally, several robots apply undercoating varnish, mastics and sealants in specific areas. Sealants are applied wherever there is a risk of water entering. It's also good for thermal and noise insulation.
The soundproofing panels are also placed in this phase and a product is sprayed to protect the underbody from the gravel. The vehicle goes through a vacuum chamber, equipped with feather dusters. As a curiosity, these feather dusters are made with female ostrich feathers. With this, it is possible to remove any minimum speck of dust, before applying the primer and paint of the vehicle. So if you want to build your own brand of cars, it seems that you will have to learn to distinguish between female and male ostriches.
After this, the parts are cleaned and we proceed to the filler, which is a primer that will serve as a support for the finishing paint, that is, the paint you choose when you configure a car at the dealership. The robots then apply the final paint in different layers. Robots equipped with electrostatic guns apply powder paint, which will adhere to the metal parts of the vehicle. There are also robots in charge of opening the moving parts of the vehicle so that they can be painted.
Then the car will go through a tunnel with infrared lights to dry the paint and after that the varnish will be applied to go through a final curing oven.
As we can see, it's an expensive, laborious and very meticulous process. The important thing here is not to perfectly learn each of the phases, but to understand how important it's to take into account the protection of the car's structure.
Once the final paint has been applied, the car goes through a visual inspection carried out by an operator in a white light room. This way, no shadows are produced and any minor imperfections are revealed.
Step 4: Assembling the components
This assembly line is less automated than the previous ones, each operator works in a specific area of the vehicle. Everything is arranged for the convenience of the operator in his daily tasks. Each work station has stools, supports, fasteners, manipulators and tools arranged according to the function to be performed, all to save time and reduce fatigue of the operators. In all production lines there are systems in place so that operators can give suggestions to improve their environment, either to save time or to reduce fatigue.
Despite the fact that there are teams of ergonomics specialists, after all, the operator is the one who spends eight hours a day in that job and knows better than anyone the discomfort caused by repeating the same movements. Therefore, the work in assembly is gradually optimized, largely by the opinion of the operators themselves.
We can divide the assembly line into two parts, a line for chassis assembly and another assembly line for the bodywork. On the chassis assembly line, the engine and chassis components are usually mounted separately.
The different components of the body will be assembled on the bodywork assembly line. The doors will be removed first and then the workers will assemble the dashboard, seats and other vehicle components. For this, the operators use pneumatic guns for light elements, but for heavier elements such as the windshield, robot arms are installed to help the operators. They also have the help of small robot arms called weightless manipulators for some specific tasks, such as placing the dashboard or the seats. These weightless manipulators are manually controlled by the operator and are used to move heavy items with little physical effort.
Collaborative robots are also increasingly used, they are easier to program than a traditional robotic arm and can operate alongside people without risk.
In the previous steps we saw how the robots had no problems joining the metal parts that make up the self-supporting chassis, mainly by rivets or welding. But for the union of non-metallic elements such as plastics, robots have serious difficulties to join the pieces. Here the work of people is needed, not just robots.
This is due to three main factors:
Each car is individually configured according to customer requirements. Therefore, not all cars will be manufactured the same, since each vehicle will have different equipment. For this, all the material will be previously placed in each of the work stations, so that the operator has everything at hand and there is no loss of time. There are self-guided robots to move the material from the factory warehouse to the operator's work station.
Here is where MRP (Material requirements planning) comes into play. MRP is the planning of materials according to their productive needs. When a buyer acquires a vehicle, the factory records what materials are necessary to manufacture it. The production plant will have to perfectly coordinate the request for materials necessary for each of the cars to be manufactured, so that they arrive just in time and that they are available at the employee workstations, in the exact order of arrival.
At the same time that the body is being formed and assembled, there is another assembly line for the powertrain. Here the workers and robots assemble the steering, suspensions, complete transmission and engine block.
Then there is a phase called marriage, in which the bodywork is joined with the motor train. It's an informal term, but recognized globally in the world of automotive production. It's a critical moment, since there are many cables and connectors that must fit correctly during the union, so this operation is usually supported by human action.
Usually, the bodywork remains suspended and moves to the correct position, while the powertrain doesn't move. Self-controlled robots are increasingly being used to transport the powertrain under the body. Then the robot rises, as a pneumatic platform to be able to stay under the bodywork. The process is increasingly automated, but it will always have to be supervised by a person. Once the parts are attached, operators will finish the process by joining the remaining wiring, tubes, or components.
Automotive Lean Manufacturing
We're going to make a paragraph to mention Lean Manufacturing, we have previously mentioned some key words in the sector that are important to know. If we are students, we are interested in knowing it since it's part of the slang.
Coordination in an automotive factory is awesome, and new systems and solutions are added every day in order to optimize production. We work under the Lean Manufacturing methodology, which seeks to reduce waste and eliminate any process that doesn't add value to the final product. Lean focuses on eliminating waiting times, avoiding overproduction, simplifying procedures, eliminating unnecessary movements and displacements, reducing inventories and minimizing defects.
Lean Manufacturing is based on the Pull strategy instead of Push. That is, the Push strategy is based on manufacturing according to a demand that the company has previously forecast, so there is a risk of over-producing, or of falling short in the forecast and not being able to supply the demand due to a stock break. That is, initially a sales forecast is made and then those units are manufactured with the hope of selling them later.
The Pull system is just the opposite, it's based on production on demand. This is useful to request the exact amount of material at the correct time, making the car supply process much faster (JIT, Just in Time). In addition, this allows a wide variety of combinations to be offered, since the material will be ordered from the supplier according to demand, and the material will not have to be purchased in advance to keep it in warehouses, which leads to significant cost savings. In addition to cost savings, by allowing us to offer the customer greater customization, they will be willing to pay more for it. For this reason, Lean Manufacturing promotes the Pull system, making the Push system obsolete. In this way we manufacture as we sell and greatly reduce waste.
Despite this, the Pull system can fail if there are unexpected demand peaks, since the factory will not be ready to meet the demand due to the lack of enough productive means. Although the Pull system is not based on producing according to market estimates, it's always necessary to initially create a master production plan and estimate demand. In fact, we can say that companies really try to use the best of both systems, plan for demand as best as possible (as in the Push system) and then build on demand (as in the Pull system).
This sales prediction is necessary for several reasons, among others, to size the factory correctly, design the logistics system, plan finances, study the feasibility and to negotiate the costs of the parts with the suppliers. Mixed Pull-Push systems are also used. In these systems, the material is pre-manufactured according to a sales forecast, and is finished according to demand. For example, a manufacturer may decide to manufacture a certain number of bodies and then they will be painted according to the ones that are sold. They are estimated to be sold, but what color is unknown.
With Lean Manufacturing, car brands seek to obtain the highest quality through the absence of defects, saving production time and costs. This absence of defects is something really important in Lean Manufacturing, as well as enhancing people's creativity and continuous improvement, known as Kaizen. This would be a great summary of a much more complex philosophy.
In large automotive manufacturers there are specialists in optimizing the manufacturing process under the Lean Manufacturing philosophy. There are many interesting concepts in this work philosophy, one of them is Poka-Yoke, the implementation of error-proof systems. An example of poka-yoke is found in any USB cable, if we make a mistake it doesn't fit into the slot. Another example of poka-yoke are children's games in which wooden figures fit in a box, it's impossible to go wrong because the piece doesn't fit if it isn't in the right place.
Step 5: Final Quality Control
At the end of the process, workers carry out tests on each of the cars that come off the production line, to check that everything is correct. Unlike the tests carried out in development, these tests are unitary, so they only affect a specific car. A failure in quality control at this stage should not lead to any design change.
First, workers check that the specification list is correct, that is, that the new owner will receive exactly the same car that he requested. There is an internal code in the brands for each of the possible combinations, except for color and other aspects, since if not, the list of codes would be practically endless. Still, there are thousands of combinations for each model. It should be noted that the codes used in the factory are usually different from those used in dealerships and will always be different from those used in design. This is done so that fewer people have access to all the complete information of the vehicle. The dealer codes would always be the most accessible and public.
Afterwards, the cars go through a motor bench to check the mechanics and look for possible anomalies in its components: in the engine, in the steering or in the braking system. The workers also check that all the buttons and electronics work correctly: lights, air conditioning, windows, etc.
The workers check for possible noises that may arise from a failure in the assembly, and then all the cars go through a pressure wash to check the tightness of the car. The cars then go through a final visual inspection in an area fully illuminated with a cool light.
Later, outside the factory, there is a small closed track where a pilot will test certain parameters. With this, we see how all the effort of the design team, during years and years of work, in the end leaves through the door of a factory on the way to a dealership.
Once at the dealership, the car will be picked up by a customer who doesn't imagine the number of hours of work, joys and troubles behind the car he is going to drive.
So far the posts regarding the car manufacturing, next week we will begin with deliveries on the marketing of the vehicle.
The marketing will be divided into two posts, in the last one we will tell some secrets about how car companies really make money. The last post will be a general review, in a very brief way to remind a bit of everything we have seen.
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