“How is the quality of your product?” This is one of the most important questions for customers when it comes to car aftermarket parts.
For us manufacturers, this question is easy to answer, but it’s not always easy to give a good answer. This is because different customers have different priorities.
For metal exterior parts, proper fit on the car is the most basic requirement.
But achieving this doesn’t necessarily mean that the quality of the product is good because there are other factors that we need to consider.
For example, the materials used for metal OEM-style parts and their thickness are the same as the genuine parts?
For another example, a certain exterior part, such as a car door, hood, etc., is a collection of many small parts.
Whether the welding between these small parts is firm and whether the position is the same as the original auto part are also parts of determining the quality.
For non-professionals, it can be difficult to understand these situations clearly, and many people also do not know how aftermarket parts are produced.
So in this article, I will roughly introduce the production process of aftermarket parts.
This will involve many professional terms and knowledge, but I will try to explain them in simple and understandable language.
Due to the limitations of space, some knowledge points may not be explained in depth.
If you have any questions or want to learn more about a certain aspect, feel free to leave a message below for me.
I will continue to write other articles to expand on this topic. (curious about me? click to know who I am).
Hopefully, this article can help you feel more confident and at ease when buying automotive aftermarket parts, rather than risking your wallet.
In general, producing a qualified aftermarket part requires three steps.
The first step is data design, followed by die production, and the last one is product manufacturing.
Each step contains many detailed and important tasks.
They are all interconnected and closely related.
If one link goes wrong, the subsequent production will be affected, and we will have to spend a lot of time, effort, and money to fix the error.
Therefore, for difficult product development, like the popular use of lightweight aluminum alloy materials on electric car bodies, such as the all-aluminum doors on Tesla Model 3, without a certain technical foundation, not many people are willing to try and invest in it.
Now Let’s break it down step by step.
Date design can be basically divided into two steps. First is 3D scanning, then UG modeling.
When we want to develop a certain exterior part for a Tesla electric vehicle, such as a car door, we need to purchase an original or a used car door as a sample.
It must be in perfect condition, without any deformation.
Otherwise, it will affect the quality of the aftermarket part and cannot match the original car’s gaps or lines.
Now that our samples are ready, let’s collect the data. Yes, you guessed it right, we’ll be using 3D scanning.
However, during this process, one thing needs to be emphasized.
Generally, a complete exterior part, whether it be a car door, a fender, or a hood, consists of many small parts.
So, we need to disassemble these small parts one by one and scan them individually.
If you are new to 3D scanning, you must be wondering what is 3D scanning and how it works.
In automotive design, 3D scanning is used to capture the shape and dimensions of a car part in a digital format.
This process involves using a device called a 3D scanner, which emits a beam of light that bounces off the object and is detected by the scanner.
By scanning the object from multiple angles, the scanner can create a three-dimensional digital model of the object.
Once the 3D scan is complete, the resulting digital model will be imported into computer-aided design (CAD) software – Unigraphics (click to know more at Siemens website).
It is now known as Siemens NX and is commonly used in the aerospace, automotive, and industrial design industries.
Our designers use the digital model to modify the part, test its fit and function in a virtual environment, and optimize it for manufacturing.
In UG, data processing is divided into 2 sections: one is product design, and the other is die design.
Based on the 3D scanning file, the process is to create a 3D model of an auto part in UG.
This involves defining the shape and details of the part, as well as any features that may be required such as holes, flanges, or tabs.
when the design is complete, we may perform a simulation analysis to ensure the part will function properly and meet any required performance specifications.
Once the part design is complete, the next step is to create a die or tooling that can be used to manufacture the auto component.
According to the part’s shape and dimensions, our engineer must ensure that the die design accounts for the material properties, the stamping process, and the required tolerances.
At this stage, we also determine how to manufacture the product, including the processing details or techniques involved, often referred to as the manufacturing process or craftsmanship.
The data processing in UG is critical because the accuracy and precision of the part’s dimensions will directly impact the final product’s quality.
Alright, now that we have completed the component data in UG, we can move forward with mold production using this data.
Before diving into the detailed explanation, there is a specific topic we need to address separately: the classification of sheet metal dies.
According to the methods of mold fabrication, sheet metal dies can be divided into two main types: casting dies and steel plate dies.
Steel Plate Dies
Generally, if the height difference of a component is less than 70mm, we would choose a steel plate die.
As the name suggests, steel plate dies are fabricated using steel plates.
This type of die involves cutting, shaping, and assembling steel plates to create the desired mold cavity.
CNC mills are often applied to perform the milling operation, removing materials from a workpiece to form complex shapes and features with high precision.
Sometimes other polishing machines that are hand-held will be needed to further polish and finish the metal surface.
So steel plate dies are commonly used for simpler part geometries, and when cost-effectiveness and faster production turnaround are important considerations.
As you may have guessed, casting dies are suitable for manufacturing more complex and bigger automotive parts, especially those with a height difference exceeding 70mm.
Therefore, the production process of casting molds is more intricate.
There are many types of casting dies that serve various functions, such as forming dies, flanging dies, trimming dies, punching dies, stretching dies, etc.
Based on their literal meanings, you can roughly guess the purpose of each die.
But the way to manufacture those dies are similar.
We can simplify it into three steps: EPS shaping, sand casting, and CNC precision machining.
In contrast to steel plate dies, for casting molds, we employ a CNC cutting machine to fabricate a trimmed Expandable Polystyrene (EPS) based on the designed data at first.
It’s to make an EPS foam die model.
The machine will carve out most of the contours and details required for the die.
Hence, it is essential to manually refine the details of the foam mold to ensure optimal performance of the mold.
Moreover, there are instances where the data may not align with the practical operation.
Relying on ALSETTE’s 20+ years of die development experience, here we will also make necessary modifications.
Once the model is cast into a metal sample through sand casting, making further modifications would require significant human and material resources, and it could even render the die unusable.
After the EPS model is completed, it is transported to the foundry where it undergoes sand casting to transform into a genuine sheet metal die.
Sand casting is widely used in the automotive parts industry.
At first, the sand coating will be painted to the surface of a foam mold.
The black sealer paint will help separate the mold and the sand, as well as improve the quality of the castings.
Then the sand casting starts.
It involves pouring molten metal into a sand mold, which is formed by packing specially prepared sand around the foam pattern.
The molten metal cools and solidifies inside the mold, taking its shape.
Once the metal has hardened, the sand mold is broken apart, revealing the solidified metal object.
The metal die is very heavy.
Unlike an EPS model that can be easily moved by individuals alone, it requires machinery like forklifts or cranes to lift and transport.
CNC Precision Machining
The surface of the die is quite rough after sand casting, hence CNC machining is for details refining.
Whenever using a computer-operated machine, we need to make necessary modifications to the UG data and convert it into a machine-readable format using certain software.
The machine’s computer control system reads the programmed instructions and directs the movement of the cutting tool.
The tool rotates at high speed to perform various cutting, drilling, and shaping operations.
After machine milling, manual polishing is usually required.
This is because the paths left by the machine knife on the die surface can be relatively coarse.
Manual polishing will make the surface smoother, enabling the production of qualified products through stamping.
Moreover, if the die surface is not sufficiently smooth, some metal components can be difficult to stamp or stretch.
Just think about car exterior parts produced by automobile manufacturers, their die surfaces are like mirrors, reflecting your face.
A complete die consists of an upper die and a lower die.
The upper die, also known as the top die, is designed to have a protruding shape.
On the other hand, the lower die, also referred to as the bottom die, has a recessed shape.
These two dies are assembled together to press our desired product.
The requirements for surface smoothness are much higher for the upper die compared to the lower die.
Therefore, we use appropriate grinding wheels and manually polish the whole top die to achieve a smooth and flat surface.
It requires a significant amount of time and can only be accomplished by skilled workers to attain the level of precision and quality we demand.
While for the bottom die, it is typically polished using a polishing machine.
After this long wait, we are entering the much-anticipated phase of product manufacturing!
This step also greatly tests the professional skills of our technicians.
To give you a clearer understanding of how sheet metal parts are produced, let’s break down this stage further: trial molding, assembly, mass production, and electrophoretic coating.
Trial molding, as the term implies, is the process of verifying whether the die we have created can successfully stamp out qualified products on certain mechanical devices.
The machines we commonly use are punch presses and hydraulic presses.
A punch press, or a mechanical press is smaller than a hydraulic press.
If a part is small and has limited deformation and extension requirements, a mechanical press is usually applied to produce it.
Most of steel plate dies are suitable for punch presses.
Larger-sized products or that need greater deformation and extension, the hydraulic press is here to help.
All casting dies work at hydraulic presses.
Auto exterior parts such as hoods and doors have higher surface quality demand because they are located on the outer part of the vehicle.
If their surfaces are rough or have ripples, it can negatively impact the consumer’s purchasing experience.
Additionally, repair shops would need to invest a significant amount of time and effort to fix such components, for example, by polishing or applying putty to smooth out these imperfections.
Therefore, this is one of the key concerns during the trial phase.
Before starting, based on the material of OEM parts, it is a must to prepare some sheet metals with proper thickness and size: iron alloy, aluminum alloy, or stainless steel.
The choice of materials is also crucial in the manufacturing process, as even materials with the same thickness can have different tensile properties.
Therefore, when producing replacement parts for Tesla, we generally use the same materials as the original manufacturer. (click to check the materials that Tesla uses.)
If a particular material is difficult to source in the market, we strive to find alternative materials that can achieve the same performance as OEM products.
The produced piece should be free from wrinkles; and for products with larger bending radii, they should not have any cracks during stretching.
When these issues occur, further modifications to the mold are necessary, such as adjusting the size of the corner radius appropriately or achieving a smoother surface finish on the die.
To achieve such results, a certain amount of sheet metals will be inevitably wasted during the trial and adjustment.
Having been deeply engaged in the die industry for over 20 years, most of the time, our trial section goes smoothly, requiring a small number of sheet metals to produce the desired product.
However, there are times when luck is not on our side, and significant issues arise, necessitating rework and repairs on the die, which can be quite troublesome.
Our technical staff also dreads such situations as it tests their patience.
Therefore, whenever such problems occur, we investigate the causes and provide feedback to the individuals responsible for the specific stage, such as the data designer or the personnel involved in EPS shaping.
This helps them avoid making similar mistakes in future and contributes to improving our production efficiency.
In the section “3D Scanning”, we mentioned that a complete exterior part is assembled from multiple smaller components.
Since we have stamped these components, we are going to finish them and then assemble them into the end product.
By now, you may understand that producing aftermarket parts is essentially deconstructing the OEM parts.
It’s like playing with LEGO, where you are given a model as a reference and then you build the blocks based on that model.
Robotic Laser Cutting
In order to obtain the desired parts, some sheet metal needs to have its excess edges and corners cut off after being pressed on the hydraulic press.
This is where we make use of the robotic laser-cutting machine.
It is a precision cutting tool that utilizes a high-powered laser beam to accurately cut through metal sheets.
And it combines the capabilities of a robotic arm and a laser cutting system to achieve efficient and precise cutting operations.
The robotic arm is equipped with advanced sensors and actuators to maneuver the laser cutting head to follow complex cutting paths, enabling intricate and detailed cuts on the workpiece.
You may have doubts that how to ensure the stable placement of the workpiece on the workbench for the successful completion of tasks.
This is a very good question.
In fact, not only for laser cutting but also for the subsequent assembly of products, there is a need for proper fixation.
So, how do we solve this in our factory?
As different parts come in various shapes and sizes, our skilled technicians will weld and assemble dedicated metal frames for each part to securely support and hold them in place.
While they are both metal frameworks, the laser cutting racks, and the assembly racks have their own distinct characteristics.
You can even notice the differences at a glance.
The metal rack used for laser cutting is typically coated with cured putty on several support points, which serves to secure the component placed on it.
The putty in its initial state is soft, after adding an appropriate curing agent, we apply a sufficient amount of putty to some frame points.
Then, we place the part on top, allowing the putty to conform to the shape of each specific component and waiting for the putty hardens.
Sometimes, we also weld a few fixtures to further secure the products that need to be cut.
Assembly frames do not use putty.
There’re only various fixtures and clamping devices on them.
Unlike a laser cutting frame, which can only hold a single component, the assembly rack, as the name suggests, is used to combine multiple components together.
Therefore, the assembly stand also serves the purpose of positioning, letting each part stays in its correct position.
How to position?
There’re many holes of different sizes and positions in metal auto parts like doors and engine hoods.
We often choose the holes designed for hinge connections to fix during assembly.
Some custom-made, elongated bolts will pass through these holes to fasten those parts to the metal rack.
Several clamping tools around the assembly frame will provide more fixed force.
Now the components are put in the right place, we can proceed with the welding process to join them.
Based on the characteristics of the materials, such as ferrous alloys and aluminum alloys, we utilize different welding machines.
Moreover, even for the same type of material, if we need to weld components with different shapes and specifications, we may require different welding machines.
The choice of welding machine depends on factors such as the geometry of the components, the thickness of the material, and the desired welding technique.
In order to produce metal body parts for Tesla vehicles, we have purchased welding equipment such as spot welding machines, handheld laser welders, and hanging spot welding machines.
Among them, spot welding machines are the most commonly used, which are stationary and not movable.
They are typically used to join two or more flat sheet metal parts together.
Unlike the conventional spot welding machines that create weld spots, handheld laser welders have a wider range of applications.
They are particularly suitable for welding long seams, effectively combining the edges of two components.
You’re right. We can also use them to form individual weld spots.
The primary purpose of these welded joints is to provide alignment, serving as positioning points.
You’ve probably already guessed the most important feature of the hanging spot welding machine!
That’s right, it is suspended and can move in a three-dimensional, 360-degree manner.
So, when the contact surface around two or more components has some irregular shapes, the stationary spot welding machine is unable to handle it.
This is where the hanging spot welding machine comes into play and shows its capabilities.
Other Assembly Methods
In addition to welding, we also adopt other build-up methods, such as edge folding, riveting, and bolted connections.
Edge folding involves bending or folding the edge of one piece of material to join it with another, creating a strong connection.
When performing edge folding, we often apply an appropriate amount of adhesive on the inner side of the edge to reinforce it.
Due to cost considerations, for low-demand goods, we manually edge-form them and use a press machine on the flanging die to refine the edges.
Conversely, when needing produce on a large scale, we will develop edge-forming tools and automate the edge-folding process to enhance production efficiency.
Riveting and bolting require securing two components together using rivets or bolts and nuts.
Riveting is a permanent joining method, and if the two elements need to be separated, the rivets have to be forcefully destroyed.
However, bolted connections allow for disassembly and reassembly, providing the flexibility to dismantle and reattach the components as needed.
At this point, all the component assemblies have been completed.
Haha, please hold on to your speculation for now. We cannot start mass production yet because we still have one very, very important step to complete.
Since we are manufacturing aftermarket parts for Tesla Model 3, Y, S, and X, it is crucial that these parts fit the original vehicles properly before they can be released for sale.
Therefore, actual on-vehicle testing and adjustment is an essential step that cannot be skipped.
Let’s first address the issue of obtaining a vehicle.
There are several methods to consider.
The first approach is to purchase a vehicle that meets our requirements.
This option offers convenience as we can have immediate access to it whenever needed.
For example, we purchased a Model Y to test our Y trunk lids, doors, etc.
However, not all companies have the necessary budget for this.
The second option is to rent a vehicle.
However, there may be limitations as not all car rental companies offer the specific vehicles we require.
The third option is to borrow someone else’s vehicle, but not everyone is willing to lend their car.
After all, during the installation process, we need to remove the original parts and install our own.
Unless we have meticulous professionals handling the task, there is a risk of causing damage to the vehicle.
With the vehicle in hand, we can now proceed to the installation phase.
Our objective is clear: to achieve seamless integration with the original vehicle.
This can be further divided into two main aspects.
Firstly, we need to ensure consistent and appropriate gap sizes between our components and the vehicle.
Secondly, we must ensure that our components align smoothly with the vehicle’s contours, creating a harmonious and cohesive appearance.
Here, we cannot overlook the significance of hinges.
They serve as the bridge between the metal exterior parts and the vehicle body, allowing these parts to move in specific directions and angles while maintaining a secure attachment to the car.
Therefore, hinges play a crucial role during our testing and installation of replacement parts.
By adjusting the hinges, we can position the parts correctly.
Some hinges have limited adjustability, such as the ones on the doors of Tesla Model 3.
In such cases, the requirements for producing these components are quite high and they need to align closely with the OEM parts.
Otherwise, the components won’t fit seamlessly onto the vehicle.
On the other hand, parts with hinges that offer more adjustability are relatively easier to work with.
If there are deviations after installation, we can use hinge adjustments to ensure perfect integration between the unit and the auto.
Generally, it takes two to three installation tests.
If everything goes smoothly, some simple products can be completed in one attempt.
In case of any issues during the installation process, such as uneven gaps or unsmooth lines, we do markings and then make corresponding modifications to the die or assembly racks.
After resolving all the issues, we can proceed with mass production.
However, for large products like trunk lids and fenders, we will start with a limited quantity in the first batch.
This approach allows us to address any potential installation problems based on customer feedback and make necessary adjustments accordingly.
Once the initial batch is sold without any quality matters, we can confidently continue with large-scale production.
Finally, the production of our metal exterior parts is nearing completion!
For iron products that are prone to rust, we need to apply an anti-rust treatment called electrocoating or electrophoretic deposition (E-coating).
Some aluminum products also require a primer coat, such as the doors of the Tesla Model 3.
This is because, in the final assembly of the vehicle, the doors will receive an additional layer of paint in different colors like red, black, blue, and so on.
If the genuine parts are black in color, we will directly electro-coat our products in black to reduce the workload for the repair shop.
The chassis components and some internal aluminum parts of Model 3 and Model Y are left unpainted, retaining the original color of the aluminum alloy, which is close to a silver color.
This may be a cost-saving measure implemented by Elon Musk.
Besides providing excellent corrosion resistance, Electrocoating can achieve a smooth and uniform finish, enhancing the visual appearance of the coated parts.
To make our parts more aesthetically pleasing, it is important to clean or remove impurities from the surface of the components prior to electrocoating.
This includes wiping or blowing off any debris such as metal shavings or oil stains that may be present from the manufacturing process.
Secondly, during the electrocoating process, slowing down the production line allows for a thicker coating and a smoother surface finish on the products.
You may have noticed that the colors of the products in the images on our website appear different.
This can be influenced by various factors, such as the lighting conditions during photography and the angles at which the photos were taken.
Additionally, slight differences in color can occur between different production batches of electrophoretic coatings.
Sometimes the coating facility may adjust the color of their coating line based on customer requirements.
Furthermore, the baking process that follows the electrophoretic coating, which is for drying the paint, can also impact the displayed color of the products.
The OEM Tesla Model 3 & Y metal parts have a slightly more yellowish color, which is primarily due to the higher temperature during the baking process.
Here, you don’t have to worry too much.
The variations in the color of the electrocoating won’t affect the later installation and painting process.
After the electrocoating primer, the repair shop will apply 2 to 3 more layers of paint to achieve the final roadworthy finish.
On the contrary, what we should pay more attention to is the quality of the electrocoating paint.
Poor adhesion of the primer can affect the subsequent layers of paint, reducing the lifespan of the paint surface.
Before packing, we conduct a careful inspection of the goods to ensure their integrity and quality.
Good packaging acts as a guardian for the product.
For larger products, it is necessary to design suitable corrugated cardboard boxes.
We will also protect sharp corners with thick and appropriate foam padding.
Due to the significantly heavier weight of iron compared to aluminum, the trunk lids for Model Y, being made of iron and large in size, can be quite difficult to handle for an individual.
So in addition to packaging it securely in cardboard boxes, we also add an extra layer of wooden frame to ensure its safety and minimize the risk of damage during transit.
Certainly, we also provide wooden frames for other products as per the customers’ requirements and for those that require additional protection.
For smaller items such as the fender brackets for Model 3, we provide customized transparent plastic bags with a suitable thickness for packaging.
If our customers prefer cardboard boxes, we can also customize them accordingly.
Located in Jiepai, Danyang, our factory benefits from a well-developed logistics system that provides direct transportation to all over China, including important ports. (click to know more about Jiepai town)
Without multiple transfers, this significantly reduces the risk of unnecessary damage to the merchandise during shipping.
The journey of manufacturing automotive metal exterior parts concludes here.
You’ve done a fantastic job reading through this lengthy article of over 4000 words!
As the author, Lina, I feel honored to have had this opportunity to showcase our product development and production process.
It’s the sweet fruit of over 20 years of dedication to the die industry.
If this article brings you a little inspiration and assistance, we’ll be truly delighted!
We welcome your feedback and suggestions. (or contact us now for help!)
Have a good time:)