In the fascinating world of the automotive industry, where performance meets elegance, the production of alloy wheels is a crucial chapter. This sophisticated process, which combines engineering and design, requires meticulous attention at every stage. In the following sections, we will explore the facets of this process, from the choice of materials to finishing and painting, which lend durability and beauty to these important car accessories.
Selection of Materials
Alloy wheels, once installed, will be subjected to high stresses. Consequently, choosing the right materials for their construction is the key step in guaranteeing the quality of the final product's performance.
An alloy wheel, as the name suggests, is composed of an alloy of various metals. The choice and proportion of these materials is based on the experience accumulated over time by the manufacturing company, and may change over time according to market needs and the latest technological innovations.
Of all metals, aluminium is the most widely used in most alloy wheels on the market today. Its popularity is due to its lightness and ease of processing. This element is never used pure, but mixed with other metals to improve its mechanical properties.
For high-end or competition alloy wheels, magnesium alloys are often used. By using this metal, it is possible to obtain rims that are just as resistant to shocks and vibrations, but up to 35 per cent lighter than their aluminium counterparts.
Fusion
Once the materials have been selected, we move on to the casting process, the aim of which is to create the metal alloy that will be used to produce the rims.
Melting takes place in a special melting furnace, at temperatures of up to 1000 degrees Celsius. The manufacturers follow this stage very carefully, carefully monitoring the composition of the alloy by means of optical emission spectral analysis. This control makes it possible to understand the exact quantities of various molten elements within the alloy.
If everything is up to standard, the metal alloy is cast into the rim mould. Here, the material is cooled and pressed to completely fill the mould.
Forging
Forging is an alternative process to casting that is adopted by manufacturers aiming to offer high-end products. It ensures a uniform distribution of the rim's physical characteristics, avoiding inhomogeneities between the various zones. A forged rim has significant improvements in terms of response to stresses and impacts, and consequently also shows a reduced risk of deformation. Another advantage is greater strength for the same material used. These characteristics allow forged rims to be thin and light.
Forging costs are higher than casting costs. This is both because it is a laborious process and because of the high material waste during production.
The forging process begins with the melting of the material, which is then subjected to very high pressure inside a round disc. Subsequently, the disc is moulded into a rim through a series of compressions and heating until it reaches the shape envisaged by the specific model.
Finishing
The finishing stage is essential to ensure not only the functionality but also the aesthetics of the alloy wheel. This stage includes various treatments, including:
- rectification, i.e. the correction of any asymmetries or imperfections
- smudge removal
- The creation of the central hole
- Anodising, which makes the rim more resistant to corrosion and improves its aesthetic impact
These operations are not easily automated, but require the experience and expertise of skilled workers.
After finishing, the dust is removed to ensure uniformity and cleanliness of the rim surface.
The production process continues with the last stage.
Painting
The painting of alloy wheels, contrary to what one might believe, is a complex and delicate activity. In order to achieve an excellent result, it is essential to keep all stages of the process under control.
The most commonly used technique is powder coating. The method involves applying a fine coloured powder to the surface of the rims, followed by heating in a paint oven. With exposure to the heat, the powder liquefies, evenly covering the rim.
A key aspect of the coating process is the correct handling of high temperatures. Accurate monitoring and control are crucial to ensure a durable and homogenous coating. Sub-optimal temperatures can cause defects and unevenness in the coating, compromising both the aesthetics and functionality of the rim.
In this context, Tecnosoft has introduced an innovative solution to ensure proper monitoring of high temperatures during painting.
Like many of our products, it all started with a very specific request from a customer.
Temperature monitoring during the painting of alloy wheels
A well-known car wheel manufacturing company was faced with a demanding challenge. Its goal was to monitor a painting process to ensure that each rim was not only aesthetically impeccable, but also exceptionally durable.
Painting in industrial ovens requires very precise temperatures and times, so constant monitoring is necessary.
This is the temperature cycle adopted by the company to paint its alloy wheels:
- The first phase takes place in a first oven heated to 250°C, where the circles remain for 15 minutes.
- This is followed by interstage, a pause where the temperature is lowered to 25°C for 30 minutes.
- The circle passes to the second oven heated to 250°C. This time for a longer period, 45 minutes.
- A second 40-minute interstage at 100°C followed by a third 30-minute interstage at 25-30°C.
- The rim is then passed into a third oven at 250°C for 35 minutes.
- Finally, we move on to the cooling phase.
To monitor temperature, it was therefore necessary to find measuring instruments that could withstand very high temperatures for relatively long periods of time. A technological challenge that we tackled step by step.
Phase 1: The Preliminary Study
We aimed to create a monitoring system that could withstand the heat and provide accurate temperature data at various points on the rim during painting.
Therefore, the feasibility study focused on verifying the performance of the TC-Log 8 S USB thermocouple system under the high temperatures typical of paint ovens.
At this stage, we checked the available thermal protection for thermocouples, but found that they were not suitable for the entire painting process, as they could only withstand up to half of the heating process.
It was therefore necessary to find a custom solution suitable for the purpose.
Step 2: Creating Solutions
To overcome the limitation, we modified the outer metal housing of the existing thermal protection, replacing the inner material with a stronger compound.
In addition, to prevent the dispersion of dust that could interfere with the painting, we covered the new material with a suitable coating.
To increase thermal insulation and delay heat penetration as much as possible, we have also added two small metal tanks containing water with a vent valve.
Our prototype had thus come to light!
Phase 3: The Final Test
Once the prototype was available, we subjected it to the same thermal cycle requested by the customer.
The result was very positive: in fact, the thermal test was brilliantly passed. The instrument was able to monitor temperatures of 250° for an extended time while maintaining a largely satisfactory safety margin.
Challenges overcome:
In the development of our thermocouple system for monitoring temperatures in painting processes, we overcame two challenges:
- The first and most challenging was the complete redesign of the thermal protection. This was not a simple overhaul, but the creation of a completely new solution that took into account the specific requirements of the high-temperature painting process.
- In parallel, we redesigned the electronics housing. This step was crucial to ensure that the system would not only withstand the high temperatures, but also remain functional and reliable under these extreme conditions. We therefore successfully tested a new insulation to offer superior thermal protection without compromising the functionality of the system.
The next challenge
For the near future we are studying an external box that can contain the thermal protection of the data logger.
The aim is to make the system usable in 100 per cent of customer projects, an ambitious goal that will require further innovation and experimentation.
These overcome and future challenges demonstrate our ongoing commitment to providing tailor-made solutions that effectively and accurately meet the specific needs of our customers.
We have been expanding our know-how for 35 years, consolidating our position as a leader in the field of monitoring in complex industrial processes.
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