Machined plastic parts have numerous applications throughout vehicles. From the manufacturing of interior door panels to exterior bumpers and housing molding, injection molding is the best alternative for traditional materials without compromising durability.
Plastic injection molding supports faster production cycle time, material versatility, and precise control over material distribution. Further in this article, we will explore the pivotal role of plastic injection molding in advancing automotive engineering.
Compression Molding for Door Panels
In the compression molding manufacturing process of door panels and their machined plastic parts, plastic raw material is often used in the form of pellets or granules. These Pallets are inserted into the mold cavity at certain pressure and temperature values depending on the material used.
The plastic material melts and takes a fluid-like shape, with a certain level of viscosity, so that it precisely fills into the mold cavity. In this stage, pressure is simultaneously increased a little bit so that the material is compressed and filled in the mold without any cavity. Once the mold is filled, it is left for the solidification process.
Compression molding supports a diverse range of materials selection for machined plastic parts. Mostly thermosetting polymers or thermoplastic are used as per the applications. Thermoplastics such as polypropylene and ABS (acrylonitrile butadiene styrene) have excellent recyclability. They are easy to process, and most importantly, they are cost-effective.
On the other hand, thermosetting polymers have superior heat resistance and mechanical properties. The temperature and pressure during the manufacturing process are set according to the material chosen. Thermoplastic requires temperature ranges from 300°F to 600°F (150°C to 315°C) and pressures between 1000 psi to 5000 psi. On the other hand, thermosetting polymers require 250°F to 400°F (120°C to 200°C) and pressures ranging from 1000 psi to 2000 psi.
This compression molding technique is most favorable in door panel manufacturing. The main reason is the ability of compression molding to produce components with uniform thickness, intricate designs, and high strength. Door panels feature mounting points, door handles, switches, and speakers that are direct to the panel. This will ultimately reduce various assembly steps.
Thermoforming For Automobile Exterior Parts
Thermoforming is the cheapest and most effective way of manufacturing automobile exterior components such as mirror housings. In this manufacturing technique, thermoplastic sheets are heated up to a certain level of temperature, which is around 300°F to 400°F. At this temperature, thermoforming sheets are available and ready to deform according to mole shape.
The heating procedure can be done through infrared heaters, radiant heaters, or hot air ovens. Once the sheet reaches above the glass transition temperature, it is transferred to the mold cavity.
The mold used in thermoforming manufacturing is another male or female mold depending upon the desired product to be created. The heated sheets are placed on the mold and pressure is created through vacuum pressure or through applying mechanical forces. The sheets take the shape of the mold and create the desired part geometry.
After the creation of the parts, the mold is said to be cooled through cooling fans or a water suppressor. If the mold is not cooled properly then it may compromise the overall quality and functionality of the parts. Proper cooling is essential to ensure consistent part quality, dimensional stability and prolonged mold durability.
Thermoforming is also widely used in automotive prototyping, allowing manufacturers to create and test new designs for automobile exterior components quickly. This technique enables the efficient evaluation and refinement of parts before moving to full-scale production, ensuring the highest quality and performance standards in the final products.
Rotational Molding for Fuel Tanks
Rotational molding is used where we have to create hollow plastic structures like plastic fuel tanks. In the manufacturing of fuel tanks, a powdered resin, which is mostly polyethylene, is placed in the mold cavity. Polyethylene Is chosen due to its flexibility, reliability, and significant resistance to chemical reactions. After that, the mold is heated up to 200 degrees and rotated around multiple axes. The purpose of the rotation is for the melted resigned to be evenly distributed throughout the mold structure.
This rotation process is continued throughout the heating phase to maintain uniformity and prevent any uneven distribution of the molten resin. Uneven filling leads affect the strength and cause high-stress points in structures. Once the resin is cooled and solidified, the mold is opened, and a desired fuel tank shape is perfectly created. Fuel tanks manufactured through traditional machining may involve a lot of welding and joining points. For that reason, the chance of leakage is always there.
However, rotational molding not only improves the structural integrity but also eliminates the need for additional welding or joining processes. Finally, the finished product is set to be machined through multi-axis CNC machining for a smooth surface finish.
Vacuum Bag Molding for Carbon Fiber Spoilers
In this technique, carbon fiber materials are spread on the mold cavity, which is mostly made from stainless steel. Once the layup is completed, a vacuum bag is used to seal the perimeter of the mold. A vacuum pump is used to evacuate all the air from the mold. This will allow the creation of appropriate pressure, which compresses the layup and facilitates adhesion between layers of carbon fibers. Which results in superior strength-to-weight ratios and aerodynamic performance.
After that, the vacuum bag is removed and the mold is set for the curing process. The curing further enhances its strength and gels the layers of carbon fiber. Finally, the mold is opened, and additional finishing processes like sanding and painting the coat are done to enhance its durability and strength further.
One of the most prominent factors in choosing this technique is that spoilers manufactured through vacuum bag molding can be refurbished or repaired by assessing the damages, such as cracks and delamination in the product. After that, sanding down affected areas and reapplying the layers of carbon fiber restore its structural integrity. If the cracks are dee, then advanced repair methods such as resin infusion or vacuum-assisted resin transfer molding (VARTM) may be applied.
Conclusion
Summing things up, plastic molding parts are revolutionizing the automobile industry. These machined plastic parts offer durable and intricately designed components. These components are vital not only for vehicle performance and aesthetics but also But they are also enhancing the structural stability, strength, and cost-effectiveness of the parts.
