CASE STUDY: the use of metal 3D printing in the high-speed rail sector

In recent years, 3D printing technology has been adopted by many different industries – from the automotive industry to the aerospace industry. The railway industry is also an area that is also a great beneficiary of additive production, however, it is not as loud in the context of 3D printing as it is in the case of other production sectors. The rail sector needs many high-quality parts. The safe and stable operation of the train is inextricably linked with the long-term guarantee of maintenance and functionality that must be ensured by the manufacturers of this type of equipment.

When parts need to be replaced but are not in stock, the rail carrier must contact the manufacturer for prompt delivery. At the moment, the management cost as well as the cost of purchasing spare parts will be relatively high. With the rapid development of additive manufacturing, this technology is being applied to assist in the operation and maintenance of trains, the supply of non-standard parts, and the replacement of damaged parts. Compared with traditional manufacturing manufacturing, 3D printing has faster response and is more cost effective.

High-speed railways may reach speeds of 350 km / h or more. Although it is relatively easy to drive, it is difficult to stop. The main difficulty is that during braking, each car of a train weighing more than 60 tons produces enormous inertia, which generates enormous kinetic energy, causing the brake discs to heat up as a result of friction during braking. Consequently, the brake pads and discs should not only withstand a high temperature of around 900 ° C, but also provide good performance. It must also be able to work normally even under difficult conditions such as rain, snow, sand or dust.

With the in-depth integration of metal 3D printing technology into the rail industry, metal 3D printer manufacturers are beginning to explore the use of metal 3D printing technology to improve brake pad and disc performance. Eplus3D, a leading Chinese manufacturer of 3D printers for metal additive sintering, enters the railroad market with its large-format 3D printers.

Earlier this year, Eplus3D collaborated with a local railway company to provide them with a customized metal 3D printing solution by printing several brake discs on the AM EP-M650 (quad-laser) large-format metal machine.

Until now, high-speed trains have used composite brakes. Due to its low mechanical strength and impact resistance, the composite brake disc used in early high-speed trains may have microcracks caused during operation. The material is also sensitive to water. When the train is running in the rainy season and in wet areas, moisture in the brake leads to less material friction and thus to reduced braking performance.

After data analysis and testing, 24CrNiMo was selected as the material for 3D printing. 24CrNiMo steel is one of the high-strength low-alloy steels with excellent mechanical properties. It has high tensile strength, good fracture toughness and thermal stability, and is widely used in the manufacture of brake discs for high-speed railways. The brake pads and discs are key components of the braking system of a high-speed train set. Printed parts of this material can effectively reduce its weight and improve the mechanical properties of the brake disc.

In the traditional manufacturing process, brake pads and brake discs are made by powder metallurgy. In the sintering process, due to the different shrinkage rates of each component in the brake disc, defects such as porosity and roughness are likely to develop, resulting in a low compactness of the brake disc, affecting its final mechanical and frictional properties.

After selecting the design and materials, a large-format metal 3d printer Quad Laser EP-M650 with a cubic capacity of 655 x 655 x 800 mm was selected for this project. Along with the high beam quality and detailed resolution, the molding accuracy and the mechanical properties of the brake disc can be guaranteed.

By using a 3D printer, Eplus3D is able to avoid material losses, shorten production time and product costs, giving you complete freedom in using the advantages of 3D printing in metal. In particular, the design of the surface hole, different from the traditional casting and forging production process, 3D printing can directly print it through the model design, and fully improve the heat dissipation of the brake disc.

The 3D printing technology directly prints the wear-resistant layer onto the steel back surface. The high-energy laser beam used in the 3D printing process can fully react and strongly compact the elements in the brake disc, thanks to which the obtained brake disc has better mechanical and frictional properties.

3D printing can optimize spare parts at a lower cost and in a shorter time to achieve a longer life cycle. In the past, the production of disposable custom parts has been very costly as it is almost impossible to produce only one part at a time, and manufacturers tend to produce a large number of parts at a time, wasting materials and property with the production cycle typically taking around two months. Now you can effectively save time with Eplus3D Metal Additive Manufacturing solutions.

By using 3D printing technology to produce spare parts, trains can start and operate faster, and the stock of spare parts, which leads to material losses, can be reduced. With the development of science and technology, it can be expected that 3D printing will play an increasingly important role in the railway field.

Traditional production of brake discs mostly adopts the “reduced material” manufacturing method combined with casting and forging, resulting in a cumbersome process, low material utilization and a long production cycle.

Source: Eplus3D press materials
Photos: Elpus3D
Cover photo: www.pixabay.com