China: Microcasting Technology in Metal 3D Printing to Produce Large Pump Propeller Blades

An industrialization team from China’s Huazhong University of Science and Technology, led by Professor Zhang Haiou, is using a relatively new technology with 3D printing to produce heavy, industrial parts like large pump propeller blades. After a request for a substantial order of large jet blades for a shipbuilding unit, the University team began using micro-casting and forging in metal 3D printing for the manufacturing of large parts.

Necessary in ship navigation, pump jet propellers can be made significantly faster with micro-casting and forging, a technological evolution from material manufacturing to subtractive manufacturing to additive manufacturing. Mechanical properties are improved, along with accuracy—elevated from 0.5mm to 0.1mm, with little to no defects like pores or cracks. Haiou explained that without forging, metal fatigue resistance may be inferior, performance of parts may not be sufficient, and defects can occur due to lack of fusion, stability, and porosity.

Attempting to improve metal 3D printing for large parts with complex geometries, Haiou and his team moved forward to disrupt industrial production with their novel micro-casting and forging technique. News of Haiou’s system, dubbed the “Micro Forging & Casting Sync Composite Device”, first emerged in 2016, when it was revealed that the technology was being used to create titanium joints for China’s jet fighters. The process consists of:

• Metal deposition, using metal wire
• Continuous cold forging and rolling
• Cooling down

“The micro-casting and forging technology can carry out the above steps simultaneously,” explained Zhang Haiou. “When the printing is completed, the casting and forging are completed at the same time, and the deposition efficiency is three times that of the former.

“We reduced the action that originally required 80,000 tons of force to 1/80,000, that is, less than one ton of force, and at the same time, one equipment completed the work that many large equipment used to complete. The power of the equipment is only 50 kilowatts, and the energy consumption per unit time is two-thousandths of that of a giant press. It is green and efficient.”

In 2016, the system made parts up to 5.5 × 4.2 × 1.5 m in size, with a surface roughness of 0.02 mm, and could use eight types of materials, including titanium and steel. The goal with the technology is to magnify the advantages of 3D printing and additive manufacturing processes, especially for industrial applications in building aircraft, engines, turbines, parts for railways, and nuclear power plants.

“Taking aircraft manufacturing as an example, the number of body structure parts of a large passenger aircraft is currently tens of thousands. If 3D printing technology can be used to produce large, complex, integral, high-performance, and lightweight components in the future, then number of body structure parts for a large passenger aircraft may only be hundreds.

“Not only that, in the future, using metal 3D printing technology and simulation technology will reduce the development and production cycle of the aircraft by an order of magnitude,” said Zhang Haiou.

This is not the only process to combine 3D printing and forging. Arconic developed a technique called Ampliforge that combines directed energy deposition with forging for the same reasons, but it lacks the built-in milling capabilities.

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