Can metal 3D printing be used for the remanufacturing of industrial equipment parts?

1. A technological breakthrough: a jump from "repair" to "rebirth"
The main benefit of metal 3D printing is that it can fix complex geometric designs with great accuracy. For example, standard remanufacturing of aircraft engine turbine blades needs manual welding to fix damage to the thermal barrier layer. This procedure can easily cause thermal stress concentration, and the repaired blade can only last 60% as long as the original design. Platinum Technology Co., Ltd. uses selective laser melting (SLM) technology to successfully print and fix the leading edge film cooling holes of turbine blades by changing the laser intensity and scanning path. The repaired blades went through 2000 thermal cycles at a high temperature of 1150 ℃ without any cracks or peeling of the coating. Compared to previous procedures, the service life was 40% longer, and the repair cycle was cut from 30 days to 72 hours.
To fix the problem of fatigue cracks in essential parts of high-speed rail bogies, CRRC has come up with a remanufacturing technology based on electron beam melting (EBM). A gradient strength structure is printed at the crack site by getting an accurate digital model of the crack area through 3D scanning and combining it with topology optimisation design. This gives the repair area a fatigue strength of 92% of the base material, while traditional welding repair can only recover 75%. This method has been used to fix CR400AF high-speed train bogies in batches, cutting the cost of fixing one by 65% and saving more than 200 million yuan a year on maintenance.
2. New materials: going from "Single" to "Multiple"
The capacity of metal 3D printing to work with different materials is a big reason why it can be used in remanufacturing. For various operational contexts of industrial machinery, research and development teams have created a range of specialised alloy powders:
Alloy system for high temperatures: GE Aviation has made IN718 nickel-based alloy powder for the combustion chambers of LEAP engines. The durability strength of printed parts at 650 ℃ is >= 900 MPa, which meets the high operating conditions requirements of aircraft engines. This is possible because the powder particle size distribution (D50=45 μ m) and oxygen concentration (<50ppm) are controlled.
System of materials that don't wear out: WC Co hard alloy composite powder was made by Xi'an Jiaotong University for use in wear parts for mining machines. The cutting teeth of the tunnelling machine made using laser selective sintering (SLS) technology are three times more wear-resistant than regular forged parts and have a hardness of HRC68. The service life is now 12 months.
Lightweight material system: BMW Group employs Ti-6Al-4V titanium alloy powder to make the motor housing for the iX3 electric vehicle again. By optimising the topology of the design, the housing's weight is cut by 35%, and the heat dissipation efficiency is improved by 22%. This results in a motor power density of 6.8kW/kg, which is the highest in the industry.
3. Process Integration: Moving from "Single Point" to "Full Chain"
Modern metal 3D printing and remanufacturing have created a full technical chain that includes "detection modelling printing post-processing."
An intelligent detecting system: Siemens Industrial Software's NX AM module can combine data from laser scanners and ultrasonic flaw detection, automatically create 3D models of fault areas, and achieve a detection accuracy of 0.02mm, which is 10 times more accurate than measuring by hand.
Adaptive printing process: The Platinum BLT-S800 has a multi-laser collaboration system that can change the power and speed of the lasers dependent on the shape of the items. When printing a certain kind of gas turbine guide vane, the system automatically finds the thin-walled area (thickness<1mm) and lowers the laser power from 300W to 200W. It also speeds up the scanning from 1000mm/s to 1500mm/s to keep the thin-walled area from changing shape by more than 0.05mm.
Digital post-processing: Airbus's hot isostatic pressing (HIP) post-processing method can make SLM printed components denser, going from 99.2% to 99.95%, which gets rid of faults in the internal pores. Compared to untreated parts, the fatigue life of A350XWB landing gear struts that have been treated with HIP is five times longer and is 98% as long as forged parts.
4. Economic analysis: the change from "high cost" to "scale"
As the rate of equipment localisation goes up and the cost of materials goes down, metal 3D printing remanufacturing has become more economically viable and has gained an edge over its competitors.
Optimising the cost structure: A remanufacturing project for a certain car engine cylinder block shows that the cost of a single piece made with the traditional forging and machining process is 1200 yuan, whereas the cost of a single piece made with the SLM printing process is 850 yuan. The cost of powder materials has gone down from 60% to 45%, while the cost of equipment depreciation and energy use has gone down from 25% to 18%.
Reducing inventory costs: Rolls Royce builds a 3D-printed digital warehouse for aviation spare parts, cutting the value of global inventory from $4.2 billion to $1.8 billion and cutting the time that customers' planes are out of service (AOG) from 72 hours to 8 hours. This saves airlines more than $500 million a year in operating costs.
Effect of scale on production: The Platinum BLT-W series arc additive manufacturing (WAAM) equipment can make aviation structural parts with a diameter of 2.5 metres that are all moulded together. The time it takes to print a single piece is 80% less than with typical multi-process manufacturing, and the material utilisation rate goes from 35% to 92%. This makes it possible to mass produce huge structural components that have been remanufactured.