1,"From scratches" on technical principle In the lifting, the difference between additive manufacturing and subtractive manufacturing is all about "from scratches to the end part".
Central to metal additive manufacturing technology is "layer by layer accumulation," in which metal powders or wires are melted and deposited layer by layer via energy sources like lasers or electron beams, resulting in direct production of solid components from digital models. Its typical process includes:
Selective Laser Melting (SLM): Additive manufacturing process which uses a high-energy laser to selectively melt metal powder layer by layer, often used to produce complex structural components such as aircraft engine combustion chambers, or nuclear reactor pressure vessels and heat exchangers.
Electron Beam Melting (EBM) A vacuum melted process using electron beam, high rate of deposition and low residual stress characteristics For manufacturing of titanium alloy aviation parts.
Arc Additive Manufacturing (WAAM): Accumulation of metal by melting metal wires and adding layer by layer with a robotic arm by an electric arc as a heat source. It is perfect for the rapid creation of large structure objects, like ship propellers and wind turbine towers.
In the subtractive manufacturing environment, 'layer by layer removal' is performed where typically turning, milling, drilling, and grinding tools are used to remove material from the source (stock) and thus obtain the final geometry. Its technical branches include:
Work_healthCNC machining:Computer-controlled tool path can realize high-accuracy complex plane machining, and is widely used in automobile engine cylinder block and aircraft structural parts.
Electric discharge machining (EDM): using electric discharge to etch metal materials, apply to the precision processing of difficult processing materials, including hard alloy, mold steel.
Laser cut / waterjet cut: this technique cuts high-energy beams or high-pressure water flow of materials for rapid production of 2D planar parts.
The essential difference: Additive manufacturing gets rid of the combination of mold and fixture dependence of traditional manufacturing that can accommodate "free design"; while subtractive manufacturing is better in precision, surface quality and especially suitable for batch-normative production.
2, Application scenarios：The difference between customization and scalability
Advantages of metal additive manufacturing:
Small-batch bespoke manufacturing: Additive can rapidly satisfy personalized requirements-something that has applications in sectors such as aerospace and medical implants. For example, the domestic large aircraft's titanium alloy structural components, which are developed by Bolite, have the 3D printed instead of a traditional technology, to reduce the delivery cycle and cost, and are also beneficial to lightweight and fuel economy.
Fabrication of complex structural parts: AM can produce geometries from topology optimized structures which are infeasible with traditional manufacturing. For instance, by EBM technology GE Aviation could design and produce TiAl blades, which weigh only half of a typical one made of nickel alloy, resulting in fuel consumption saving for the engine.
Lightweight and high-integration: Integrated design will reduce parts quantity, and the part reliability will be increased under the conditions of additive manufacturing (AM) technology. For instance, there is an enterprise, which develops a 3D-printed hip-joint implant that is based on gradient material design, enable it to gradually absorb in the body without the occurrence of secondary operation.
Applicable scenarios for subtractive manufacturing:
Mass standard production: In some areas like automobile and home appliance, subtractive manufacturing can achieve large-quantity production with the help of mold and automatic line. The motor housing of the Tesla Model for example, is CNC machined, with single part cost relatively low and surface roughness relatively low.
High precision machining requirement: there are fields that can not be replaced by the efficiency of the removal, such as in the field of optical equipment and semiconductor components. For instance, Zeiss optical lenses produce surface accuracy in the nanometer range using ultra precision grinding technology.
Large structural assembly manufacturing: For components longer than a few meters, subtractive manufacturing is cost and efficiency more advantageous. For instance, such ship propeller blades can be compliant with ocean engineering extremely high requirement for size and intensity is made through the processing of CNC milling.
3,Cost Efficiency: The battle between Short term Investment and Long term Value
THE COST7 OF ADDITIVE MANUFACTURE:
Price: Industrial metal 3D printers are costly and must be run alongside post-processing equipment such as hot isostatic pressing furnaces and CNC machine tools.
High cost of materials: the price of a metal powder (such as a titanium alloy, a nickel-based alloy) is several times higher than that of a common rod, and is restricted by the technology for use.
Scale bottleneck: The production time of a single workpiece is exponentially related to the complexity of the workpiece, and the scale production efficiency is higher than that of subtractive manufacturing.
Cost advantages of subtractive manufacturing:
Low unit price: After the mold is made, the cost of per piece is much lower when the quantity is larger; it is suitable for the annual output quantity is more than thousand.
High material utilization: the material utilization of CNC machining is over 90%, and the scrap can be recycled and reused.
Factors affecting the formation of layer imperfections are high: The subtractive manufacturing technology has experienced decades of iteration, and it has developed to an industrial level in terms of equipment stability and accuracy.
Synergy infusion: The combination of additive manufacturing and subtractive manufacturing is altering the math. For instance, the "additive subtractive" hybrid machine developed by Platinum Technology manufactures the body partly by 3D printing and then refines it by CNC, which cuts down the manufacturing cost of aeroengine blades in an all-around way.
Material adaptability: from single metal to composite material is broken through.
Material innovation in additive manufacturing:
Multi-material printing: Metal CERAMIC and Metal POLYREAD can be printed by using various nozzle number or mixed powder technology. For instance, one company has developed a 3D-printed orthopedic implant employing a composite of titanium-allay and hydroxyapatite for better efficiency of bone bonding.
Gradient material design: By controlling powder components distribution, coaxial varying in the material properties could be achieved. For instance, a rocket engine nozzle created by one company is made of a special nickel based alloy that can withstand high temperature in the inner layer and of lightweight aluminum alloy material in the outer layer, all of which are therefore connected seamlessly applying 3D printing.
Material limitations of subtractive manufacturing:
Degree of processing difficulty classification: subtractive manufacturing of close material hardness and plasticity requirements. E.g. new materials like high entropy alloys or titanium aluminum intermetallic compounds may not be processed in conventional processing techniques due to their low cutting performance.
Difficulties in composites processing: Carbon fiber reinforced composites (CFRP) tend to delaminate, form burrs, and generate other problems in subtractive processing and they need specific cutting conditions.