3D Printing (Introduction, Principles, and Technology)

CAM 3D printing
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Introduction:

3D printing, also known as additive manufacturing, is a process where a three-dimensional object is created from a digital file by using materials such as powder-based metals or plastics. This technique involves layering materials to form the object (also known as “layered molding”). Initially, it was used for creating prototypes in mold manufacturing, industrial design, etc., but now it’s increasingly used for direct manufacturing of products. This includes high-value applications, such as hip joints, teeth, or certain airplane parts, demonstrating the growing popularity of 3D printing.

This technology is used in various industries, including jewelry, footwear, industrial design, architecture, construction (AEC), automotive, aerospace, dental, medical, education, geographic information systems (GIS), civil engineering, firearms, and more.

Principles:

  1. 3D Design: The design process for 3D printing starts with creating a 3D model using computer-aided design (CAD) or computer animation modeling software. The completed 3D model is then sliced into layers to guide the printer for layer-by-layer printing.The standard file format used for collaboration between design software and printers is the STL file format. An STL file uses triangular faces to approximate the surface of the object. The smaller the triangular faces, the higher the resolution of the surface.
  2. Printing Process: The printer reads the cross-sectional information from the file and uses liquid, powder, or sheet materials to print the layers. The material layers are bonded together using various methods to create a solid object. This technology is characterized by its ability to create nearly any shape of object.The thickness of the printed layers (along the Z-axis) and the resolution in the X-Y plane are measured in dpi (dots per inch) or microns. Typically, the layer thickness is 100 microns (0.1 mm), though some printers can print layers as thin as 16 microns. The resolution in the X-Y plane can be similar to a laser printer’s resolution. The printed “ink droplets” typically have a diameter ranging from 50 to 100 microns. Traditional manufacturing methods typically take hours or days to create a model, while 3D printing can reduce this to a few hours, depending on the printer’s performance and the model’s complexity.Traditional manufacturing methods like injection molding can produce polymer products in large quantities at a lower cost, while 3D printing allows for faster, more flexible, and lower-cost production of smaller quantities of products. A desktop 3D printer can meet the needs of designers or concept development teams for model creation.
  3. Completion: The resolution of most 3D printers is now sufficient for most applications (though curved surfaces may still appear rough, resembling jagged edges in images). To achieve higher resolution, larger objects can be printed first and then slightly polished to achieve a smooth surface.Some technologies allow for the use of multiple materials in the printing process. Some methods also require support materials, for example, when printing objects with hanging sections, soluble materials are used as support.

Technologies:

There are several different 3D printing technologies, each differing in the materials used and how parts are created layer by layer.

Types:

  1. Extrusion Technology:
  • Fused Deposition Modeling (FDM): Uses thermoplastic materials, metal alloys, and edible materials in filament form. FDM prints by extruding the material through a nozzle.
  • Electron-Beam Freeform Fabrication (EBF): Uses nearly any alloy for 3D printing, with an electron beam as the energy source for melting materials.
  1. Powder-Based Technology:
  • Direct Metal Laser Sintering (DMLS): Uses nearly any alloy, particularly metals, with a laser to sinter the powder, forming solid objects.
  • Electron Beam Melting (EBM): Uses titanium alloys in powder form and an electron beam for sintering. This is ideal for creating metal parts.
  • Selective Laser Melting (SLM): A laser-based method for sintering powder materials, including titanium alloys, cobalt-chromium alloys, stainless steel, and aluminum.
  • Selective Heat Sintering (SHS): Uses thermoplastic powders for 3D printing.
  1. Layer-Based Technology:
  • Laminated Object Manufacturing (LOM): Uses paper, metal, and plastic films in layer-by-layer manufacturing.
  1. Light-Based Technology:
  • Stereolithography (SLA): Uses photopolymer resins cured by UV light. This method is known for high precision and smooth surface finish.
  • Digital-Light Processing (DLP): Similar to SLA, but uses a digital projector for faster curing of resin layers.

Three Main Technologies:

  1. Fused Deposition Modeling (FDM): Some 3D printers use an “inkjet” method where plastic is melted inside a nozzle and then deposited as thin layers to build the object.
  • Advantages: Higher precision, stronger parts, and color capability, though the surface can be rough post-printing.
  1. Stereolithography (SLA): This method “slices” the 3D model into cross-sections, which are then built up layer by layer in a liquid resin bath, cured by UV light.
  • Advantages: High precision and smooth finishes, with a layer thickness from 0.05mm to 0.15mm. However, material options are limited, and color printing is not possible.
  1. Selective Laser Sintering (SLS): SLS uses a laser to sinter powder materials layer by layer. It is commonly used for creating functional parts from nylon and elastomers, with growing applications in metals.
  • Advantages: Stronger than SLA prints, capable of printing structural and functional parts with a wide range of materials.

Each of these technologies is tailored for specific applications, offering unique advantages in terms of material use, part complexity, and finishing precision.