Additive Manufacturing Overview

Additive Manufacturing (AM)

• Converting a CAD model to STL format simplifies the model's geometry for additive manufacturing (AM).
• The conversion process is manual and requires user intervention.
• AM has an application area in medical modeling that does not involve traditional CAD modeling.
• The eight steps of the AM process are: conceptualization and CAD, conversion to STL, transfer and manipulation of STL file, machine setup, build, part removal and cleanup, post-processing of part, and application.
• Key considerations in AM design include part orientation and removal of supports.
• Energy density is a critical factor in metal AM systems.
• Before building a part, use the visualization tool for verification.
• Part removal and cleanup ensure the final product is free from excess material and ready for use.
• All AM machines require specific setup parameters for different materials.
• Repositioning the part before building allows for precise placement within the machine.
• Parts may require shrinkage or coating allowances during production.
• The machine setup phase involves configuring operating parameters.
• Segmentation of STL files divides parts for easier handling.
• The manufacturing process switches to computer-controlled building during the layer-based manufacturing phase.
• AM machines alert the user when the build is complete or when there is no material remaining.
• Significant manual finishing for AM parts typically involves cleaning and preparing them for use.
• Support structures stabilize parts during the building process.
• Post-processing tasks may not always require power tools.
• Common post-processing techniques include abrasive finishing, polishing, sandpapering, and applying coatings.
• AM materials often contain trapped voids, which can lead to failure under stress.
• Poor support removal technique can result in low-quality output.
• Anisotropic properties in AM materials mean different properties in different directions.
• Material degradation in AM can result from improper bonding or crystallization.
• Support removal often requires manual skill to avoid damaging parts.
• Application specificity refers to the specific requirements of the final product.
• Many AM applications do not require high performance from components.
• Parts produced by AM can behave differently from conventionally made parts due to voids, anisotropic properties, or material degradation.

Stereolithography (SL)

• The nominal layer thickness range for most SL machines is 0.05 - 0.1 mm.
• Thicker layers in AM lead to less precise parts.
• Heat resistance or melting temperature of the material must be considered during post-processing involving heat.
• Powder-based systems do not require support structures.
• Photopolymer-based systems require support structures made from the same material as the part.
• Powder-based systems deposit a bed of powder layer-by-layer.
• Droplet deposition systems allow for modifying the support material during printing.
• Binder printing systems can color parts using colored binder material.
• Photopolymer-based systems offer good accuracy with thin layers.
• Newer resins in photopolymer systems provide improved temperature resistance and strength.
• FDM Dimension machines typically have a nominal layer thickness of 0.254 mm.
• Molten material systems require support structures because materials melt and are deposited in a molten state.
• Extrusion processes in FDM do not always generate supports automatically.
• Cleaning parts produced by lamination methods is a laborious process due to waste material removal.
• Material handling requires protection from moisture and excessive light.

Vat Photopolymerization (VP)

• Vat photopolymerization is a type of additive manufacturing process that uses light to solidify a liquid resin.
• It is used in applications like medical modeling.
• The most common radiation type for curing commercial photopolymers is UV light.
• Photopolymer resins require cleaning, post-curing, and finishing after building.
• Free radical polymerization is typically found in acrylate-based photopolymer resins.
• Epoxy and vinylether are used in cationic polymerization.
• Resin formulation involves the use of multifunctional monomers.
• Interpenetrating polymer networks are formed by acrylate and epoxides.
• The recoater system in VP machines applies liquid resin.
• Both di-functional and higher functionality monomers are commonly used in SL resins.
• Vector scan VP machines have subsystems for laser and optics, and control systems.
• The two-photon approach does not require recoating of the resin layer in VP.
• Visible light is not predominantly used for photomask materials in the microelectronic industry.
• A digital micromirror device is used to pattern the radiation beam in the mask projection approach.
• The vector scan approach is common in commercial SL machines.
• Layer-wise approach involves successive layer applications in photopolymerization.\
• The mask projection approach involves scanning laser beams across the resin bath.
• The two-photon approach provides high resolution point-by-point solidification.
• Charles Hull discovered solid polymer patterns by exposing UV-curable materials to a scanning laser.
• UV-curable materials were used in the early experiments of SL technology in the mid 1980s.
• Gamma rays are used for various curing applications, while X-rays are used in treating medical materials.
• A significant drawback of vat photopolymerization technology is the limited chemistries for photopolymers.
• The surface finish of SL parts can vary depending on the orientation of the surfaces.
• Microsterolithography can produce fabrication structures up to 10 mm x 10 mm x 10 mm in size.
• The minimum hardened polymer unit size in microsterolithography is 5 µm in both the x and y directions.
• Microsterolithography offers accuracy of 0.25 µm in the x-y directions.

Lasers

• Laser technology is well suited for integration into modern CAD and CAM systems.
• Focusing laser light on a particular area for an extended period will heat that specific area.
• Mobile phones utilize radio waves for communication.
• Laser material processing is driven by interactions between lasers and solid materials.
• The relationship between wavelength (λ) and frequency is inversely proportional.
• Different types of electromagnetic radiation have different wavelengths.
• LASER stands for Light Amplification by Stimulated Emission of Radiations.
• Photons are the smallest particles (quanta) in light.

This quiz covers the essential steps and considerations in the additive manufacturing (AM) process. It focuses on model conversion, machine setup, and key design factors needed for successful AM applications, especially in the medical field. Test your knowledge about the AM workflow and critical parameters involved.