Will 3D printing shift into high gear in the Covid-19 fight?David Wagman | March 23, 2020
German automaker Volkswagen (VW) said it has created a task force to look into producing medical equipment using additive manufacturing to help in the fight against coronavirus, also known as COVID-19.
Governments around the world have asked automakers, including Ford, General Motors, Ferrari and Nissan, to investigate producing ventilators and other medical equipment that face shortages and are critical to saving lives.
VW said in a statement that its task force would explore how to use 3D printing to help manufacture ventilators. The company currently has more than 125 industrial 3D printers.
"Medical equipment is a new field for us. But as soon as we understand the requirements and receive a blueprint, we can get started," Volkswagen said.
In 2018, VW said it planned to work with HP to expand its use of 3D printing in its production lines.
3D printers fabricate three-dimensional solid objects from a digital model using an additive manufacturing (AM) process where successive layers of material are deposited in different shapes to form the final piece.
3D printing (3DP) typically offers fast fabrication and low material cost. In many ways, 3DP is probably the fastest of all rapid prototyping methods. Recently there have been significant advances in printing resolution, product options and finishing, overall part size and material specifications.
Types of printers
Stereolithography (SLA) — This was the first 3D printing method and was developed in the 1980s. A UV-curing resin is located in a reservoir with a submerged elevator platform. UV light from a DLP projector or laser traces an outline in the resin that causes it to harden. The elevator platform descends and another layer of the component is traced and cured. SLA has very high resolutions compared to other methods, though it is also slower due to curing times. Finished parts are not UV stable.
Fused filament fabrication (FFF) or fused deposition modeling (FDM) — This technique extrudes thermoplastic filament through a small nozzle, similar in concept to a hot glue gun. This process is done slowly to maintain uniform part thickness and accuracy. The plastic cools and cures so another layer can be built on top of it.
Selective laser sintering (SLS) and selective laser melting (SLM) — These two methods are similar but not the same. SLS and SLM printers both use a laser to heat a powdered print material, where a laser is precisely aimed. In the case of SLM the material is melted, in the case of SLS it is sintered. Similar to SLA, parts are cured on a descending piston; however, additional powder material is added to the vat between layers from a separate reservoir. The printing material can be anything that can be melted with the laser, which is typically thermoplastics but can be metals with the correct laser.
Polyjet — This technique uses inkjet heads to deposit a UV-curing resin that is immediately cured so that a new layer can be built on top of it.
Powder bed inkjet/binder jetting — This techniques deposits thin layers of powder on a binder or adhesive to bond layers together. Additional layers of powder are applied and the inkjet bonds it to the layer below. Parts tend to be weak and require additional processing before being used.
(Learn more about 3D printing equipment.)
Multiple engineering standards have been developed related to additive manufacturing. Here are a few of the major standards. Additional standards may be found here.
ASTM International — ASTM ISO/ASTM52910-18: This document gives requirements, guidelines and recommendations for using additive manufacturing in product design.
ASTM ISO/ASTM 52900 Standard Terminology for Additive Manufacturing — General Principles — Terminology: This International Standard establishes and defines terms used in additive manufacturing technology, which applies the additive shaping principle and thereby builds physical 3D geometries by successive addition of material. The terms have been classified into specific fields of application.
ASTM International — ASTM ISO/ASTM52907-19 Additive Manufacturing — Feedstock materials — Methods to characterize metallic powders: This document provides technical specifications for metallic powders intended to be used in additive manufacturing and covers documentation and traceability, sampling, particle size distribution, chemical composition, characteristic densities, morphology, flowability, contamination, packaging and storage.
Many materials can be used for additive manufacturing and 3D printing and new ones are being developed. Depending on the manufacturing machine, different materials in different form factors are used.
Many metals are used in producing an additive manufactured part. They include iron based sintered powder metal, stainless steel, bronze and nickel, steel, gold, titanium and aluminum.
Metal additive manufacturing processes that use a layering technique include laser sintering (LM/SLS/SLFS), electron beam melting, fused deposition modeling/extrusion, laser powder forming and selective inkjet binding.
Water atomization is the most prevalent metal powder production methodology and typically is also the most economical. High pressure water impacts a molten metal stream and small particles that are created have a rapid cooling rate.
Gas atomization is commonly preferred as a production method for MAM bound metal powders. Here, the feedstock is melted and the molten mixture is forced through a nozzle. High-velocity gas impinges into the flowing molten metal and reduces it to fine droplets. Spheres form as the metal droplets fall to the bottom of an atomization tower.
In addition to metals, thermoplastics, carbon fiber and other composites are also used in additive manufacturing.
ABS is one of the most common plastics for AM. It has good strength and heat resistance and many printers are capable of printing with it. It is a plastic that is suitable as a finished product as well as for prototyping. It requires a heated bed for printing and has a tendency to curl as it cools making it a little more difficult to print with.
PLA is a very common plastic to print with due to its ease of use and low temperature requirements. It has good strength but is not very flexible, making it somewhat brittle. It also has poor heat resistance and can melt in a hot environment.
Polyamide (nylon) is one of the stronger materials used in the AM process. It can be difficult to print with due to its temperature requirements, but can be printed in many FDM printers with minor modifications to the hot end nozzle.
ULTEM is an amorphous thermoplastic polyetherimide (PEI) resin. This is one of the strongest materials available for FDM printing, but is difficult to print with due to its temperature requirements. Most printers are not capable of using this material unless they have been designed for it. In addition to producing strong finished parts, they also have high thermal and chemical resistance.
(Learn more about materials used in 3D printing.)